WO2014085869A1

WO2014085869A1 - Bioreactor and method of use

Info

Publication number: WO2014085869A1
Application number: PCT/AU2013/001424
Authority: WO
Inventors: Florian BERNER; Kirsten Heimann; Madoc SHEEHAN
Original assignee: James Cook University
Priority date: 2012-12-07
Filing date: 2013-12-06
Publication date: 2014-06-12

Abstract

An improved bioreactor, method and system for cultivating microorganisms, in particular photosynthetic microorganisms. The bioreactor comprises at least one or a plurality of liquid permeable layers comprising a first surface and a second surface, wherein microorganisms are cultivatable on the first surface of the liquid permeable layer and the second surface is connectable in fluid communication with a fluid source, and wherein the liquid permeable layer is rotatable.

Description

TITLE

BIOREACTOR AND METHOD OF USE

FIELD OF THE INVENTION THIS INVENTION described herein relates generally to a bioreactor for cultivating microorganisms. In particular, the invention relates to a bioreactor, method and system for cultivating photosynthetic microorganisms.

BACKGROUND TO THE INVENTION

Culture systems for microorganisms are generally classified according to their engineering and hydraulic characteristics in open systems, examples of which include ponds, deep channel and shallow circulating units and closed or fully hydraulic systems commonly called bioreactors or photo-bioreactors (if cultured organisms are capable of using light as an energy source). Most microorganisms and in particular, photosynthetic microorganisms, are capable of growing both in suspension cultures and as a biofilm attached to a surface (examples of which include benthic microorganisms such as algae, microalgae and cyanobacteria).

When algae and other benthic microorganisms are grown as a biofilm attached to a cultivating surface, the biomass is naturally concentrated (containing less water) and more easily harvested, leading to more direct removal of the algal biomass and reduced processing. The cultivation of algae is currently being considered for a number of different applications, including: removal of C0₂ or other gases from industrial flue gases by algae bio-fixation; the reduction of Green House Gas (GHG) emissions from a company or process while producing biodiesel; wastewater treatment through the removal of unwanted compounds; the production of biomass for processing into ethanol and methane, the production of hydrogen gas, livestock feed, use as organic fertilizer due to its high N:P ratio, energy cogeneration (electricity and heat); and the extraction of compounds including a large range of fine chemicals and bulk products, such as fats, polyunsaturated fatty acids, oil, natural dyes, sugars, pigments, antioxidants and high-value bioactive compounds. Other cultivatable microorganisms include but are not limited to methanotrophic bacteria for the remediation of methane, a GHG with a warming potential 23 times that of C0₂ over a 100 year period and saprophytic fungi (for the treatment of problematic waste waters with a high load of complex and often chemically inert organic materials). The biomass of these organisms can be utilised as described above for algae and microalgae.

Because of this variety of high-value biological derivatives, with many possible commercial applications, microorganisms, in particular phototrophic microorganisms, could potentially revolutionise a large number of biotechnology areas including biofuels, cosmetics, pharmaceuticals, nutrition and food additives, aquaculture, and pollution prevention.

SUMMARY OF THE INVENTION

With such an important commodity, an improved bioreactor, method and system for cultivating microorganisms, in particular photosynthetic microorganisms, including algae and microalgae, is required.

Accordingly, it is an aim of the present invention to provide an improved bioreactor, method and/or system for cultivating microorganisms, in particular photosynthetic microorganisms.

The present invention has arisen, after the inventors discovered a novel bioreactor system for the cultivation of microorganisms. The system provides a bioreactor and method for generating high density cultivated biomass with an increased productivity and reduced harvesting time when compared to existing technologies.

The present invention is broadly directed to a bioreactor and/or a method and system for cultivating microorganisms, preferably photosynthetic microorganisms.

In one aspect, although not necessarily the broadest aspect, there is provided a bioreactor comprising:

at least one or a plurality of liquid permeable layers comprising a first surface and a second surface;

wherein microorganisms are cultivatable on the first surface of the liquid permeable layer and the second surface is connectable in fluid communication with a fluid source; and wherein the liquid permeable layer is rotatable.

In a second aspect of the invention, there is provided a method for cultivating microorganisms, the method comprising:

rotating at least one or a plurality of liquid permeable layers comprising a first surface and a second surface, wherein the second surface is in fluid communication with a fluid source while cultivating the microorganisms on the first surface.

In a third aspect of the invention, there is provided a system for cultivating microorganisms, the system comprising:

at least one or a plurality of liquid permeable layers comprising a first surface comprising microorganisms and a second surface in fluid communication with a fluid source; and

a rotation member for rotating the liquid permeable layer, to facilitate microorganism growth.

