Abstract: The effects of the glucose, ammonium, metal ion, buffer agents, surfactants and culture temperature on GLA synthesized by Mortierella isabellina were studied, and the mechanism of the change of GLA yield was analyzed by calculating the values of ΣC18/ΣC16, IUFA, (L+G)/O and G/L as the index of fatty acids composition analysis. The results showed that ammonium obviously affected fatty acid △6- desaturation, unsaturated degree and carbon chain elongation with the production of GLA ; Ca2+ enhanced fatty acid △12- desaturation and unsaturated degree; additional 0.3% sodium acetate further enhanced fatty acid △6 -and △12- desaturation;there was significant improvement in fatty acid △6- desaturation and carbon chain elongation at relative low culture temperature.

Key words: GLA (&gamma, -linolenic acid)； fatty acids composition； biosynthesis； Mortierella isabellina；