The intricate structure of lignin in straw makes it challenging to hydrolyze, making it a key focus of current research. However, there has been limited study on the effect of enzyme inducer (MnSO4) combined with functional microorganisms on lignin degradation during straw composting. Based on this, four composting treatment groups were set up in this study. Control (CK), functional microorganism addition treatment (F), Mn2+ enzyme inducer (Mn), and Mn2+ enzyme inducer coupled with functional microorganism addition treatment (FMn) were tested for composting. Manganese(II)-coupled microorganisms improved lignin degradation: FMn > Mn > F > CK. They increased the lignin loss rate from 25.54 % to 42.61 %. Laccase activity increased from 3.45 to 43.74 U/g and manganese peroxidase activity increased from 145.52 to 264.91 U/g. And gene abundance was increased. Microbial community structure and dominant genera changed. Structural equations support the idea that functional microorganisms coupled with manganese can modify physicochemical indices, thereby regulating gene expression and enhancing enzyme activity. Furthermore, the stimulation of fungal growth and increased extracellular laccase and manganese peroxidase activities can affect the degradation of lignin. This study provides new insights and theoretical support for efficient lignin degradation and efficient resource utilization of compost products.

This study investigated the impact of adding enzyme inducer (MnSO4) on humic substance (HS) formation during straw composting. The results demonstrated that both enzyme inducer treatment group (Mn) and functional microorganism treatment group (F) led to an increase in the content of HS compared to the treatment group without enzyme inducer and functional microorganism (CK). Interestingly, the enzyme inducer exhibited a higher promoting effect on HS (57.80 % ~ 58.58 %) than functional microbial (46.54 %). This was because enzyme inducer stimulated the growth of key microorganisms and changed the interaction relationship between microorganisms. The structural equation model suggested that the enzyme inducer promoted the utilization of amino acids by the fungus and facilitated the conversion of precursors to humic substance components. These findings provided a direction for improving the quality of composting products from agricultural straw waste. It also provided theoretical support for adding MnSO4 to compost.

Pyrethroid residues in food and the environment can be bio-transformed into 3-phenoxybenzoic acid (3-PBA); It is more toxic than the parent compounds, and has been detected in milk, soil, and human urine. In this study, when incubated at 30 °C and 180 rpm for 48 h, mycelial pellets during logarithmic growth phase were obtained and washed 2 times by phosphate buffer. The cell debris solutions and filter liquor from inducible and non-inducible samples were cultured with 3-PBA and its intermediate metabolites at same condition, and the location and induction of enzymes were analyzed by the degradation. Then Cytochrome P450 (CYP450), lignin peroxidase (LiP), laccase, manganese peroxidase (MnP), and dioxygenase were selected as candidate enzymes due to these oxidases existing in the fungi and capable of degrading the contaminants with similar structures of these compounds, and CuSO4, NaN3, AgNO3, EDTA or piperonyl butoxide (PBO) were used as the enzymes inhibitors and inducers. The degradation of 3-PBA and its intermediate metabolites and the fungal biomass in presence of enzymes inhibitors and inducers was arranged to analyze the possible degrading-enzymes, and the co-metabolic enzymes and pathways can be reasoned. This study provided a promising method for studying the co-metabolic enzymes of 3-PBA degradation by fungi. •The presented MethodsX was conducted for co-metabolic enzymes and pathways of 3-PBA degradation.•The culturing condition for presenting enzyme properties were investigated.•The candidate enzymes were analyzing based on location, induction of enzymes, fungal enzyme systems and chemical structures of these compounds.