Bamboo Sawdust as an Alternative Substrate Alters Metabolite Profiles and Quality Traits of Lentinula edodes Fruiting Bodies

Abstract Lentinula edodes (shiitake mushroom) is a widely consumed edible fungus valued for its nutritional properties. With the depletion of traditional wood-based substrates, the exploration of sustainable alternatives has become necessary and urgent. Bamboo sawdust has emerged as a promising substitute; however, its effects on mushroom metabolism and quality remain poorly understood. In this study, the quality and metabolic responses of L. edodes fruiting bodies cultivated on substrates in which hardwood sawdust was replaced with 0% (CK), 50% (GH), or 100% (GZ) bamboo were investigated. Bamboo supplementation significantly influenced key quality traits. Both bamboo treatments (GH and GZ) led to lighter cap coloration, reduced melanin and chitin contents, and increased polysaccharide levels. Moderate substitution (GH) did not affect fruiting body weight, whereas high substitution (GZ) significantly reduced it. Metabolomic analysis identified 517 metabolites, of which 163 were differentially accumulated across treatments, primarily consisting of phenolic acids, organic acids, amino acids and their derivatives, and alkaloids. The bamboo substrate selectively modulated several metabolites downstream of phenylalanine metabolism, particularly those involved in melanin, phenolic acid, and flavonoid biosynthesis, consistent with the observed changes in pigmentation and the accumulation of specific bioactive compounds. These findings demonstrate that bamboo-based substrates induce distinct, dose-dependent metabolic responses in L. edodes, affecting key traits related to nutrition, pigmentation, and flavor. This study provides mechanistic insights into substrate-driven metabolic regulation and supports the application of bamboo sawdust as a sustainable and effective alternative substrate for shiitake mushroom cultivation.