Effect of immobilized lignin-degrading bacteria on green waste composting

Objective  The purpose of this research is to prepare a kind of solid microbial inoculant to promote green waste composting by immobilizing lignin-degrading bacteria No.11, with biochar-rice bran as a carrier. Method  Through single factor experiment, the optimal range of inoculation amount (5%, 10%, 15%, 20%, 25%), volume fraction of protective agent (0, 4%, 8%, 12%, 16%, 20%) and water content (5%, 10%, 15%, 20%, 25%) were explored, and the best preparation conditions of solid microbial inoculant were found by orthogonal test. Taking a common commercially available microbial inoculant (EM) as an example, the microbial agent was added to the composting process of green waste to explore its effects on lignin and cellulose degradation and related enzyme activities. Result  The optimal immobilization conditions of lignin-degrading bacteria No.11 were as follows: 10% inoculation amount, 8% protectant volume fraction and 15% water content. The amount of the effective living bacteria in the prepared fungus reached 1.26×1011 CFU·g−1. Enzyme activities related to lignin degradation(laccase, manganese peroxidase, and lignin peroxidase) were promoted after adding self-made microbial inoculant. Lignin degradation rate increased by 8.69% compared with the addition of EM bacteria. Compared with the control (without inoculant), the degradation rate of lignin and cellulose increased by 23.91% and 8.34%, respectively, and the compost products reached the maturity standard. Conclusion  The number of effective viable bacteria of the solid microbial inoculant prepared by immobilizing lignin-degrading bacteria complies with the requirements in Microbial Inoculants in Agriculture (GB 20287−2006). Adding the inoculant to green waste compost can improve the degradation rate of lignin and cellulose and promote the maturity of compost products. [Ch, 3 fig. 3 tab. 36 ref.]