U.S. patent application number 10/633448 was filed with the patent office on 2004-06-24 for microreactor.
This patent application is currently assigned to BioProcessors Corp.. Invention is credited to Angelino, Mark D., Jury, Andrey Zarur.
Application Number | 20040121454 10/633448 |
Document ID | / |
Family ID | 22692479 |
Filed Date | 2004-06-24 |
United States Patent
Application |
20040121454 |
Kind Code |
A1 |
Jury, Andrey Zarur ; et
al. |
June 24, 2004 |
Microreactor
Abstract
Chemical and biological reactors, including microreactors, are
provided. Exemplary reactors include a plurality of reactors
operable in parallel, where each reactor has a small volume and,
together, the reactors produce a large volume of product. Reaction
systems can include mixing chambers, heating/dispersion units,
reaction chambers, and separation units. Components of the reactors
can be readily formed from a variety of materials. For example,
they can be etched from silicon. Components are connectable to and
separable from each other to form a variety of types of reactors,
and the reactors can be attachable to and separable from each other
to add significant flexibility in parallel and/or series reactor
operation.
Inventors: |
Jury, Andrey Zarur;
(Emeryville, CA) ; Angelino, Mark D.; (Wilmington,
DE) |
Correspondence
Address: |
Timothy J. Oyer, Ph.D.
Wolf, Greenfield & Sacks, P.C.
600 Atlantic Avenue
Boston
MA
02210
US
|
Assignee: |
BioProcessors Corp.
Woburn
MA
01801
|
Family ID: |
22692479 |
Appl. No.: |
10/633448 |
Filed: |
August 1, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10633448 |
Aug 1, 2003 |
|
|
|
09707852 |
Nov 7, 2000 |
|
|
|
60188275 |
Mar 10, 2000 |
|
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Current U.S.
Class: |
435/288.5 ;
435/289.1 |
Current CPC
Class: |
B01J 2219/00828
20130101; B01F 25/4331 20220101; B01F 33/3017 20220101; B01J
2219/00889 20130101; B01F 25/433 20220101; B01F 25/431 20220101;
B01F 25/23 20220101; B01J 2219/00862 20130101; B01J 2219/00961
20130101; B01J 2219/00963 20130101; B01F 33/304 20220101; B01J
2219/00907 20130101; B01J 2219/00835 20130101; B01J 2219/00966
20130101; B01F 35/561 20220101; B01J 2219/00871 20130101; C12M
23/16 20130101; B01J 19/0093 20130101; B01J 2219/00957 20130101;
B01J 2219/00783 20130101; B01F 25/4317 20220101; B01J 2219/00873
20130101 |
Class at
Publication: |
435/288.5 ;
435/289.1 |
International
Class: |
C12M 001/00 |
Claims
What is claimed is:
1. A chemical or biochemical reactor comprising: a reaction unit
including a chamber having a volume of less than 1 ml, an inlet to
the chamber connectable to a source of a chemical or biological
starting material, and an outlet of the chamber for release of a
product of a chemical or biological reaction involving the starting
material; and a collection chamber connectable to the outlet of the
reaction chamber, the collection chamber having a volume of greater
than 1 liter.
Description
RELATED APPLICATION
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn.120 to U.S. patent application Ser. No. 09/707,852,
filed Nov. 7, 2000, which application claims the benefit of
priority under 35 U.S.C. .sctn.119(e) of U.S. Provisional Patent
Application Serial No. 60/188,275, filed Mar. 10, 2000. These
applications are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to chemical or
biochemical microreactors, and more particularly to a microreactor
for the production of the product of a chemical or biochemical
reaction, including a plurality of individuated microreactors
constructed to operate in parallel.
BACKGROUND OF THE INVENTION
[0003] A wide variety of reaction systems are known for the
production of the product of chemical or biochemical reactions.
Chemical plants involving catalysis, biochemical fermenters,
pharmaceutical production plants, and a host of other systems are
well-known.
[0004] Systems for housing chemical and biochemical reactions not
necessarily for the production of product also are known. For
example, continuous-flow systems for the detection of various
analytes in bodily fluids including blood, such as oxygen, glucose,
and the like are well known.
