U.S. patent application number 11/077969 was filed with the patent office on 2005-10-20 for methods and systems for producing ethanol using raw starch and fractionation.
This patent application is currently assigned to Broin and Associates, Inc.. Invention is credited to Lewis, Steven M., Van Hulzen, Shon Erron.
Application Number | 20050233030 11/077969 |
Document ID | / |
Family ID | 35096565 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050233030 |
Kind Code |
A1 |
Lewis, Steven M. ; et
al. |
October 20, 2005 |
Methods and systems for producing ethanol using raw starch and
fractionation
Abstract
The present invention relates to methods for producing high
levels of alcohol during fermentation of plant material, and to the
high alcohol beer produced. The method can include fractionating
the plant material. The present invention also relates to methods
for producing high protein distiller's dried grain from
fermentation of plant material, and to the high protein distiller's
dried grain produced. The method can include drying a co-product by
ring drying, flash drying, or fluid bed drying. The present
invention further relates to reduced stack emissions from drying
distillation products from the production of ethanol.
Inventors: |
Lewis, Steven M.; (Sioux
Falls, SD) ; Van Hulzen, Shon Erron; (Brandon,
SD) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
Broin and Associates, Inc.
Sioux Falls
SD
|
Family ID: |
35096565 |
Appl. No.: |
11/077969 |
Filed: |
March 10, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11077969 |
Mar 10, 2005 |
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10798226 |
Mar 10, 2004 |
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60614916 |
Sep 30, 2004 |
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60615155 |
Oct 1, 2004 |
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60552108 |
Mar 10, 2004 |
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Current U.S.
Class: |
426/49 |
Current CPC
Class: |
C12C 12/006 20130101;
Y02E 50/17 20130101; A01H 5/10 20130101; C12P 7/06 20130101; C12P
19/14 20130101; Y02E 50/10 20130101; C12C 12/00 20130101 |
Class at
Publication: |
426/049 |
International
Class: |
A23K 001/00 |
Claims
We claim:
1. A process for producing ethanol from plant material, comprising:
fractionating the plant material; reducing the plant material to
produce material comprising starch; the reduced plant material
having particle size such that at least about 50% of the particles
fit through a sieve with a 0.1-0.5 mm mesh; saccharifying the
starch, without cooking, with an enzyme composition; fermenting the
incubated starch to yield a composition comprising at least 15
vol-% ethanol; fermenting comprising reducing temperature of
fermenting mixture; and recovering the ethanol and co-products from
the fermentation.
2. The process of claim 1, wherein plant material comprises corn,
which comprises high amylopectin starch.
3. The process of claim 1, wherein the plant material comprises
corn, sorghum, millet, wheat, barley, rye, or mixtures thereof.
4. The process of claim 3, wherein the corn comprises waxy
corn.
5. The process of claim 3, wherein the corn comprises high protein
corn.
6. The process of claim 3, wherein the corn comprises #2 yellow
dent corn.
7. The process of claim 1, comprising reducing the plant material
with hammer mill, roller mill, or both hammer mill and roller
mill.
8. The process of claim 7, comprising reducing the plant material
to produce plant material of a size that at least 35% of the
reduced plant material fits through a 0.1-0.5 mm screen.
9. The process of claim 1, comprising reducing the plant material
with particle size reduction emulsion technology.
10. The process of claim 1, comprising simultaneous saccharifying
and fermenting.
11. The process of claim 1, comprising decreasing temperature
during saccharifying, fermenting, or simultaneous saccharifying and
fermenting.
12. The process of claim 1, comprising saccharifying, fermenting,
or simultaneous saccharifying and fermenting at temperature of
25-40.degree. C.
13. The process of claim 1, comprising saccharifying, fermenting,
or simultaneous saccharifying and fermenting at temperature of
27-35.degree. C.
14. The process of claim 1, comprising reducing temperature from
about 40.degree. C. and to about 25.degree. C. during
saccharifying, fermenting, or simultaneous saccharifying and
fermenting.
15. The process of claim 1, comprising saccharifying, fermenting,
or simultaneous saccharifying and fermenting at pH of about 3.0 to
about 6.0.
16. The process of claim 1, comprising saccharifying, fermenting,
or simultaneous saccharifying and fermenting at pH of about 4.1 to
about 5.3.
17. The process of claim 1, comprising a pH of about 4 to about 4.5
at start of fermentation fill.
18. The process of claim 1, comprising a pH of about 5 to about 5.5
as ethanol production reaches maximum level.
19. The process of claim 1, comprising increasing pH from about 4
to about 5.3 during saccharifying, fermenting, or simultaneous
saccharifying and fermenting.
20. The process of claim 1, comprising decreasing solid content
from about 40% to about 15% during saccharifying, fermenting, or
simultaneous saccharifying and fermenting.
21. The process of claim 1, wherein the enzyme composition
comprises alpha amylase, glucoamylase, protease, or mixtures
thereof.
22. The process of claim 1, wherein saccharifying, fermenting, or
simultaneous saccharifying and fermenting comprises adding
protease.
23. The process of claim 1, wherein saccharifying, fermenting, or
simultaneous saccharifying and fermenting comprises adding
backset.
24. The process of claim 1, wherein saccharifying, fermenting, or
simultaneous saccharifying and fermenting comprising adding
nitrogen.
25. The process of claim 1, comprising saccharifying and fermenting
at rates that maintain concentration of glucose less than 3 wt-% in
fermentation.
26. The process of claim 1, comprising saccharifying, fermenting,
or both saccharifying and fermenting with about 0.1 to about 10
acid fungal amylase units (AFAU) per gram of dry solids reduced
plant material and about 0.1 to about 6 glucoamylase units (AGU)
per gram dry solids reduced plant material.
27. The process of claim 1, comprising starting saccharifying,
fermenting, or both saccharifying and fermenting with about 25 to
about 45 wt-% reduced plant material in water.
28. The process of claim 1, comprising starting saccharifying,
fermenting, or both saccharifying and fermenting with residual
starch at up to 20%.
29. The process of claim 1, comprising producing greater than 18
vol-% ethanol in about 48 to 96 hours.
30. The process of claim 1, comprising producing 18 vol-% to about
23 vol-% ethanol.
31. The process of claim 1, further comprising recovering the
solids from the fermentation.
32. The process of claim 31, recovering before, during, and after
recovering the ethanol.
33. The process of claim 31, comprising recovering distiller's
dried grain.
34. The process of claim 31, wherein the distiller's dried grain
comprises about 30-38 wt-% protein, about 11-19 wt-% fat, about
25-37 wt-% fiber.
35. The process of claim 31, wherein the distiller's dried grain
comprises at least about 30% protein.
36. The process of claim 1, comprising running the process as a
batch process or as a continuous process.
37. A process for producing ethanol from plant material,
comprising: fractionating the plant material; reducing the plant
material to produce material comprising starch; saccharifying the
starch, without cooking, with an enzyme composition comprising acid
fungal amylase; fermenting the incubated starch to yield a
composition comprising at least about 18 vol-% ethanol; recovering
ethanol from the fermentation.
38. A distiller's dried gain comprising at least about 40 wt-%
protein.
39. A process for producing ethanol from plant material,
comprising: reducing the plant material to produce material
comprising starch; the reduced plant material having particle size
such that at least about 50% of the particles fit through a sieve
with a 0.1-0.5 mm mesh; saccharifying the starch, without cooking,
with an enzyme composition; fermenting the incubated starch to
yield a composition comprising at least 15 vol-% ethanol;
fermenting comprising reducing temperature of fermenting mixture;
and recovering the ethanol and co-products from the fermentation;
drying a co-product by ring drying, flash drying, or fluid bed
drying.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application Nos. 60/615,155, filed Oct. 1, 2004, 60/614,916
, filed Sep. 30, 2004, and 60/552,108, filed Mar. 10, 2004, and is
a continuation in part of U.S. patent application Ser. No.
10/798,226, filed Mar. 10, 2004.
FIELD OF THE INVENTION
[0002] The present invention relates to methods for producing high
levels of alcohol during fermentation of plant material, and to the
high alcohol beer produced. The method can include fractionating
the plant material. The present invention also relates to methods
for producing high protein distiller's dried grain from
fermentation of plant material, and to the high protein distiller's
dried grain produced. The method can include drying a co-product by
ring drying, flash drying, or fluid bed drying. The present
invention further relates to reduced stack emissions from drying
distillation products from the production of ethanol.
BACKGROUND OF THE INVENTION
[0003] Numerous conventional methods exist for converting plant
material to ethanol. However, these methods suffer from numerous
inefficiencies. There remains a need for additional more effective
methods for converting plant material to ethanol and for producing
improved fermentation products.
SUMMARY OF THE INVENTION
[0004] The present invention relates to methods for producing high
levels of alcohol during fermentation of plant material, and to the
high alcohol beer produced. The method can include fractionating
the plant material. The present invention also relates to methods
for producing high protein distiller's dried grain from
fermentation of plant material, and to the high protein distiller's
dried grain produced. The method can include drying a co-product by
ring drying, flash drying, or fluid bed drying.
[0005] In an embodiment, the present invention relates to a process
for producing ethanol from plant material (e.g., fractionated plant
material). This method includes fractionating the plant material;
grinding the plant material (e.g., fractionated plant material) to
produce ground plant material (e.g., fractionated plant material)
including starch; saccharifying the starch, without cooking;
fermenting the incubated starch; and recovering the ethanol from
the fermentation. The present method can include varying the
temperature during fermentation. The present method can include
employing plant material (e.g., fractionated plant material) with a
particle size such that more than 50% of the material fits though a
sieve with a 0.5 mm mesh. The present method can yield a
composition including at least 18 vol-% ethanol.
[0006] In an embodiment, the present invention relates to a process
for producing high protein distiller's dried grain from plant
material (e.g., fractionated plant material). This method includes
fractionating the plant material; grinding the plant material
(e.g., fractionated plant material) to produce ground plant
material (e.g., fractionated plant material) including starch;
producing sugars from the starch without cooking; fermenting the
uncooked sugars to yield a composition including ethanol; and
recovering distiller's dried grain from the fermentation. The
distiller's dried grain can include at least about 30% protein. The
distillers dried grain can include increased levels of the protein
zein.
[0007] In an embodiment, the present invention relates to a process
of producing ethanol from corn. This process includes producing
starch from corn and ethanol from the starch; producing dryer stack
emissions including a significantly lower level of volatile organic
compounds than conventional technologies.
BRIEF DESCRIPTION OF THE FIGURES
[0008] FIG. 1 schematically illustrates a fermentation system
according to an embodiment of the present invention.
[0009] FIGS. 2A through 2C schematically illustrate that the
present process provides improved efficiency for fermentation of
corn fractions produced by dry milling fractionation processes.
[0010] FIGS. 3A through 3C schematically illustrate that the
present process provides improved efficiency for fermentation of
corn fractions produced by dry milling fractionation processes.
DETAILED DESCRIPTION OF THE INVENTION
DEFINITIONS
[0011] As used herein, the phrase "without cooking" refers to a
process for converting starch to ethanol without heat treatment for
gelatinization and dextrinization of starch using alpha-amylase.
Generally, for the process of the present invention, "without
cooking" refers to maintaining a temperature below starch
gelatinization temperatures, so that saccharification occurs
directly from the raw native insoluble starch to soluble glucose
while bypassing conventional starch gelatinization conditions.
