Construction of lignocellulose-degrading compound microbial inoculum and its effects on green waste composting

The high content of recalcitrant lignocellulose in green waste (GW) makes composting and degradation challenging. Conventional GW composting typically employs single-strain microbial inoculants (MIs) with limited enzyme production capabilities, resulting in low composting efficiency and suboptimal compost product quality. In this study, Bacillus amyloliquefaciens (J1), Clonostachys rogersoniana (B2), and Streptomyces thermoviolaceus (J3) was utilized to optimize cultivation conditions and strain ratios based on enzyme activity indicators. The aim was to develop a potent three-strain lignocellulose-degrading MIs and test the hypothesis that its performance is superior to that of single-strain and two-strain MIs in terms of lignocellulose degradation and compost maturation. The results indicated that, the optimal treatment was T7, which was inoculated with a three-strain MIs composed of the spore suspensions of J1, B2, and J3 with a volume ratio of 3:3:2. Specifically, compared to the control (without MI), T7 increased the content of particle size between 0.25 and 2.00 mm and humic acid by 17% and 291%, respectively. Furthermore, T7 enhanced the degradation rates of cellulose, hemicellulose, and lignin by 197%, 145%, and 113%, respectively, and increased the activities of laccase, manganese peroxidase, lignin peroxidase, and carboxymethyl cellulase by 605%, 269%, 180%, and 228%, respectively. Additionally, T7 increased the relative abundance of bacteria (e.g. Pseudomonas) and fungi (e.g. Parascedosporium) that facilitated lignocellulose degradation, enhanced the alpha diversity index and promoted the formation of a microbial community structure characterized by prominent dominant species and greater diversity. Remarkably, the inoculation with the three-strain MI yielded high-quality compost within 32 days.