Valorization of agricultural by-product for cleaner and sustainable production of microbial pigments and cellulolytic enzymes in a zero-waste approach

This work presents a zero-waste concept for the valorization of banana peel into Monascus value-added metabolites, such as pigments and cellulolytic enzymes, and for evaluation of the feasibility of treated peel as a promising source for animal feedstuff. M. purpureus YRU01 exhibited satisfactory pigment and cellulolytic enzyme production in solid-state fermentation. Particularly, repeated solid-state fermentation of non-sterile peel with 90% substrate replacement was effective in offering high recovery of pigments, xylanase, and cellulase (7.19-, 31.19-, and 92.62-fold higher than those of solid-state fermentation, respectively). The LC/MS profile of fermented peel provided important evidence of fungal metabolites (>100 metabolites) for understanding and evaluating the fermentation. Moreover, citrinin-related mycotoxin fragments were not found. The treated peel had high carbohydrate, neutral detergent fiber, and acid detergent fiber contents, but low protein content, indicating its potential to be used as a roughage in animal feed.