Starch gelatinization temperatures are typically in a range of
57.degree. C. to 93.degree. C. depending on the starch source and
polymer type. In the method of the present invention,
dextrinization of starch using conventional liquefaction techniques
is not necessary for efficient fermentation of the carbohydrate in
the grain.
[0012] As used herein, the phrase "plant material" refers to all or
part of any plant (e.g., cereal grain), typically a material
including starch. Suitable plant material includes grains such as
maize (corn, e.g., whole ground corn), sorghum (milo), barley,
wheat, rye, rice, and millet; and starchy root crops, tubers, or
roots such as sweet potato and cassava. The plant material can be a
mixture of such materials and byproducts of such materials, e.g.,
corn fiber, corn cobs, stover, or other cellulose and hemicellulose
containing materials such as wood or plant residues. Suitable plant
materials include corn, either standard corn or waxy corn.
[0013] As used herein, the phrase "fractionated plant material"
refers to plant material that includes only a portion or fraction
of the total plant material, typically a material including starch.
Fractionated plant material can include fractionated grains such as
fractionated maize (fractionated corn), fractionated sorghum
(fractionated milo), fractionated barley, fractionated wheat,
fractionated rye, fractionated rice, and fractionated millet; and
fractionated starchy root crops, tubers, or roots such as
fractionated sweet potato and fractionated cassava. Suitable
fractionated plant materials include fractionated corn, either
fractionated standard corn or fractionated waxy corn.
[0014] As used herein, the terms "saccharification" and
"saccharifying" refer to the process of converting starch to
smaller polysaccharides and eventually to monosaccharides, such as
glucose. Conventional saccharification uses liquefaction of
gelatinized starch to create soluble dextrinized substrate which
glucoamylase enzyme hydrolyzes to glucose. In the present method,
saccharification refers to converting raw starch to glucose with
enzymes, e.g., glucoamylase and acid fungal amylase (AFAU).
According to the present method, the raw starch is not subjected to
conventional liquefaction and gelatinization to create a
conventional dextrinized substrate.
[0015] As used herein, a unit of acid fungal amylase activity
(AFAU) refers to the standard Novozymes units for measuring acid
fungal amylase activity. The Novozymes units are described in a
Novozymes technical bulletin SOP No.: EB-SM-0259.02/01. Such units
can be measured by detecting products of starch degradation by
iodine titration. I unit is defined as the amount of enzyme that
degrades 5.260 mg starch dry matter per hour under standard
conditions.
[0016] As used herein, a unit of glucoamylase activity (GAU) refers
to the standard Novozymes units for measuring glucoamylase
activity. The Novozymes units and assays for determining
glucoamylase activity are described in a publicly available
Novozymes technical bulletin.
[0017] As used herein, a unit of amyloglucosidase activity (AGU)
refers to the standard Novozymes units for measuring
amyloglucosidase activity. The Novozymes units are described in a
Novozymes technical bulletin SOP No.: EB-SM-0131.02/01. Such units
can be measured by detecting conversion of maltose to glucose. The
glucose can be determined using the glucose dehydrogenase reaction.
1 unit is defined as the amount of enzyme that catalyzes the
conversion of 1 mmol maltose per minute under the given
conditions.
[0018] As used herein, the term "about" modifying any amount refers
to the variation in that amount encountered in real world
conditions of producing sugars and ethanol, e.g., in the lab, pilot
plant, or production facility. For example, an amount of an
ingredient employed in a mixture when modified by "about" includes
the variation and degree of care typically employed in measuring in
an ethanol production plant or lab. For example, the amount of a
component of a product when modified by "about" includes the
variation between batches in an ethanol production plant or lab and
the variation inherent in the analytical method. Whether or not
modified by "about," the amounts include equivalents to those
amounts. Any quantity stated herein and modified by "about" can
also be employed in the present invention as the amount not
modified by "about."
[0019] Converting Starch to Ethanol
[0020] The present invention relates to methods for producing high
levels of alcohol during fermentation of plant material (e.g.,
fractionated plant material), and to the high alcohol beer
produced. The present invention also relates to methods for
producing high protein distiller's dried grain from fermentation of
plant material (e.g., fractionated plant material), to the high
protein distiller's dried grain produced, and to the cleaner dryer
stack emissions.
[0021] The present method converts starch from plant material
(e.g., fractionated plant material) to ethanol. In an embodiment,
the present method can include preparing the plant material (e.g.,
fractionated plant material) for saccharification, converting the
prepared plant material (e.g., fractionated plant material) to
sugars without cooking, and fermenting the sugars.
[0022] The plant material (e.g., fractionated plant material) can
be prepared for saccharification by any a variety of methods, e.g.,
by grinding, to make the starch available for saccharification and
fermentation. In an embodiment, the vegetable material can be
ground so that a substantial portion, e.g., a majority, of the
ground material fits through a sieve with a 0.1-0.5 mm screen. For
example, in an embodiment, about 70% or more, of the ground
vegetable material can fit through a sieve with a 0.1-0.5 mm
screen. In an embodiment, the reduced plant material (e.g.,
fractionated plant material) can be mixed with liquid at about 20
to about 50 wt-% or about 25 to about 45 wt-% dry reduced plant
material (e.g., fractionated plant material).
[0023] The present process can include converting reduced plant
material (e.g., fractionated plant material) to sugars that can be
fermented by a microorganism such as yeast. This conversion can be
effected by saccharifying the reduced plant material (e.g.,
fractionated plant material) with an enzyme preparation, such as a
saccharifying enzyme composition. A saccharifying enzyme
composition can include any of a variety of known enzymes suitable
for converting reduced plant material (e.g., fractionated plant
material) to fermentable sugars, such as amylases (e.g.,
.alpha.-amylase and/or glucoamylase). In an embodiment,
saccharification is conducted at a pH of about 6.0 or less, for
example, about 4.5 to about 5.0, for example, about 4.5 to about
4.8.
[0024] The present process includes fermenting sugars from reduced
plant material (e.g., fractionated plant material) to ethanol.
Fermenting can be effected by a microorganism, such as yeast. In an
embodiment, fermentation is conducted at a pH of about 6 or less,
for example, about 4.5 to about 5, for example, about 4.5 to about
4.8. In an embodiment, the present method can include varying the
pH. For example, fermentation can include filling the fermenter at
pH of about 3 to about 4.5 during the first half of fill and at a
pH of about 4.5 to about 6 (e.g., about 4.5 to about 4.8) during
the second half of the fermenter fill cycle. In an embodiment,
fermentation is conducted at a temperature of about 25 to about
40.degree. C. or about 30 to about 35.degree. C. In an embodiment,
during fermentation the temperature is decreased from about
40.degree. C. to about 30.degree. C. or about 25.degree. C., or
from about 35.degree. C. to about 30.degree. C., during the first
half of the fermentation, and the temperature is held at the lower
temperature for the second half of the fermentation. In an
embodiment, fermentation is conducted for about 25 (e.g., 24) to
about to 150 hours, for example, for about 48 (e.g., 47) to about
96 hours.
[0025] The present process can include simultaneously converting
reduced plant material (e.g., fractionated plant material) to
sugars and fermenting those sugars with a microorganism such as
yeast.
[0026] The product of the fermentation process is referred to
herein as "beer". Ethanol can be recovered from the fermentation
mixture, from the beer, by any of a variety of known processes,
such as by distilling. The remaining stillage includes both liquid
and solid material. The liquid and solid can be separated by, for
example, centrifugation.
[0027] Preparing the Plant Material
[0028] The present method converts starch from plant material
(e.g., fractionated plant material) to ethanol. The plant material
(e.g., fractionated plant material) can be reduced by a variety of
methods, e.g., by grinding, to make the starch available for
saccharification and fermentation. Other methods of plant material
reduction are available. For example, vegetable material, such as
kernels of corn, can be ground with a ball mill, a roller mill, a
hammer mill, or another mill known for grinding vegetable material,
and/or other materials for the purposes of particle size reduction.
The use of emulsion technology, rotary pulsation, and other means
of particle size reduction can be employed to increase surface area
of plant material (e.g., fractionated plant material) while raising
the effectiveness of flowing the liquefied media. The prepared
plant material (e.g., fractionated plant material) can be referred
to as being or including "raw starch".
[0029] A fine grind exposes more surface area of the plant material
(e.g., fractionated plant material), or vegetable material, and can
facilitate saccharification and fermentation. In an embodiment, the
vegetable material is ground so that a substantial portion, e.g., a
majority, of the ground material fits through a sieve with a
0.1-0.5 mm screen. In an embodiment, about 35% or more of the
ground vegetable material can fit through a sieve with a 0.1-0.5 mm
screen. In an embodiment, about 35 to about 70% of the ground
vegetable material can fit through a sieve with a 0.1-0.5 mm
screen. In an embodiment, about 50% or more of the ground vegetable
material can fit through a sieve with a 0.1-0.5 mm screen. In an
embodiment, about 90% of the ground vegetable material can fit
through a sieve with a 0.1-0.5 mm screen. In an embodiment, all of
the ground vegetable material can fit through a sieve with a
0.1-0.5 mm screen. In an embodiment, the ground vegetable material
has an average particle size of about 0.25 mm.
[0030] Plant Material Reduction
[0031] Preparing the plant material (e.g., fractionated plant
material) can employ any of a variety of techniques for plant
material (e.g., fractionated plant material) reduction. For
example, the present method of preparing plant material (e.g.,
fractionated plant material) can employ emulsion technology, rotary
pulsation, sonication, magnetostriction, ferromagnetic materials,
or the like. These methods of plant material reduction can be
employed for substrate pretreatment. Although not limiting to the
present invention, it is believed that these methods can increase
surface area of plant material (e.g., fractionated plant material)
while raising the effectiveness of flowing of liquefied media (i.e.
decreased viscosity). These methods can include electrical to
mechanical, mechanical to electrical, pulse, and sound based
vibrations at varying speeds. This can provide varying frequencies
over a wide range of frequencies, which can be effective for
pretreating the plant material (e.g., fractionated plant material)
and/or reducing particle size.
[0032] Although not limiting to the present invention, it is
believed that certain of these sonic methods create low pressure
around a particle of plant material (e.g., fractionated plant
material) and induce cavitation of the particle or disruption of
the particle structure. The cavitated or disrupted particle can
increase availability of plant material (e.g., starch) to an
enzyme, for example, by increasing surface area. It is believed
that such pretreatment can decrease quantity of enzyme rates in the
present method for ethanol production.
[0033] In an embodiment, the present method includes vibrating
plant material (e.g., fractionated plant material) and cavitating
the fluid containing the plant material. This can result in
disrupting the plant material and/or decreasing the size of the
plant material (e.g., fractionated plant material). In certain
embodiments, the present method includes treating plant material
(e.g., fractionated plant material) with emulsion technology, with
rotary pulsation, with magnetostriction, or with ferromagnetic
materials. This can result in disrupting the plant material and/or
decreasing the size of the plant material (e.g., fractionated plant
material). In an embodiment, the present method includes sonicating
the plant material (e.g., fractionated plant material). This can
result in disrupting the plant material and/or decreasing the size
of the plant material (e.g., fractionated plant material).
