Abstract: Mortierella isabellina was found to be used to synthesize unsaturated fatty acids when the fungus was cultivated in a medium consisting of 2% octadecanol,1% yeast extract and Mg ²⁺ with concentration at 25 mmol/Lat 23 ℃ for120 h. The harvested dry cells contained 47.5% lipids, 28.9% carbohydrate and 31.5% protein. The results showed that the lipid selectivity was 30.6%, at a yield of 20.6%. The data also indicated the selectivity of fatty acids in the lipids, was palmatioleic(0.81%), oleic(20.75%), linoleic(1.95%), linolenic(2.19%) respectively. Lowering the concentration of substrates in the medium led to increasing selectivities of both lipids and unsaturated fatty acids synthesized by the fungus, and when mass fraction of octadecanol was 0.5%, the maximal selectivities of the corresponding fatty acid were obtained. Astudy of initial pHof the medium suggested that the maximal selectivity and yield of lipids were obtained at a pHvalue of 7. The octadecanol conversion reached a maximum(88%) when cultivated at 33 ℃, however, the lipid yield reached a maximum(9.7%) at 23 ℃. Mg ²⁺ was found to strongly influence the productivity of lipids and unsaturated fatty acids. For instance, a concentration of 25 mmol/Lof Mg ²⁺ in the culture broth may cause a maximal selectivity(25.7%) and yield(17.6%) of lipids.

Key words: Mortierella isbellina, Octadecanol, Unsaturated fatty acids, Biosynthesis