Partially composting reshapes substrate chemistry and microbial communities to suppress green mold and improve oyster mushroom quality

Oyster mushroom cultivation is often constrained by green mold contamination caused by Trichoderma spp . Management of green mold remains challenging because Trichoderma and oyster mushrooms are both lignocellulosic fungi that depend on similar nutrient sources, which makes selective suppression difficult. Therefore, we partially decomposed the substrate to make lignin more accessible for mushroom mycelium colonization and limit green mold. Sawdust substrate was composted at ambient temperatures (28-34°C), and a composting period of 9-12 days was found to provide the best balance between substrate quality and mushroom yield. Throughout the composting process, physicochemical parameters, substrate morphology, enzyme activity, and microbial community dynamics were systematically monitored. The results showed that labile sugar, total carbon, and total nitrogen decreased markedly during composting. The Mantel correlation test indicated that these changes significantly correlated with the composting microbial community. Analysis of 16S rRNA amplicon sequences revealed that carbon-cycling microorganisms, especially cellulolytic and hemicellulolytic bacteria, are dominant at the initial stage of composting. Notably, Verrucomicrobiota are the most abundant, followed by Proteobacteria, Firmicutes, Actinobacteria , and Bacteroidetes . Notably, significant laccase activity was observed in compost colonized by mushroom mycelium, rather than in compost alone. Molecular docking analyses further elucidated distinct binding features of Pleurotus ostreatus laccase, which exhibited superior binding affinity for lignin compared to laccases derived from Trichoderma spp . Moreover, the more porous composted substrate supported the formation of a dense mushroom mycelium network, thereby reducing spatial competition with Trichoderma. In addition, composting improved yield and produced mushrooms enriched with iron (Fe) and zinc (Zn). This approach provides a safer, substrate-driven strategy for sustainable mushroom production worldwide.