[0034] In an embodiment, the present method can include employing
sound waves for reducing plant material (e.g., fractionated plant
material). The sound waves can be ultrasound. The present method
can include sonicating the plant material (e.g., fractionated plant
material). The method can include sonicating the plant material at
a frequency (e.g., measured in kHz), power (e.g., measured in
watts), and for a time effective to reduce (or to assist in
reducing) the particle size to sizes described hereinabove. For
example, the method can include sonicating the plant material
(e.g., fractionated plant material) at 20,000 Hz and up to about
3000 W for a sufficient time and at a suitable temperature. Such
sonicating can be carried out with commercially available
apparatus, such as high powered ultrasonics available from ETREMA
(Ames, Iowa).
[0035] In an embodiment, the present method can include employing
rotary pulsation for reducing plant material (e.g., fractionated
plant material). The method can include rotary pulsating the plant
material (e.g., fractionated plant material) at a frequency (e.g.,
measured in Hz), power (e.g., measured in watts), and for a time
effective to reduce (or to assist in reducing) the particle size to
sizes described hereinabove. Such rotary pulsating can be carried
out with known apparatus, such as apparatus described in U.S. Pat.
No. 6,648,500, the disclosure of which is incorporated herein by
reference.
[0036] In an embodiment, the present method can include employing
pulse wave technology for reducing plant material (e.g.,
fractionated plant material). The method can include rotary pulsing
the plant material at a frequency (e.g., measured in Hz), power
(e.g., measured in watts), and for a time effective to reduce (or
to assist in reducing) the particle size to sizes described
hereinabove. Such pulsing can be carried out with known apparatus,
such as apparatus described in U.S. Pat. No. 6,726,133, the
disclosure of which is incorporated herein by reference.
[0037] Fractionation
[0038] In an embodiment, the vegetable material can be fractionated
into one or more components. For example, a vegetable material such
as a cereal grain or corn can be fractionated into components such
as fiber (e.g., corn fiber), germ (e.g., corn germ), and a mixture
of starch and protein (e.g., a mixture of corn starch and corn
protein). One or a mixture of these components can be fermented in
a process according to the present invention. Fractionation of corn
or another plant material can be accomplished by any of a variety
of methods or apparatus. For example, a system manufactured by
Satake can be used to fractionate plant material such as corn.
[0039] In an embodiment, the germ and fiber components of the
vegetable material can be fractionated and separated from the
remaining portion of the vegetable material. In an embodiment, the
remaining portion of the vegetable material (e.g., corn endosperm)
can be further milled and reduced in particle size and then
combined with the larger pieces of the fractioned germ and fiber
components for fermenting.
[0040] In an embodiment, the vegetable material can be milled to
access value added products (such as neutraceuticals, leutein,
carotenoids, xanthrophils, pectin, cellulose, lignin, mannose,
xylose, arabinose, galactose, galacturonic acid, GABA, corn oil,
albumins, globulins, prolamins, gluetelins, zein and the like).
[0041] Fractionation can be accomplished by any of a variety of
methods and apparatus, such as those disclosed in U.S. patent
application Publication No.2004/0043117, the disclosure of which is
incorporated herein by reference. Suitable methods and apparatus
for fractionation include a sieve, sieving, and elutriation.
Suitable apparatus include a frictional mill such as a rice or
grain polishing mill (e.g., those manufactured by Satake, Kett, or
Rapsco).
[0042] Saccharification and Fermentation
[0043] Saccharification
[0044] The present process can include converting reduced plant
material (e.g., fractionated plant material) to sugars that can be
fermented by a microorganism such as yeast. This conversion can be
effected by saccharifying the reduced plant material (e.g.,
fractionated plant material) with any of a variety of known
saccharifying enzyme compositions. In an embodiment, the
saccharifying enzyme composition includes an amylase, such as an
alpha amylase (e.g., an acid fungal amylase). The enzyme
preparation can also include glucoamylase. The enzyme preparation
need not, and, in an embodiment, does not include protease.
However, ethanol production methods according to the present
invention can conserve water by reusing process waters (backset)
which may contain protease. In an embodiment, the present method
employs acid fungal amylase for hydrolyzing raw starch.
[0045] Saccharifying can be conducted without cooking. For example,
saccharifying can be conducted by mixing source of saccharifying
enzyme composition (e.g., commercial enzyme), yeast, and
fermentation ingredients with ground grain and process waters
without cooking.
[0046] In an embodiment, saccharifying can include mixing the
reduced plant material (e.g., fractionated plant material) with a
liquid, which can form a slurry or suspension and adding
saccharifying enzyme composition to the liquid. In an embodiment,
the method includes mixing the reduced plant material (e.g.,
fractionated plant material) and liquid and then adding the
saccharifying enzyme composition. Alternatively, adding enzyme
composition can precede or occur simultaneously with mixing.
[0047] In an embodiment, the reduced plant material (e.g.,
fractionated plant material) can be mixed with liquid at about 20
to about 50 wt-%, about 25 to about 45 (e.g., 44) wt-%, about 30 to
about 40 (e.g., 39) wt-%, or about 35 wt-% dry reduced plant
material (e.g., fractionated plant material). As used herein, wt-%
of reduced plant material in a liquid refers to the percentage of
dry substance reduced plant material or dry solids. In an
embodiment, the method of the present invention can convert raw or
native starch (e.g., in dry reduced plant material) to ethanol at a
faster rate at higher dry solids levels compared to conventional
saccharification with cooking. Although not limiting to the present
invention, it is believed that the present method can be practiced
at higher dry solids levels because, unlike the conventional
process, it does not include gelatinization, which increases
viscosity.
[0048] Suitable liquids include water and a mixture of water and
process waters, such as stillage (backset), scrubber water,
evaporator condensate or distillate, side stripper water from
distillation, or other ethanol plant process waters. In an
embodiment, the liquid includes water. In an embodiment, the liquid
includes water in a mixture with about 1 to about 70 vol-%
stillage, about 15 to about 60 vol-% stillage, about 30 to about 50
vol-% stillage, or about 40 vol-% stillage.
[0049] In the conventional process employing gelatinization and
liquefaction, stillage provides nutrients for efficient yeast
fermentation, especially free amino nitrogen (FAN) required by
yeast. The present invention can provide effective fermentation
with reduced levels of stillage and even without added stillage. In
an embodiment, the present method employs a preparation of plant
material (e.g., fractionated plant material) that supplies
sufficient quantity and quality of nitrogen for efficient
fermentation under high gravity conditions (e.g., in the presence
of high levels of reduced plant material). Thus, in an embodiment,
no or only low levels of stillage can suffice.
[0050] However, the present method provides the flexibility to
employ high levels of stillage if desired. The present method does
not employ conventional liquefaction. Conventional liquefaction
increases viscosity of the fermentation mixture and the resulting
stillage. The present method produces lower viscosity stillage.
Therefore, in an embodiment, increased levels of stillage can be
employed in the present method without detrimental increases in
viscosity of the fermentation mixture or resulting stillage.
[0051] Further, although not limiting to the present invention, it
is believed that conventional saccharification and fermentation
processes require added FAN due to undesirable "Maillard Reactions"
which occur during high temperature gelatinization and
liquefaction. The Maillard Reactions consume FAN during cooking. As
a result, the conventional process requires adding stillage (or
another source of FAN) to increase levels of FAN in fermentation.
It is believed that the present process avoids temperature induced
Maillard Reactions and provides increased levels of FAN in the
reduced plant material, which are effectively utilized by the yeast
in fermentation.
[0052] Saccharification can employ any of a variety of known enzyme
sources (e.g., a microorganism) or compositions to produce
fermentable sugars from the reduced plant material (e.g.,
fractionated plant material). In an embodiment, the saccharifying
enzyme composition includes an amylase, such as an alpha amylase
(e.g., an acid fungal amylase) or a glucoamylase.
[0053] In an embodiment, saccharification is conducted at a pH of
about 6.0 or less, pH of about 3.0 to about 6.0, about 3.5 to about
6.0, about 4.0 to about 5.0, about 4.0 to about 4.5, about 4.5 to
about 5.0, or about 4.5 to about 4.8. In an embodiment,
saccharification is conducted at a pH of about 4.1 to about 4.6 or
about 4.9 to about 5.3. The initial pH of the saccharification
mixture can be adjusted by addition of, for example, ammonia,
sulfuric acid, phosphoric acid, process waters (e.g., stillage
(backset), evaporator condensate (distillate), side stripper
bottoms, and the like), and the like. Activity of certain
saccharifying enzyme compositions (e.g., one including acid fungal
amylase) can be enhanced at pH lower than the above ranges.
[0054] In an embodiment, saccharification is conducted at a
temperature of about 25 to about 40.degree. C. or about 30 to about
35.degree. C.
[0055] In an embodiment, saccharifying can be carried out employing
quantities of saccharifying enzyme composition selected to maintain
low concentrations of dextrin in the fermentation broth. For
example, the present process can employ quantities of saccharifying
enzyme composition selected to maintain maltotriose (DP3) at levels
at or below about 0.2 wt-% or at or below about 0.1 wt-%. For
example, the present process can employ quantities of saccharifying
enzyme composition selected to maintain dextrin with a degree of
polymerization of 4 or more (DP4+) at levels at or below about 1
wt-% or at or below about 0.5 wt-%.
[0056] In an embodiment, saccharifying can be carried out employing
quantities of saccharifying enzyme composition selected to maintain
low concentrations of maltose in the fermentation broth. For
example, the present process can employ quantities of saccharifying
enzyme composition selected to maintain maltose at levels at or
below about 0.3 wt-%. For maintaining low levels of maltose,
suitable levels of acid fungal amylase and glucoamylase include
about 0.05 to about 3 AFAU/gram dry solids reduced plant material
(e.g., DSC) of acid fungal amylase and about 1 to about 2.5 (e.g.,
2.4) AGU per gram dry solids reduced plant material (e.g., DSC) of
glucoamylase. In an embodiment, the reaction mixture includes about
0.1 to about 2 AFAU/gram dry solids reduced plant material (e.g.,
DSC) of acid fungal amylase and about 1 to about 2.5 AGU per gram
dry solids reduced plant material (e.g., DSC) of glucoamylase. In
an embodiment, the reaction mixture includes about 0.3 to about 2
AFAU/gram dry solids reduced plant material (e.g., DSC) of acid
fungal amylase and about 1 to about 2.5 AGU per gram dry solids
reduced plant material (e.g., DSC) of glucoamylase. In an
embodiment, the reaction mixture includes about 1 to about 2
AFAU/gram dry solids reduced plant material (e.g., DSC) of acid
fungal amylase and about 1 to about 1.5 AGU per gram dry solids
reduced plant material (e.g., DSC) of glucoamylase.
[0057] Glucoamylase
[0058] In certain embodiments, the present method can employ a
glucoamylase. Glucoamylase is also known as amyloglucosidase and
has the systematic name 1,4-alpha-D-glucan glucohydrolase (E.C.
3.2.1.3). Glucoamylase refers to an enzyme that removes successive
glucose units from the non-reducing ends of starch. For example,
certain glucoamylases can hydrolyze both the linear and branched
glucosidic linkages of starch, amylose, and amylopectin. A variety
of suitable glucoamylases are known and commercially available. For
example, suppliers such as Novozymes and Genencor provide
glucoamylases. The glucoamylase can be of fungal origin.
