Note: Descriptions are shown in the official language in which they were submitted.
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A PHOTOBIOREACTOR BAG WITH BUILT-IN SPARGER TUBE, AGITATOR
AND WATER JACKET
FIELD OF THE INVENTION
This invention relates to the field of photobioreactor bags for culturing
algae and cyanobacteria. In
particular, this invention combines a pond-like elongate container enclosing a
reusable
photobioreactor sleeve that incorporates two sparger tubes, an agitation
system and a water jacket for
temperature control, all built-in into the bag.
BACKGROUND OF THE INVENTION
Current photobioreactor equipment are often complex and expensive. These
factors make their use
valid only for production of expensive pharmaceuticals, nutraceuticals and
chemicals.
To address environmental or energy issues such as need for capturing of carbon
dioxide emissions,
treatment of waste waters, food security, shortness of fresh water, need for
renewable energy, cost of
photobioreactors must come down For this, major technology breakthrough are
needed.
Furthermore, for large-scale culture of algae and cyanobacteria to become
viable, agricultural farmers
experienced with sustainable large-scale farming may need to become involved
in algae farming.
Supplementing their crops with algae farming will make the process even more
sustainable. For this,
the complexity of algae farming must be reduced to a minimum, scale-up has to
become within reach
and costs have to be reduced by many folds.
The present invention therefore represents a fresh solution to the
aforementioned problems, providing
a low-cost photobioreactor system that integrates the scalability of ponds
with the controls provided by
photobioreactors. In the present cultivation system, a low-cost semi-
disposable bioreactor bag is
provided with all the controls of photobioreactors and is made to line the
interior space of a durable
pond-like container, thus enabling the large-scale production of algae and
cyanobacteria in a
controlled environment by people not specifically trained in microbiology or
aseptic technique.
The reusable, modular bag of the present invention, while essentially
disposable, may be used
continuously for multiple consecutive culturing/harvesting cycles.
The multiple features of the modular bioreactor bag of the present invention
when associated with the
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versatility in shapes provided by an associated container that encloses the
bag, enables the bag to
aerate, agitate, cool, cultivate, milk cyanobacteria and harvest secretions in
an all-in-one bioreactor
bag, thus keeping sterility and costs of the process within control.
When eventually the reusable bioreactor bag does become contaminated, it may
then be disposed of
with relatively little economic loss. Such modules may be cheaply
manufactured, even for production
volumes of 1,500 liters or more of culture. Further, the ability to perform a
number of
culturing/harvesting cycles is economically lucrative, lowering even further
the effective cost per
module. A farm of such modular bags in associated containers can be
economically arranged, and the
number of modules in the farm may be controlled to closely match production to
demand. Thus, the
transition from pilot plant bioreactors to large scale production may be
achieved in a relatively simple
and economic manner by adding more modules to the farm.
Furthermore, eliminating the need for external sparger piping systems, for
external motive device to
agitate the medium, for external heat exchangers to control temperature, for
pumps to flow a portion of
the medium to milk cyanobacteria and aseptic equipment to harvest the rich
secretions, enables to
keep capital costs down and attracts more investors and farmers to invest in
algae farming.
SUMMARY OF THE INVENTION
According to a preferred embodiment of a combination bag/container
photobioreactor for culturing and
agitating algae and cyanobacteria in a medium, the bag comprises a flexible
light transmitting plastic
sheet forming a closed chamber that further includes at least two alternately
pressurized sparger
tubes spaced apart from each other and formed from the light transmitting
plastic sheet itself. The two
sparger tubes are located preferably at locations not difficult to effect
circulation of medium with
bubbles alone.
For generally oval-shape containers, sparger tubes are located on the
bioreactor close to bag
extreme borders. For bioreactor bag associated with container having multiple
recesses, the distance
between sparger tubes may vary according on the size and shape of the
bioreactor, but preferably,
tubes may be located as far as possible to each other as long as they don't
interfere with the
bioreactor's operation such as culturing, milking and harvesting in the case
of cyanobacteria.
While one end of sparger tubes is closed, the other end is in fluid
communication with a three-way
valve that alternately diverts incoming gases to each tube in a timely manner.
This alternating flow
creates pressure variation from two opposite directions and causes increased
agitation of the medium.
