Method and system for the culture of microalgae

• US 9,738,869 B2
• Filed: 05/28/2014
• Issued: 08/22/2017
• Est. Priority Date: 05/29/2013
• Status: Active Grant

• Current Assignee: Centre de recherche industrielle du Québec, Institut national d'optique
• Original Assignee: Centre de recherche industrielle du Québec, Institut national d'optique
• Inventors: Le Bihan, Yann, Daigle, Marc, Grenier, Paul, Levesque, Marc
• Primary Examiner(s): Claytor, Renee
• Assistant Examiner(s): FERNANDEZ, SUSAN EMILY
• Application Number:
  US14/289,277
• Publication Number:
  US 20140356931A1
• Time in Patent Office: 1,182 Days
• Field of Search: None
• CPC Class Codes: C12M 21/02 Photobioreactors culturing algae A01G33/00, A01H4/001, C12N1/12
• CPC Class Codes: C12M 23/18 Open ponds; Greenhouse type or underground installations
• CPC Class Codes: C12M 29/06 Nozzles; Sprayers; Spargers; Diffusers per se B01F23/231, B01J19/26
• CPC Class Codes: C12M 31/08 by conducting or reflecting elements located inside the reactor or in its structure
• CPC Class Codes: C12M 41/06 of illumination
• CPC Class Codes: C12M 41/42 of agitation speed
• CPC Class Codes: C12N 1/02 Separating microorganisms from their culture media
• CPC Class Codes: C12N 1/12 Unicellular algae; Culture media therefor as new plants A01H13/00

Abstract

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.

Claims

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:

CO₂ 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, CO₂, SO₂, NO₂, 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).