Studies On Breeding High-yield Lipid Strain And Optimizing Its Fermented Conditions

With the growth of population, animal and vegetable oil have already couldn't meet the needs of human for daily life. The oil manufactured through microbial is characterized with low cost, short period, not affected by weather etc. In this study, different carbohydrates were used to screen strains for lipids manufacturing, Described herein are preliminary screening studies on strains for different carbohydrates assimilation to produce microbial lipids, and on strains which can decompose the cellulose of rice straw. The bioconversion of the rice straw hydrolysate to lipid by oleaginous microorganism was studied, the results are as follows:1. Oleaginous fungi F-3 and oleaginous yeast F-6 were obtained by shaking flask fermentation with glucose, D-xylose, L-arabinose and the mixture of the three respectly as carbohydrate resource, which have potential ability of lipids manufacturing under the condition of mixed sugar.2. Strain screening was conducted on a large scale to decompose the cellulose of rice straw. The result of the experiment displayed that the degradation ratio of cellulose and hemicellulose were 7.86% and 9.82% for F-3 after 5d cultivation in solid state fermentation; strains D6/D7 got better degradation productivity in liquid solid state fermentation. The concentration of soluble total sugar was up to 2.62 mg/mL in the seventh day of flask culturing.3. The rice straw was used as substrate, by virtue of single-factor text and uniform design to optimize the solid-state fermenting conditions of F-3. The results indicated that the lipid content reached up to 14.54% (close to the lipid content of 15.13% by shaking flask fermentation of glucose), which improved 52.89% compared with 9.51% before optimized. And the lipid yield reached 5.42%. Meanwhile, the degradation ratio of hemi-cellulose and cellulose of rice straw were 8.79% and 11.32% respectively.4. To increase the yield, oleaginous yeast F-6, as an original strain, was mutated by UV treatment. A enhanced variant called FUV-6 was obtained, after optimized, the oil production of FUV-6 was up to 5.202g/L, and 21.00% higher compared with 4.299g/L before optimized. The oil production of FUV-6 reached 2.712g/L,32.21% using the rice straw hydrolysate as carbon source through shaking flask fermentation, which increased 127.90% compared with 1.191g/L before mutated using mixed sugar as carbon source.