Process for the heterotrophic production of microbial products with high concentrations of omega-3 highly unsaturated fatty acids
A process for the heterotrophic or predominantly heterotrophic production of whole-celled or extracted microbial products with a high concentration of omega-3 highly unsaturated fatty acids, producible in a aerobic culture under controlled conditions using biologically pure cultures of heterotrophic single-celled fungi microorganisms of the order Thraustochytriales. The harvested whole-cell microbial product can be added to processed foods as a nutritional supplement, or to fish and animal feeds to enhance the omega-3 highly unsaturated fatty acid content of products produced from these animals. The lipids containing these fatty acids can also be extracted and used in nutritional, pharmaceutical and industrial applications.
1 . A method of producing omega-3 HUFAs, comprising culturing Thraustochytriales in a medium comprising a source of organic carbon and a source of assimilable nitrogen.
2 . A method, as claimed in claim 1 , wherein said Thraustochytriales are selected from the group consisting of Thraustochytrium, Schizochytrium, and mixtures thereof.
3 . A method, as claimed in claim 2 , further comprising culturing said Thraustochytrium, Schizochytrium, or mixtures thereof under nutrient-limited conditions for an effective amount of time, preferably about 6 to 24 hours.
4 . A method, as claimed in claim 1 , further comprising adding to said omega-3 HUFAs or said Thraustochytriales during post-harvest processing of said omega-3 HUFAs or said Thraustochytriales a compound selected from the group consisting of BHT, BHA, TBHQ, ethoxyquin, beta-carotene, vitamin E and vitamin C.
5 . A method, as claimed in claim 1 , wherein said culturing step further comprises limiting the concentration in the medium of said source of assimilable nitrogen and harvesting said Thraustochytriales during said nitrogen limitation.
6 . A method, as claimed in claim 2 , further comprising stressing said Thraustochytrium, Schizochytrium, or mixtures thereof with low temperatures during culturing.
7 . A method, as claimed in claim 1 , further comprising maintaining a high dissolved oxygen concentration in said medium during culturing.
8 . A method, as claimed in claim 2 , wherein said medium further comprises an effective amount of phosphorous to provide sustained growth of said Thraustochytrium, Schizochytrium, or mixtures thereof.
9 . A method, as claimed in claim 2 , wherein said medium further comprises an effective amount of microbial growth factor to provide sustained growth of said Thraustochytrium, Schizochytrium, or mixtures thereof.
10 . A method, as claimed in claim 9 , wherein said microbial growth factor comprises yeast extract.
11 . A method, as claimed in claim 9 , wherein said microbial growth factor comprises corn steep liquor.
12 . A method of producing omega-3 HUFAs, as claimed in claim 1 , further comprising extracting lipids from said Thraustochytriales.
13 . A method, as claimed in claim 12 , further comprising fractional crystallization of the extracted lipids to separate omega-3 HUFAs therefrom.
14 . A method, as claimed in claim 13 , wherein said fractional crystallization comprises the steps of:
a. rupturing microorganism cells to yield ruptured cells;
b. solvent extracting a lipid mixture from the ruptured cells;
c. hydrolyzing the lipid mixture;
d. cold-crystallizing non-HUFAs in said lipid mixture.
15 . A method, as claimed in claim 14 , further comprising removing non-saponifiable compounds from said lipid mixture prior to said cold-crystallization.
16 . A method, as claimed in claim 1 , wherein said carbon source and said nitrogen source comprise ground grain.
17 . A method of producing omega-3 HUFAs, comprising culturing Thraustochytrium in a medium comprising ground grain.