| With the development of international economy, coal, oil and other fossil fuels are drying up gradually. Still carbon dioxide released by fossil fuels caused environment pollution. It’s urgent to look for renewable clean energy to instead the fossil energy. Biomass energy as the most potential renewable energy has variety of advantages, such as low-cost, renewable, lower pollution an so on. Fuel ethanol is derived from renewable biomass sources, and further by ethanol dehydration and the formation of different forms of degeneration treatment, has great importance on social and economic development. Bagasse as the major byproducts of the cane sugar industry was the fibrous residue of sugarcane after extraction of cane juice, which can be used as bioethanol production materials. Sugar industry is one of the traditional pillar industry in Guangxi, the sugar yield over the years has consistently ranked first in the country, therefore there are a lot of by-product bagasse, and some of them was used as paper raw materials and boiler fuel, but much of them was abandoned. Therefore it is urgent to exploit energy utilization methods of sugarcane bagasse..In this theme, bagasse was pretreatment by different alkali such as NaOH, Ca (OH)2and NH3·H2O, to study effects of bagasse lignin removal and the optimum conditions of enzymatic hydrolysis and fermentation. The results showed that trival molasses adding in the fermentation medium can effectively increase the final alcohol concentration The details are as follows:The bagasse pretreated with NaOH superior to Ca (OH)2and NH3·H2O treatment can remove54%of the lignin, and retain almost all of the cellulose and part of the hemicellulose. The optimume enzyme hydrolysis codition as follows:particle size of40-100mesh, temperature of50℃, pH4.8, amount of enzyme30Fpu/g, speed120rpm, hydrolysis time was72h, liquid to solid ratio of15%.Based on the above-mentioned single factor, Minitab software was adopted to optimize sugarcane bagasse enzymatic hydrolysis process. Firstly, Plackett-Burman design was used to evaluate five variables including temperature, pH value, cellulase adding dosage, ratio of liquid and solid, agitation speed. The significant impact factors were screened as temperature, pH value and cellulase adding dosage. Then the response surface method (RSM) was used for further optimization studies. The results showed that the optimum conditions are temperature47.6℃, pH4.76, cellulase adding dosage of37.76FPU/g, the holocellulose conversion rate can attain to74.5%. Under these conditions, the actual concentration of the holocellulose conversion rate is74.44%, is in good agreement with the predicted values.Inoculated with optimized enzymatic hydrolyzate, the concentration of ethanol was amount to25.4g/L after incubation of Saccharomyce scerevisiae for12h, with10%of inoculum, at initial pH5.0to6.0, and the yield of ethanol could also attained to8.12%.To improve the economy of fuel ethanol production, the concentration of ethanol in the fermented mash is best to above4%, which can reduce energy consumption in the subsequent distillation process.Bagasse hydrolysate, co-fermentation of sugarcane bagasse hydrolysates and molasses were studied to improve ethanol concentration. The sugarcane bagasse hydrolysis was carried out at solid-liquid ratio of1:5, cellulase adding dosage of30FPU/g, fed-batch hydrolysis condition (first adding10%, then6%after12h, and another4%after24h), hydrolysis time of120h. And after that the hydrolysates were fermented with10%incubation of Saccharomyce scerevisiae for12h. The final ethanol concentration was amount to7.68%after36hours of co-fermentation mixed with10%of molasses, the fermentation efficiency could attain to99.03%of theroetics value. |
