Preparation Of Biodiesel From Corn Straw Hydrolysate

Single cell oil is an important component of biodiesel.Although biodiesel has a wide range of applications,its high fermentation cost limits its commercial production.In order to effectively reduce the cost of raw materials and realize the industrial conversion of cheap biomass materials,a series of mutagenesis and optimization of fermentation conditions for biodiesel producing strain—Sporobolomvces were studied based on the economical fermentation process of biomass resources.Based on the development of biomass resources for microbial lipid fermentation,the effects of inhibitors in hydrolysate of corn straw on lipid synthesis and metabolism were discussed in order to provide theoretical basis for the breeding of single-cell lipids and the utilization of cheap carbon sources.And,we conducted a series of investigation to it,specific operations are as follows:1.Optimized mutagenesis methods were investigated and compared between UV mutagenesis and NTG and DES mutagenesis respectively.Maleic hydrazide and cerulenin were used for primary screening,and shaking flask fermentation was used for re-screening.When UV irradiation time was 30 seconds,DES mutation time was 100 min,and cerulenin concentration was 17.9 ?mol/L,the biomass,oil content and total lipid of mutant strain were 42.2 %,60.0 %,127.8 % higher than that of original strain,respectively.The results showed that the compound mutagenesis and screening method could effectively improve the oil production performance of the strain.After mutagenesis,the content of unsaturated fatty acid increased,and the content of 20-carbon fatty acid decreased,which indicated that the low-temperature fluidity of oil was higher than that of the original strain.2.The effect of mixed carbon source fermentation on oil production was investigated.Xylose,glucose and glycerol were used as the sole carbon source for fermentation to produce oil,respectively,as the control result of mixed sugar.The strain had the best fermentation performance in glucose medium,with biomass of 30.7 g/L,oil content of 27.1% and total lipid of 8.3 g/L.In mixed-carbon fermentation,when xylose and glucose were 3:1,the biomass was 27.3 g/L,the oil content was 28.6%,and the total lipid was 7.8 g/L.However,the proportion in glucose-glycerol medium had little effect on the fermentation results,and the yield of the target product was better than glycerol.In xylose medium,the biomass of the strain decreased sharply,the minimum was only 15.3 g/L,resulting in the inadequate yield of the target product,which was 2.9 g/L.3.The effects of inhibitors in corn straw hydrolysate on oil production of strains were investigated.When the concentration of furfural was 0.5 g/L,the strains in xylose medium were significantly inhibited,the biomass,oil content and total lipid were reduced by 27.5%,13.9% and 37.7% respectively.The strains in glucose medium were significantly inhibited when the concentration of furfural reached 1.0 g/L,which proved that the strains in glucose medium were more tolerant to furfural than those in xylose medium.High concentration of phenol inhibited the strain obviously.Relatively speaking,the strain in xylose-containing medium was more tolerant to phenol than that in glucose medium,but when the concentration of phenol was low(0.2 g/L),it had a positive effect on xylose-containing medium.When acetic acid was 0.9 g/L,the strains in xylose-containing medium were significantly inhibited;when it was 1.2 g/L,the fermentation of strains in glucose medium was poor,and the biomass,oil content and total lipid decreased by 29.6%,39.6% and 55.9%.4.The fermentation ability of corn straw hydrolysate with different treatments was investigated.The biomass of the strain in dilute acid hydrolysate of corn straw was 23.2 g/L,the oil content was 18.9%,and the total lipid was 4.4 g/L.In the complete hydrolysate,the optimum fermentation time of the strain was 144 h,the biomass was 24.4 g/L,the oil content was 22.3%,and the total lipid was 5.4 g/L.