To further increase agitation's amplitude, an elongate pivotable flap
comprised of a strip of flexible
plastic that extends along the bag length is bonded on one edge end to the
plastic sheet with the other
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edge end being positioned above a sparger tube; as a sparger tube is inflated
and deflates by
incoming flowing gases, the flap moves cyclically up and down increasing
agitations of the medium.
By coordinating movement of two flaps in a timely manner, agitation is further
amplified.
According to some embodiments of the bioreactor, the bag includes two side
water jackets for
circulating a conditioning fluid to control temperature of the medium in the
bag. Inflating alternatingly
these two side water jackets generates waves, solar reflector film bonded to
the bottom portion of the
bag added side layer increases sunlight penetration from the bag two sides.
According to some preferred embodiments, the bag cooperates liningly with the
inner surface of a
semi-rigid flexible translucent W-shape container configured with multiple
recesses. This arrangement
associated with an expandable chamber in one of the recesses, enables to raise
or lower the level of
the medium in the bag. Deflating the expandable chamber in a main recess
causes the medium to
retrieve in that main recess while portions of the medium sunk in other
recesses becomes isolated for
being processed, for example for milking cyanobacteria.
The present invention also discloses a method of building a sparger tube into
a closed bag. This
method teaches to first perforate near one edge a folded portion of a bag laid
in a layflat position, then
tuck in this perforated portion to form a gusset and finally heat bond the
newly created gusset edge to
seal the bag.
Thus, a bioreactor bag of the present invention may incorporate concurrently a
sparger tube, an
agitation system, a temperature control system, a medium isolation system, a
bacteria milking space,
and a harvesting, all-in-one built in the same bag, eliminating the need for
costly accessories.
Other features and advantages of the present invention will be better
understood by reference to the
drawings and detailed description that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 Perspective view of a photobioreactor bag with two built-in sparger
tubes, delivering gases
alternately.
FIG. 2 Close-up view A of the cross-sectional view of sparger tube of FIG. 1
illustrating how gases
exit sideways.
FIG. 3 Cross-sectional view of a photobioreactor bag and two side water
jackets inside a container
with two sparger tubes each enclosing a flap.
FIG. 4 Cross-sectional view of a photobioreactor bag and two side water
jackets inside a container
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with two sparger tubes each activating an external flap welded to the bag.
FIG. 5 Cross-sectional view of a photobioreactor bag and two side water
jackets inside a container
with two sparger tubes each activating an external flap enclosed in a closed
tube.
FIG. 6. Cross-sectional view of a photobioreactor bag lining a reverse U-shape
container enclosing an
expanded height-adjustable chamber.
FIG. 7. Cross-sectional view of photobioreactor bag of FIG. 6 with a retracted
chamber.
FIG. 8. Perspective view of compacting roller over a land shaped for
supporting a bioreactor
container.
FIG. 9 Perspective view of compacting roller over a land shaped for supporting
a W-shape
bioreactor container
FIG. 10 Perspective view of a W-shape bioreactor container resting over a
shaped land.
FIG. 11 Perspective view of a method for building a sparger tube in a
bioreactor bag.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a combination photobioreactor bag lining a
trough-like container for
culturing microalgae cells and cyanobacteria organisms. The combination is
easy to use, inexpensive
and versatile. The invention enables the preparation of microorganisms by
people such as rural and
urban algae farmers not specifically trained in microbiology or aseptic
technique. It enables
microorganisms to be grown safely, for a variety of purposes, without the need
for specialized facilities
such as temperature controlled rooms, externally driven agitators, external
insertable aeration and
cooling pipes and other associated accessories.
The photobioreactor bag of the present invention, also referred
interchangeably as bioreactor, bag
chamber and sleeve are designed for culturing a wide variety of
microorganisms, both aerobic and
anaerobic. They are suitable for culturing microorganisms in generally sunny
and environmentally
friendly temperatures, and preferably in arid lands and other locations not
competing with food
production. They can also be used for fermentation of organic and non-organic
products including
fruits, vegetables and grains; or be used for growing marine organisms as
small as 1 micron to as big
as larvae and smaller fishes. Some of microorganisms that may be successfully
cultured in the
present reusable bioreactor bags of the present invention include, but not
limited to, bacteria,
cyanobacteria, fungi, algae, protozoans and nematodes.
