Optimization Of Conditions For Producing Ethanol By Fermentation Of Sweet Sorghum Straw Cellulose With Pichia M1

The use of rich and inexpensive lignocellulosic resources and using bioconversion to produce fuel ethanol are of great significance to the sustainable economy and social development of our country.In this paper,aiming at the bottleneck problem in the study of cellulosic ethanol,the strains that can use ethanol to produce ethanol are first screened and applied to the simultaneous saccharification and fermentation of sweet sorghum stalks.Secondly,the pretreatment,enzymolysis and fermentation conditions of sweet sorghum stalk cellulose ethanol were optimized.The specific findings are as follows:1.In this dissertation,a highly productive and well-tolerant strain,Pichia M1,was selected.The strain grew well at 40 °C,with ethanol and glucose tolerances of 12% and55%,respectively.The strain used sweet sorghum stalks for simultaneous saccharification and fermentation to produce alcohol with a content of 31.08 g/L,an ethanol conversion rate of 42.52%,and an ethanol yield of 0.388 g ethanol/g substrate.The ethanol yield of this strain reached 96.55 % of industrial yeast,which has good commercial utilization value.2.This paper optimizes the production conditions of cellulose stalks from sweet sorghum stalks.First,the straw was crushed,soaked with NaOH,pretreated,collected by filtration,and crude lignin was recovered by acid precipitation.After treatment,the residue of straw was washed to neutrality,and then cellulase,xylanase,and ?-glucosidase were added for complex enzymolysis to optimize the hydrolysis conditions.The treated sweet sorghum stalks were used as substrates,and enzymes and yeasts were simultaneously added for simultaneous saccharification and fermentation.On this basis,fed-batch simultaneous saccharification and fermentation were carried out and fed at 0 h,12 h,24 h,and 48 h,respectively,so that the final substrate concentration reached 24% and the enzymatic method was divided into 0 h.Add two ways at the same time as feeding.The results show:(1)The optimal conditions for NaOH pretreatment conditions were particle size: 40 mesh,solid-liquid ratio: 1:10,NaOH concentration: 10%,treatment temperature: 60°C,treatment time: 24 h.After pretreatment,the cellulose content of sweet sorghum stalk was72.45 %,the removal rate of lignin was 87.21 %,and the recovery rate of crude lignin reached 18.6 g/100 g sweet sorghum stalk.The enzymatic hydrolysis of pre-treated sweetsorghum stalks yielded 41.01 % of enzymatic hydrolysis after 48 h,an increase of 86.6 %relative to the raw material.(2)The amount of cellulase,xylanase,and ?-glucosidase added during enzymolysis was 32 U/g substrate,350 U/g substrate,and 35 U/g substrate,respectively.The enzymolysis conditions were as follows: substrate concentration: 6 %;enzymolysis promoter: PEG 4000(0.05 g/g substrate);enzymolysis time 72 h;?-glucosidase was added6 h after enzymolysis.The other conditions were constant.After enzymatic hydrolysis for72 h,the enzymolysis yield of the complex enzyme was 55.42 % higher than that of the enzyme added only with cellulase.(3)In this experiment,the wild strain M1 was selected as the fermentation strain,the optimum fermentation temperature was 37?,the yeast inoculum was 2 %,and the optimal substrate concentration was 8 %.The bacteria was used for simultaneous saccharification and fermentation,and the final ethanol content reached 31.08.The g/L,the ethanol conversion rate was 42.52 %,and the ethanol yield reached 0.388 g ethanol/g substrate.The simultaneous saccharification and fermentation with a single batch of enzyme-enriched feeds resulted in a final ethanol content of 70.54 g/L,an ethanol conversion rate of approximately 39 %,and an ethanol yield of 0.294 g ethanol/g substrate.The above results show that the strain M1 screened in this paper has good tolerance,good alcohol production by fermentation,and has industrial application value.Using the optimized process conditions to ferment sweet sorghum stalks to produce ethanol,the final ethanol yield was 70.54 g/L,the ethanol conversion rate was maintained at about 39 %,and the ethanol yield was 0.294 g ethanol/g substrate.Compared with other research methods,this paper's finally optimized method is economical and efficient,and has industrial application value.