Comparative secretome analysis of Oudemansiella raphanipes grown on different agricultural residues

Oudemansiella raphanipes can degrade lignocellulose-rich biomass, especially agricultural residues. However, its substrate utilization and degradation mechanisms remain poorly understood. To explore this, we cultured O. raphanipes mycelium in Kirk's liquid medium supplemented with eight distinct substrates and conducted studies on extracellular enzyme activities and secretome analysis. A total of 905 secreted proteins were identified, with the cornstalk group having the highest counts. Carbohydrate-active enzymes (CAZymes) were the predominant type (32.8–48.9 %), followed by oxidoreductases (2.8 %–13.3 %), while lipase and phosphatase were minor categories. Functional annotation of the secreted proteins comprehensively revealed their diversity in various biological processes. Among the 340 secreted proteins with Enzyme Commission codes, (Methyl)glyoxal oxidase, chitinase, and β-glucosidase were most prominent. Bran, cottonseed hulls, corncobs, and the mixture promoted mycelium growth and conserved CAZymes expression patterns. In contrast, sawdust, corn steep liquor, and cornstalk induced divergent secretome profiles. Sawdust led to a higher proportion of hemicellulose- and lignin-degrading enzymes. Corn steep liquor induced relatively high activities and abundances of laccase and MnP, while cornstalk induced a broad spectrum of oxidoreductases, lipases, and protease & peptidases. In addition, redundancy analysis further indicated that the extracellular enzyme activities (notably laccase, MnP, and xylanase) induced by different substrates significantly impacted the secretome.

Significance

O. raphanipes can efficiently utilize a variety of lignocellulosic materials, and genomic sequencing has confirmed the presence of abundant CAZymes in its genome. This study employed various agricultural residues as substrate inducers to elucidate the extracellular enzyme profiles of O. raphanipes involved in lignocellulose degradation, which indicated its metabolic plasticity in response to varying substrate composition. These findings facilitate further exploration of the biomass bioconversion mechanism of O. raphanipes and provide novel perspectives for the induction of combined agro-residues in its industrial cultivation.