Referring now to the drawings, FIG. 1 shows a preferred embodiment of the
photobioreactor bag 10
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made of a light transmitting flexible plastic sheet 12 forming an elongate
closed chamber lining a
generally horizontal translucent surface provided with optional recesses,
including two sparger tubes
22 and 24 which are formed by shaping portions of plastic material 12.
FIG. 2 illustrates a close-up view of the sparger tube 22 perforated with two
side holes for exiting
gases such as air and carbon dioxide. The bioreactor bag 10 is provided with
multiple ports (not
shown) for introduction or removal of gases or liquids. These ports are
located at the transversal ends
of plastic sheet 12.
FIG. 3 shows in a preferred embodiment of a combination bioreactor bag 10
lining the interior of a
translucent C-shape container 40. In this illustration, agitation is provided
with flaps 16 and 18 being
encased in sparger tube 26 and 28 having holes on one side of the tube. Flaps
16 and 18 increase
amplitude of the agitation provided by bubbles exiting from sparger tubes 26
and 28.
FIG. 3 also illustrates two side water jackets 32 and 34 that envelop from one
side the shape of the
centrally-located bioreactor bag 10 and from the other side adopt the interior
shape of the translucent
container 40 that supports and contains all three bags 32,10, and 34. Water
jackets 32 and 34 contain
fluids that are displaced therein for controlling temperature of medium 50
contained in bioreactor bag
10. Inflating alternatingly water jackets 32 and 34 generates waves.
Additionally, fluids in water jackets 32 and 34 may contain electrochromic
polymers or nanoparticles
62 that electrically change their color to reduce bag 10 exposure to excess
sunlight or to provide an
on-off filtering effect, such as biotuning by flickering the color change at
desired frequencies to
enhance algae and cyanobacteria growth. Water jackets 32 and 34 may be made of
the same or of a
different material than the light transmitting plastic sheet used for
bioreactor bag 12.
The translucent container 40 illustrated in FIG. 3 is made of a semi-rigid
flexible plastic such as, but
not limited to, a fiberglass sheet 40 provided with a plastic memory C-shape
designed to keep its
trough-like borders in an elevated position, like a container. Wedges 70
further assist container 40 to
maintain and reinforce its trough-like shape. Container 40 is made of a semi-
rigid material such as
fiberglass or of thin plastic sheet that is bendable so that the container 40
elevated borders may flatten
when container 40 is rolled-up, thus reducing costs in packaging, transport,
installation and
maintenance.
Furthermore, FIG. 3 illustrates a solar reflector 60 positioned underneath the
translucent container 40.
This reflector 60 directs added solar reflection to container 40 two sides and
partially to the container
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40 underside. To prevent container 40 from rocking sideways bricks or wedges
70 block movement of
container 40.
FIG. 4 shows a preferred embodiments of a combination container and bioreactor
bag 10 wherein
spargers tubes 26 or 28 expand when pressured by flowing gases. This causes to
lift pivotable flaps
16 or 18. The welding of flap 16 to plastic sheet 12 along the flap 16 one
elongate edge creates a
spring effect bringing back flap 16 to its lowest position. By alternating gas
flow from one sparger tube
26 to another sparger tube 28, flap 16 and 18 are radially moved, causing
agitation of medium 50.
Using a programmable timer to alternate an incoming gas flow in flow
communication with sparger
tubes 26 and 28 via a three-way valve (not shown) enables to harmonize the
interplay between flaps
16 and 18 in order to maximize agitation amplitude which leads to the creation
of waves. This flow
alternation between two sparger tubes 26 and 28 eliminates the need for an
external drive that agitate
a medium as practiced in prior art.
FIG. 5 shows in an embodiment of a combination container 40 and bioreactor bag
10, wherein a
gusseted sealed tube 20 encloses a flap 16 that is resting over a sparger tube
26. Inflating sparger
tube 26 causes radial pivoting and lifting of flap 16. This in turn causes
agitation of medium 50.
Keeping the sealing line portion of the sparger tube 26 as close as possible
to the bonded edge of the
gusseted tube 20 increases the amplitude of flap 16 by virtue of the
leveraging effect. By alternating
gas flow from one sparger tube 26 to another sparger tube 28, flap 16 and flap
18 (not shown)
respectively pivot, causing increased agitation of medium 50. Using a
programmable timer to control
gas flow via a three-way valve (not shown) enables to harmonize the interplay
between flaps 16 and
18 in order to maximize amplitude of waves. This arrangement eliminates the
need of external drive
that agitate a medium as practiced in prior art.
