The Study On Pretreatment And Enzymatic Sacchariifcation Of Bagasse

Along with the global consumption of fossil resources, it is the inevitable trend to usebio-refinery to take place of fossil refining to satisfy human rising energy and chemicaldemand. This paper chose bagasse, a by-product of sugar industry, as raw material, from threedifferent angle of making the lignosulphinate, seperation hemicelluloses and graduallyseparation of hemicelluloses and lignin, and we studied process conditions of the weak alkalisulfite pretreatment, liquid hot water pretreatment catalyzed by pure water and by formic acidand liquid hot water/ethanol lignin degradation pretreatment. We also focused on the changeof components, functional group, crystallinity and fiber surtace morphology of the bagassesamples, during the whole process.The optimum condition of weak alkali sulfite pretreatment was operating as follow:NaOH1.5%, Na2SO310%, the maximum temperature160℃and the time of temperaturekeeping1h, and the conversion rate of reducing sugar reached61.13%after enzymehydrolysis. During the whole process of the pretreatment and enzymolysis, the crytallinity ofcellulose of bagasse increased firstly and then minished, and part of lignin was sulfonated bythe pretreatment, and on the fiber surface many fines were exposed, and the specific surfacearea of cellulose became lager, improving the enzymolysis accessibility.The optimum condition of liquid hot water pretreatment catalyzed by pure water wasoperating temperature180℃, the time of temperature keeping20min and the substrateconcentration10%. Under this condition, the conversion rate of xylose reached75.79%in thehydrolysate, and the conversion rate of glucose reached78.2%after enzymolysis. In thehydrolysate, the proportion of the xylooligosaccharide and free xylose to total xylose wasrespectively79.40%and20.60%, and furfural and hydroxymethyl furfural concentration wasvery too low to inhbit fermentation. During the whole process the crytallinity of celluloseincreased firstly and then minished. And the characteristic peak of hemicelluloses of1735cm-1disappeared completely. Many fines were exposed on the surface, and the specificsurface area of cellulose became lager, and the enzymolysis accessibility improved after thehot liquid water pretreatment. What is more, there were many granular lignin on the fibersurface. And after the enzyme solution, the fiber structure was severely damaged. The optimum condition of liquid hot water pretreatment catalyzed by formic acid wasoperating temperature180℃, the time of temperature keeping20min, the substrateconcentration10%and the formic acid concentration0.02%(v/v). Under this condition, theconversion rate of xylose reached75.16%in the hydrolysate, and the conversion rate ofglucose reached60.74%after enzymolysis. In the hydrolysate, the proportion of thexylooligosaccharide and free xylose to total xylose was respectively60.53%and29.74%, andfurfural and hydroxymethyl furfural concentration was very too low to inhbit fermentation.During the whole process the crytallinity of cellulose increased firstly and then minished. Andthe characteristic peak of hemicelluloses of1735cm-1disappeared completely. Many fineswere exposed on the surface, and the specific surface area of cellulose became lager, and theenzymolysis accessibility improved after the hot liquid water pretreatment.The study of liquid hot water/ethanol lignin degradation pretreatment indicated that theexcessive degradation of lignin would inhbit the enzyme solution glycosylated. The bestcondition of ethanol lignin degradation process was operating temperature195℃, ethanolconcentration65%and the time of temperature keeping30min. At this time, although lignindegradation rate was only52.17%, but the glucose conversion rate reached48.02%. Duringthe whole process the crytallinity of cellulose increased firstly and then minished. And thecharacteristic peak of hemicelluloses of1735cm-1disappeared completely, and part ofguaiacyl structure lignin was degraded. Many fines were exposed on the surface, and thespecific surface area of cellulose became lager, improving the enzymolysis accessibility.The four pretreatment each had its own characteristics. The weak alkali alkali sulfitepretreatment made lignin sulfonated to improve the enzymolysis accessibility. For pure waterand formic acid catelysis of liquid hot water pretreatment, the strength is that it is easy toseparate the xylose and glucose. What is more, the fomer had sugar utilization efficiency andmore and advantage. The enzymolysis efficiency was improved for liquid hot water/ethanollignin degradation pretreatment, and the ethanol lignin had high purity, more active groups,and was easy to be modified, so it still had certain prospects.