BIOTECHNOLOGICAL PROCESSES FOR PRODUCTION OF POLY-UNSATURATED FATTY ACIDS

Abstract

Fungal mycelia were found to be new and rich sources of C_2O?-polyunsaturated fatty acids through our screening for wide variety of microorganisms. A soil isolate, Mortierella alpine 1S-4 produced 4.3 g/L (274 mg/g dry mycelia) of arachidonic on cultivation in a medium containing glucose. The value accounted for more than 65% of the total fatty acids in the extracted lipids from the mycelia. The mycelial dihomo-gamma-linolenic acid content of the same fungus was found to increase, (107 mg/g dry mycelia), with an accompanying marked decrease in its arachidonic acid content, on cultivation with sesame oil. This phenomenon was found to be due to a specific repression of the conversion of dihomo-gamma-linolenic acid to arachidonic acid. The fungus produced eicosapentaenoic acid (EPA) when grown at low temperature (12 C). The experimental results with cell-free extracts showed that this temperature-dependent formation of EPA is due to the activation of enzymes(s) in EPA production, probably from arachidonic acid at low temperature. The fungus efficietly converted an oil containing alpha-linolenic acid to an oil containing EPA (yield, 1.8 g/L). This conversion was found to be temperature-independent. Possible advantages of microorganisms as practical sources of the polyunsaturated fatty acids are also described.