[0059] The amount of glucoamylase employed in the present process
can vary according to the enzymatic activity of the amylase
preparation. Suitable amounts include about 0.05 to about 6.0
glucoamylase units (AGU) per gram dry solids reduced plant material
(e.g., DSC). In an embodiment, the reaction mixture can include
about 1 to about 6 AGU per gram dry solids reduced plant material
(e.g., DSC). In an embodiment, the reaction mixture can include
about 1 to about 3 AGU per gram dry solids reduced plant material
(e.g., DSC). In an embodiment, the reaction mixture can include
about 1 to about 2.5 (e.g., 2.4) AGU per gram dry solids reduced
plant material (e.g., DSC). In an embodiment, the reaction mixture
can include about 1 to about 2 AGU per gram dry solids reduced
plant material (e.g., DSC). In an embodiment, the reaction mixture
can include about 1 to about 1.5 AGU per gram dry solids reduced
plant material (e.g., DSC). In an embodiment, the reaction mixture
can include about 1.2 to about 1.5 AGU per gram dry solids reduced
plant material (e.g., DSC).
[0060] Acid Fungal Amylase
[0061] In certain embodiments, the present method employs an
.alpha.-amylase. The .alpha.-amylase can be one produced by fungi.
The .alpha.-amylase can be one characterized by its ability to
hydrolyze carbohydrates under acidic conditions. An amylase
produced by fungi and able to hydrolyze carbohydrates under acidic
conditions is referred to herein as acid fungal amylase, and is
also known as an acid stable fungal .alpha.-amylase. Acid fungal
amylase can catalyze the hydrolysis of partially hydrolyzed starch
and large oligosaccharides to sugars such as glucose. The acid
fungal amylase that can be employed in the present process can be
characterized by its ability to aid the hydrolysis of raw or native
starch, enhancing the saccharification provided by glucoamylase. In
an embodiment, the acid fungal amylase produces more maltose than
conventional (e.g., bacterial) .alpha.-amylases.
[0062] Suitable acid fungal amylase can be isolated from any of a
variety of fungal species, including Aspergillus, Rhizopus, Mucor,
Candida, Coriolus, Endothia, Enthomophtora, Irpex, Penicillium,
Sclerotium and Torulopsis species. In an embodiment, the acid
fungal amylase is thermally stable and is isolated from Aspergillus
species, such as A. niger, A. saitoi or A. oryzae, from Mucor
species such as M. pusillus or M. miehei, or from Endothia species
such as E. parasitica. In an embodiment, the acid fungal amylase is
isolated from Aspergillus niger. The acid fungal amylase activity
can be supplied as an activity in a glucoamylase preparation, or it
can be added as a separate enzyme. A suitable acid fungal amylase
can be obtained from Novozymes, for example in combination with
glucoamylase.
[0063] The amount of acid fungal amylase employed in the present
process can vary according to the enzymatic activity of the amylase
preparation. Suitable amounts include about 0.1 to about 10 acid
fungal amylase units (AFAU) per gram of dry solids reduced plant
material (e.g., dry solids corn (DSC)). In an embodiment, the
reaction mixture can include about 0.05 to about 3 AFAU/gram dry
solids reduced plant material (e.g., DSC). In an embodiment, the
reaction mixture can include about 0.1 to about 3 AFAU/gram dry
solids reduced plant material (e.g., DSC). In an embodiment, the
reaction mixture can include about 0.3 to about 3 AFAU/gram dry
solids reduced plant material (e.g., DSC). In an embodiment, the
reaction mixture can include about 1 to about 2 AFAU/gram dry
solids reduced plant material (e.g., DSC).
[0064] Fermenting
[0065] The present process includes fermenting sugars from reduced
plant material (e.g., fractionated plant material) to ethanol.
Fermenting can be effected by a microorganism, such as yeast. The
fermentation mixture need not, and in an embodiment does not,
include protease. However, the process waters may contain protease.
The amount of protease can be less than that used in the
conventional process. According to the present invention,
fermenting is conducted on a starch composition that has not been
cooked. In an embodiment, the present fermentation process produces
potable alcohol. Potable alcohol has only acceptable, nontoxic
levels of other alcohols, such as fusel oils. Fermenting can
include contacting a mixture including sugars from the reduced
plant material (e.g., fractionated plant material) with yeast under
conditions suitable for growth of the yeast and production of
ethanol. In an embodiment, fermenting employs the saccharification
mixture.
[0066] Any of a variety of yeasts can be employed as the yeast
starter in the present process. Suitable yeasts include any of a
variety of commercially available yeasts, such as commercial
strains of Saccharomyces cerevisiae. Suitable strains include
"Fali" (Fleischmann's), Thermosac (Alltech), Ethanol Red (LeSafre),
BioFerm AFT (North American Bioproducts), and the like. In an
embodiment, the yeast is selected to provide rapid growth and
fermentation rates in the presence of high temperature and high
ethanol levels. In an embodiment, Fali yeast has been found to
provide good performance as measured by final alcohol content of
greater than 17% by volume.
[0067] The amount of yeast starter employed is selected to
effectively produce a commercially significant quantity of ethanol
in a suitable time, e.g., less than 75 hours.
[0068] Yeast can be added to the fermentation by any of a variety
of methods known for adding yeast to fermentation processes. For
example, yeast starter can be added as a dry batch, or by
conditioning/propagating- . In an embodiment, yeast starter is
added as a single inoculation. In an embodiment, yeast is added to
the fermentation during the fermenter fill at a rate of 5 to 100
pounds of active dry yeast (ADY) per 100,000 gallons of
fermentation mash. In an embodiment, the yeast can be acclimated or
conditioned by incubating about 5 to 50 pounds of ADY per 10,000
gallon volume of fermenter volume in a prefermenter or propagation
tank. Incubation can be from 8 to 16 hours during the propagation
stage, which is also aerated to encourage yeast growth. The
prefermenter used to inoculate the main fermenter can be from 1 to
10% by volume capacity of the main fermenter, for example, from 2.5
to 5% by volume capacity relative to the main fermenter.
[0069] In an embodiment, the fermentation is conducted at a pH of
about 6 or less, pH of about 3 to about 6, about 3 to about 4.5,
about 3.5 to about 6, about 4 to about 5, about 4 to about 4.5,
about 4.5 to about 5, or about 4.5 to about 4.8. The initial pH of
the fermentation mixture can be adjusted by addition of, for
example, ammonia, sulfuric acid, phosphoric acid, process waters
(e.g., stillage (backset), evaporator condensate (distillate), side
stripper bottoms, and the like), and the like.
[0070] Although not limiting to the present invention, it is
believed that known distillery yeast grow well over the pH range of
3 to 6, but are more tolerant of lower pH's down to 3.0 than most
contaminant bacterial strains. Contaminating lactic and acetic acid
bacteria grow best at pH of 5.0 and above. Thus, in the pH range of
3.0 to 4.5, it is believed that ethanol fermentation will
predominate because yeast will grow better than contaminating
bacteria.
[0071] In an embodiment, the present method can include varying the
pH. It is believed that varying the pH can be conducted to reduce
the likelihood of contamination early in fermentation and/or to
increase yeast growth and fermentation during the latter stages of
fermentation. For example, fermentation can include filling the
fermenter at pH of about 3 to about 4.5 during the first half of
fill. Fermentation can include increasing the slurry pH to pH of
about 4.5 to about 6 during the second half of the fermenter fill
cycle. Fermentation can include maintaining pH by adding fresh
substrate slurry at the desired pH as described above. In an
embodiment, during fermentation (after filling), pH is not
adjusted. Rather, in this embodiment, the pH is determined by the
pH of the components during filling.
[0072] In an embodiment, the pH is decreased to about five (5) or
below in the corn process waters. In an embodiment, the pH is about
pH 4 (e.g. 4.1) at the start of fermentation fill and is increased
to about pH 5 (e.g. 5.2) toward the end of fermentation fill. In an
embodiment, the method includes stopping pH control of the mash
slurry after the yeast culture becomes established during the
initial process of filling the fermenter, and then allowing the pH
to drift up in the corn process waters during the end stages of
filling the fermenter.
[0073] In an embodiment, fermentation is conducted for about to 25
(e.g., 24) to about to 150 hours, about 25 (e.g., 24) to about 96
hours, about 40 to about 96 hours, about 45 (e.g., 44) to about 96
hours, about 48 (e.g., 47) to about 96 hours. For example,
fermentation can be conducted for about 30, about 40, about 50,
about 60, or about 70 hours. For example, fermentation can be
conducted for about 35, about 45, about 55, about 65, or about 75
hours.
[0074] In an embodiment, fermentation is conducted at a temperature
of about 25 to about 40.degree. C. or about 30 to about 35.degree.
C. In an embodiment, during fermentation the temperature is
decreased from about 40.degree. C. to about 30.degree. C. or about
25.degree. C., or from about 35.degree. C. to about 30.degree. C.,
during the first half of the fermentation, and the temperature is
held at the lower temperature for the second half of the
fermentation. In an embodiment, the temperature can be decreased as
ethanol is produced. For example, in an embodiment, during
fermentation the temperature can be as high as about 99.degree. F.
and then reduced to about 79.degree. F. This temperature reduction
can be coordinated with increased ethanol titers (%) in the
fermenter.
[0075] In an embodiment, the present method includes solids
staging. Solids staging includes filling at a disproportionately
higher level of solids during the initial phase of the fermenter
fill cycle to increase initial fermentation rates. The solids
concentration of the mash entering the fermenter can then be
decreased as ethanol titers increase and/or as the fermenter fill
cycle nears completion. In an embodiment, the solids concentration
can be about 40% (e.g. 41%) during the first half of the
fermentation fill. This can be decreased to about 25% after the
fermenter is 50% full and continuing until the fermenter fill cycle
is concluded. In the above example, such a strategy results in a
full fermenter with solids at 33%.
[0076] It is believed that solids staging can accelerate enzyme
hydrolysis rates and encourage a rapid onset to fermentation by
using higher initial fill solids. It is believed that lowering
solids in the last half of fill can reduce osmotic pressure related
stress effects on the yeast. By maintaining overall fermenter fill
solids within a specified range of fermentability, solids staging
improves the capacity of the yeast to ferment high gravity mashes
toward the end of fermentation.
[0077] Simultaneous Saccharification and Fermentation
[0078] The present process can include simultaneously converting
reduced plant material (e.g., fractionated plant material) to
sugars and fermenting those sugars with a microorganism such as
yeast. Simultaneous saccharifying and fermenting can be conducted
using the reagents and conditions described above for saccharifying
and fermenting.
[0079] In an embodiment, saccharification and fermentation is
conducted at a temperature of about 25 to about 40.degree. C. or
about 30 to about 35.degree. C. In an embodiment, during
saccharification and fermentation the temperature is decreased from
about 40 to about 25.degree. C. or from about 35 to about
30.degree. C. during the first half of the saccharification, and
the temperature is held at the lower temperature for the second
half of the saccharification.
[0080] Although not limiting to the present invention, it is
believed that higher temperatures early during saccharification and
fermentation can increase conversion of starch to fermentable sugar
when ethanol concentrations are low. This can aid in increasing
ethanol yield. At higher ethanol concentrations, this alcohol can
adversely affect the yeast. Thus, it is believed that lower
temperatures later during saccharification and fermentation are
beneficial to decrease stress on the yeast. This can aid in
increasing ethanol yield.