The liquid permeable layer is rotated or rotatable to provide the microorganisms being cultured with sufficient conditions for maximum growth, such as for example, light and C0₂.

In one embodiment* the bioreactor further comprises at least one rotation member.

Suitably, the rotation of the at least one liquid permeable layer is facilitated by said rotation member.

The rotation member may be manually operated and/or may be automated. For example, the rotation member may be manually operated by a handle or may be automated by a motor, or by wind, solar and/or water powered apparatus, or a combination of the above.

In one embodiment, the at least one liquid permeable layer may be rotated or rotatable by a handle.

In another embodiment, the at least one liquid permeable layer may be rotated or rotatable by a motor.

In one embodiment, the at least one liquid permeable layer may be rotated or rotatable by wind, solar and/or water powered apparatus.

In one embodiment, the at least one liquid permeable layer is rotated or rotatable continuously.

In another embodiment, the at least one liquid permeable layer is rotated or rotatable intermittently.

In one embodiment, the rotation member rotates a platform comprising said at least one liquid permeable layer. Preferably said at least one liquid permeable layer is rotated or rotatable about an axis. More preferably said at least one liquid permeable layer is rotated or rotatable about a central axis of the liquid permeable layer or the bioreactor.

Suitably, rotation provides light exposure to a substantial portion of the first surface of the at least one liquid permeable layer.

In one embodiment, the bioreactor comprises a single liquid permeable layer. In a particular embodiment, the single liquid permeable layer may be cultivated with microorganisms.

Preferably, the single liquid permeable layer may be cultivated with photosynthetic microorganisms.

In another embodiment, the bioreactor comprises a plurality of liquid permeable layers. In a particular embodiment, the plurality of liquid permeable layers may be cultivated with microorganisms.

Preferably, the plurality of liquid permeable layers may be cultivated with photosynthetic microorganisms.

Suitably, the liquid permeable layers may be provided in a double layer, between which a fluid source is located. The liquid permeable layers may comprise a first surface upon which microorganisms may be cultured to form a biofilm and a second surface connectable in fluid communication with the fluid source. In one embodiment, the same fluid source supplies fluid and nutrients to both liquid permeable layers. In one embodiment, a separate fluid source for each liquid permeable layer may be provided.

In one embodiment, the liquid permeable layer is configured as a sheet. The sheet may be of any size or shape, according to the culturing requirements of the microorganisms. Shapes contemplated by the invention, include without limitation, cylindrical, octahedral, tetrahedral etc. In one embodiment the liquid permeable layer is substantially cylindrical. The liquid permeable layer acts like a membrane allowing fluid to pass from the second surface of the liquid permeable layer through to the first surface of the liquid permeable layer, upon which microorganisms are capable of being cultured.

Preferably, the liquid permeable layer does not allow the passage of microorganisms from the first surface of the liquid permeable layer to the second surface of the liquid permeable layer, thereby reducing the risk of contamination. The liquid permeable layer may be formed from porous and/or perforated material.

Preferably the liquid permeable layer is formed from porous and/or perforated material that allows the selective passing of fluid. Such materials may include but are not limited to any woven, knitted, pleated, printed (e.g., by a 3D printer), felted or otherwise cross-linked synthetic or natural material (e.g., cotton, wool, silk, tree fibres, celluloses, including differing grades of paper (e.g., -acetate, -sulfonate, nitro- ), chitins (e.g., sponges)) or synthetic polymers (e.g., polyesters, artificial sponges, polyacrylates, polyesters, polyamines, polysulfone, polyamides) or specifically nanotechnologically engineered 3-D nano-fibres of either natural or synthetic origin, with or without surface modifications, (e.g., bonded enzymes, adhesive proteins etc.); polystyrene, silicon, nitrocellulose, cellulose acetate, glass fibre, polycarbonate, polyethylene, ceramics, glass, or metallic surfaces. Suitably, these materials may be used alone or in combination and may be modified to allow for the cultivation of a selected microorganism.

In one embodiment, the fluid source may comprise any one or more of the following, without limitation: water; nutrients; water and nutrients; growth media for microorganism cultivation; waste waters and/or secondary treated sewage.

In one embodiment, the waste water and/or secondary treated sewage may be treated and/or filtered by the microorganisms.

In a particular embodiment, the fluid source is provided in the form of a fluid conducting layer. Preferably, the fluid conducting layer is in fluid communication with the second surface of the liquid permeable layer. Preferably the fluid conducting layer is configured to provide fluid to a substantial portion of the liquid permeable layer. Suitably, the fluid conducting layer comprises a fluid conducting material, examples of which include but are not limited to: fabric; foam; glass fibres; synthetic polymers (e.g., polyesters, polyacrylate, polyamine, polyamide, artificial sponge etc); natural fibres (e.g., cotton, wool, sponge, hemp, tree fibre etc); 3D materials (e.g., meshed nano-fibres, spun or printed 3D matrixes) or a combination thereof. Preferably, the fluid conducting material comprises fabric. The fabric maybe woven, knitted, a felt, mesh, cross-linked, or a combination thereof. More preferably, the fluid conducting material comprises capillary matting. The fluid conducting material provides at least fluid and/or nutrients and/or support to the growing microorganisms. · In one embodiment, the bioreactor further comprises a fluid reservoir.