[0005] In many of these and other systems, the capacity of the
system (the volume of material that the system is designed to
produce, process, or analyze) is adjusted in accordance with the
volume of reactant, product, or analyte desirably processed or
analyzed. For example, in large-scale chemical or pharmaceutical
production, reactors are generally made as large as possible to
generate as large a volume of product as possible. Conversely, in
many areas of clinical diagnosis, where it is desirable to obtain
as much information as possible from as small a physiological
sample as possible (e.g., from a tiny drop of blood), it is a goal
to minimize the size of reaction chambers of sensors. Several
examples of small-scale reactor systems, including those used in
clinical diagnoses and other applications, follow.
[0006] U.S. Pat. No. 5,387,329 (Foos, et al.; Feb. 7, 1995)
describes an extended use planar clinical sensor for sensing oxygen
levels in a blood sample.
[0007] U.S. Pat. No. 5,985,119 (Zanzucchi, et al.; Nov. 16, 1999)
describes small reaction cells for performing synthetic processes
in a liquid distribution system. A variety of chemical reactions
including catabolic, anabolic reactions, oxidation, reduction, DNA
synthesis, etc. are described.
[0008] U.S. Pat. No. 5,674,742 (Northrup, et al.; Oct. 7, 1997)
describes an integrated microfabricated instrument for
manipulation, reaction, and detection of microliter to picoliter
samples. The system purported by is suitable for biochemical
reactions, particularly DNA-based reactions such as the polymerase
chain reaction.
[0009] U.S. Pat. No. 5,993,750 (Ghosh, et al.; Nov. 30, 1999)
describes an integrated micro-ceramic chemical plant having a
unitary ceramic body formed from multiple ceramic layers in the
green state which are sintered together defining a mixing chamber,
passages for delivering and reacting fluids, and means for
delivering mixed chemicals to exit from the device.
[0010] Biochemical processing typically involve the use of a live
microorganism (cells) to produce a substance of interest.
Biochemical and biomedical processing account for about 50% of the
total drug, protein and raw amino-acid production worldwide.
Approximately 90% of the research and development (R&D) budget
in pharmaceutical industries is currently spent in biotechnology
areas.
[0011] Currently bioreactors (fermentors) have several significant
operational limitations. The most important being maximum reactor
size which is linked to aeration properties, to nutrient
distribution, and to heat transfer properties. During the
progression of fermentation, the growth rate for cells accelerates,
and the measures required to supply the necessary nutrients and
oxygen sets physical and mechanical constraints on the vessel
within which the cells are contained. Powerful and costly drives
are needed to compensate for inefficient mixing and low
mass-transfer rates. Additionally, as metabolism of cells
accelerates, the cells generate increased heat which needs to be
dissipated from the broth.
[0012] The heat transfer characteristics of the broth and the
vessel (including heat exchanger) impose serious constraints on the
reaction scale possible (see Table 1). While the particular heat
load and power requirements are specific to the reaction, the scale
of reaction generally approaches limitations at .about.10 m.sup.3
as in the case of E. coli fermentation (Table 1). The amount of
heat to be dissipated becomes excessive due to limits on heat
transfer coefficients of the broth and vessel. Consequently, the
system of vessel and broth will rise in temperature. Unfortunately,
biological compounds often have a relatively low upper limit on
temperature for which to survive (<45.degree. C. for many).
Additionally, power consumption to disperse nutrients and oxygen
and coolant requirements to control temperature make the process
economically unfeasible (see Table 1).
1TABLE 1 Oxygen- and Heat- Transfer Requirements for E. coli:
Effects of Scale OTR (mmol/ Volume.sup.a Pressure Power Heat Load
Coolant.sup.b L .multidot. h) (m.sup.3) (psig) (hp) (Btu/h)
(.degree. F.) 150 1 15 5.0 84 000 40 200 1 25 4.9 107 000 40 300 1
35 7.1 161 000 40 400 1 35 6.9 208 000 40 150 10 15 50.2 884 000 40
200 10 25 50.0 1 078 000 40 300 10 35 75.7 1 621 000 22 400 10 35
77.0 2 096 000 5 .sup.aLiquid volume .sup.bCoolant flow is 35
gal/min for 1-m.sup.3 vessel and 100 gal/min for 10-m.sup.3 vessel
.sup.cCharles, M. and Wilson, J. Fermentor Design; In: Bioprocess
Engineering; Lydersen, B. K., D'Elia, N. A., Nelson, K. L., Ed.;
John Wiley & Sons, Inc., New York, 1994.
