Label-free comparative proteomic analysis of Pleurotus eryngii grown on sawdust, bagasse, and peanut shell substrates.

The white rot fungi Pleurotus eryngii are environmental microorganisms that can effectively break down lignocellulosic biomass. However, understanding of the mechanisms by which P. eryngii is effective in degrading lignocellulose is still limited. This work aimed to examine the extracellular secretory proteins implicated in the breakdown of lignocellulose in P. eryngii and identify degradation tactics across various cultivation substrates. Thus, a comparative analysis of the secretory proteins based on Nanoliquid chromatography combined with tandem mass spectrometry was conducted among P. eryngii cultivated on sawdusts, bagasse, peanut shells, and glucose. In total, 647, 616, 604, and 511 proteins were identified from the four samples, respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis of protein expression differences identified pathways (hydrolytic enzymes, catalytic activity, metabolic processes, cellular processes, and response to stimuli) significantly enriched in proteins associated with lignocellulose degradation in P. eryngii. An integrated analysis of proteome data revealed specifically or differentially expressed genes secreted by P. eryngii in different cultivation substrates. The most prevalent carbohydrate-active enzymes involved in lignocellulose degradation in the secretome of the four samples were laccase (Lac), manganese peroxidase (MnP), aryl alcohol oxidase (AaO), and copper radical oxidase (CRO). Among them, Lac 2 mainly involved in the lignin degradation of sawdust peanut shells, and bagasse by P. eryngii, and Mnp 3 was mainly involved in the degradation of peanut shells. AaO and Lac 4 were mainly involved in glucose substrate defense and oxidative stress. It was found that exogenous addition of sawdust and peanut shells significantly increased lignolytic enzyme abundance. These findings provide insight and guidance for improving agricultural waste resource recovery. In this study, the secretomes of P. eryngii grown on four different carbon sources were compared. The findings revealed the extracellular enzymes implicated in the degradation of lignocellulose, offering avenues for further investigation into the biotransformation mechanisms of P. eryngii biomass and the potential utilization of agricultural wastes. SIGNIFICANCE: The cost of the substrate for mushroom cultivation has increased as the production of edible fungus has risen year after year. Therefore, the use of these locally available lignocellulosic wastes as substrates offers a cost-cutting option. Further, the overuse of wood for the cultivation of edible mushrooms is also detrimental to the conservation of forest resources or the ecological environment. Consequently, the use of other agricultural wastes as an alternative to sawdust or other woody substrates is a viable approach for cultivating P. eryngii. The distribution of extracellular lignocellulosic degrading enzymes, inferred in the present study could help improve the cultivation efficiency of P. eryngii vis-à-vis managing agricultural waste.