Mechanisms of gradient enzymatic conversion of lignin by a dual-fungal system consisting of Phanerochaete chrysosporium and Pleurotus eryngii.

Abstract

Chinese Distillers' grains (CDGs), a typical agro-industrial byproduct, contain a highly recalcitrant lignin that limits the utilization. In this study, a dual-fungal solid-state fermentation system consisting of Phanerochaete chrysosporium and Pleurotus eryngii was constructed for lignin conversion in CDGs. The lignin degradation ratio reached 58.66%, indicating that the system can effectively convert lignin. Laccase (Lac) and manganese peroxidase (MnP) activities peaked at 10 d, reaching 38.54 and 50.36 U/g, respectively, whereas lignin peroxidase (LiP) reached its maximum activity (51.67 U/g) at 15 d. Integrated transcriptomic and metabolomic analyses revealed a clear temporal division of labor between the dual-fungal. During the early stage, P. chrysosporium predominantly expressed AA2 family peroxidase genes, promoting oxidative cleavage of lignin β-O-4 linkages and the generation of aromatic intermediates. In contrast, P. eryngii became dominant during the middle and late stages through the upregulation of AA1 family laccase genes and aromatic catabolic pathways, facilitating the further conversion of lignin-derived compounds. Metabolic pathway reconstruction showed that H- and G-type lignin-derived intermediates converged into 1,2,4-benzenetriol, whereas S-type lignin-derived was primarily degraded through the gallic acid pathway. This study systematically elucidates the synergistic lignin conversion mechanism of CDGs by a fungal consortium from structural, enzymatic, and metabolic perspectives, uncovering a temporal division of labor together with new lignin catabolic pathways that provide a mechanistic framework for the biological valorization of lignocellulosic biomass.