Suitably, the fluid reservoir supplies the fluid source with fluid and optionally nutrients. Suitably, the fluid source may be transported from the fluid reservoir to the second surface of the liquid permeable layer.

In one embodiment the bioreactor further comprises a pump. Preferably, fluid may be pumped from the fluid reservoir to the second surface of the liquid permeable layer. More preferably, fluid may be pumped from the fluid reservoir to the fluid conducting layer. Alternate examples of fluid transport, include without limitation, capillary action, gravity, rotational forces, etc.

In one embodiment, the bioreactor further comprises a light source.

Preferably, the light source provides light to a substantial portion of the first surface of the liquid permeable layer.

In one embodiment, the light source provides continuous light.

In another embodiment the light source provides intermittent light. The light source may provide a combination of both continuous and intermittent light. The light requirements may depend on the requirements of the microorganisms. The light source may be provided by natural light (e.g., sunlight) or may be provided by an artificial source such as a lamp.

In a further embodiment, the bioreactor is contained within a housing. Preferably, the housing allows light to penetrate through to the culturing microorganisms. More preferably, the housing is transparent.

In one embodiment, the bioreactor further comprises a gas source for the supply of C0₂ or other gases to the liquid permeable layer (e.g., methane). The gas requirements may depend on the requirements of the microorganisms for facilitating growth.

The present invention is applicable to all microorganisms. Preferably, the microorganisms are photosynthetic microorganisms. More preferably, the microorganisms are algae, microalgae or cyanobacteria.

Suitably, the microorganisms are capable of forming a biofilm, examples of which include, without limitation: photosynthetic microorganisms (e.g., algae, microalgae and blue algae); methanotrophic microorganisms; yeast; benthic microorganisms and combinations thereof.

More suitably, the photosynthetic microorganisms include cyanobacteria, the Rhodophyta (red algae), the Chlorophyta (green algae), Dinophyta, Chrysophyta (golden-brown algae), Prymnesiophyta (haptophyta), Bacillariophyta (diatoms), Xanthophyta, Eustigatophya, Rhaphidophyta and Phaeophyta (brown algae) or a combination thereof. Non-limiting examples of photosynthetic microorganisms that form biofilms include: Scenedesmus obliquus (Chlorophyta), Isocrysis glabana (haptophyta), Nannochloropsis sp. (Eustigatophya), Tetraselmis Suecica (Chlorophyta), Phaeodactylum tricomutum (Bacillariophyta), Botryococcus braunii (Chlorophyta) and Spirulina (Cyanobacteria).

According to the invention, after cultivation, the microorganisms may be harvested from the liquid permeable layer. Harvesting may occur through loosening the microorganisms from the liquid permeable layer with a variety of means, examples of which include, although are not limited to physical scraping, fluid washing, chemical treatment, agitation, mechanical manipulation and/or drying. Harvesting may be undertaken with the liquid permeable layer in place, or after removal of the liquid permeable layer.

In one embodiment, the microorganisms are harvested from the liquid permeable layer when the desired level of biomass is cultivated.

In a further aspect, the bioreactor, method and system for cultivating microorganisms of the invention may be used for the production of biomass, biofuels, animal feed, waste water remediation, the production of high value compounds (e.g., oils), C0₂ remediation and/or the production of fertilizer or a combination thereof.

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prioT art is widely known or forms part of the common general knowledge in the field.

As used in this specification the indefinite articles "a" and "an" may refer to one entity or a plurality of entities and are not to be read or understood as being limited to a single entity.

As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

BRIEF DESCRIPTION OF THE DRAWINGS

To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, preferred embodiments of the invention will be described by way of example only with reference to the accompanying drawings, wherein:

FIG. 1 shows a perspective view of the bioreactor according to an embodiment.

FIG. 2 shows a cross section view of a portion of the bioreactor according to an embodiment.

FIG. 3 shows a cross-sectional view of the bioreactor, according to an embodiment.

FIG. 4 shows a cross-sectional view of the bioreactor according to an embodiment.

FIG. 5 shows a perspective view of the bioreactor according to two different embodiments.

FIG. 6 shows both a side view and top view of six alternate embodiments of the bioreactor (labeled I- VI).

FIG. 7 shows a perspective view of the bioreactor as shown in embodiment V of FIG. 6.