FIGS. 6 and 7 show some embodiments of the combination container 40 and
bioreactor bag 10
wherein the level medium 50 is made to vary as per need. This embodiment of
the invention may be
preferably used for culturing, milking cyanobacteria and harvesting secretions
in a single bioreactor
bag 10. In this embodiment, bioreactor bag 10 further includes an expandable
chamber 36
cooperating with a translucent container 40 configured with a generally flat
surface 80 flanked
between two recesses 82 and 84. Chamber 36 may be created as an integral part
of plastic sheet 12
formed by an elongate sealing line that separates bag 12 major portion from a
chamber portion 36.
This chamber 36 may optionally be positioned inside bag 12 resulting from the
creation of an internal
sealed gusset. Alternatively, this chamber 36 may be annexed to bag 12 as a
separate tubular, flexible
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expandable plastic container 36 in wall contact with bag 10. In this
embodiment, height of medium 50
in bag 12 can be elevated above the level of flat surface 80 when chamber 36
is fully expanded
maximizing surface exposure of medium 50 to sunlight.
Similarly, as shown in FIG. 7, level in medium 50 can be lowered below flat
surface 80. To achieve
this, chamber 36 in emptied from its fluid content causing in turn medium 50
to retrieve itself driven by
gravity force into the bag portion present in recess 82. This causes in turn
one or multiple portions of
medium 50 trapped into one or more other recesses, such as in recess 84, to
become isolated from
the medium portion retrieved in recess 82. Once isolated, medium portions in
each recess may be
processed separately.
As an example of such a process, the bag portion associated with recess 84 may
contain highly
porous matrices or gel, such as gel silica 90, for entrapping cyanobacteria.
Subjecting said entrapped
cyanobacteria to conditions that trigger secretions, such as, but not limited
to an acidic condition,
through injection of a product via one or multiple entry ports associated to
said recess portion 84
causes cyanobacteria to release secretions that can be collected and retrieved
through associated exit
ports.
FIG. 7 shows other processes associated with a same or a separate recess 82
and 84. These
processes may include, but are not limited to, exposing medium 50 to intense
light of selected
wavelength 92, to heat, to cold, to electromagnetic fields 94, to osmosis
exchange, to catalysts, to cell
density counting, to physical measurement, to continuous removal of secondary
metabolites, to bio
organic solvents, to electrocatalysts, to biocatalytic reductions, to
fermentation and to a combination
thereof.
The bag portion present in recess 82 containing height-adjustable chamber 36
may be insulated from
outside environmental conditions such as, but not limited to, excess heat,
excess cold, excess light,
excess wind, or a combination thereof.
Medium 50 contained in the bag portion associated with some of the recesses
such as 82 and 84
may be further subject to downstream processes such as, but not limited to,
dewatering, harvesting,
extraction, bacteria milking, collection of secretion or to a combination
thereof.
FIGS. 8 and 9 show an embodiment of an embossed surface acting as support for
container 40. The
configuration of such an embossed support enables light penetration to support
40 from all directions.
To emboss a C-shape, a W-shape or other shapes in land 200, a soil compacting
roller 100 is
provided with protrusions and recesses. These are configured to provide
protrusions that will support
intermittently the bottom of the translucent container 40 for containing the
heavy medium content 50.
configuration having and recesses that enable light entry from all directions
around container 40. It is
known that dirt roads in rural areas are stabilized by various means such as
by addition of lime,
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cement or enzymes to withstand harsh environmental conditions. Similarly,
supports made of
embossed dirt and clay may be stabilized to withstand environmental
conditions. To bring added light
to underside of container 40, recesses may be covered with a solar reflector
material such as a solar
reflector film 60 or a reflective mineral.
FIG. 10 shows a land surface 200 embossed with protrusions and recesses
configured for supporting
a W-shape container 40. Such a configuration is particularly suitable for
growing cyanobacteria as the
container surface is provided with recesses that enable to isolate medium 50
for milking bacteria using
a single bioreactor bag 10 rather than requiring multiple accessories and
equipment as practiced in
practiced in prior art.
