Biodelignification is widely regarded as a low-efficiency process because it is usually slow and difficult to control. To improve its efficiency and understand its mechanism, the present study analyzed the delignification characteristics of Pleurotus ostreatus grown on a cotton stalk medium. The results demonstrated that all strains of P. ostreatus can selectively degrade the cotton stalk lignin. When cultured in a cotton stalk medium for 60 days, P. ostreatus degraded lignin primarily during its mycelium growth with up to 54.04% lignin degradation and produced laccase and manganese dependent peroxidase with high activity levels at the peaks of 70.17 U/ml and 62.39 U/ml, respectively, but no detectable lignin peroxidase. The results of nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy analyses of significant changes in lignin structure revealed that syringyl (S) lignin units were more degraded than guaiacyl (G) lignin units, with a significantly elevated G/S ratio. The Gas Chromatography-Mass Spectrometer analysis of low-molecular-weight compounds revealed that the delignification resulted in the formation of alcohols, organic acids, benzodiazepines, and alkanes. Identified benzodiazepines implied the degradation of G and S units of lignin. These findings will help to improve the efficiency of biodelignification and expand our understanding of its mechanism.

Fungal laccases play important roles in the degradation of lignocellulose. In this study, the laccase producing cotton straw medium for Pleurotus ostreatus was optimized by single-factor and orthogonal experiments, and to investigate the role of Lacc1 gene, one of the laccase-encoding genes, in the degradation of cotton straw lignin, an overexpression strain of Lacc1 gene was constructed, which was analyzed for the characteristics of lignin degradation. The results demonstrated that the culture conditions with the highest lignin degradation efficiency of the P. ostreatus were the cotton straw particle size of 0.75 mm, a solid–liquid ratio of 1:3 and containing 0.25 g/L of Tween in the medium, as well as an incubation temperature of 26 °C. Two overexpression strains (OE L1-1 and OE L1-4) of Lacc1 gene were obtained, and the gene expression increased 12.08- and 33.04-fold, respectively. The results of ¹H-NMR and FTIR analyses of significant changes in lignin structure revealed that Lacc1 gene accelerated the degradation of lignin G-units and involved in the cleavage of β-O-4 linkages and the demethylation of lignin units. These findings will help to improve the efficiency of biodelignification and expand our understanding of its mechanism.

With the increasing scarcity of traditional hardwood sawdust resources, developing sustainable substrates for edible fungi cultivation has become an urgent industrial priority. This study systematically evaluated the effects of bamboo sawdust substitutions (20%, 30%, 40%, and 50%) on mycelial growth, fruiting body development, and nutritional quality of Auricularia heimuer, while elucidating the underlying molecular mechanisms through transcriptome sequencing. The results demonstrated that bamboo substitution of ≤30% maintained normal mycelial growth and fruiting body differentiation, with 20% and 30% substitutions increasing yields by 5.30% and 3.70%, respectively, compared to the control. However, 50% substitution significantly reduced yield by 9.49%. Nutritional analysis revealed that 20–40% bamboo substitution significantly enhanced the contents of crude protein, polysaccharides, and essential minerals (calcium, iron, and selenium) in fruiting bodies. Transcriptome analysis identified upregulation of glycosyl hydrolase family genes and downregulation of redox-related genes with increasing bamboo proportions. Biochemical assays confirmed these findings, showing decreased oxidative substances and increased reductive compounds in mycelia grown with high bamboo content, which indicate disrupted cellular redox homeostasis. This study provides both a practical solution to alleviate the “edible mushrooms derived from lignicolous fungi–forest conflict” and fundamental insights into fungal adaptation mechanisms to non-wood substrates, thus establishing a theoretical foundation for the valorization of agricultural and forestry wastes.