FIG. 8 shows an example of a bioreactor arrangement as shown in embodiment IV of FIG. 6.

FIG. 9 shows a dense bio film of algae growing on a first surface of a vertical liquid permeable layer.

FIG. 10 shows the harvesting process of three different microalgal cultivation systems, including an algal culture grown on a liquid permeable layer; a conventional laboratory algal liquid suspension culture; and a further algal liquid suspension culture sourced from a different location, as discussed in the Examples.

DETAILED DESCRIPTION OF THE INVENTION

In one general embodiment, the present invention resides in a method and/or system for cultivating microorganisms, preferably photosynthetic and other benthic microorganisms and a bioreactor comprising at least one liquid permeable layer, comprising a first surface and a second surface, wherein photosynthetic microorganisms are cultivatable on the first surface of the liquid permeable layer and the second surface is connectable in fluid communication with a fluid source, and wherein the liquid permeable layer(s) is rotatable.

The bioreactor may further comprise a rotation member, the rotation member operating to rotate the liquid permeable layer(s).

As shown in FIG. 1 , which is a perspective view of a bioreactor 100 according to one embodiment, bioreactor 100 comprises a liquid permeable layer 110 comprising a first surface 1 1 1 and a second surface 1 12, which in the embodiment shown in FIG. 1, the liquid permeable layer 110 is cylindrical and in a vertical orientation. As further shown in FIG. 1 , the first surface 1 1 1 of the liquid permeable layer 1 10 is shown to cultivate photosynthetic microorganisms 150, such as algae inclusive of micro algae. The bioreactor 100 of FIG. 1 is mounted on a stand 140 with a rotation member 130, which when in use, in the embodiment shown facilitates the rotation of the liquid permeable layer 110 vertically about a central axis 180. The liquid permeable layer 110 of the bioreactor 100 of FIG. 1 is supplied with water and nutrients from a fluid reservoir 160.

Liquid permeable layer 1 10 may be constructed from any materials, either naturally porous or engineered to be porous, and/or perforated, for allowing fluid to permeate and facilitating adherence of the photosynthetic microorganisms 150 to be cultivated. The bioreactor 100 shown in FIG. 1, in one embodiment is situated in a housing 200, which allows light to penetrate through to the culturing photosynthetic microorganisms 150.

FIG. 2 shows a cross section view of a portion of a bioreactor. The liquid permeable layer 110 is shown to comprise a first surface 111 upon which photosynthetic microorganisms 150 are cultivated as a biofilm 151 and a second surface 112. The second surface 112 of the liquid permeable layer 110 is shown to be in fluid communication with a fluid source 120. In one embodiment, the fluid source 120 comprises a fluid conducting layer 121. It will be appreciated that fluid conducting material may be used to provide fluid and nutrients to the photosynthetic microorganisms 150. In the embodiment shown in FIG. 2, when in use, the photosynthetic microorganisms 150 are constantly supplied with water and nutrients via the liquid permeable layer 110 while also being provided with light and C0₂.

FIG. 3 shows a cross sectional view of one embodiment of the bioreactor 100. The inventors as described in the examples, cultivated photosynthetic microorganisms on two static liquid permeable layers either in full light or limited light to determine whether the level of light had an effect on the level of cultivated biomass. The liquid permeable layers were static during the experiments, although are capable of being rotated. In the embodiment shown in FIG. 3, the bioreactor 100 may be static as described above or may be rotated. The bioreactor 100, is arranged vertically on a stand 140, and comprises two liquid permeable layers 110, between which a fluid source 120 is located and wherein the liquid permeable layers 110 comprise a first surface 1 1 1 wherein photosynthetic microorganisms 150 are cultured to form a biofilm 151 and a second surface 1 12 in fluid communication with the fluid source 120. In this embodiment, the same fluid source 120 supplies fluid and nutrients to both liquid permeable layers 110 and the fluid source is shown to comprise a fluid conducting layer 121. The fluid source can be seen in FIG. 3 to be supplied with water and nutrients from a fluid reservoir 160, wherein, when in use, the water and nutrients are pumped via pump 170 to the fluid conducting layer 121. Although a separate fluid source 120 for each liquid permeable layer 110 is also contemplated. It will also be appreciated that varying the growth conditions of photosynthetic microorganisms 150, and in particular algae, will vary the rate of culturing and the final biomass concentration. As further shown in FIG. 3, photosynthetic microorganisms 150 provided with limited light grown on a liquid permeable layer 1 10 of the bioreactor 100 results in a reduced culturing rate and a reduced overall biomass concentration when compared with photosynthetic microorganisms 150 provided with full light grown on a liquid permeable layer 1 10 of the bioreactor 100. In one embodiment, the light source 190 as shown in FIG. 3 may be natural light (e.g., the sun) or may be provided by an artificial source.