[0013] Aside from reactor scalability, the design of conventional
fermentors has other drawbacks. Due to the batch and semi-batch
nature of the process, product throughput is low. Also, the
complexity and coupled nature of the reaction parameters, as well
as the requirement of narrow ranges for these parameters, makes
control of the system difficult. Internal to the system,
heterogeneity in nutrient and oxygen distribution due to mixing
dynamics creates pockets in the broth characterized by insufficient
nutrients or oxygen resulting in cell death. Finally, agitation
used to produce as homogeneous a solution as possible (typically
involving impellar string to simultaneously mix both cells and
feeds of oxygen and nutrients) causes high strains which can
fracture cell membranes and cause denaturation.
[0014] While a wide variety of useful reactors for a variety of
chemical and biological reactions, on a variety of size scales
exist, a need exists in the art for improved reactors. In
particular, there is a current need to significantly improve the
design of bioreactors especially as the pharmaceutical and
biomedical industries shift increasingly towards bioprocessing.
SUMMARY OF THE INVENTION
[0015] The present invention provides systems, methods, and
reactors associated with small-scale chemical or biochemical
reactions.
[0016] In one aspect the invention provides a chemical or
biochemical reactor. The reactor includes a reaction unit including
a chamber having a volume of less than one milliliter. The chamber
includes an inlet connectable to a source of a chemical or
biological starting material and an outlet for release of a product
of a chemical or biological reaction involving the starting
material. A collection chamber is connectable to the outlet of the
reaction chamber. The collection chamber has a volume of greater
than one liter.
[0017] In another aspect the invention involves a chemical or
biochemical reactor system. The system includes a mixing chamber
including a plurality of inlets connectable to a plurality of
sources of chemical or biochemical reagents, and an outlet. A
reaction chamber is connectable to and removable from the mixing
chamber, and has a volume of less than one milliliter. The reaction
chamber includes an inlet connectable to and removable from the
outlet of the mixing chamber, and an outlet for release of a
product of a chemical or biological reaction involving the starting
material.
[0018] In another aspect the invention provides methods. One method
includes carrying out a chemical or biological reaction in a
plurality of reaction chambers operable in parallel, where each
reaction chamber has a volume of less than one milliliter. Product
of the reaction is discharged from the plurality of reaction
chambers simultaneously into a collection chamber having a volume
of greater than one liter.
[0019] Other advantages, novel features, and objects of the
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings, which are schematic and which are not
intended to be drawn to scale. In the figures, each identical or
nearly identical component that is illustrated in various figures
is represented by a single numeral. For purposes of clarity, not
every component is labeled in every figure, nor is every component
of each embodiment of the invention shown where illustration is not
necessary to allow those of ordinary skill in the art to understand
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 illustrates a microbioreactor of the invention
including mixing, heating/dispersion, reaction, and separation
units, in expanded view;
[0021] FIG. 2 illustrates the system of FIG. 1 as assembled;
[0022] FIG. 3 illustrates the mixing unit of the system of FIG.
1;
[0023] FIG. 4 is an expanded view of the heating/dispersion unit of
the system of FIG. 1;
[0024] FIG. 5 is an expanded view of the reaction chamber of the
system of FIG. 1; and
[0025] FIG. 6 is an expanded view of the separation unit of the
system of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The present invention provides a chemical or biochemical
reactor that can be used for a variety of very small-scale
techniques. In one embodiment, a microreactor of the invention
comprises a matrix of a few millimeters to a few centimeters in
size containing reaction channels with dimensions on the order of
hundreds of microns. Reagents of interest are allowed to flow
through these microchannels, mixed, and reacted together. The
products can be recovered, separated, and treated within the
system. While one microreactor may be able only to hold and react a
few microliters of the substances of interest, the technology
allows for easy scalability and tremendous parallelization. With
enhanced oxygen and nutrient distribution, a microreactor of the
invention demonstrates increased performance in terms of cell
viability. The microreactor geometry resembles closely the natural
environment of cells whereby diffusional oxygen and nutrient
transfer take place through a high surface area, thin layer
interface.
