Strain Breeding And Fermentation Research On γ-linolenic Acid Production By Mortierella Ramanniana

γ- linolenic acid(Gamma linolenic Acid, GLA) is an essential polyunsaturated fatty acids in our bod y, but it has a few content and short duration. It is wide ly used in food, nutrition, medicine, cosmetics, animal feed and other aspects. In recent years, GLA produced from plants and animals has been unable to meet the market demand, however, the one femented by microo rganisms has a lot of adva ntages, such as: fast grow th, easy to cultivate, without geographical restrictions, time characteristics of higher oil prod uction and content, making oil has wide prospect of development [1].In this study Mortierella ramanniana NBRC 8187, the origina l strain, was mutated with a composite method of LUV-LiC l- DES(diethyl sulfate). The mutated strain was prescreeninged by maleic hydrazid plate, and rescreeninged by means of fermentation in shaking flasks. A strain, named M. ramanniana HLY 0902 producing oils with high yield and genetic stability, was successfully ob tained. The dry cell biomass, oil content and yield of GLA reached 31.62 g/L, 52.57% and 0.7197 g/L respectively, which improved by 50.17%, 95.74% and 732.12% than be fore.The culture medium of M. ramanniana HLY 0902 was op timized by or thogonal expe riment, the optimal culture medium compo nent was as follow(g/L): glucose 100, yeast extract 10, KH2PO4 4, NaNO3 1, MgSO4 1. Under the opt imum condition, the yield of GLA reached 1.0344 g/L, which increased by 43.83% than it be fore opt imization. Different metal ions in place of Mg2+ were determined for the effect on GLA production, such as Cu2+, Mn2+, Fe2+ and Zn2+. It was found that Zn2+ had a great impact on the GLA yield which made a 57.37% increase on that be fore opt imization. In add ition, fermentation conditions of the strain HLY 0902 was op timized by single factor experiment: inoculation amount 5mL, broth content 50 mL/250 mL,temperature 22 ℃, duration 168 h, pH 5.5.