FIG. 4 shows a cross section view of a bioreactor 100, in use, wherein the photosynthetic microorganisms 150, are shown as a uniform layer cultured on the first surface 111 of liquid permeable layer 1 10, wherein the liquid permeable layer 1 10 has been configured as a cylinder and mounted on a stand 140 in a vertical orientation. The stand 140 comprises a rotation member 130 which in the embodiment shown in FIG. 4 is releasably coupled or connected to a motor 210 which facilitates rotation. The stand 140 upon which the bioreactor 100 shown in FIG. 4 is positioned, is constructed such that the substantially cylindrical liquid permeable layer 110 rotates about a central axis 180. The second surface 1 12 of the liquid permeable layer 110 as shown in FIG. 4 is in fluid communication with a fluid source 120 which is shown to comprise a fluid conducting layer 121. The fluid conducting layer 121 can be seen in FIG. 4 to be supplied with water and nutrients from a fluid reservoir 160, wherein, when in use, the water and nutrients are pumped via a pump 170 to the fluid conducting layer 120. When in use, the bioreactor 100 shown in FIG. 4 is rotated about a central axis 180 and the first surface 1 11 of the liquid permeable layer 1 10 upon which the photosynthetic microorganisms 150 are cultured is exposed to full light and limited light intermittently as shown by the light sources 190.

FIG. 5 shows a perspective view of the bioreactor 100 according to two different embodiments. It will be appreciated that the positioning of the liquid permeable layer 1 10, upon which the photosynthetic microorganisms 150 are cultured relative to the light source 190 and/or any further required growth conditions may be varied to enhance the culturing of the specific photosynthetic microorganisms 150. In the embodiment shown in FIG. 5 A, the liquid permeable layer 110 is cylindrical and mounted on a stand 140 in a vertical orientation. The stand 140 comprises a rotation member 130 which in the embodiment shown in FIG. 5 is releasably coupled or connected to a motor 210 which facilitates rotation. The stand 140 pon which the bioreactor 100 shown in FIG. 5 is positioned, is constructed such that the cylindrical liquid permeable layer 110, when in use, rotates about a central axis 180, wherein the light source 190 emits light from above the bioreactor 100. The liquid permeable layer 110 in FIG. 5A is in fluid communication with a fluid source. The fluid source in FIG. 5A is supplied with water and nutrients from a fluid reservoir 160, wherein, when in use, the water and nutrients are pumped via a pump 170 to the fluid source. In the embodiment shown in FIG. 5B, the cylindrical liquid permeable layer 110 is positioned at an angle to the light source 190 to ensure the greatest exposure of the photosynthetic microorganisms 150 cultured on the liquid permeable later 1 10 to the light source 190. It will be appreciated that in some embodiments, an intermittent source of light may be preferred. As in FIG. 5B, the liquid permeable layer 110 is in fluid communication with a fluid source. The fluid source in FIG. 5B, is supplied with water and nutrients from a fluid reservoir 160, wherein, when in use, the water and nutrients are pumped via a pump 170 to the liquid permeable layer 110. As shown in FIG. 5A and 5B, the bioreactor 100 is situated in a housing 200, which allows light to penetrate through to the cultivating photosynthetic microorganisms 150.

FIG. 6 shows both a side view and top view of six alternate embodiments of the bioreactor 100 (labeled I- VI), wherein the liquid permeable layer 110 is configured to comprise different structures arranged around a central axis 180 and when in use, rotated about that axis 180. Embodiment I of FIG.6 comprises at least one liquid permeable layer 1 10 as a panel, wherein, either one or both sides of the panel comprise a first surface of the liquid penneable layer 1 10 for culturing photosynthetic microorganisms. Embodiment II of FIG. 6 comprises one liquid permeable layer 110 as a cylinder. Embodiment III of FIG. 6 comprises at least one liquid permeable layer 110 as an octagon. Embodiment IV of FIG. 6 comprises at least one liquid permeable layer 1 10 as two panels forming a cross. Embodiment V of FIG.6 comprises at least one liquid permeable layer 110 as three intersecting panels forming a stellate structure and embodiment VI of FIG. 6 comprises at least one liquid permeable layer 110 configured as four intersecting panels forming a stellate structure. Each of the six different embodiments in use, would be rotated around a central axis 180 to ensure maximum culturing conditions.

