Production Of γ-linolenic Acid By Mortierella Isabellina Using Crude Glycerol As Carbon Source

Currently? glucose and other traditional carbon sources which come from cereals were used as materials in y-linolenic acid production by fungus fermentation. It may cause some problems with supply of human food and animal feed. Therefore, it has significance to find low cost and easily available carbon sources for fermentation. As the development of biodiesel and olechemical industry, more and more crude glycerol byproduct, which could not be used in food and pharmaceuticals without costly purification, was produced. It will lead to oversupply and waste of crude glycerol.In this paper, crude glycerol was used as a carbon source to produceγ-linolenic acid by Mortierellia isabellina.(1) Through the rejuvenation of Mortierellina isabellina, a No.13 strain which contains high oil and high y-linolenic acid was singled out among 13 strains.(2) In addition, No.5 culture medium was chosen as best from 9 different culture mediums, and would be used in the following fermentations.(3) The effect of glucose,80% concentration glycerol of biodiesel,88% concentration glycerol of oil & fat hydrolysis and pure glycerol as carbon sources on y-linolenic acid production by Mortierellina isabellina were investigated. The results showed that glycerol of biodiesel byproduct was the best carbon source.(4) The single-factor experiment was employed to investigate the effect of culture condition and culture medium component on y-linolenic acid production by using glycerol of biodiesel byproduct as a carbon source. The results indicated that the optimal culture conditions were: temperature 28℃, liquid volume 50mL broth per 250mL flask, fermentation time 9d, initial pH 5 and inoculum 10mL. The optimal concentrations of Mn2+, Cu2+, Ca2+, Zn2+ and Fe2+ were 1.03 mg/L,1.15 mg/L,1.96mg/L,0.68 mg/L,15 mg/L, respectively. The optimal concentrations of peptone, sodium chloride, yeast extract, potassium dihydrogen phosphate, urea, magnesium sulfate and sodium citrate were separately 0.7 g/L,0.6 g/L,0.9 g/L,7.0 g/L, 1.0g/L,0.1g/L,4.0g/L.(5) According to the results of the single-factor experiments, Plackett-Burman design was employed to determine the most important factors. It was found that fermentation temperature, time and urea concentration were the most important factors. (6) Based on the results of Single-factor experiment and Plackett-Burman, the Box-behnken design and response surface methodology were used to optimize the the conditions ofγ-linolenic acid production by Mortierellina isabellina. The results indicated that the optimal conditions were:urea concentration 1.0g/L, fermentation temperature 27.5℃and fermentation time 12 d.(7) Finally, fermentation using the optimized culture conditions produced yield of y-linolenic acid, which was in good agreement with the predicted value.