FIG. 11 shows an embodiment of plastic sleeve 2 being processed by various
equipment for building
a sparger tube 22 in sleeve 12. The continuous manufacturing process can be
applied in-line with a
blown film extrusion process or applied post extrusion after the film is made.
In both cases, the folded
plastic film or sleeve 12 is first drawn over a perforating equipment 120,
such as a punch or a needle
wheel, then is pushed by a gusseting wheel 130 to tuck the perforated portion
inside bag 12 before a
sealing machine 140 bonds the newly formed edge. Sealing may be performed
using ultrasonic, heat
or radio-wave welding 140.
The process of FIG. 11 creates a sparger tube 22 with two side-holes. This
overcomes disadvantages
present in prior art with single-hole sparger tubes that shoot gases away from
a bioreactor surface
and creates "dead space" around single-hole sparger tubes and where it would
be difficult to effect
circulation with bubbles alone. In the present invention, sparger tubes 22,
24, 26 and 28 exit bubbles
sideways, slightly downwards, just slightly above tube's sealing line. The
generally oval-shape of
bioreactor bag 10 eliminates corners, therefore minimizing settling of
microorganisms. Similarly,
sparger tubes such as 26 and 28 located on recess walls of W-shape bioreactors
shoot in both
directions therefore dislodging cells in dead spaces.
In a standard photobioreactor, two means are used to achieve proper aeration
and optimum exposure
of micro organisms to light (1) bubbling of gases through the growth medium
and (2) agitation by a
pump, a stirrer or other means to effect a mechanical circulation. Using the
present photobioreactor 10
, aeration and mechanical agitation are combined into a single process ¨ this
maximizes the use of
existing components for creating a multifunctional bioreactor 10, thus
avoiding the need of a pump or
a stirrer that add capital, maintenance and operation costs with additional
use of energy. This has
been accomplished by coordinating alternately generation of gas bubbles from
two opposite directions
exiting from two sparger tubes spaced apart. In this bioreactor 10, each
sparger tubes 22 and 24 also
project gas bubbles from two opposite directions. Thus, in this bioreactor 10,
four sources of bubbles
provide aeration, mixing and agitation without need of additional mechanical
equipment, air supply or
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energy except for operating a small controller that operates a three-way
valve.
The bioreactor bag 10 is constructed from flexible or semi-flexible,
waterproof material, preferably
plastic. Low Density Polyethylene LDPE has been used in the instant
bioreactor, but other kinds of
plastic such as, but not limited to, High Density Polyethylene (HDPE) are
suitable, and may be
desirable in special circumstances. Plastic may be chosen for light
transmitting qualities. Certain cells
may be sensitive to bright white light or ultraviolet radiation, and for these
cells the container can be
made of plastics that absorb these wavelengths. Likewise, other kinds of
cells, plant cells for example,
may be developmentally regulated by the spectral quality of light, and for
these cells the bioreactor
bag 10 can be made of plastics that selectively transmit the desired
wavelengths of light.
The strength of the plastic is also an important consideration. Different
thicknesses of plastic can be
used, according to end purposes and standard practice. For example, for single-
use bioreactor bags
thicknesses between 75 microns to 150 microns may be sufficient. For multiple-
use bioreactor
bags 10, thicknesses may vary from 100 micron to 300 microns.
Shaping thin, durable fiberglass container 40 with a plastic memory shape to
contain a bioreactor bag
10 is not only cost-effective but protects the bag from harsh environmental
conditions by providing it
with very durable skin. Manufacturing complex-shape containers such as a W-
shape container 40 with
multiple recesses may be accomplished by joining transversally, side-by-side
shaped fiberglass sheets
that have one recess in each sheet. This enables also to increase the width of
the bioreactor 10.
Accordingly the overall size of the bioreactor bag width shall be adjusted
when using a wider
container.
Inserting two pre-shaped fiberglass sheets with plastic memory shape into each
other creates a
container 40 that has reinforced structure. Inserting a spacer for creating a
space between the two
pre-shaped fiberglass sheets enables to create a water jacket for circulating
a temperature
conditioning fluid in between them. Inserting a reversed pre-shaped sheet that
has plastic memory to
envelop the borders of another pre-shaped sheet creates a closed container 40
with excellent
resistance to harsh weather conditions.