[0081] Also not limiting to the present invention, it is believed
that higher temperatures early during saccharification and
fermentation can reduce viscosity during at least a portion of the
fermentation. This can aid in temperature control. It is also
believed that lower temperatures later during saccharification and
fermentation are beneficial to reduce the formation of glucose
after the yeast has stopped fermenting. Glucose formation late in
fermentation can be detrimental to the color of the distillers
dried grain co-product.
[0082] In an embodiment, saccharification and fermentation is
conducted at a pH of about 6 or less, pH of about 3 to about 6,
about 3.5 to about 6, about 4 to about 5, about 4 to about 4.5,
about 4.5 to about 5, or about 4.5 to about 4.8. The initial pH of
the saccharification and fermentation mixture can be adjusted by
addition of, for example, ammonia, sulfuric acid, phosphoric acid,
process waters (e.g., stillage (backset), evaporator condensate
(distillate), side stripper bottoms, and the like), and the
like.
[0083] In an embodiment, saccharification and fermentation is
conducted for about to 25 (e.g., 24) to about to 150 hours, about
25 (e.g., 24) to about 72 hours, about 45 to about 55 hours, about
50 (e.g., 48) to about 96 hours, about 50 to about 75 hours, or
about 60 to about 70 hours. For example, saccharification and
fermentation can be conducted for about 30, about 40, about 50,
about 60, or about 70 hours. For example, saccharification and
fermentation can be conducted for about 35, about 45, about 55,
about 65, or about 75 hours.
[0084] In an embodiment, simultaneous saccharifying and fermenting
can be carried out employing quantities of enzyme and yeast
selected to maintain high concentrations of yeast and high levels
of budding of the yeast in the fermentation broth. For example, the
present process can employ quantities of enzyme and yeast selected
to maintain yeast at or above about 200 cells/mL, at or above about
300 cells/mL, or at about 300 to about 600 cells/mL.
[0085] In an embodiment, simultaneous saccharifying and fermenting
can be carried out employing quantities of enzyme and yeast
selected for effective fermentation without added exogenous
nitrogen; without added protease; and/or without added backset.
Backset can be added, if desired, to consume process water and
reduce the amount of wastewater produced by the process. In
addition, the present process maintains low viscosity during
saccharifying and fermenting.
[0086] In an embodiment, simultaneous saccharifying and fermenting
can be carried out employing quantities of enzyme and yeast
selected to maintain low concentrations of soluble sugar in the
fermentation broth. In an embodiment, simultaneous saccharifying
and fermenting can be carried out employing quantities of enzyme
and yeast selected to maintain low concentrations of glucose in the
fermentation broth. For example, the present process can employ
quantities of enzyme and yeast selected to maintain glucose at
levels at or below about 2 wt-%, at or below about 1 wt-%, at or
below about 0.5 wt-%, or at or below about 0.1 wt-%. For example,
the present process can employ quantities of enzyme and yeast
selected to maintain glucose at levels at or below about 2 wt-%
during saccharifying and fermenting. For example, the present
process can employ quantities of enzyme and yeast selected to
maintain glucose at levels at or below about 2 wt-% from hours 0-10
(or from 0 to about 15% of the time) of saccharifying and
fermenting. For example, the present process can employ quantities
of enzyme and yeast selected to maintain glucose at levels at or
below about 1 wt-%, at or below about 0.5 wt-%, or at or below
about 0.1 wt-% from hours 12-54 (or from about 15% to about 80% of
the time) of saccharifying and fermenting. For example, the present
process can employ quantities of enzyme and yeast selected to
maintain glucose at levels at or below about 1 wt-% from hours
54-66 (or about from 80% to about 100% of the time) of
saccharifying and fermenting.
[0087] In an embodiment, simultaneous saccharifying and fermenting
can be carried out employing quantities of enzyme and yeast
selected to maintain low concentrations of maltose (DP2) in the
fermentation broth. For example, the present process can employ
quantities of enzyme and yeast selected to maintain maltose at
levels at or below about 0.5 wt-% or at or below about 0.2
wt-%.
[0088] In an embodiment, simultaneous saccharifying and fermenting
can be carried out employing quantities of enzyme and yeast
selected to maintain low concentrations of dextrin in the
fermentation broth. For example, the present process can employ
quantities of enzyme and yeast selected to maintain maltotriose
(DP3) at levels at or below about 0.5 wt-%, at or below about 0.2
wt-%, or at or below about 0.1 wt-%. For example, the present
process can employ quantities of enzyme and yeast selected to
maintain dextrin with a degree of polymerization of 4 or more
(DP4+) at levels at or below about 1 wt-% or at or below about 0.5
wt-%.
[0089] In an embodiment, simultaneous saccharifying and fermenting
can be carried out employing quantities of enzyme and yeast
selected to maintain low concentrations of fusel oils in the
fermentation broth. For example, the present process can employ
quantities of enzyme and yeast selected to maintain fusel oils at
levels at or below about 0.4 to about 0.5 wt-%.
[0090] For example, simultaneous saccharifying and fermenting can
employ acid fungal amylase at about 0.05 to about 10 AFAU per gram
of dry solids reduced plant material (e.g., DSC) and glucoamylase
at about 0.5 to about 6 AGU per gram dry solids reduced plant
material (e.g., DSC). For example, simultaneous saccharifying and
fermenting can employ acid fungal amylase at about 0.1 to about 10
AFAU per gram of dry solids reduced plant material (e.g., DSC) and
glucoamylase at about 0.5 to about 6 AGU per gram dry solids
reduced plant material (e.g., DSC). For example, simultaneous
saccharifying and fermenting can employ acid fungal amylase at
about 0.3 to about 3 AFAU per gram of dry solids reduced plant
material (e.g., DSC) and glucoamylase at about 1 to about 3 AGU per
gram dry solids reduced plant material (e.g., DSC). For example,
simultaneous saccharifying and fermenting can employ acid fungal
amylase at about 1 to about 2 AFAU per gram of dry solids reduced
plant material (e.g., DSC) and glucoamylase at about 1 to about 1.5
AGU per gram dry solids reduced plant material (e.g., DSC).
[0091] Additional Ingredients for Saccharification and/or
Fermentation
[0092] The saccharification and/or fermentation mixture can include
additional ingredients to increase the effectiveness of the
process. For example, the mixture can include added nutrients
(e.g., yeast micronutrients), antibiotics, salts, added enzymes,
and the like. Nutrients can be derived from stillage or backset
added to the liquid. Suitable salts can include zinc or magnesium
salts, such as zinc sulfate, magnesium sulfate, and the like.
Suitable added enzymes include those added to conventional
processes, such as protease, phytase, cellulase, hemicellulase,
exo- and endo- glucanase, xylanase, and the like.
[0093] Recovering Ethanol from the Beer
[0094] The product of the fermentation process is referred to
herein as "beer". For example, fermenting corn produces "corn
beer". Ethanol can be recovered from the fermentation mixture, from
the beer, by any of a variety of known processes. For example,
ethanol can be recovered by distillation.
[0095] The remaining stillage includes both liquid and solid
material. The liquid and solid can be separated by, for example,
centrifugation. The recovered liquid, thin stillage, can be
employed as at least part of the liquid for forming the
saccharification and fermentation mixture for subsequent batches or
runs.
[0096] The recovered solids, distiller's dried grain, include
unfermented grain solids and spent yeast solids. Thin stillage can
be concentrated to a syrup, which can be added to the distiller's
dried grain and the mixture then dried to form distiller's dried
grain plus solubles. Distiller's dried grain and/or distiller's
dried grain plus solubles can be sold as animal feed.
[0097] Burn-out of Residual Starches for Subsequent Secondary
Fermentation
[0098] In an embodiment, the present method can include heat
treatment of the beer or stillage, e.g., between the beer well and
distillation. In an embodiment, the present method can include heat
treatment of the beer or stillage and enzyme addition, e.g.,
between the beer well and distillation. This heat treatment can
convert starches to dextrins and sugars for subsequent fermentation
in a process known as burn-out. Such a treatment step can also
reduce fouling of distillation trays and evaporator heat exchange
surfaces. In an embodiment, heat treatment staging can be performed
on whole stillage or thin stillage. Following enzymatic treatment
of the residual starches, in an embodiment, the resulting dextrins
and sugars can be fermented within the main fermentation process as
recycled backset or processed in a separate fermentation train to
produce ethanol. In an embodiment, the liquefaction and
saccharification on whole stillage or thin stillage produced by
centrifugation can be accelerated after distillation.
[0099] Fractionation of Solids from Fermentation
[0100] Large pieces of germ and fiber can ferment the residual
starch in the fermenter. After fermentation, the fractions could be
removed prior to or after distillation. Removal can be effected
with a surface skimmer before to distillation. In an embodiment,
screening can be performed on the beer. The screened material can
then be separated from the ethanol/water mix by, for example,
centrifugation and rotary steam drum drying, which can remove the
residual ethanol from the cake. In embodiments in which the larger
fiber and germ pieces are removed prior to bulk beer distillation,
a separate stripper column for the fiber/germ stream can be
utilized. Alternatively, fiber and germ could be removed by
screening the whole stillage after distillation.
[0101] In an embodiment, all the components are blended and dried
together. The fiber and germ can be removed from the finished
product by aspiration and/or size classification. The fiber from
the DDGS can be aspirated. Removal of fiber by aspiration after
drying can increase the amount of oil and protein in the residual
DDGS, for example, by 0.2 to 1.9% and 0.4 to 1.4%, respectively.
The amount of NDF in the residual DDGS can decrease, for example,
by 0.1 to 2.8%.
[0102] In an embodiment, fractionation can employ the larger fiber
and germ pieces to increase the particle size of that part of the
DDGS derived from the endosperm, as well as to improve syrup
carrying capacity. A ring dryer disintegrator can provide some
particle size reduction and homogenization.
[0103] Methods and Systems for Drying Wet Cake to Make Distiller's
Dried Grains
[0104] The beer produced by fermentation includes ethanol, other
liquids, and solid material. Centrifugation and/or distillation of
the beer can yield solids known as wet cake and liquids known as
thin stillage. The wet cake can be dried to produce distiller's
dried grain. The thin stillage can be concentrated to a syrup,
which can be added to the wet cake or distiller's dried grain and
the mixture then dried to form distiller's dried grain plus
solubles. The present method can include drying the wet cake to
produce distiller's dried grain. The present method can include
drying the syrup plus distiller's dried grain to produce
distiller's dried grain plus solubles. The distiller's dried grain
can be produced from whole grain (e.g., corn) or from fractionated
grain (e.g., corn). The present method can produce high protein
distiller's dried grain and/or distiller's dried grain with
improved physical characteristics. Such distiller's dried grains
are described hereinbelow.
[0105] Conventional ethanol production processes employed drum
dryers. Advantageously, in an embodiment, the present method and
system can employ a flash or ring dryer. Flash or ring dryers have
not previously been employed in processes like the present one.
