Methods of recovering oil from microorganisms
Provided herein are methods of recovering oil from microorganisms. The methods are useful, for example, in obtaining nutritional oils and/or lipid biofuels. The methods of recovering oil described herein include contacting a population of microorganisms with one or more enzymes under conditions that cause disruption of the microorganisms, concentrating the disrupted microorganisms, and extracting lipids from the disrupted microorganisms at high temperature in the presence of a salt and in the absence of solvent.
1. A method of recovering oil from oil-producing microorganisms comprising
(a) culturing the microorganisms in an aqueous fermentation medium comprising aqueous components;
(b) contacting the microorganisms in the aqueous fermentation medium with an enzyme under conditions that causes enzymatic hydrolysis of the microorganisms, wherein the hydrolyzed microorganisms comprise the oil;
(c) separating the hydrolyzed microorganisms comprising the oil from the aqueous fermentation medium;
(d) extracting the oil from the separated hydrolyzed microorganisms of step (c) at a high temperature, in the presence of a salt and in the absence of an organic solvent, wherein extraction separates the oil from the hydrolyzed microorganisms; and
(e) recovering the oil of step (d).
2. The method of claim 1 , wherein the fermentation medium has a salt concentration of from about 5 g/L to about 20 g/L.
3. The method of claim 2 , wherein the salt comprises sodium chloride.
4. The method of claim 1 , wherein the contacting step is performed in the presence of 0.05% to 1% enzyme.
5. The method of claim 1 , wherein the contacting step is performed in the presence of 0.001% to 0.4% enzyme.
6. The method of claim 1 , wherein the contacting step is performed at a pH of from 5 to 8.5.
7. The method of claim 1 , wherein the contacting step is performed at a temperature of from about 50° C. to about 70° C.
8. The method of claim 1 , wherein the enzyme is a protease.
9. The method of claim 1 , wherein the concentration of salt added during the extraction step is from 1% to 5% (v/v).
10. The method of claim 9 , wherein the concentration of salt added during the extraction step is from 4% to 5% (v/v).
11. The method of claim 9 , wherein the salt comprises sodium sulfate.
12. The method of claim 1 , wherein the oil-producing microorganisms are selected from the group consisting of algae, fungi, bacteria and protists.
13. The method of claim 1 , wherein the oil-producing microorganisms are selected from the genus Thraustochytrium, Schizochytrium and mixtures thereof.
14. The method of claim 1 , wherein the oil comprises docosahexaenoic acid.
15. The method of claim 1 , wherein 80-90% of the aqueous components are separated from the hydrolyzed microorganisms comprising the oil.
16. The method of claim 1 , wherein the contacting step is performed at pH 8.0.
17. The method of claim 1 , wherein the high temperature during the extraction step is 85° C.
18. The method of claim 1 , wherein the separating step comprises centrifugation.
19. The method of claim 1 , wherein at least 80% of the oil is recovered.
20. The method of claim 1 , wherein at least 90% of the oil is recovered.