Study On Screening, Identification Of Cellulose-decomposing Bacteria Under High Temperature And The Conditions Of Cellulase Production

Cellulose is a class of biodegradable and renewable energy sources, and widely exists in nature. Agricultural organic wastes contain abundant cellulose, and the comprehensive utilization of cellulose is currently a hot subject of research. In our experiment,21strains that have cellulose degradation ability were isolated from compost under culture condition of50℃by two kinds of medium, cellulose congo red medium, and fitter paper liquid medium. In following experiment, three strains (D-4,J-C-2,N2-1) with high cellulase activity were obtained, after primary screening by cellulose congo red medium and secondary screening by liquid fermentation method for determination of cellulase activity. The carboxymethyl cellulase (CMCase) activities of the three strains were6.14U,4.20U,5.37U, respectively, and their filter paper enzyme (FPase) activities were3.03U,2.68U,2.42U, respectively. Identification of the optimal strain D-4by using16S rDNA sequencing indicated that D-4had the closest relative to Bacillus with99%sequence similarity. Therefore, D-4strain was identified as Bacillus sp. and named Bacillus sp. D-4.Effects of different cultivation time,nitrogen sources, initial pH and temperature were studied, to determine the optimum condition for producing cellulase of the strain D-4. The results showed that, the enzyme production was the optimum under the medium conditions using a mixture of peptone, yeast and ammonium sulfate as nitrogen source with initial pH at7.0, and culture temperature30℃after48hours shake flake cultivation. And under the optimum conditions, the CMCase and FPase activities were1.6and1.3times compared with before optimization.The impacts of the three strains (D-4,J-C-2,N2-1) with efficient cellulose degradation ability on CO2release from rice straw and pig manure composting were also studied. All three cellulose-degradation bacterium could accelerate CO2release from organic wastes, and the cumulative CO2release was increased by35.3%,27.2%and18.3%,respectively, compared to the control (no inoculation) and increased by20.6%,]3.4%and5.5%, respectively, compared to the original strain-inoculated treatment.