Configurations of flash and ring dryers are known. Briefly, a flash
or ring dryer can include a vertical column through which a
pre-heated air stream moves the wet cake. For example, a flash or
ring dryer can include one or more inlets that provide entry of
heat or heated air into the dryer. This dries the wet cake. The
dried wet cake is transported to the top of a column. In a ring
dryer, further drying can be accomplished by moving the wet cake
through one or more rings connected to the column. For example, a
ring dryer can include one or more inlets through which heated air
enters a ring structure which propels or circulates the wet cake in
or around the ring structure. The dried wet cake can then be
pneumatically conveyed to down-stream separating equipment such as
a cyclone or dust collector.
[0106] The present method can include employing a flash dryer to
dry (i.e., flash drying) the wet cake and to produce distiller's
dried grain. The present method can include employing a flash dryer
to dry (i.e., flash drying) the syrup plus distiller's dried grain
to produce distiller's dried grain plus solubles. Employing a flash
dryer can produce high protein distiller's dried grain and/or
distiller's dried grain with improved physical characteristics.
Such distiller's dried grains are described hereinbelow.
[0107] The present method can include employing a ring dryer to dry
(i.e., ring drying) the wet cake and to produce distiller's dried
grain. The present method can include employing a ring dryer (i.e.,
ring drying) to dry the syrup plus distiller's dried grain to
produce distiller's dried grain plus solubles. Employing a ring
dryer can produce high protein distiller's dried grain and/or
distiller's dried grain with improved physical characteristics.
Such distiller's dried grains are described hereinbelow.
[0108] The present method can include employing a fluid bed dryer
to dry (i.e., fluid bed drying) the wet cake and to produce
distiller's dried grain. The present method can include employing a
fluid bed dryer to dry (i.e., fluid bed drying) the syrup plus
distiller's dried grain to produce distiller's dried grain plus
solubles. Employing a fluid bed dryer can produce high protein
distiller's dried grain and/or distiller's dried grain with
improved physical characteristics. Such distiller's dried grains
are described hereinbelow.
[0109] The present method can include adding syrup (backset or thin
stillage) to the wet cake before, during, or after drying. In an
embodiment, the present method includes adding syrup (backset or
thin stillage) to the wet cake during drying. For example, the
method can include mixing wet cake and syrup in the dryer. For
example, the method can include flowing or injecting syrup into the
flash, ring, or fluid bed dryer. In an embodiment, the present
method includes adding syrup into the column or ring of the dryer
in the presence of wet cake and/or distiller's dried grain.
[0110] Although not limiting to the present invention, it is
believed that flash and/or ring dryers differ from rotary or drum
dryers by providing decreased exposure of wet cake to high
temperatures of the drying process. A rotary or drum dryer
generally has high temperature metal that is in prolonged contact
with the wet cake product. It is believed that prolonged contact of
this high temperature metal with the wet cake can result in
browned, burned, or denatured distiller's dried grains or
distiller's dried grains plus solubles. Further, the internal air
temperature can be higher in a rotary or drum dryer.
[0111] Accordingly, in an embodiment, the present method can
include drying the wet cake or wet cake plus syrup for a shorter
time than employed with a rotary or drum dryer, and obtaining
distiller's dried grain or distiller's dried grain plus solubles
that has been sufficiently dried. Accordingly, in an embodiment,
the present method can include drying the wet cake or wet cake plus
syrup at a lower temperature than employed with a rotary or drum
dryer, and obtaining distiller's dried grain or distiller's dried
grain plus solubles that has been sufficiently dried. In an
embodiment, the method includes changing the drying temperature
during drying.
[0112] Although not limiting to the present invention, in certain
embodiments, such drying systems and methods can provide one or
more advantages such as decreased energy consumption in drying,
decreased leakage from the drying system.
[0113] An embodiment of this invention is the use of flash or ring
dryer(s) to change the conditions inside the dryer system to
increase or decrease temperature. An embodiment of this invention
is the use of flash or ring dryer(s) to change the conditions
inside the dryer system to increase or decrease the moisture. An
embodiment of this invention is the use of flash or ring dryer(s)
to change the conditions inside the dryer system to increase or
decrease recycle speed. An embodiment of this invention is the use
of flash or ring dryer(s) to change the conditions inside the dryer
system to increase or decrease the feed rate into the dryer
system.
[0114] Continuous Fermentation
[0115] The present process can be run via a batch or continuous
process. A continuous process includes moving (pumping) the
saccharifying and/or fermenting mixtures through a series of
vessels (e.g., tanks) to provide a sufficient duration for the
process. For example, a multiple stage fermentation system can be
employed for a continuous process with 48-96 hours residence time.
For example, reduced plant material (e.g., fractionated plant
material) can be fed into the top of a first vessel for
saccharifying and fermenting. Partially incubated and fermented
mixture can then be drawn out of the bottom of the first vessel and
fed in to the top of a second vessel, and so on.
[0116] Although not limiting to the present invention, it is
believed that the present method is more suitable than conventional
methods for running as a continuous process. It is believed that
the present process provides reduced opportunity for growth of
contaminating organisms in a continuous process. At present, the
majority of dry grind ethanol facilities employ batch fermentation
technology. This is in part due to the difficulty of preventing
losses due to contamination in these conventional processes. For
efficient continuous fermentation using traditional liquefaction
technology, the conventional belief is that a separate
saccharification stage prior to fermentation is necessary to
pre-saccharify the mash for fermentation. Such pre-saccharification
insures that there is adequate fermentable glucose for the
continuous fermentation process.
[0117] The present method achieves efficient production of high
concentrations of ethanol without a liquefaction or
saccharification stage prior to fermentation. This is surprising
since this conventional wisdom teaches that it is necessary to have
adequate levels of fermentable sugar available during the
fermentation process when practiced in a continuous mode. In
contrast the present method can provide low concentrations of
glucose and efficient fermentation. In the present method, it
appears that the glucose is consumed rapidly by the fermenting
yeast cell. It is believed that such low glucose levels reduce
stress on the yeast, such as stress caused by osmotic inhibition
and bacterial contamination pressures. According to the present
invention, ethanol levels greater than 18% by volume can be
achieved in about 45 to about 96 hours.
[0118] Endosperm, Fibers and Germ Fermentation
[0119] In an embodiment, the present process can ferment a portion
of a reduced plant material, such as corn. For example, the process
can ferment at least one of endosperm, fiber, or germ. The present
process can increase ethanol production from such a portion of
corn. In an embodiment, the present process can saccharify and
ferment endosperm. Endosperm fermentation is lower in free amino
nitrogen (FAN) towards the beginning of fermentation due to the
removal of germ, which contains FAN. The present process can, for
example, preserve the FAN quality of the endosperm compared to
conventional high temperature liquefaction. An embodiment of the
present invention includes the use of endosperm FAN, which can
increase flexibility and efficiency of fermentation.
[0120] In an embodiment, the present process can employ endogenous
enzyme activity in the grain. In an embodiment, dramatic increase
in FAN in whole corn and defibered corn fermentations are reached
compared to the initial mash slurry.
[0121] Conventional grain dry milling operations separate germ
(containing oil) and bran or pericarp (fiber fraction) from the
endosperm (starch and protein) portion of the grain using a series
of steps and procedures. These steps and procedures include: grain
cleaning, tempering, degerming, particle size reduction, roller
milling, aspirating, and sifting. This process differs from the
traditional wet milling of grains (commonly corn) which are more
expensive and water intensive, but capable of achieving cleaner
separations of the components of the grain. Dry milling processes
offer a version of separating components using lower capital costs
for facilities. Also, these processes require less water for
operation. The tempering process in dry milling requires less water
than required in wet milling.
[0122] The competitiveness of dry grain fractionation processes is
enhanced when the process of the present invention is utilized for
ethanol conversion of these fractions. Traditionally dry milling
processes produce various grades of each fraction (germ, bran, and
endosperm). In an embodiment, the present method provides bran and
endosperm fractions that can be more readily fermented. Depending
on the desired purity of each fraction, the fractions can either be
pooled to create composites of each stream, or the fractions can be
processed individually.
[0123] Yeast uses FAN in the present process. In the conventional
liquefaction process, FAN levels fall throughout fermentation as
yeast cells assimilate and metabolize available FAN during the
course of fermentation. Toward the end of fermentation in the
conventional process, FAN levels rise illustrating the liberation
of cellular FAN coinciding with death and lysis of yeast cells. In
contrast, FAN utilization kinetics in the raw starch process is
more rapid. FAN levels reach a minimum at least 24 hours earlier,
and then begin increasing dramatically. Some of the increase of FAN
is due to yeast cell death resulting from the accelerated
fermentation.
[0124] High Alcohol Beer
[0125] The present invention also relates to a high alcohol beer.
In an embodiment, the process of the present invention produces
beer containing greater than 18 vol-% ethanol. The present process
can produce such a high alcohol beer in about 40 to about 96 hours
or about 45 to about 96 hours. In an embodiment, the beer includes
18 vol-% to about 23 vol-% ethanol. For example, the present method
can produce alcohol contents in the fermenter of 18 to 23 % by
volume in about 45 to 96 hours.
[0126] By way of further example, the present method can produce
alcohol content in the fermenter of 18 to 23 % by volume in about
45 to 96 hours. In certain embodiments, the majority of the alcohol
(80% or more of the final concentration) is produced in the first
45 hours. Then, an additional 2 to 5 vol-% alcohol can be produced
in the final 12-48 hours. Concentrations of ethanol up to 23 vol-%
can be achieved with fermentation time up to 96 hours. It can be
economically advantageous to harvest after 48 to 72 hours of
fermentation to increase fermenter productivity.
[0127] The present beer can include this high level of ethanol even
when it includes high levels of residual starch. For example, the
present beer can include ethanol at 18 to 23 vol-% when it contains
0 to 30% residual starch. The present beer can contain residual
starches as low as 0% to as high as 20% residual starch.
[0128] By conventional measures, high levels of residual starch
indicate inefficient fermentation, which yields only low levels of
ethanol. In contrast, although not limiting to the present
invention, it is believed that the present method results in fewer
Maillard type reaction products and more efficient yeast
fermentation (e.g., reduced levels of secondary metabolites). This
is believed to be due to the low glucose levels and low
temperatures of the present method compared to conventional
saccharification and liquefaction. Thus, the present method can
produce more alcohol even with higher levels of residual
starch.
[0129] In an embodiment, the present beer includes fewer residual
byproducts than conventional beers, even though residual starch can
be higher. For example, residual glucose, maltose, and higher
dextrins (DP3+) can be as much as 0.8 wt-% lower than in
conventional beers produced under similar fermentation conditions.
By way of further example, residual glycerol can be as much as 0.7
wt-% less. Lactic acid and fusel oils can also be significantly
reduced. For example, the present beer can include less than or
equal to about 0.2 wt-% glucose, about 0.4 wt-%, about 0.1 wt-%
DP3, undetectable DP4+, 0.7 wt-% glycerol, about 0.01 wt-% lactic
acid, and/or about 0.4 wt-% fusel oils.
