Lignocellulosic residue valorization in a sequential process of solid-state fermentation and solid substrate anaerobic digestion

BACKGROUND Lignocellulosic residue valorization is a relevant topic because the study of residue and waste recycling is essential for circular economy development. This area is focused on treatment development for value-added compound production. This work presents a sequential process of solid-state fermentation (SSF) by white-rot fungi (WRF) followed by solid substrate anaerobic digestion (SSAD) with the objective of producing bioenergy and other ancillary product. The agricultural residue from common bean pod (Phaseolus vulgaris) has never been studied for the purpose of a biorefinery concept. In addition, the intermediate stage for enzyme recovery was evaluated, comparing two extractants on their enzyme stability and effectiveness effect and the subsequence SSAD process effect. RESULTS Trametes versicolor produced the highest enzymatic activity of laccase, reaching 1588 U L-1 at 12 days of SSF. Under this condition, both extractants showed excellent enzymatic stability at 17 degrees C, but only the enzymes recovered with phosphate buffer were capable of the micropollutant degradation. SSF caused an increase in biodegradability of the lignocellulosic residue, providing an increase in biogas yield between 0% and 75.5%; however, high volatile solids consumption during fungal growth decreased the amount of biogas per volatile solid mass before treatment. CONCLUSION Common bean pods were successfully valorized through the sequential process by SSF of the WRF T. versicolor and SSAD, producing enzymes as a value-added product and biogas from the remaining solids. The enzymes produced were stable and effective for micropollutant degradation when they were recovered with phosphate buffer. (c) 2021 Society of Chemical Industry (SCI).