Utilization of lignocellulosic mushroom cultivation residues for bioethanol production via consolidated bioprocessing

In the context of the energy transition, there is an increasing need for research focused on low-cost feedstocks, such as lignocellulosic biomass, and on process optimization for the sustainable production of biofuels. Traditionally, processing lignocellulosic materials requires multiple stages. In this scenario, consolidated bioprocessing (CBP) emerges as a promising alternative by integrating enzyme production, hydrolysis, and fermentation into a single step. This study aimed to develop a CBP for bioethanol production using residues from oyster mushroom cultivation (Pleurotus ostreatus), composed of Pinus elliottii sawdust and soybean hulls (Glycine max). Preliminary tests were conducted to define the CBP conditions: the effects of biological (mushroom cultivation) and alkaline (sodium hydroxide) pretreatments were evaluated, and the production of cellulolytic enzymes by Trichoderma sp. was investigated in solid-state fermentation (SSF) and submerged fermentation (SmF) using the raw and pretreated residues. After selecting the optimal conditions, a 2³ experimental design was carried out to assess the influence of wheat bran supplementation, commercial enzyme addition, and co-culturing (Saccharomyces cerevisiae and Bacillus velezensis) on ethanol production. Cellulolytic enzyme production was observed in both fermentation types, with the SSF using only biologically pretreated substrate yielding the highest activity (2.04 ± 0.17 U/g). In CBP, the supplementation with commercial enzyme extracts, wheat bran addition, and co-culture showed positive effects on ethanol production, resulting in 7.07 ± 0.22 g/L, representing a 15-fold increase compared to the unenhanced process. These results highlight the potential of reusing mushroom cultivation residues for sustainable bioethanol production through CBP.