Screening, identification, and enzyme production condition optimization of a cellulose-degrading bacterial strain

Abstract:

[Background] Cellulose is ubiquitous in nature and has great resource potential, and its efficient degradation is of great significance to alleviate the energy crisis and environmental pollution. [Objective] To screen cellulose-degrading bacteria and improve cellulase activity by optimizing enzyme production conditions. [Methods] Congo red staining was used for primary screening and DNS colorimetric method for secondary screening. The target strain was identified. The enzyme production conditions of the target strain were optimized by the single factor tests, Plackett-Burman design, path of steepest ascent method, and Box-Behnken design. [Results] A strain 26-2-2 with high cellulase activity was screened out and identified as Bacillus cereus. The optimal fermentation conditions of this strain were determined as follows: CMC-Na mass concentration of 31.2 g/L, (NH₄)₂SO₄ mass concentration of 13.6 g/L, KH₂PO₄ mass concentration of 4.0 g/L, rotation speed of 180 r/min, inoculation amount of 5.0%, fermentation time of 24 h, initial pH 7.0, and fermentation temperature of 35 ℃. Under these conditions, the cellulase activity of strain 26-2-2 reached (61.14±0.23) U/mL, which was 24.0% higher than that before optimization. [Conclusion] This study provides new strain resources for the bioconversion of cellulose and data reference for subsequent research on cellulose-degrading strains.