Vlicrobial Lipid Production By Mortierella Isabellina M2Using Corn Fibre Hydrolysates

Lipids is one of primary substance which is makes up sustain life activity, and it is also an important industrial raw materials which is widely applications. Currently, lipids were mainly from animals and plants. As study in depth, lipids obtained from microbial fermentation provides a new way to obtain lipids resources, it is not only can alleviate the situation of scarce resources of animal and plant lipids, but also can reuse waste resource by oil-producing strains. Mortierella isabellina M2has been screened out and proved to be able to accumulate lipid with5-carbon sugar and6-carbon sugar in our previous study. The effects of acidic hydrolysis condition on hydrolysis rate were studied systematically. It also discussed the feasibility of replacement of glucouse by corn fiber acidic hydrolysate as the carbon source for fermentation microbial lipid. The fermentation parameters on the flask batch culture and bioreactor culture useing enzymic hydrolysate as the carbon souses were also studied. Finally the conditions of microbial lipids extracted by supercritical CO2were studied.The optimal conditions through orthogonal experiment for corn fiber acidic hydrolysis were as follows:sulfuric acid0.75%, hydrolysis temperature140℃, solid-liquid ratio1:6, reaction time90min. Under this condition, the corn fiber hydrolysis rate reached65.57%, and the hydrolysate sugars composition was analysed by HPLC:29.76%glucose,26.32%xylose,17.20%fructose.Corn fibre acidic hydrolysates were used as feedstock for microbial lipids production by Mortierella isabellina M2. The technological conditions in shake-flask scale on the yield of microbial oil were as follow:Corn fiber hydrolysates concentration, pH and fermentation time. For the optimized production with a26.47g/L biomass and12.93%lipid concentration, the technological parameters were as follow:Com fiber hydrolysates concentration60g/L, initial pH of6.0and fermentation time96h. Microbial lipid production by corn fibre enzymic hydrolysates is more suitable for industrial production than acidic hydrolysates.Microbial lipid was produced by Mortierella isabellina M2using corn fibre enzymic hydrolysates. The fermentation conditions were systemically investigated in flask batch culture, bioreactor culture, respectly. Such as corn fibre hydrolysate concentration, nitrogen source, stirring speed and air flow rate. The optimal conditions were as follow:corn fibre hydrolysate concentration at60g/L,0.2%(NH4)2SO4as nitrogen source, stirring speed200rpm, air flow rate0.5v/v/m,28℃culture96h. Under this condition, the biomass and lipid content reached19.43g/L and41.58%, respectly. Supercritical CO2fluid technology was used for microbial lipid obtained. The results of single factor experiments showed that the optimal extraction temperature, pressure and time were40℃,30Mpa,3h, respectly, and the extraction rate is41.72%. GC analysis demonstrated that the lipid composition from fermentation was similar to vegetable oil, while the major fatty acids were oleic, palmitic and linoleic acids. Thus the microbial oil is a promising feedstock for biodiesel production, and its unsaturated fatty acid which show great potential applications in food, medicine and cosmetics industries were reached77.12%. After purification by molecular distillation, the unsaturated fatty acid in the product can reach94.62%. This study is of great significance to realize the high-value utilization of biomass resources and reduce the microbial oil production cost as well. It also helps to solve the bottleneck problem of oil raw material which hinders the large-scale production and wide application of biodiesel.