Studies On Enzymatic Hydrolysis Of Cellulosic Materials And Ethanol Fermentation

Cellulase production by Trichoderma reesei, hydrolysis of pretreated cellulosic materials and ethanol fermentation from the cellulosic hydrolysate were studied in this thesis.The main factors influencing the biosynthesis of cellulase by T. reesei were evaluated. The results indicated that cellulase could be induced by different cellulosic materials, and the enzyme activity was higher when the pretreated cellulosic materials was used. The cellulase production could be repressed by glucose.The C/N and the composition of inorganic nitride played important roles on cellulase synthesis. Increasing oxygen supply would promote cell growth and enhance the production of cellulase. The optimized medium composition was: 40g/l pulp powder, 39g/l (NH4) 2SO4, 20g/l KH2PO4, 4g/l CaCl2.2H2O, 1.5g/l MgSO4, lml/1 Tween 80 and lml/1 Mandels trace element solution. Under initial pH value 4.8 and incubation temperature 28 , the maximum cellulase activity was 14.31IU/ml.The properties of the cellulase produced by T. reesei were also evaluated. The optimal reaction pH and temperature were pH 5.0 and 50 .It was found that the pretreatment methods, the cellulosic substrate concentration, the proportion of cellulase and cellobiase were very important to the hydrolysis of cellulosic materials.The results of ethanol fermentation on the cellulosic hydrolysate showed that the optimized condition were initial pH5.0, incubation temperature 31-37 , the hydrolysate could be used directly , the filtering and adding nutrition were notnecessary. The result in the 1.2M3 fermentor showed: ethanol concentration could reach 2.408% in 38 hr, with the efficiency of sugar utilization and ethanol yield were 92.9 % and 92.7%, respectively.