Screening for yeasts incorporating the exogenous eicosapentaenoic and docosahexaenoic acids from crude fish oil

The screening for yeasts incorporating exogenons eicosapentaenoic acid (EPA ) and docosahexaenoic acid (DHA) into their cellular lipids was conducted. Two percent of oil from fish scraps was added to a yeast isolation medium a s a sole carbon source. From 143 soil samples, we isolated 23 yeast strains , nine of them were found to be capable of quickly assimilating the scrap t sh oil. These nine strains, in addition to four previously isolated triglyc eride-assimilating and lipase-producing strains, Yarrowia lipolytica and th ree Geotrichum species (FO274A, FO347-2 and FO401B), were cultured in a gro wth medium at 30 degrees C. Strains FO726A, FO765A and FO347-2 were selecte d on the basis of dry cell weight production and ability to store EPA and D HA in their cells, and their performance was further compared by varying cu ltivation temperature and time. From 1g of the scrap Lh oil, FO726A yielded 620 mg of dry cells, containing 47.1% lipid, 38.1% triglyceride, 3.3% EPA, and 4.9% DHA, when cultured at 25 degrees C for 36 h. Strain FO726A appare ntly has the highest ability to incorporate EPA and DHA into its cellular l ipids. Results from further experiments showed that the incorporated EPA an d DHA mainly existed in the form of triglyceride in the FO726A cell. These results suggest that FO726A is suitable for the production of cell mass ric h in EPA and DHA for feed.