Study On The Pretreatment Technology Of Corncob And Preparation Of Bio-ethanol

Corncob can be used to Produce fuel ethanol as a cheap and abundantly available lignocellulosic resource instead of limited grain feedstocks. Bioconversion of corncob to fuel ethanol is very meaningful in the aspects of new energy development and environmental protection.In this thesis, technologies in pretreatment of corncob, enzymatic hydrolysis, ethanol production from cellulosic hydrolysate, were investigated. The technology of producing alcohol from corncob by microorganism and cellulase methods was studied. It breaks a new way to make the full use of corncob.Serials of standards were built to check the intermediate and final product. The standards including the follow:the glucose's concentrations and the yields of the ethanol. The dinitrosalicylic acid reagent(DNS) method was chosen to check glucose's concentration and the factors including sensitive wavelength, boiling time and the dosage of dinitrosalicylic acid reagent which influence the results when the raw material was corncob were studied. As the results show, it is suggested that 500nm is more sensitive wavelength for determination, the boiling time for developing should be 2min, the dosage of dinitrosalicylic acid reagent is 2.0mL. Build an accurate way for the qualitative and the quantitative analysis of ethanol content. The result is analysis by the Gas chromatography. The qualitative analysis is by the retention time and the quantitative analysis by the internal standard method. The gas chromatography retention time of ethanol is 2.0min,and the retention time of n-propanol is 5.6min. The internal standard method showed the linear equation of peak area was y=7.4211x-1.1182 (R2=0.995).The factors including concentration of sulfuric acid, pretreatment time and feed-to-liquid ratio, and the orthogonal experiment are studied for optimizing the hydrolysis of corncobs. The effective sequence of each factor on corncobs pretreated is feed-to-liquid ratio> pretreatment time> concentration of sulfuric acid, and the optimal conditions are as follows:1% of H2SO4,1h of pretreatment time,1:12 of feed-to-liquid ratio. Morphological changes on the cellulosic surface of corncobs by pretreatment were observed using SEM and FTIR. The observation revealed that the pretreatment with H2SO4 could break down the structural rigidity of corncobs. Use the corncob as biomass material, follow the microbial technology and use the filter strains including LⅡand L2". As the results shows, the best craft of hydrolysis conditions are:filter strain L2" is better than LⅡthen choose the filter strain L2",the dosage of L2" in every 10.Og corncob is 30 ml, pH nearly 7, control the temperature at 35℃for 48 hours, the glucose concentration can reach the climax. The fermentation conditions are:add the cultured yeast of 40mL, control the temperature at 35℃for 36h, the yield of the ethanol can reach to 0.42g/g glucose, contrast to the theoretical yield, the yield is reached 82.3%.Use the corncob as biomass material, and the celluase technology only use the cellulase including NS50010 and NS50013 which were afforded by novozyme company. As the results shows,the dosages of cellulase were every 10.Og corncob joined in NS500130.4mL and NS500100.04mL, pH 5-6, control the temperature at 40℃for 48h,1% Tween-80 and 0.5% trace element, the glucose concentration can reach the climax. The fermentation conditions are:add the cultured yeast of 40mL, control the temperature at 35℃for 36h, the yield of the ethanol can reach to 0.45g/g glucose, contrast to the theoretical yield, the yield is reached 88.2%.