Culture Medium Optimization And Fermentation Kinetics Analysis Of γ-Linolenic Acid Production By Mortierella Ramanniana

γ-Linoleic acid（Gamma Linolenic Acid,GLA）is one of an essential polyunsaturated fatty acid（PUFA）in human body,commonly used in foods,pharmaceuticals,dietary supplements et al.There are a great deal of physiological activities and properties,such as killing cancer cells selectively,effective treatment of osteoporosis,allergic rhinitis,and heart diseases.In the meantime,GLA has the ability of controlling several other metabolic pathways and minimizing cholesterol levels.Currently,although most commercial GLA products are derived from plant oil,mainly from evening primrose oil,plant-based GLA products cannot meet the increasing market demand.The plant sources can not match advantage with the one femented by microorganisms as a potential origin in development.In this paper,Mortierella ramanniana HLY0902 was taken as the producing strains.By adding a series of exogenous substances in metabolic process,we discussed the effect of these intermediary metabolites on the synthesis of GLA in metabolic regulation.The optimal concentration of nutrients for promoting GLA production by Mortierella ramanniana HLY0902 was determined through single factor experiment with acetate 4 mg/L,pyruvate 6 mg/L,oxaloacetate 10 mg/L,malate 2 mg/L,glutamate 2mg/L,succinate 2 mg/L,citrate 8 mg/L,vitamin B1 2mg/L,vitamin B2 10 mg/L,vitamin PP 4 mg/L,vitamin B6 6 mg/L,vitamin M 8 mg/L.After that,with the preliminary study in laboratory,Plackett-Burman design was applied to screen the significant factors among 16 kinds of nutrient substances which influence the GLA accumulation.The results showed that glucose,yeast extract,KH₂PO₄,citrate were four key factors during the fermentation process.Then,the quadratic mathematical model for the optimal concentration of these four significant factors was established with GLA yield by Box-Behnken design and response surface analysis.Comprehensive these statistic analysis of these designs and the optimum medium formula were glucose 96 g/L,yeast extract 10 g/L,KH₂PO₄ 5 g/L,NaNO₃ 3 g/L,MgSO₄1 g/L,CuSO₄ 0.1 mg/L,citrate 7 mg/L,ZnSO₄ 20 mg/L,MnSO₄ 0.5 mg/L,FeSO₄ 40mg/L,vitamin B1 0mg/L,vitamin B2 10 mg/L,vitamin PP 4 mg/L,vitamin B6 4 mg/L,vitamin M 10 mg/L,acetate 8 mg/L.Under the optimal conditions GLA yield was improved to 1323.6 mg/L,and it increased by 20.67%compared with the result（1050.0mg/L）before optionization.Finally,the shaking-flask-batch fermentation kinetic models of cell growth,lipid formation and glucose consumption were established by Mortierella ramanniana HLY0902.Basing on the experimental data with the method of non-line fitting,the mathematical function was created.The results shows that the fitting precision of these models was high,and the dynamic models could described the metabolic changes largely in the fermentation by Mortierella ramanniana HLY0902,GLA production strains.