Research On Screening Of Oleaginous Mucor And Optimization Of Lipid Fermentation Technology

Biodiesel had been one of most promising substitute of fossile energy because of its biodegradation, reduced toxicity and a lower emission profile. Short supply of raw oil had been a bottleneck for biodiesel production. Microbial lipid could be a potential and ideal raw material for biodiesel production. In this thesis, a potential lipid producer for biodiesel production was screened and identified. Then the optimal lipid fermentation technology was determined. Finally the source of NADPH was investigated through analyzing the effects of yeast extract and peptone on lipid synthesis. Research results were as followed:(1) An oleaginous fungus with lipid content 30.2% was isolated from rangeland soil. The fatty acids of the strain were composed primarily of oleic acid(46.26%), palmitic acid(22.58%), γ-linolenic acid(13.68%), linoleic acid(6.68%). The biodiesel properties were evaluated based on predictive equations and basically satisfied the specifications of biodiesel standards. Therefore, the strain could be considered as potential strain to produce lipid for biodiesel manufacture.(2) The strain 1-5 was identified based on an integrated approach including morphological characteristics, biochemical characteristics and 18 S rDNA sequences analysis. The morphological and biochemical characteristics were similar to Mucor sp. The 18 S rDNA sequences had 99% identity with Mucor sp. EA 2010 b stain ERRL. Therefore, it was concluded that the strain RBB 1-5 was belonged to Mucor sp. and named as Mucor sp. RBB 1-5.(3) Single factor experiment and response surface analysis were used to determin the fermentation technology for lipid production. Peptone was found to be more suitable for lipid accumulation than yeast extract. The optimal culture medium components obtained were glucose 103.32 g/L, peptone 3.21 g/L, soybean meal 3.29 g/L, KNO3 3.0 g/L, Na2HPO4 2.0 g/L, MgSO4·7H2O 1.0 g/L respectively. The optimal culture conditions were pH 6.0 and loading volume 50 m L/250 m L, temperature 28℃, culture time 5 days. Lipid yield 10.38 g/L was achieved under these conditions, enhancing about 2.15 times compared to the value before optimization.(4) The influencing mechanism of peptone and yeast extract on lipid accumulation was studied. By analyzing the influence of peptone on enzymatic activities of ME and G6 PDH, respectively invovled in tricarboxylic acid cycle and pentose phosphate pathway the influencing mechanism of peptone and yeast extract on lipid accumulation was studied. It was indicated the change of ME enzymatic activity was consistent with lipid dynamic change and the change of G6 DPH enzymatic activity is not associated with lipid accumulation. Peptone group was shown high ME enzymatic activity compared with yeast extract. Therefore, peptone benefited lipid accumulation through influencing TCA pathway, enhancing ME enzymatic activity, thus increaseing the supply of NADPH.