Optimization Of Xylose Fermentation To Ethanol In Bioreactor And The Pretreatment Of Corn Cob For Ethanol Fermenting

Due to environmental pollution, resource depletion and the grim world grain situation,using cheap and abundant and renewable lignocellulosic materials to develop fuel ethanol,which was one of the most effective ways to solve them. Xylose content in lignocellulosichydrolysate was next only to glucose. Consequently, efficient fermenting xylose to ethanolwas the important segment for lignocellulosic materials biogenesis. These contents werestudied in this paper: taking fermentation condition optimizing experiments in bioreactor tofix optimum conditions of producing ethanol for batch fermentation; studying the fed-batchfermentation to fix the best technology for produce ethanol; the conditions of pretreatmentand enzymolysis for corn cob with calcium oxide, alkaline hydrogen peroxide, and dilutesulfuric acid were optimized and fermentation by isolated yeast strain was also studied.The effects of the different culture conditions on the ethanol production from xylose bypichia stipitis m4were investigated in a5-L bioreactor. The results indicate that optimalfermentation conditions were as follows: initial xylose content108g/L, fermentationtemperature28℃, aeration rate30L/h, the agitation speed300r/min, inoculation ratio12.5%,pH value4.8. The concentration of ethanol reached to50.0g/L under the optimal fermentationconditions after60h. Compared with batch fermentation, the fed-batch fermentation time wasextended to84h. The yeast growth was stronger, and the rate of xylose into ethanol waslarger when once adding at36hthcompared with adding at24hthand48hth, and then theconcentration of ethanol was53.4g/L. The concentration of ethanol was54.9g/L whenadding xylose two times before and after36hth. Compared with batch fermentation, fed-batchfermentation technology increased ethanol production by5.5g/L.Corn cob was pretreated with lime, alkaline hydrogen peroxide, and dilute sulfuric acidrespectively and hydrolyzed by cellulose and hemicellulose enzymes, which was designed byone-factor experiment. The optimal conditions of three methods were by response surface testanalysis followed. The best conditions of lime pretreatment and enzymolysis were:53.0mg/glime at121℃for45min,7.9%enzyme （cellulase and hemicellulase7.9%respectively） for72.5hours, then the sugar conversion amount was373.76mg/g. The optimal conditions ofalkaline hydrogen peroxide pretreatment and enzymolysis were: soaked in6.2%H₂O₂,solid-liquid ratio1:18, at40℃for7.5h,7.4%enzyme （cellulase and hemicellulase7.4%respectively） for60hours, then the sugar conversion amount was485.09mg/g. The conditions of dilute sulphuric acid pretreatment and enzymolysis were: acid concentration0.8%, solid-liquid ratio1:15, at121℃for60min,7.0%enzyme （cellulase and hemicellulase7.0%respectively） for70.9h, then the sugar conversion amount was462.62mg/g. The resultsindicate that sugar conversion amount was highest by dilute sulphuric acid pretreatment andenzymolysis（xylose214.09mg/g, glucose271mg/g）. Enzymed liquid of Corn cob wasfermented by domesticated Pichia stipitis m4in bioreactor, the concentration of ethanol was7.05g/L at36hth, and the conversion rate of ethanol was11.8%.