[0027] With regard to throughput, an array of many microreactors
can be built in parallel to generate capacity on a level exceeding
that allowed by current vessels and more uniform in product quality
than can be obtained in a batch method. Additionally, an advantage
is obtained by maintaining production capacity at the scale of
reactions typically performed in the laboratory. In general, the
coupled parameters for heat and mass transfer that are determined
on the lab-scale for a process do not scale linearly with volume.
With conventional reactors, as the magnitude of volume is increased
1,000-1,000,000 times for production, these parameters need to be
re-evaluated, often involving a large capital-investment. The use
of small production volumes, although scaled in parallel, reduces
the cost of current scale-up schemes.
[0028] Furthermore, the process can be implemented on a simple
platform, such as an etched article for example, a silicon wafer.
With the effort of semiconductor manufacturing being towards the
reduction in the dimensions of channels, an opportunity to utilize
excess capacity within these production facilities (with unused
equipment for the larger dimensions) is provided. Mass production
of these units can be carried out at very low cost and an array of
many reactors, for example thousands of microreactors typically can
be built for a price lower than one traditional bioreactor.
[0029] Referring now to FIG. 1, a chemical or biochemical reactor
in accordance with one embodiment of the invention is illustrated
schematically. The reactor of FIG. 1 is, specifically, a
microbioreactor for cell cultivation. It is to be understood that
this is shown by way of example only, and the invention is not to
be limited to this embodiment. For example, systems of the
invention can be adapted for pharmaceutical production, hazardous
chemical production, or chemical remediation of warfare reagents,
etc.
[0030] Microreactor 10 includes four general units. A mixing unit
12, a heating/dispersion unit 14, a reaction unit 16, and a
separation unit 18. That is, in the embodiment illustrated,
processes of mixing, heating, reaction, purification are
implemented in series. Although not shown, pressure, temperature,
pH, and oxygen sensors can be included, for example embedded within
the network to monitor and provide control for the system. Due to
the series format, the opportunity for several reaction units in
series for multi-step chemical syntheses, for several levels of
increased purification, or for micro-analysis units is provided as
well.
[0031] FIG. 1 shows microreactor 10 in expanded view. As
illustrated, each of units 14 and 16 (heating/dispersion and
reaction units, respectively) includes at least one adjacent
temperature control element 20-26 including a channel 28 through
which a temperature-control fluid can be made to flow. As
illustrated, temperature control units 20 and 24 are positioned
above and below unit 14 and units 22 and 26 are positioned above
and below unit 16. Separation unit 18 includes upper and lower
extraction solvent fluid units 30 and 32, respectively, separated
from unit 18 by membranes 34 and 36, respectively.
[0032] Referring now to FIG. 2, reactor 10 is illustrated as
assembled. The individual units of microreactor 10 will now be
described in greater detail.
[0033] Referring now to FIG. 3, mixing unit 12 is illustrated.
Mixing unit 12 is designed to provide a homogeneous mixture of
starting materials or reactants to be provided to the reaction
units, optionally via the heating/dispersion unit. In the specific
example of the microbioreactor, mixing unit 12 is designed to
provide a homogeneous broth with sufficient nutrients and oxygen,
and at the required pH, for cells. Rather than combine the mixing
process with simultaneous nourishment of the cells, the process is
performed in a preliminary stage and then fed to the reaction stage
where cells are immobilized. In this manner, the cells do not
experience any shear stress due to mixing and a homogeneous mixture
of feed requirements is guaranteed.