[0130] Distiller's Dried Grain
[0131] High Protein Distiller's Dried Grain
[0132] The present invention also relates to a distiller's dried
grain product. The distiller's dried grain can also include
elevated levels of one or more of protein, fat, fiber (e.g.,
neutral detergent fiber (NDF)), and starch. For example, the
present distiller's dried grain can include 34 or more wt-%
protein, about 25 to about 60 wt-% protein, about 25 to about 50
wt-% protein, or about 30 to about 45 wt-% protein. In certain
circumstances the amount of protein is about 1 to about 2 wt-% more
protein than produced by the conventional process. For example, the
distiller's dried grain can include 15 or more wt-% fat, about 13
to about 17 wt-% fat, or about 1 to about 6 wt-% more fat than
produced by the conventional process. For example, the distiller's
dried grain can include 31 or more wt-% fiber, about 23 to about 37
wt-% fiber, or about 3 to about 13 wt-% more fiber than produced by
the conventional process. For example, the distiller's dried grain
can include 12 or more wt-% starch, about 1 to about 23 wt-%
starch, or about 1 to about 18 wt-% more starch than produced by
the conventional process.
[0133] In an embodiment, the present distiller's dried grain
includes elevated levels of B vitamins, vitamin C, vitamin E, folic
acid, and/or vitamin A, compared to conventional distiller's dried
grain products. The present distiller's dried grain has a richer
gold color compared to conventional distiller's dried grain
products.
[0134] Distiller's Dried Grain with Improved Physical
Characteristics
[0135] The present invention also relates to a distiller's dried
grain with one or more improved physical characteristics, such as
decreased caking or compaction or increased ability to flow. The
present process can produce such an improved distiller's dried
grain.
[0136] Although not limiting to the present invention, it is
believed that the present process can produce fermentation solids
including higher molecular weight forms of carbohydrates. Such
fermentation solids can, it is believed, exhibit a higher glass
transition temperature (i.e. higher T.sub.g values) compared to
solids from the conventional process. For example, residual
starches can have a high T.sub.g value. Thus, through control of
starch content in the DDG and DDGS, the present process can
manufacture DDG or DDGS with target T.sub.g values.
[0137] Further, according to the present invention, adding an
alkaline syrup blend (e.g., syrup plus added lime or other alkaline
material) to the fermentation solids (e.g., distiller's dried
grains) can provide decreased caking or compaction or increase
ability to flow to the distiller's dried grain with solubles
(DDGS).
[0138] Although not limiting to the present invention, it is
believed that organic acids such as lactic, acetic, and succinic
acids which are produced in fermentation have a lower T.sub.g value
than their corresponding calcium salts. Maintenance of residual
carbohydrate in higher molecular weight form, or addition of lime
to form calcium salts of organic acids, are two strategies for
forming higher T.sub.g value co-products that will be less likely
to undergo the glass transition, resulting in the deleterious
phenomenon known as caking.
[0139] In an embodiment, DDG or DDGS of or produced by the method
of the present invention flows more readily than DDG or DDGS
produced by the conventional process.
[0140] Although not limiting to the present invention, it is
believed that process of the present invention can need not destroy
protein in the fermented plant material (e.g., fractionated plant
material). Corn contains prolamins, such as zein. Grain sorghum,
for example, contains a class of zein-like proteins known as
kafirins, which resemble zein in amino acid composition. The
thermal degradation that occurs during liquefaction, distillation,
and high temperature drying produces DDG and DDGS including
significant amounts of degraded protein. It is believed that the
process of the present invention can provides improved levels of
the prolamin fraction of cereal grains.
[0141] It is believed that extended exposure to high alcohol
concentrations that can be achieved by the present process can
condition the proteins in the plant material (e.g., fractionated
plant material). This can solubilize some of the proteins. For
example, it is believed that in distillation the ethanol
concentration reaches levels that can solubilize prolamins (e.g.,
zein) in the beer. Upon the removal, or "stripping," of ethanol
from the beer, prolamins (such as zein) can be recovered in
concentrated form in DDG and DDGS. The resulting high protein
content of DDG and DDGS can be advantageous for various end uses of
DDG and DDGS, for example in further processing or compounding.
[0142] In an embodiment, efficient fermentation of the present
process removes from the DDG or DDGS non zein components such as
starch. Fractionating the plant material, e.g., corn, can also
increase levels of proteins, such as zein, in the DDG or DDGS. For
example, removing the bran and germ fractions prior to fermentation
can concentrate zein in the substrate. Zein in corn is isolated in
the endosperm. Fermentation of zein enriched endosperm results in
concentration of the zein in the residuals from fermentation.
[0143] In an embodiment, the present method can operate on
fractionated plant material (such as endosperm, fiber, other parts
of cereal grain) to provide a protein enriched solid product from
fermentation. For example, the present method operated on
fractionated plant material can produce a DDG enriched in prolamin,
such as zein.
[0144] In an embodiment, the process of the present invention can
provide DDG and DDGS with different, predetermined T.sub.g values.
The process of the present invention can ferment fractions
containing high, medium, or low levels of zein, thus varying the
glass transition temperature of the resulting DDG or DDGS. The
resulting co-product T.sub.g can be directly proportional to the
prolamin protein (such as zein) content. The process of the current
invention is desirable for the fermentation of high protein corn.
This also allows production of DDG and DDGS with a higher prolamin
(zein) content.
[0145] Residual starch remaining at the end of fermentation
preferentially segregates into the thin stillage fraction, which is
subsequently evaporated to produce syrup. The wet cake fraction
produced by the present method, which can be dried separately to
produce DDG, can be higher in prolamin protein (such as zein) than
conventional DDG. The present process allows syrup and wet cake
blend ratios to be varied. This results in DDG/DDGS with varying
ratios of prolamin protein (such as zein) and residual starch. As
the residual starch in the wet cake reduces the protein in the wet
cake increases. This indicates an inverse relationship. A similar
response occurs in the syrup fraction.
[0146] It is believed that starch can segregate into the liquid
fraction. The amount of starch in the DDGS can be varied by
blending syrup at rates ranging from 0 lbs. dry weight of syrup
solids to 1.2 lbs. of syrup solids per lb. of wet cake solids
before, and various times during drying to create the final DDGS
product. The disproportionate segregation of residual starches into
the backset or thin stillage fraction can provide both the
aforementioned burn-out and secondary fermentation to be performed
on these fractions. Since the thin stillage is evaporated to
produce syrup, the centrifuge mass balance also enables DDGS
production at various T.sub.g values depending on the desired
properties and their dependence on T.sub.g.
[0147] Emissions
[0148] The present invention has emissions benefits. Emissions
benefits result in the reduction in byproducts created in the
ethanol manufacturing process. There is a marked reduction in
extraction of fats and oils in the mash from the germ fraction of
cereal grains. There is a reduction of byproducts from Maillard
reactions typically formed during cooking and liquefaction. And
there is a reduction in fermentation byproducts. These observations
result in reduced emissions during the recovery of co-products. The
concentration and emission rates of volatile organic compounds
(VOC), carbon monoxide (CO), nitric oxide compounds (NOx), sulfur
oxides (SO2), and other emissions are considerably lower. See Table
1. Note that other manufacturers have attempted to lower emissions
by manufacturing wet cake instead of drying to DDG or DDGS.
[0149] The present invention also relates to volatile organic
compounds (VOC), such as those produced by drying products of a
fermentation process. The present method includes producing
ethanol, distiller's dried grain, and additional useful
fermentation products with production of lower levels of VOC
compared to conventional processes. For example, in the present
method, drying distillation products (e.g., spent grain) produces
reduced levels of VOC.
[0150] Conventional fermentation processes using corn, for example,
produces about 2.1 pounds of VOC's from drying distillation
products from each ton of corn processed. The actual stack
emissions can be less due to pollution control equipment. The
present method results in at least 30% reduction in VOC production
to about 1.47 or less pounds per ton of corn processed. These
emissions reductions are unexpected yet highly significant, and
provide for more efficient use of emissions reduction control
technology, such as thermal oxidizers.
[0151] VOC produced by fermentation processes include ethanol,
acetic acid, formaldehyde, methanol, acetaldehyde, acrolein,
furfural, lactic acid, formic acid, and glycerol.
[0152] The present invention also relates to carbon monoxide (CO),
such as those produced by drying products of a fermentation
process. The present method includes producing ethanol, distiller's
dried grain, and additional useful fermentation products with
production of lower levels of CO compared to conventional
processes. For example, in the present method, drying distillation
products (e.g., spent grain) produces reduced levels of CO.
[0153] Conventional fermentation processes using corn, for example,
produces about 1.4 pounds of CO's from drying distillation products
from each ton of corn processed. The actual stack emissions can be
less due to pollution control equipment. The present method results
in a 30% reduction in CO production to about 0.98 or less pounds
per ton of corn processed. These emissions reductions are
unexpected yet highly significant, and provide for more efficient
use of emissions reduction control technology, such as thermal
oxidizers.
1TABLE 1 Emissions Reductions Conven- Emissions Emission tional
Inventive Reduction Type Units Run Process % VOC Concentration ppmv
663 459.65 30.67 lb/dscf Emission lb/hr 13.35 7.91 40.75 Rate CO
Concentration ppmv 434 234.13 46.05 lb/dscf Emission lb/hr 9.1 4.94
45.71 Rate
[0154] System for Producing Ethanol
[0155] In an embodiment, the invention relates to a system that
produces ethanol. The present system can include a saccharification
apparatus 1, a fermentation apparatus 2, a distillation apparatus
3, and a dryer apparatus 4.
[0156] The saccharification apparatus 1 can be any of a variety of
apparatus suitable for containing or conducting saccharification.
The saccharification apparatus 1 can be, for example, a vessel in
which reduced plant material can be converted to a sugar, which can
be fermented by a microorganism such as yeast. The saccharification
apparatus 1 can be configured to maintain a saccharification
mixture under conditions suitable for saccharification. The
saccharification apparatus 1 can be configured to provide for the
conversion of reduced plant material with the addition of enzymes.
In an embodiment, the saccharification apparatus 1 is configured
for mixing reduced plant material with a liquid and adding a
saccharifying enzyme composition to the liquid. In an embodiment,
the saccharification apparatus 1 is configured for saccharification
at a variety of pHs and temperatures, but preferably at a pH of 6.0
or less, and at a temperature of about 25 to about 40.degree.
C.
[0157] The fermentation apparatus 2 can be any of a variety of
apparatus suitable for containing or conducting fermentation. The
saccharification apparatus 1 can be, for example, a vessel in which
sugar from reduced plant material can be fermented to ethanol. The
fermentation apparatus 2 can be configured to maintain a
fermentation mixture under conditions suitable for fermentation. In
an embodiment, the fermentation apparatus 2 can be configured for
fermenting through use of a microorganism, such as yeast. In an
embodiment, the fermentation apparatus 2 can be configured to
ferment a starch composition that has not been cooked, specifically
the saccharification mixture. In an embodiment, the apparatus can
employ any variety of yeasts that yields a commercially significant
quantity of ethanol in a suitable time. Yeast can be added to the
apparatus by any of a variety of methods known for adding yeast to
a system that conducts fermentation. The fermentation apparatus 2
can be configured for fermentation for about 25 to 150 hours at a
temperature of about 25 to about 40 degrees C.
[0158] The saccharification apparatus 1 and the fermentation
apparatus 2 can be a single, integrated apparatus. In an
embodiment, this apparatus is configured to provide higher
temperatures early on during simultaneous conversion of reduced
plant material to sugars and fermentation of those sugars. In an
embodiment, this apparatus is configured to provide lower
temperatures later during the simultaneous saccharification and
fermentation. The apparatus also may utilize the reagents and
conditions described above for saccharification and fermentation,
including enzymes and yeast.
