Resource Utilization Of Corncob Residue

With energy and environment problems being increasingly serious, high efficient utilization of lignocelluloses is becoming more and more important. Corncob residue(CCR), which is a solid waste to be rich in cellulose, generally produced from corncobs hydrolyzed by dilute-acid treatment for xylose production.To improve the cellulase production and reduce the cost, we optimized the solid-state fermentation medium and cellulase production conditions of Trichoderma Longibrachiatum G26 by using CCR, wheat bran and corn stover as the main raw materials. Following this, in order to increase the enzymatic hydrolysis efficiency and obtain higher titer of sugars by using the crude cellulase from G26, the saccharification technique of CCR was optimized. In addition, we studied the optimal medium for reproduction of cellulose from the fermentation residue of G26, and also explore the feasibility of the waste residue as a fertilizer for maize.The main results were as follows:1、We optimized the components of a natural medium to produce cellulase from strain G26 under solid state fermentation conditions by Plackett–Burman design and response surface methodology. The optimum natural medium consisted of a solid component(20% wheat bran, 53.3% corn stover, 26.7% CCR) and a nutrient salt solution(1.00 w/v % KH2PO4, 1.80 w/v %(NH4)2SO4, 88.8 w/v % soybean cake powder, 1.0 w/v % urea, 3.47 v/v % corn steep liquor). The ratio of the solid component to the nutrient salt solution was 1:1.5(w/v). The cellulase extraction condition was 10 ml of citric acid buffer per gram of the solid component. Compared with that before optimization, FPA improved 13.34% and finally reached 8.07 IU/m L after incubating in the optimized media at 32℃ for 96 h.2、The results of saccharifiying CCR confirmed that the multi-stage process presented an advantage over the traditional one. As the Total amount of enzyme is constant, the optimum enzymolysis conditions were determined: 6.00 IU/m L the enzyme activities for FPA, 12.5% CCR, 60% initial enzyme, 20% enzyme supplementation(18h & 36h). Under this condition for 60 h, the concentration of glucose and the hydrolysis rate of cellulose reached 52.30g/L, 70.65% respectively. In addition, the obtained hydrolysate, containing 60.1 g/l glucose, is suitable for the production of L-lactic acid. After a 44 h fermentation, the production of L-lactic acid and the sugar-acid conversion(as to glucose) were up to 52.0 g/l and 86.5%.3、By researching the reproduction of cellulose from the fermentation residue of G26, a optimized conditions were established as follows: the quality ratio of new and old materials 3:7, nutrient salt solution(except soybean cake powder) and 4.44% soybean cake powder. After a 96 h fermentation, FPA reached 5.75IU/m L. Meanwhile, the study indicated that fermentation residue was feasible in being the maize fertilizer.In conclusion, culturing the Trichoderma Longibrachiatum G26 in the optimized solid fermentation medium can significantly improve the ability in the production of cellulase and reduce the cost of raw materials. Besides, the enzymatic hydrolysis efficiency and sugars titer were improved by optimizing the saccharification technique of CCR. At last, the fermentation residue in producting cellulase of G26 had a good effect on reproduction of cellulose and was suitable for a fertilizer for maize.