[0034] As is the case for other components of the reactor, mixing
unit 12 can be manufactured using any convenient process. In
preferred embodiments the unit is etched into a substrate such as
silicon via known processes such as lithography. Other materials
from which mixing unit 12, or other components of the systems of
the. invention can be fabricated, include glass, fused silica,
quartz, ceramics, or suitable plastics. Silicon is preferred. The
mixing unit includes a plurality of inlets 40-50 which can receive
any of a variety of reactants and/or fluid carriers. Although six
inlets are illustrated, essentially any number of inlets from one
to tens of hundreds of inlets can be provided. Typically, less than
ten inlets are needed for a given reaction. Mixing unit 12 includes
an outlet 52 and, between the plurality of inlets and the outlet, a
mixing chamber 54 constructed and arranged to coalesce a plurality
of reactant fluids provided through the inlets. It is a feature of
the embodiment illustrated that the mixing chamber is free of
active mixing elements. Instead, the mixing chamber is constructed
to cause turbulence in the fluids provided through the inlets
thereby mixing and delivering a mixture of the fluids through the
outlet without active mixing. Specifically, the mixing unit
includes a plurality of obstructions 56 in the flow path that
causes mixture of fluid flowing through the flow path. These
obstructions can be of essentially any geometrical arrangement. As
illustrated, they define small pillars about which the fluid must
turbulently flow as it passes from the inlets through the mixing
chamber toward the outlet. As used herein "active mixing elements"
is meant to define mixing elements such as blades, stirrers, or the
like which are movable relative to the reaction chamber itself,
that is, movable relative to the walls defining the reaction
chamber.
[0035] The volume of the mixing chamber, that is, the volume of the
interior of mixing unit 12 between the inlets and the outlet, can
be very small in preferred embodiments. Specifically, the mixing
chamber generally has a volume of less than one liter, preferably
less than about 100 microliters, and in some embodiments less than
about 10 microliters. The chamber can have a volume of less than
about five microliters, or even less than about one microliter.
[0036] Specifically, in the microbioreactor illustrated, six
separate feed streams empty into the mixing chamber under pressure.
One feed stream provides gaseous oxygen (O.sub.2) as a cell
requirement. One stream, respectively, provides carbon dioxide
(CO.sub.2) and nitrogen (N.sub.2) for altering pH. The remaining
three channels provide the broth solution including solvent and
nutrients. One of these latter streams can also be utilized to
provide any additional requirements for the system such as
antifoaming agents. Antifoaming agents are sometimes necessary to
prevent production of foam and bubbles that can damage cells within
the broth. The feed of the various streams into the chamber
provides enough turbulence for mixing of the different streams.
Flow within microfluidic devices is characterized by a low Reynolds
number indicating the formation of lamina. While the turbulence
created by the injection streams should provide sufficient mixing
before the development of laminar flow, pilon-like obstructions 56
are placed in the flow path of the stream leaving the primary
mixing chamber in order to enhance mixing of the lamina. By
splitting a main stream into substreams followed by reunification,
turbulence is introduced in the flow path, and a mechanism other
than simple diffusion is used to facilitate further mixing. The
length of this mixing field can be lengthened or shortened
depending on the system requirements.
[0037] Referring now to FIG. 4, heating/dispersion unit 14 is
shown. Unit 14 can be formed as described above with respect to
other units of the invention. Unit 14 includes an inlet 60 in fluid
communication with a plurality of outlets 62 in embodiments where
dispersion as described below is desirable. In operation, a stream
of homogeneous fluid exiting the mixing unit (feed broth in the
specific microbioreactor embodiment shown) enters a dispersion
matrix defined by a plurality of obstructions dividing the stream
into separate flow paths directed toward the separate outlets 62.
The dispersion matrix is sandwiched between two temperature control
elements 20 and 24 which, as illustrated, include fluid flow
channels 28 etched in a silicon article. Control unit 24 is
positioned underneath unit 14, thus etched channel 28 is sealed by
the bottom of unit 14. Control unit 20 is positioned atop unit 14
such that the bottom of unit 20 seals and defines the top of
diffusion unit 14. A cover (not shown) can be placed a top unit 20
to seal channel 28.
[0038] Rather than for mixing, as in the previous case (FIG. 3),
the splitting of the streams is to disperse the medium for its
entrance into the reactive chamber in the next unit operation. In
traditional reactor systems, fluid flow about a packing material
containing catalysts produces the desired reaction. However, if the
fluid is not evenly dispersed entering the chamber, the fluid will
flow through a low resistance path through the reactor and full,
active surface area will not be utilized. Dispersion in this case
is to optimize reactor efficiency in the next stage.
[0039] With regard to the heating function of this unit, the
platform functions as a miniaturized, traditional heat exchanger.
Etched silicon platforms both above and below the central platform
serve to carry a heated fluid. Cells typically require their
environment to have a temperature of .about.30.degree. C. The
fluids flowing in the etched coils both above and below the broth
flow channel heating the broth through the thin silicon layer. The
temperature of the fluid in the upper and lower heat exchangers can
be modified to ensure proper temperature for the broth.
