Buoyant triacylglycerol-filled green algae and methods therefor
Cultures of Chlamydomonas are disclosed comprising greater than 340 mg/l triacylglycerols (TAG). The cultures can include buoyant Chlamydomonas . Methods of forming the cultures are also disclosed. In some embodiments, these methods comprise providing Chlamydomonas growing in log phase in a first culture medium comprising a nitrogen source and acetate, replacing the first culture medium with a second medium comprising acetate but no nitrogen source, and subsequently supplementing the second medium with additional acetate. In some embodiments, a culture can comprise at least 1,300 mg/l triacyglycerols. In some embodiments, cultures can be used to produce a biofuel such as biodiesel.
1. A microorganism of strain Chlamydomonas reinhardtii CC4348, wherein said microorganism is buoyant in an aqueous medium.
2. A microorganism in accordance with claim 1 , comprising more than 50% by dry weight triacylglycerides.
3. A microorganism in accordance with claim 1 , comprising at least 60% by dry weight triacylglycerides.
4. A microorganism in accordance with claim 1 , comprising at least 70% by dry weight triacylglycerides.
5. A microorganism in accordance with claim 1 , wherein the microorganism is an isolated microorganism.
6. A culture of microorganisms comprising:
a culture medium comprising an acetate; and
a plurality of microorganisms of claim 1 .
7. A culture in accordance with claim 6 , wherein the culture is a culture of isolated microorganisms.
8. A culture of microorganisms comprising:
a plurality of microorganisms of strain Chlamydomonas reinhardtii CC4348; and
a culture medium, wherein the culture comprises greater than 340 mg/l triacylglycerols, wherein the plurality of microorganisms comprises microorganisms which are buoyant in an aqueous medium.
9. A culture in accordance with claim 8 , wherein the culture comprises at least 360 mg/l triacylglycerols.
10. A culture in accordance with claim 8 , comprising greater than 400 mg/l triacylglycerols.
11. A culture in accordance with claim 8 , comprising at least 800 mg/l triacylglycerols.
12. A culture in accordance with claim 8 , comprising at least 1000 mg/l triacylglycerols.
13. A culture in accordance with claim 8 , comprising at least 1200 mg/l triacylglycerols.
14. A culture in accordance with claim 8 , wherein the culture is a culture of isolated microorganisms.
15. A method of forming a culture comprising microorganisms of claim 1 , comprising, in order:
i) providing a population of the microorganisms growing at log phase in a first aqueous medium comprising a) at least one nitrogen source and b) at least one acetate,
ii) replacing the first aqueous medium with a second aqueous medium, wherein the second aqueous medium comprises at least one acetate but lacks a nitrogen source;
iii) growing the population of microorganisms in the second aqueous medium;
iv) supplementing the second aqueous medium with additional acetate after the replacing the first aqueous medium with a second aqueous medium; and
v) growing the population of microorganisms for at least about 3 days after supplementing the second aqueous medium with additional acetate, whereby the culture comprises greater than 340 mg/l TAG.
16. A method of forming a culture in accordance with claim 15 , wherein growing the microorganisms for at least about 3 days after supplementing the second aqueous medium with additional acetate consists of growing the microorganisms for at least about 3 days up to about 12 days after supplementing the second aqueous medium with additional acetate.
17. A method of forming a culture in accordance with claim 15 , wherein growing the microorganisms for at least about 3 days after supplementing the second aqueous medium with additional acetate consists of growing the microorganisms for at least 5 days up to about 7 days after supplementing the second aqueous medium with additional acetate.
18. A method of forming a culture in accordance with claim 15 , wherein the growing the at least one microorganism to log phase in it liquid medium comprises growing the at least one microorganism for from about 1 day to about 3 days.
19. A method of forming a culture in accordance with claim 15 , wherein the growing the at least one microorganism to log phase in a liquid medium comprises growing the at least one microorganism for about 2 days.
20. A method of forming a biofuel, comprising:
growing a culture in accordance with claim 15 ; and
harvesting cells from the culture.
21. A method of forming a biofuel in accordance with claim 20 , wherein the harvesting cells comprises harvesting buoyant cells.