Screening and Identification of High Cellulase-Producing Strain Bacillus cereus and Optimization of Enzyme Production Conditions
The high cellulase-producing strains were screened and the enzyme production conditions were optimized, providing strain resources for the effective utilization of agricultural solid waste. A promising cellulolytic strain S3 was isolated from the soil of Hengshui Lake Wetland Park. The isolation process employed Congo red plate staining method for primary screening, followed by secondary screening through cellulase activity determination and straw degradation experiments. Through morphological observation and molecular biology identification, the strain S3 was identified to be Bacillus cereus. The ratio of transparent circle to colony diameter of strain S3 was 4.01±0.17. The filter paper enzyme activity of strain S3 was 42.09 U·mL−1, and the degradation rate of corn stover reached 19.29% after 10 days of fermentation. It was found that the optimum carbon source of strain S3 was the mixture of microcrystalline cellulose and wheat bran with the addition amount of 4%, and the optimum nitrogen source was soybean powder with the addition amount of 2%. Single factor experiment and response surface methodology were used to optimize the enzyme production conditions of the strain S3. The optimal conditions were fermentation time of 76 h, fermentation temperature of 36℃, initial pH of 6, and inoculation volume of 4%. Under these conditions, the filter paper enzyme activity reached 60.13 U·mL−1, which was 1.43 times higher than that before optimization. The strain S3 showed the high cellulase-producing capability, demonstrating its potential as an efficient microbial candidate for the degradation and utilization of agricultural solid waste.