FIG. 7 shows a perspective view of an embodiment of the bioreactor 100 as shown in embodiment V of FIG. 6. In the embodiment shown in FIG. 7, there are two liquid permeable layers 110, comprising a first surface 11 1 wherein photosynthetic microorganisms 150 are cultured to form a biofilm 151 and a second surface 112 in fluid communication with a fluid source 120 which is shown to comprise a fluid conducting layer 121 provided on each separately spaced panel 220. In this embodiment, a separate fluid conducting layer 121 supplies fluid and nutrients to the liquid permeable layers 1 10. Although the same fluid conducting layer 121 for each liquid permeable layer 1 10 is also contemplated. When in use, the bioreactor 100 of the embodiment shown in FIG. 7 is rotated about a central axis 180 via rotation member 130, which in this particular embodiment is releasably coupled or connected to a motor 210 which facilitates rotation. Fluid source 120 is supplied with water and nutrients via a pump 170 from fluid reservoir 160 and situated on stand 140.

FIG. 8 shows an example of a bioreactor 100 as shown in embodiment IV of FIG. 6, which rotates about a central axis, via rotation member 130, which in this particular embodiment is releasably coupled or connected to a motor 210, which facilitates rotation and acts as a stand 140.

FIG. 9 shows a dense biofilm of photosynthetic microorganisms 150, specifically a proprietary mix of freshwater algae, growing on a first surface 111 of a vertical liquid permeable layer 110, as cultivated in the experiments undertaken by the inventors.

EXAMPLES

Example 1 is a non-limiting example of a bioreactor.

Proprietary mixed freshwater algae culture was successfully grown on two vertical 50cm x 13cm liquid permeable layers (FIG. 3 and FIG. 10), A and B, constantly supplied with nutrients and water from a fluid source through the liquid permeable layers. For the initial experiment, the vertical liquid permeable layers (A and B) did not rotate. The first surface of liquid permeable layer A was exposed to artificial light 12 hours a day and the first surface of liquid permeable layer B was shaded. A conventional suspended culture in a 2 Litre Schott-bottle was grown in parallel to allow for direct comparison.

In this instance the liquid permeable layers were formed from unprinted newspaper and the fluid source was fibre capillary matting fed with water and nutrients from a fluid reservoir. The algae culture was cultivated for 28 days, using LI medium. Nitrate and phosphate consumption were monitored daily and both nutrients replenished as necessary. In addition, the culture medium for the algae biofilm culture was completely replaced after 7 and 14 days.

The biofilm culture grown on liquid permeable layer A grew the most during the experiment on the top half of the first surface and less well on the bottom half and on the first side of liquid permeable layer B, due to shading.

At the end of cultivating the algae biofilm, both biofilms from the first and second liquid permeable layers A and B, in full light and shade were harvested and analysed for ash-free biomass, Fatty Acid Methyl Ester content (FAME) profile and carbohydrate content. The biofilms from liquid permeable layers A and B were harvested by scraping the algae off the liquid permeable layers with pre-weighted glass microscope slides.

Ash-free dry weight was measured directly on the slides and for biochemical profiling, the biofilm was washed off the slides with deionising water. The suspended algal culture was harvested by centrifugation of 40 ml of culture in a laboratory centrifuge and then transferred into glass beakers for dry weight determination. For biochemical profiling, 400 ml of culture was centrifuged and collected in several steps. Both cultures were then freeze-dried and analyzed.

It was immediately apparent during harvesting that the biofilm harvested from liquid permeable layers A and B was much denser than the suspended culture tested. This was confirmed by the dry weight measurements (Table 1, FIG. 10). On each side, 240 cm² (8 cm x 30 cm) of biofilm were harvested for dry weight, yielding a wet biomass of 2.3596 g for the light exposed side of liquid permeable layer A and 0.0994 g for the shaded side of liquid permeable layer B. After drying, this resulted in 0.2996 g and 0.0177 g of dried biomass, respectively. Adjusted for the whole cultivation surface (50 cm x 13 cm), this equalled 0.9783 g biomass on the light exposed side of liquid permeable layer A and 0.0420 g on the shaded side of liquid permeable layer B, for a total of 0.9783 g biomass from the biofilm. For comparison, the suspended control culture yielded 0.9600 g of dried biomass from 2 litres.

From the dry weight measurements, the biomass density/total solid content of the cultures could be calculated: 13.60% for the light exposed first surface of liquid permeable layer A, 14.49% for the shaded first surface of liquid permeable layer B and 0.048% for the suspended culture. The biofilm was 283 and 302 times more concentrated, depending on the cultivation side. On average, adjusted for total biomass produced on each surface, the biofilm has a total solid content of 13.64% equivalent to a concentration factor of 284 compared to the suspended culture.

For comparison, the same calculations were performed for an exemplary culture from a site in Townsville, Australia. Approximately 10Ό00 litres of culture were harvested with an Evodos centrifuge, yielding ca. 15000 g of wet algal paste. The paste was freeze-dried for ca 1900 g of dried biomass. The results in a biomass density/solid content of 0.019% for the original culture and a solid content of 13% for the algal paste coming out of the centrifuge, which was marginally lower than the solid content of the biofilm in the pilot experiment.