The container 40 includes one or more ports to serve as inlets or outlets for
gases or liquids. The
ports are constructed of rigid or semi-rigid materials that are compatible
with the material used for
construction of bag 10. In preferred embodiments, any standard plastic tubing
or molded plastic can
be used to construct the ports, and they are welded into the seams of the
container according to
standard techniques. A variety of such ports are commercially available, e.g.,
for use in medical bags
and similar water containers.
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The disposable bioreactors of the present invention preferably are pre-
sterilized prior to shipping to the
local user. Various sterilization techniques may be used. Sterilization
techniques that are common in
the art include, but are not limited to, dry heat, autoclaving, radiation, and
ethylene oxide gas.
Air or other gases are introduced into the bioreactor bag10 via a gas inlet
port. Tubing connecting the
port to a gas pump is fitted with at least one filter, for filtering microbes
from the airstream prior to
introduction of the gas into the bioreactor bag 10.
The bioreactor bag 10 comprises a vent to exhaust gases. The vent in the
bioreactor bag 10 of the
present invention preferably comprises an outlet port fitted with tubing, of
varying length.
For convenience and ease of use, the reusable bioreactor bag 10 of the present
invention is packaged
and sold as a kit. Typically, a kit can contain one or more reusable
bioreactor bags (e.g., 1500 L in
size), a 15m long and lm wide container with a C-shape configuration by virtue
of its plastic memory
shape imparted during manufacturing. When rolled, the elevated walls of the C-
shape container
flatten and regain their original flat dimension of1.2m wide. Also is included
in the kit, a
programmable three-way valve for alternating flow of incoming gases between
the two sparger tubes
in bioreactor bag 10. An optional air pump is also included. The user supplies
water, electricity,
wedges such as bricks to keep the container borders elevated and a land space
to support the
combination container / bioreactor bag. Not only the length of the container
can be increased but also
the width of the container can be augmented by joining multiple sheets side-by-
side. Accordingly, the
size of the bag can also be increased to line the associated container.
To operate the combination container / bioreactor bag, the user unrolls the
container which
automatically takes its plastic memory shape and places the elongate bag or
sleeve inside the
container by also unrolling it. If temperature control is required, a separate
plastic bag with two side
water jackets or the side pockets in the bioreactor bag are filled with water
at a desired temperature.
The filling is done by connecting a water hose to the jacket entry port. The
jacket exit port is either
connected to an evaporative cooler or to other temperature conditioning
device, which in turn
connects to the jacket entry port.
Then, the user connects a first gas inlet port with tubing containing an in-
line micro-filter to sterilize the
air to one side to the air pump and the other side via an air flow meter to a
first entry port of a double
entry connector; the hose carrying CO<sub>2</sub> is connected via a CO<sub>2</sub>
flowmeter to the second
entry port of the double entry connector. The double entry connector feeds
gases to entry of the the
three-way valve. The user then connects the two exiting hoses from the three-
way valve to the two
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sparger tubes entry ports attached to the bag. The user fills the bioreactor
bag with a medium
comprising of tapwater (or sterilized sea water) mixed with nutrients, via
faucet or garden hose using
the existing third inlet port. The incoming water is sterilized via one or
more in-line filters (e.g., 5 µM
pre-filter obtained from a household water filtration unit, combined with a
microbiological final filter
(0.45 µM). The exhaust port, namely for 0<sub>2</sub> is fitted with an exhaust
tube. Finally algae or
cyanobacteria inoculum is introduced in the bag before electricity is turned
on.
Once the combination container / bioreactor bag kit is filled with medium,
inoculated and connected to
the air pump, the microorganisms are cultured for a pre-determined amount of
time, under specified
culture conditions, according to standard procedures. When the culture is
complete the contents are
harvested, e.g., by draining the container through one of the bag exit ports.
The aforementioned bioreactor kit has been exemplified for the cultivation of
algae and cyanobacteria.
However modest adjustments can adapt the kit for use with many other cells and
organisms.
Adjustments include different media and inoculum formulations, all of which
would be known to one
skilled in the art.
The present invention may be embodied in other specific forms without
departing from its spirit or
essential characteristics. The described implementations are to be considered
in all respects only as
illustrative and not restrictive. The scope of the invention is, therefore,
indicated by the appended
claims rather than by the foregoing description. All changes which come within
the meaning and range
of equivalency of the claims are to be embraced within their scope.
