Gaining insight into the effect of laccase expression on humic substance formation during lignocellulosic biomass composting.

The aim is to enhance lignin humification by promoting laccase activities which can promote lignin depolymerization and reaggregation during composting. 1-Hydroxybenzotriazole (HBT) is employed to conduct laccase mediator system (LMS), application of oxidized graphene (GO) in combination to strengthen LMS. Compared with control, the addition of GO, HBT, and GH (GO coupled with HBT) significantly improved laccase expression and activities (P < 0.05), with lignin humification efficiency also increased by 68.6 %, 36.7 %, and 107.8 %. GH treatment induces microbial expression of laccase by increasing the abundance and synergy of core microbes. The unsupervised learning model, vector autoregressive model and Mantel test function were combined to elucidate the mechanism of action of exogenous materials. The results showed that GO stabilized the composting environment on the one hand, and acted as a support vector to stabilize the LMS and promote the function of laccase on the other. In GH treatment, degradation of macromolecules and humification of small molecules were promoted simultaneously by activating the dual function of laccase. Additionally, it also reveals the GH enhances the humification of lignocellulosic compost by converting phenolic pollutants into aggregates. These findings provide a new way to enhance the dual function of laccase and promote lignin humification during composting. It could effectively achieve the resource utilization of organic solid waste and reduce composting pollution.