The biochemical analysis showed that the biofilm had a higher lipid content than the suspended culture: 21.09% for the biofilm cultured on the light exposed first surface of liquid permeable layer A and 19.54% for the biofilm cultured on the shaded first surface of liquid permeable layer B, compared to 12.54% for the suspended culture. FAME content and carbohydrate content was only measured for the biofilm on the light exposed first surface of liquid permeable layer A and the suspended culture, as there was not enough biomass on the shaded first surface of liquid permeable layer B. FAME content was 9.45% (44.9% of total lipid) for the biofilm vs. 5.30% (42.3% of total lipid) for the suspended culture. Carbohydrate content was 46.01% for the biofilm versus 41.96% for the suspended culture. In summary, it was demonstrated that the biomass productivity and quality were equal to or better than that of a suspended algae culture under the same conditions. However, as also demonstrated, the biomass was about 300 times more concentrated during cultivation on a liquid permeable layer and could be easily harvested by scraping the algae off the surface. As determined, productivity clearly differed when the algae growing on the first surface of the liquid permeable layer was provided with differing amounts of light.

As will be appreciated from the foregoing, the present invention provides an improved bioreactor, method and/or system for culturing microorganisms, preferably photosynthetic microorganisms. The bioreactor, method and system disclosed herein advantageously exhibits increased and uniform microorganism growth and productivity for generating high density cultivated biomass, specifically photosynthetic microorganisms, such as algae, as well as reduced contamination of the microorganisms and reduced harvesting time.

It will be apparent to persons skilled in the art that many modifications and variations may be made to the embodiments described without departing from the spirit or scope of the invention.

Each of the embodiments described herein may be used alone or in combination with one or more other embodiments of a bioreactor, method and system.

Throughout the specification, the aim has been to describe the preferred embodiments of the invention without limiting the invention to anyone embodiment or specific collection of features. Various changes and modifications maybe made to the embodiments described and illustrated without departing from the present invention. Table 1: Productivity of a non-rotating, bioreactor compared to a suspended culture

a: Based on the vertical cross-section of a 2 L Schott bottle,

b: Average weighted by dry biomass for each side.

5 c: Not sufficient biomass for this assay.

Claims

CLAIMS:

1. A bioreactor for cultivating microorganisms, comprising;

wherein microorganisms are cultivatable on the first surface of the liquid permeable layer and the second surface is connectable in fluid communication with a fluid source; and

wherein the liquid permeable layer is rotatable.

2. The bioreactor of claim 1 , further comprising a rotation member for rotating the liquid permeable layer.

3. The bioreactor of claim 2, wherein the rotation member is automated and/or manually operated.

4. The bioreactor of any one of claims 1 to 3, wherein the liquid permeable layer is rotatable continuously and/or intermittently.

5. The bioreactor of any one of claims 1 to 4, wherein the liquid permeable layer is rotatable about a central axis of the liquid permeable layer or the bioreactor.

6. The bioreactor of any one of claims 1 to 5, wherein the fluid source comprises a fluid conducting layer.

7. The bioreactor of claim 6, wherein the fluid conducting layer is in fluid communication with the second surface of the liquid permeable layer.

8. The bioreactor of claim 6 or claim 7, wherein the fluid conducting layer comprises a fluid conducting material.

9. The bioreactor of claim 8, wherein the fluid conducting material is selected from the group consisting of: fabric, foam, glass fibres, synthetic polymers, natural fibres and printed materials.

10. The bioreactor of claim 9, wherein the fluid conducting material comprises capillary matting.

11. The bioreactor of any one of claims 1 to 10, wherein the fluid source is selected from the group consisting of: water, nutrients, growth media, waste water and secondary treated sewage.

12. The bioreactor of any one of claims 1 to 11, further comprising a fluid reservoir.

13. The bioreactor of any one of claims 1 to 12, further comprising a light source.

14. The bioreactor of claim 13, wherein the light source is provided by natural light.

15. The bioreactor of claim 13, wherein the light source is provided by an artificial light source.

16. The bioreactor of claim 15, wherein a substantial portion of the first surface of the liquid permeable layer is exposed to light.

17. The bioreactor of any one of claims 13 to 16, wherein the light source provides light intermittently.

18. The bioreactor of any one of claims 13 to 17, wherein the light source provides light continuously.

19. The bioreactor of any one of claims 1 to 18, further comprising a housing.

20. The bioreactor of claim 19, wherein the housing is transparent.

21. The bioreactor of any one of claims 1 to 20, wherein the microorganisms are photosynthetic microorganisms, methanotrophic microorganisms, yeast, benthic microorganisms and combinations thereof.

