Method and system for the culture of microalgae
Described is a method for the culture of microalgae, comprising: providing a consortium of at least two living species of microalgae; culturing under illumination the consortium in a controllable bioreactor and under non-sterile aqueous culture conditions; and controlling the culture conditions for affecting at least one of the following output: (i) flocculation and/or settling of said consortium of microalgae; and (ii) adhesion of the microalgae to surfaces of the bioreactor; wherein said culture conditions are controlled to promote (i) and/or to minimize (ii), without adversely affecting growth of the consortium of microalgae. It is also possible to control the culture conditions for affecting iii) the protein, carbohydrate, and/or fat content of the said microalgae consortium. A system for carrying out the method is also described.
1. A method for the culture of microalgae, comprising:
providing a consortium of at least two living species of microalgae;
culturing under illumination said consortium in a controllable bioreactor and under non-sterile aqueous culture conditions; and
controlling an amount and/or type of nutrients to minimize adhesion of the microalgae to surfaces of the bioreactor without adversely affecting growth of said consortium of microalgae;
wherein controlling the amount and/or type of nutrients consists essentially of providing a combined source of nitrogen-phosphorus-potassium (N—P—K).
2. The method of claim 1 , wherein said adhesion is controlled to facilitate and/or promote harvesting of microalga.
3. The method of claim 1 , further comprising the step of harvesting sediments or flocks of microalgae.
4. The method of claim 1 , further comprising controlling culture conditions for affecting proteins, carbohydrates and/or lipids content of said consortium.
5. The method of claim 1 , further comprising regulating mixing of the consortium.
6. The method of claim 5 , wherein said mixing comprises a mixing at an aqueous culture speed of about 1 cm/sec to about 10 cm/sec.
7. The method of claim 5 , wherein said mixing comprises a gaseous bubbling at a flow rate of about 0.001 to about 0.1 volume of gas per volume of reactor per minute (VVM).
8. The method of claim 1 , wherein controlling the amount and/or type of nutrients comprises maintaining in culture a nitrogen concentration between 0.5 mg/L and 5 mg/L.
9. The method of claim 1 , further comprising controlling the culture conditions according to a predetermined use of the consortium that is selected from the group consisting of: CO 2 biofixation, elimination or capture of undesirable gaseous substances, production of a protein-rich algal biomass, production of a lipid-rich algal biomass, and production of a carbohydrate-rich algal biomass.
10. The method of claim 9 , wherein said controlling comprises maintaining the culture conditions at a temperature between about 9° C. and about 12.5° C.
11. The method of claim 10 , wherein maintaining said temperature increases a relative content of omega-3 fatty acid of algal biomass.
12. The method of claim 1 , further comprising the step of bubbling into the bioreactor a gas comprising one or more of the following gaseous substances: CO, CO 2 , SO 2 , NO 2 , and COS.
13. The method of claim 10 , wherein said gas is a gas originating from an industrial effluent.
14. The method of claim 1 , further comprising maintaining a minimal microalgae concentration between about 70 mg/l and about 1000 mg/l of culture.
15. The method of claim 1 , further comprising maintaining the culture conditions at a temperature between about 9° C. and about 29° C.
16. The method of claim 1 , further comprising maintaining the culture conditions at a pH between about 6.5 and about 8.5.
17. The method of claim 1 , wherein said consortium comprises indigenous species of microalgae.
18. The method of claim 1 , wherein the bioreactor is an outdoor open bioreactor.
19. The method of claim 18 , further comprising regulating said illumination of the consortium, and wherein regulating illumination comprises optimizing amount of sunlight exposure and/or sunlight intensity by using a sunlight distribution device.
20. The method of claim 19 , wherein regulating illumination further comprises using a mechanical sun-tracking device.
21. The method of claim 19 wherein the sunlight distribution device is partially immersed in the bioreactor.
22. The method of claim 1 , further comprising controlling said culture conditions for promoting flocculation and/or settling of said consortium of microalgae.
23. The method of claim 1 , wherein controlling the amount and/or type of nutrients to minimize adhesion of the microalgae to surfaces of the bioreactor without adversely affecting growth of said consortium of microalgae consists of providing a combined source of nitrogen-phosphorus-potassium (N—P—K).
24. A method for the culture of microalgae comprising:
providing a consortium of at least two living species of microalgae;
culturing under illumination said consortium in a controllable bioreactor and under non-sterile aqueous culture conditions;
maintaining the culture conditions at a pH between about 6.5 and about 8.5; and
controlling a nitrogen concentration in the culture between 0.5 mg/L and 5 mg/L
to minimize adhesion of the microalgae to surfaces of the bioreactor, without adversely affecting growth of said consortium of microalgae.
25. The method of claim 24 , wherein maintaining said nitrogen concentration consists essentially of providing a combined source of nitrogen-phosphorus-potassium (N—P—K).
26. The method of claim 24 , further comprising controlling said culture conditions for promoting flocculation and/or settling of said consortium of microalgae.
27. The method of claim 24 , wherein maintaining said nitrogen concentration consists of providing a combined source of nitrogen-phosphorus-potassium (N—P—K).