Screening of efficient cellulose degrading bacteria in cow manure compost and optimization of enzyme production conditions

Abstract:

[Background] Cellulose is a biomass resource to be developed and utilized, which is important for solving energy crisis and environmental pollution. [Objective] To isolate cellulase-producing bacteria from cow manure compost and investigate their cellulose degradation ability. [Methods] The cellulose solid plate Congo red staining method was used for preliminary screening, followed by liquid fermentation and cellulase activity measurement for secondary screening. [Results] A bacterium with high cellulase activity was isolated and identified as Bacillus amyloliquefaciens strain N5. Single-factor analysis experiments demonstrated that strain N5 exhibited good tolerance to pH, temperature, and salinity. Orthogonal optimization experiments revealed that the optimal conditions for cellulase production by strain N5 were an initial fermentation pH of 5.0, fermentation time of 96 hours, and fermentation temperature of 40 ℃. Under these conditions, the enzyme activity reached 189.27 U/mL. Furthermore, strain N5 achieved a 19.35% reduction in weight of rice straw within 7 days, indicating its effective promotion of rice straw degradation. Scanning electron microscopy results confirmed the ability of strain N5 to facilitate rice straw decomposition. [Conclusion] Strain N5 exhibits high cellulase activity and holds potential for developing efficient aerobic composting agents. It provides a valuable bacterial resource for the biological transformation of cellulose in solid waste.