Additionally, the platform can be extended for increased heating
loads.
[0040] Although a combination heating/dispersion unit is shown,
unit 14 can be either a dispersion unit or a heating unit. For
example, dispersion can be provided as shown, without any
temperature control. Alternatively, no dispersion need be provided
(inlet 60 can communicate with a single outlet 62, which can be
larger than the outlets as illustrated) and heating units can be
provided. Cooling units can be provided as well, where cooling is
desired. Units 20 and 24 can carry any temperature-control fluid,
whether to heat or cool.
[0041] Referring now to FIG. 5, reaction chamber 16 is shown,
including temperature control units 22 and 26, in expanded form.
Units 22 and 26 can be the same as units 20 and 24 as shown in FIG.
4, with unit 22 defining the top of reaction chamber 16. Reaction
unit 16 includes an inlet 70 fluidly communicating with an outlet
72 and a reaction chamber defined therebetween. The reaction
chamber, in microreactor embodiments of the invention, has a volume
of less than one milliliter, or other lower volumes as described
above in connection with mixing unit 12. Inlet 70 is connectable to
a source of a chemical or biological starting material, optionally
supplied by mixing unit 12 and heating/dispersion unit 14, and
outlet 70 is designed to release the product of a chemical or
biological reaction occurring within the chamber involving the
starting material. Unit 16 can be formed from materials as
described above.
[0042] The reactor unit is the core of the process. While the unit
is designed to be interchangeable for biological or pharmaceutical
reactions, the specific application as shown is for cell
cultivation. As in the case of the previous unit, temperature
control units such as heat exchanger platforms will sandwich the
central reaction chamber. The heat exchangers will maintain the
temperature of the reaction unit at the same temperature as
discussed for the cell broth.
[0043] A feature of the unit is heterogeneous reaction on a
supported matrix. Cell feed enters the reaction chamber under the
proper pH, O.sub.2 concentration, and temperature for cell
cultivation. Cells, immobilized onto the silicon framework at
locations 74 either by surface functionalization and subsequent
reaction or entrapment within a host membrane, metabolize the
nutrients provided by the feed stream and produce a product
protein. The initial reaction platform can be a two-dimensional
array of cells both on the top and bottom of the reaction chamber.
This arrangement is to prevent a large pressure drop across the
unit which would be detrimental to flow.
[0044] In this unit, oxygen and nutrients are diffused from the
flowing stream to the immobilized cells. The cells, in turn
metabolize the feed, and produce proteins which are swept away in
the flowing stream. The flowing stream then enters the fourth
chamber which removes the protein product from the solution.
[0045] Referring again to FIG. 1, it can be seen how dispersion
unit 14 creates an evenly-divided flow of fluid (reactant fluid
such as oxygen and nutrients in the case of cell cultivation)
across each of locations 74 in reaction to chamber 16.
[0046] Referring now to FIG. 6, separation unit 18 is shown in
greater detail, in expanded view. Separation unit 18 defines a
central unit including an inlet 80 communicating with an outlet 82,
and a fluid pathway 84 connecting the inlet with the outlet. Unit
18 can be fabricated as described above with respect to other
components of the invention, and preferably is etched silicon. It
may be desirable for fluid path 84 to completely span the thickness
of unit 18 such that the pathway is exposed both above and below
the unit. To maintain structural integrity, pathway 84 can be
etched to some extent but not completely through unit 18 as
illustrated, and a plurality of holes or channels can be formed
through the bottom of the pathway exposing the bottom of the
pathway to areas below the unit. Inlet 80 can be connectable to the
outlet of reaction chamber 16, and outlet 82 to a container for
recovery of carrier fluid.
[0047] In the embodiment illustrated, membranes 34 and 36 cover
exposed portions of fluid pathway 84 facing upward or downward as
illustrated. Membranes 30 and/or 36 can be any membranes suitable
for separation, i.e. extraction of product through the membrane
with passage of effluent, or carrier fluid, through outlet 82.
