The Study On Ethanol Production Using Straw By Fractional Step Saccharification And Fermentation And Simultaneous Saccharification And Fermentation

Cellulose is renewable materials which quantity is large in nature and it has great potential to produce ethanol and solve the energy problem in the future.China is rich in straw resources,so the study of producing ethanol by straw material is of great significance.In this research,we carried out the experiment to optimize the saccharification condition of straw by Streptomyce.sp which was screened by our lab and has high ability to saccharify straw.We aslo screen the Saccharomyces cerevisiae,Saccharomyces cerevisiae As2.458 and angel yeast for the yeast which has highest ability to produce ethanol by utilizing the reducing sugar degrade by straw. We carried out the ethanol producing experiment by Streptomyce.sp and angel yeast using the fractional step saccharification and fermentation method and simultaneous saccharification and fermentation method.We optimize fermention conditions by using SAS software and compare with each other.At last,we optimize the fermentation conditions of ethanol production by solid simultaneous saccharification and fermentation method,and compare with the liquid simultaneous saccharification and fermentation method.The results are as follows:1,With the experiments of some single factors and analysis by the SAS software, we optimized the fermentation conditions in which Streptomyce.sp produces reducing sugar:by the methods of PB,we found the most significant factors that affect the production of reducing sugar are addition of straw powder,pH and addition of calcium chloride.And with the design of BB,we got the optimum fermentation conditions as following:strow powder7.4%,bran3.0%,bean powder3.0%,corn flour2.0%,KH₂PO₄ 0.5%,CaCL₂ 0.73%,pH6.2,inoculum size 2mL,37℃, fermentation period 7days.Resrult of this experiment are steady with this optimum fermentation conditions,the yield of reducing sugar after optimized is 31.32mg/mL which is about 1.5 times of the yield in original fermentation conditions.2,In the study of the ability of producing ethnol by utilizing the reducing sugar degrade by straw of Saccharomyces cerevisiae,Saccharomyces cerevisiae As2.458 and angel yeast,we find that the angel yeast has the highest ability of producing ethnol.The ethanol is 5.217%(V/V) and the amount of residual sugar is 10.19mg/mL.In the study of influence by additional kinds of nitrogen sources to the ethanol yield that angel yeast produce,we find that the ethanol yield is highest and residual sugar is lowest by using ammonium sulfate as the nitrogen sources,so ammonium sulfate is selected as the additional nitrogen sources in further study.3,After a series of single-factor experiments and response surface experiment to optimize the fermentation conditions of ethanol production using straw by fractional step saccharification and fermentation method,the optimum fermentation conditions are as follows:strow powder7.4%,bran3.0%,bean powder3.0%,corn flour2.0%, KH₂PO₄ 0.5%,CaCL₂ 0.73%,pH 6.2,inoculate the seed liquid of Streptomyce.sp, inoculum size 2mL,37℃,fermentation period 7days.Add 0.8%ammonium sulfate then adjust the pH to 5.3 and sterilize.Inoculate the seed liquid of yeast,inoculum size 4mL,fermente 1.9 days under 32.3℃.The yield of ethanol is 6.41%which is 1.19 times of the yield in original fermentation conditions.4,By the methods of PB,we found the most significant factors that affect the production of ethanol by simultaneous saccharification and fermentation method are adding of yeast inoculum,the time inoculate yeast seed liquid and the ferment time the yeast need.And with the design of BB,we got the optimum fermentation conditions as following:strow powder7.4%,bran3.0%,bean powder3.0%,corn flour2.0%,KH₂PO₄ 0.5%,CaCL₂ 0.73%,pH 5.5,inoculate the seed liquid of Streptomyce.sp,inoculum size 2mL,37℃,fermentation period 3.2days.Add 1.0% ammonium sulfate and inoculate the seed liquid of yeast,inoculum size 1.8mL, fermente 4.2 days under 34℃.The yield of ethanol is 7.52%which is 1.17 times of the yield in original fermentation conditions.5,Compare the optimized results of producing ethanol by fractional step saccharification and fermentation method and simultaneous saccharification and fermentation method,we can find that simultaneous saccharification and fermentation method has some advantages:the ethanol yield by fractional step saccharification and fermentation method afer optimize is 6.41%while the ethanol yield by simultaneous saccharification and fermentation method afer optimize is 7.52%which is 1.17 times than the former.The cycle of fractional step saccharification and fermentation method is 8.9days and the inoculum size of yeast is 4mL while the cycle of simultaneous saccharification and fermentation method is 7.4days and the inoculum size of yeast is 1.8mL.The simultaneous saccharification and fermentation method reduce the fermention cycle 1.5days and more than half of yeast inoculum amount,so the simultaneous saccharification and fermentation method reduce the production cycle significantly and reduces the cost of production.6,After a series of single-factor experiments to optimize the fermentation conditions of ethanol production using straw by solid simultaneous saccharification and fermentation method,the optimum fermentation conditions are as follows:ratio of material to water1:3,pH 5.0,inoculum size 3mL,inoculate the seed liquid of yeast the third day after inoculate the seed liquid of Streptomyce.sp,add 0.8%ammonium sulfate and change the temperature to 34℃as soon as inoculate the seed liquid of yeast.The total culture time is 5 days and the yield of ethanol is 0.13g ethanol/g.