22. The bioreactor of claim 21 , wherein the microorganisms are

photosynthetic microorganisms.

23. The bioreactor of claim 22, wherein the photosynthetic microorganisms are algae, microalgae and/or cyanobacteria.

24. The bioreactor of any one of claims 1 to 23, further comprising a gas source.

25. A method for cultivating microorganisms, the method comprising:

rotating at least one or a plurality of liquid permeable layers comprising a first surface and a second surface, wherein the second surface is in fluid communication with a fluid source; and

cultivating the microorganisms on the first surface.

26. The method of claim 25, wherein at least one liquid permeable layer is rotated by a rotation member.

27. The method of claim 26, wherein the rotation member is automated and/or manually operated.

28. The method of any one of claims 25 to 27, wherein the liquid permeable layer is rotated continuously and/or intermittently.

29. The method of any one of claims 26 to 28, wherein the rotation member rotates a platform comprising the liquid permeable layer.

30. The method of any one of claims 25 to 29, wherein the liquid permeable layer is rotated about a central axis of the liquid permeable layer.

31. The method of any one of claims 25 to 30, wherein the fluid source comprises a fluid conducting layer.

32. The method of claim 31 , wherein the fluid conducting layer comprises a fluid conducting material.

33. The method of claim 32, wherein the fluid conducting material is selected from the group consisting of: fabric, foam, glass fibres, synthetic polymers, natural fibres and printed materials.

34. The method of claim 33, wherein the fluid conducting material comprises capillary matting.

35. The method of any one of claims 25 to 34, wherein the fluid source is selected from the group consisting of: water, nutrients, growth media, waste water and secondary treated sewage.

36. The method of any one of claims 25 to 35, wherein the fluid source is supplied by a fluid reservoir.

37. The method of any one of claims 25 to 36, wherein the liquid permeable layer is provided with a light source.

38. The method of claim 37, wherein the light source is natural light.

39. The method of claim 37, wherein the light source is an artificial light source.

40. The method of any one of claims 37 to 39, wherein a substantial portion of the first surface of the liquid permeable layer is exposed to the light source.

41. The method of any one of claims 25 to 40, wherein the microorganisms are photosynthetic microorganisms, methanotrophic microorganisms, yeast, benthic microorganisms and combinations thereof.

42. The method of claim 41, wherein the microorganisms are photosynthetic microorganisms.

43. The method of claim 42, wherein the photosynthetic microorganisms are algae, micro-algae and/or cyanobacteria.

44. The method of any one of claims 25 to 43, wherein the liquid permeable layer is provided with one or more gases.

45. A system for cultivating microorganisms, the system comprising:

at least one or a plurality of liquid permeable layers comprising a first surface comprising microorganisms and a second surface in fluid

communication with a fluid source; and

46. The system of claim 45, wherein the rotation member is automated and/or manually operated.

47. The system of claim 45 or claim 46, wherein the liquid permeable layer is rotated continuously and/or intermittently.

48. The system of any one of claims 45 to 47, wherein the rotation member rotates a platform comprising the liquid permeable layer.

49. The method of any one of claims 45 to 48, wherein the liquid permeable layer is rotated about a central axis of the liquid permeable layer.

50. The system of any one of claims 45 to 49, wherein the fluid source comprises a fluid conducting layer.

51. The system of claim 50, wherein the fluid conducting layer comprises a fluid conducting material.

52. The system of claim 51 , wherein the fluid conducting material is selected from the group consisting of: fabric, foam, glass fibres, synthetic polymers, natural fibres and printed materials.

53. The system of claim 52, wherein the fluid conducting material comprises capillary matting.

54. The system of any one of claims 45 to 53, wherein the fluid source is selected from the group consisting of: water, nutrients, growth media, waste water and secondary treated sewage.

55. The system of any one of claims 45 to 54, further comprising a fluid reservoir which provides the fluid source.

56. The system of any one of claims 45 to 55, further comprising a light source to facilitate microorganism growth.

57. The system of claim 56, wherein the light source is natural light.

58. The system of claim 56, wherein the light source is an artificial light source.

59. The system of any one of claims 56 to 58, wherein a substantial portion of the first surface of the liquid permeable layer is exposed to the light source.

60. The system of any one of claims 45 to 59, wherein the microorganisms are photosynthetic microorganisms, methanotrophic microorganisms, yeast, benthic microorganisms and combinations thereof.

61. The system of claim 60, wherein the photosynthetic microorganisms are algae, microalgae and/or cyanobacteria.

62. The system of any one of claims 45 to 61, further comprising a gas source for the supply of one or more gases to the liquid permeable layer, to facilitate microorganism growth.