Those of ordinary skill in the art will recognize a wide variety of
suitable membranes including size-selective membranes, ionic
membranes, and the like. Upper and lower extraction solvent fluid
units 30 and 32, which can comprise materials as described above
including etched silicon, each include a fluid pathway 86
connecting an inlet 88 with an outlet 90. Fluid pathway 86
preferably is positioned in register with fluid pathway 84 of unit
18 when the separation unit is assembled. In this way, two flowing
streams of solvent through channels 86 of units 30 and 32 flow
counter to the direction of flow of fluid in channel 84 of unit 18,
the fluids separated only by membranes 34 and 36. This establishes
a counter-current tangential flow filtration membrane system. By
concentration gradients, products are selectively extracted from
channel 84 into solvent streams flowing within channels 86 of unit
30 or 32. Product is recovered through the outlet 90 of units 30 or
32 and recovered in a container (not shown) having a volume that
can be greater than 1 liter. Outlets 90 thereby define carrier
fluid outlets, and a fluid pathway connects inlet 80 of unit 18
with the carrier fluid outlets 90 of units 30 and 32, breached only
by membranes 34 and 36. Carrier fluid outlet 82 can be made
connectable to a recovery container for recycling of reaction
carrier fluids. In the example of a microbioreactor, residual
oxygen and nutrients are recovered from outlet 82 and recycled back
into the feed for the process.
[0048] The flowing streams of extraction solvent in channels 86 can
be set at any desired temperature using temperature control units
(not illustrated). In the case of a microbioreactor, these fluids
can be set at approximately 4.degree. C. The low temperature is
needed to maintain the efficacy of the protein products and prevent
denaturation. Additionally, several purification and clarification
steps are often performed in industrial application. The necessity
of further purification is remedied by the use of additional units
in series.
[0049] Embedded within the production process can be control
systems and detectors for the manipulation of temperature, pH,
nutrients, and oxygen concentration. Where a microbioreactor is
used, the viability of cells is dependent upon strict limits for
the parameters mentioned above. Narrow set-point ranges, dependent
on the cell system selected, can be maintained using thermocouples,
pH detectors, O.sub.2 solubility detectors, and glucose detectors
between each unit. These measurements will determine the heat
exchanger requirements, O.sub.2, CO.sub.2, N.sub.2, and nutrient
inputs.
[0050] Diaphragm and peristaltic pumps can be used to provide the
necessary driving force for fluid flow in the units. Such pumps are
also used to maintain flow in the heat exchanger units.
[0051] It is a feature of the invention that many of the
microreactors as illustrated can be arranged in parallel.
Specifically, at least ten reactors can be constructed to operate
in parallel, or in other cases at least about 100, 500, 1,000, or
even 10,000 reactors can be constructed to operate in parallel.
These reactors can be assembled and disassembled as desired.
[0052] It is another feature of the invention that individual units
12, 14, 16, and 18 can be constructed and arranged to be
connectable to and separable from each other. That is, any
arrangement of individual components can be created for a desired
reaction. For example, with reference to FIG. 1, heating/dispersion
unit 14 may not be necessary. That is, outlet 52 of mixing unit 12
can be connectable to either inlet 60 of heating/dispersion unit
14, or inlet 70 of reaction unit 16 where a heating/dispersion unit
is not used. Moreover, assembly and disassembly of reactors to
create a system including many, many reactors operating in
parallel, as described above, or in series is possible because of
the connectability and separability of the components from each
other to form systems containing specific desired components, and
any number of those or other systems operating together. Equipment
for connection and separation of individual components of a reactor
can be selected among those known in the art, as can systems for
connection of a variety of reactors in parallel or in series.
Systems should be selected such that the individual components can
be connectable to and separable from each other readily by
laboratory or production-facility technicians without irreversible
destruction of components such as welding, sawing, or the like.
Examples of known systems for making readily reversible connections
between components of reactors or between reactors to form parallel
reactors or series reactors include male/female interconnections,
clips, cartridge housings where components comprise inserts within
the housings, screws, or the like.
[0053] Those skilled in the art would readily appreciate that all
parameters listed herein are meant to be exemplary and that actual
parameters will depend upon the specific application for which the
methods and apparatus of the present invention are used. It is,
therefore, to be understood that the foregoing embodiments are
presented by way of example only and that, within the scope of the
appended claims and equivalents thereto, the invention may be
practiced otherwise than as specifically described. In the claims
the words "including", "carrying", "having", and the like mean, as
"comprising", including but not limited to.
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