[0159] The distillation apparatus 3 can be any of a variety of
apparatus suitable for distilling products of fermentation. The
distillation apparatus 3 can be, for example, configured to recover
ethanol from the fermentation mixture ("beer"). In an embodiment,
the fermentation mixture is treated with heat prior to entering the
distillation apparatus 3. In another embodiment, fractions of large
pieces of germ and fiber are removed with a surface skimmer or
screen prior to or after entering the distillation apparatus 3.
[0160] The dryer apparatus 4 can be any of a variety of apparatus
suitable for drying solids remaining after distillation (and
optional centrifugation, for example, in a centrifuge system). In
an embodiment, the dryer apparatus 4 is configured to dry recovered
solids, which can result in production of distiller's dried grain.
After the distillation system separates the ethanol from the beer,
recovered solids remain. These recovered solids can then be dried
in the dryer apparatus 4. This produces distiller's dried grain
and/or distiller's dried grain plus solubles. In an embodiment, the
dryer apparatus 4 can be or include a ring dryer. In an embodiment,
the dryer apparatus 4 can be or include a flash dryer. In an
embodiment, the dryer apparatus 4 can be or include a fluid bed
dryer.
[0161] The present invention may be better understood with
reference to the following examples. These examples are intended to
be representative of specific embodiments of the invention, and are
not intended as limiting the scope of the invention.
EXAMPLES
Example 1
The Present Process Provides Improved Efficiency With Substrates
Derived From Grain Dry Milling Operations (Endosperm, Fiber, &
Germ)
[0162] The present invention provides an improved method for
fermenting substrates derived from grain milling (dry
fractionation) processes. The present process is useful for
endosperm fermentation since FAN levels in the mash are reduced to
the removal of germ. The present process contributes to the
endogenous enzymes activity in the grain. Dramatic increase in FAN
in whole corn and defibered corn fermentations are reached compared
to the initial mash slurry.
[0163] Results and Discussion
[0164] The present process is useful for endosperm fermentation
since FAN levels in the mash are reduced due to the removal of
germ, as shown in FIG. 2A. FAN supplies necessary nitrogen for
yeast growth and reducing ethanol related stress in high gravity
ethanol fermentations. FIG. 2A also reveals the negative impact of
liquefaction on reducing the amount of FAN available in
fermentation. The generation of dextrins and soluble sugars during
the high temperature liquefaction results in Maillard condensation
reactions between carbonyl groups on sugars and amino groups on
amino acids and peptides. This results in a loss in potential yield
(due to unavailable carbohydrate) as well as a reduction in the
nutritional quality of the mash for sustaining efficient high
gravity fermentation (due to reduction in FAN). The present process
also enables the endogenous enzyme activity in the grain to
contribute to the generation of soluble sugars and amino nitrogen
in the mash. These beneficial activities are lost during the
conventional liquefaction stage. The kinetics of FAN utilization is
illustrated in FIG. 2B for fermentation of various dry milled grain
fractions.
[0165] It is interesting to note that FAN kinetics in the
conventional process all follow a similar utilization pathway for
each corn fraction. During the first half of fermentation, FAN is
consumed in the course of yeast growth. Later, FAN levels are
observed to increase, presumably due the liberation of cellular FAN
corresponding to yeast cell death and lysis. Initial FAN
utilization in the raw starch process is observed to be much more
rapid. Also note the dramatic increase in FAN at the end of raw
starch fermentations. This increase in FAN could be the result of
yeast cell death since the rate of ethanol production is much
faster in raw starch fermentations. It could also be due to
generation of FAN from endogenous enzymes in the grain. Note that
when germ is removed, there is less of an increase in FAN during
the latter half of the fermentation. These observations suggest an
additional aspect of the raw starch process.
[0166] FIG. 2C illustrates the impact of FAN on corn fraction
fermentations run in the absence of backset, comparing and
contrasting the sensitivity of the two processes to additional FAN
addition. It is apparent that the process of the present invention
significantly improves the potential substrate quality from a dry
milling fractionation facility for fermentation, reducing the
importance of additional FAN. The present process is superior to
the conventional liquefaction process, since the conventional
liquefaction process is more sensitive to disruptive impact of
substrate quality as measured by FAN levels.
Example 2
The Present Method Produced High Protein DDG from Fractionated
Plant Product
[0167] The present invention demonstrated that fractionation of
corn prior to fermentation provides high levels of protein in the
resulting DDG.
[0168] Materials and Methods
[0169] Corn was fractionated prior to fermentation through use of a
Satake fractionation system. After fractionation, the corn was
fermented according to the present invention employing for
saccharification glucoamylase and acid fungal amylase without
cooking. The fermentation was conducted at 90.degree. F. and at a
pH of 5. After the corn solids were fermented, the ethanol was
distilled out. The remaining solids were then dried, and samples of
fiber, germ, and starch were taken. All fractionation samples were
ground for twenty seconds on a Knifetec. These samples were then
analyzed for starch, protein, fat, and neutral detergent fiber
content. The percent ethanol yield was also calculated for each
sample. See also the Materials and Methods sections for the other
examples for additional information about how these experiments
were conducted.
[0170] Results and Discussion
[0171] The present method produced high protein DDG and high levels
of ethanol compared to a conventional process (Table 2). Table 2
shows results for ethanol and DDG produced from two representative
samples of each of fiber, starch, and germ samples. Fermentations B
and C, the representative starch samples, resulted in the highest
yield of ethanol and produced DDG with the largest percentage of
protein (Table 2). The two germ samples generated the lowest yield
of ethanol and the highest percentage of fat (Table 2). The fiber
samples produced the lowest amount of protein (Table 2). In
general, this table illustrates that fractionation increased the
rate of protein retention throughout the fermentation and
distillation process (Table 2).
2TABLE 2 Ethanol and DDG Proximate Levels Produced From Corn
Fractions Ethanol Starch Protein NDR % Sample Fermentation vol-% %
dw % dw Fat % dw dw Type A 8.10 0.00 22.51 17.93 30.90 Fiber B
12.11 3.58 42.46 5.66 12.99 Starch C 11.75 0.55 43.83 7.73 13.84
Starch D 6.39 0.57 26.18 26.81 13.33 Germ E 6.58 0.00 18.31 14.43
42.34 Fiber F 4.68 0.34 22.70 29.49 17.63 Germ
Example 3
The Present Process Provided Improved Corn Fiber Fermentation
[0172] The present invention provides an improved method for
fermenting corn fiber substrates derived from grain milling (dry
fractionation) processes. The present process was useful for
gentler removal of starch from corn fiber fractions via
fermentation. Typically, corn fiber fractions contain recalcitrant
starch deposits. The present method provided improved access to the
starch present in the corn fiber.
[0173] Materials and Methods
[0174] Final fiber obtained from Broin Enterprises, Inc. (BEI) in
Scotland, S. Dak. U.S.A. was used in this experiment. The makeup
water used was deionized water. The 550,000 gallon fermenters were
pH adjusted to 4.5 with sulfuric acid (0.5 ml of 10.times. solution
required). The wet fiber was ground in the Knifetech mill two times
for ten seconds. A 20,000 gallon yeast propagator temperature was
maintained at ninety degrees Fahrenheit (90.degree. F.) with a
propagator time of eight (8) hours and pH adjusted to 5.0 with
sulfuric acid. Fali yeast, obtained from Fleischmann's Yeast, was
prepared using makeup water from plant operations. A commercially
available glucoamylase with a dosage of 400 L was used.
[0175] Results and Discussion
3TABLE 3 0 hrs. (% 16 hrs. (% 24 hrs. (% 40 hrs. (% GA (L)
Temp.(.degree. F.) EtOH) EtOH) EtOH) EtOH) 400 98 0 4.685 6.141
7.328 400 95 0 4.349 5.649 6.961 400 101 0 4.897 6.351 7.265 400
104 0 5.005 6.419 7.565
[0176] The present process provided effective corn fiber
fermentation (Table 3). The data in Table 3 indicate the positive
impact of fiber fermentation as measured by ethanol yield using the
present method. Varying the temperature displays the effect on
ethanol recovery, with efficient ethanol recovery produced at lower
temperatures. The present method effectively fermented a corn fiber
fraction that in a conventional process typically stalls
fermentation.
Example 4
The Present Process Provided Improved Ethanol Kinetics in Endosperm
Fermentation Via Additional Germ or Germ Meal
[0177] The present invention provides an improved method for
fermenting fractionated grain, such as fractionated corn derived
from a grain milling (dry fractionation) process.
[0178] Materials and Methods
[0179] Cook Standard Ingredients at Plant Equivalent Dose (Lab
Dose) of 308 L Liquizyme SC AA (0.30 ml of a 25.times.) was used.
Fermentation standard ingredients at plant equivalent dose (lab
dose) to include 660 L Spirizyme Plus glucoamylase (0.25 ml of a
10.times.), 33 L protease (0.13 ml of a 100.times.), 4.4 lbs
Lactrol (0.16 ml of a 2,000.times.), and no urea liquor.
Fermentation temperature staging conditions included 90.degree. F.
from 0-24 hours, 84.degree. F. from 24-48 hours, and 82.degree. F.
from 48-65 hours. Yeast propagator standard ingredients at
laboratory dose to include 230 mL deionized water, 100 mL backset,
70 grams maltodextrin MO40, 0.44 mL of a 5.times., 1.76 mL of a
100.times., 1.07 grams, 1.07 grams, 1.70 mL of a 1000.times., 0.13
grams zinc sulfate, 0.48 grams Fali Yeast for an eight (8) hour
propagation, propagation temperature of ninety degrees (90.degree.
F.), with a 2.88 mL transfer of yeast propagator to each fermenter
for inoculation.
[0180] Plant scale dosages refer to 550,000 gallon fermenters with
80 mL lab fermenters used. The grams of flour used and the makeup
water added was adjusted for each fermenter to keep the starch
content consistent. The pH of all fermenters was adjusted to 6.0
with sulfuric acid. All endosperm flour used was collected from BEI
already ground, and all germ flour was ground in the KnifeTech mill
(3.times.10 sec). The whole corn used as control was ground through
a Lab 1.0 mm Screen. The pH of all drop samples was adjusted to
less than 3.50 with sulfuric acid to deactivate residual enzyme
activity prior to drying samples for proximate analysis.
[0181] Results and Discussion
[0182] At the start of fermentation there was a measured difference
in the ethanol percentage in the germ produced according to the
present method compared to the liquefied germ. This difference
continued throughout forty-seven hours of fermentation. A similar
trend was observed between the present invention germ meal and the
liquefied germ meal. The present process provided improved ethanol
kinetics in endosperm fermentation via additional germ or germ
meal. These results are illustrated in FIGS. 3A, 3B, and 3C.
[0183] It should be noted that, as used in this specification and
the appended claims, the singular forms "a," "an," and "the"
include plural referents unless the content clearly dictates
otherwise. Thus, for example, reference to a composition containing
"a compound" includes a mixture of two or more compounds. It should
also be noted that the term "or" is generally employed in its sense
including "and/or" unless the content clearly dictates
otherwise.
[0184] All publications and patent applications in this
specification are indicative of the level of ordinary skill in the
art to which this invention pertains.
[0185] The invention has been described with reference to various
specific and preferred embodiments and techniques. However, it
should be understood that many variations and modifications may be
made while remaining within the spirit and scope of the
invention.
* * * * *