The Process Optimization Of Hydrolysis And Fermentation In Ethanol Production By Waste Cellulose

With the developing of energy shortage, environmental pollution andglobal warming, people become more and more emphasis on clean,sustainable energy development. Recently, biomass energy has come intofocus by researchers. Because of the advantages like great potential,renewable and pollution-free of lignocellulosic ethanol production, it has beenwidely concerned and studied around the world. The United States, Canada,Japan and Sweden, used the technology of cellulose enzyme, theimprovement of process and other measures to achieve the industrialization oflignocellulosic ethanol production. China also has begun to develop thelignocellulosic ethanol industry.The project focused on the fermentation and hydrolysis process oflignocellulosic ethanol production. To determine the optimal reactionconditions by studying the impact factor of two phases. The research studiedthe efficiency of SSF and SHF under the optimal conditions of each step.First, fermentation of sugar by Saccharomyces cerevisiae BY4742, forproduction of ethanol in a batch experiment was conducted to improve theperformance of the fermentation process. The influences of temperature,substrate concentration and pH on ethanol fermentation were observed. Theyield for ethanol production and changes in the fermentation pathway werecompared under different conditions. The optimal conditions of fermentationof sugar by Saccharomyces cerevisiae BY4742is35℃, pH4.5, substrateconcentration of80g/L, in this condition for the efficiency of ethanolfermentation can reach nearly100%of the theoretical value. Second, Enzymatic hydrolysis of cellulose and straw was investigatedunder different hydrolysis conditions, such as reaction time, temperature andpH value. The structural change of the substrates in the process was alsoanalyzed by scanning electron microscope (SEM). Results indicate that, theefficiency of enzymatic hydrolysis significantly varied with different pHvalues, and the optimal pH value was found to be in the range of4.0~5.0.Moreover, enzymatic hydrolysis efficiency was sensitive to temperature, andthe optimal value of temperature was40℃. Under this condition, theproduction rate of glucose by straw and cellulose reached56.32%and35.80%,respectively. Furthermore, hydrolysis process of both substrates was almostcompleted within24hours, and reached the highest efficiency after48hour.SEM results show, the substrate structure changed obviously during the first6hours.Finally，the aim of the research was to explore the efficiency of ethanolproduction under optimal conditions of Separate Hydrolysis and Fermentation(SHF) and simultaneous saccharification and fermentation (SSF). In thispaper, the optimal conditions of hydrolysis and fermentation were consideredto design the SHF and SSF process. In SHF process, the optimal conditions ofhydrolysis and fermentation were used separately. In SSF process, theoptimum temperature conditions of both steps were studied. In SHF process,the efficiency of ethanol production was similar in both SupernatantFermentation and Mixture Fermentation, and the yeast activity was better inmixture fermentation. In SSF process, the efficiency of ethanol productionwas higher in35℃.The production of xylose in SSF process was higher thanthat in hydrolysis process. Under the experimental conditions, the efficiencyof ethanol production in simultaneous saccharification and fermentation ishigher than the Separate Hydrolysis and Fermentation.