Construction Of High Efficient Degradation Of Corn Straw Compound Bacteria

As a great agricultural country, around 800 million tons of straw lignin is generated annually in China. Valuable as lignin is, it is largely wasted because of the low comprehensive utilization rate. Not to mention that straw burning has aroused quantities of environment problems. Therefore, rational use of crops straw is of significant importance. Cellulase, as a complicated hydrolytic enzyme system, can not only make full use of straws but also have the advantage of regeneration, environmentprotection and economy due to the fact that co-fermentation by multiple microorganisms can make up the low utilization caused by a single strain of enzyme, which is of low activity because of the incomplete enzyme system. Above all, multi fermentation is becoming the focus in the degradation of straws at present.The strains of high efficient fiber degradation were selected from strains preserved in our laboratory. Multiple enzyme system of cellulase production was build by co-fermentation to make the enzymes more complete, more balanced matching and complementary advantages so that the utilization rate can be improved. Furthermore, Candidum lipolytica was used to pre-process the corn stalks and the deczyme ompose ability improved significantly. Finally, multiple enzyme system was used to degrade corn stalks, evaluated by degradation rate, cellulose content, hemicellulase content and lignin content. Tha results were as following:(1) Aspergillus niger Z3,Bacillus T7, and Trichoderma reesei 3 can produce cellulase separately and multiplely, with the latter presented obviously higher enzyme activity, earlier peak value, more complete enzyme system and stronger synergistic effect. The enzyme activity of FPA was 288.94U/mL, which was 1.85 times of Aspergillus niger Z3,2.37 times Bacillus T7, and 1.65 Trichoderma reesei 3.(2) The optimization of inoculation sequence was the simultaneous inoculation of Aspergillus niger Z3 and Trichoderma reesei 3 12h before inoculating Bacillus T7, with the enzyme activity to be 339.54 U/mL. The best inoculation proportion was 2:1:2 of Aspergillus niger Z3,Bacillus T7, and Trichoderma reesei 3, with a balanced enzyme proportion, the best synergistic effect and the highest enzyme activity, which was 365.98U/mL.(3) Fermentation temperature, fermentation time and inoculation level were chosen from various impacting factors by Plackett-Burman method. Box-Behnken model in response surface was taken to study these three factors impacting the cellulase content of multiple strains. It showed that 29.76?,3.Id, and 8.93% inoculation level to be optimized. An experimental of a scaled model was carried out to test its reliability and applicability. It showed that, in this case, the enzyme activity of FPA was 442.38U/mL, extremely close to the predicted value of U/mL.(4)Pretreatment of Candidum lipolytica presented that the multiple strains can produce cellulase of the highest activity with 2% of inoculation content for 36h. in this case, the enzyme activity was 553.81U/mL and 548.06U/mL of CMC and FPA respectively. Then the fermentation conditions were optimized, with 29.92?,3.18d, and 141.81r/min to be the best. The experimental of a scaled model showed that the enzyme activity of FPA was615.32U/mL, extremely close to the predicted value of 613.851U/mL.(5) Enzymatic property of the cellulase produced by multiple strains showed that pH of 5.0 and temperature of 50? were the most appropriate condition for enzymatic reaction. For the pH of enzymes and the stability of temperature, it showed that CMC and FPA had higher activity when pH was of 4.5?6.0 or the temperature was 45??60?.(6) Degradation of solid state fermentation showed that the effect of multiple degradation was better than a single strain, with the degradation rate to be 34.8%,cellulase content to be 13.2%. hemicellulase content to be 13.2%, lignin content to be 10.9%. the preprocess of Candidum lipolytica can obviously increase the degradation rate to 42.1%, with the content of cellulase, hemicellulase, and lignin to be 22.8%,10.3%,8.8%, respectively.