Full utilization of poplar sawdust with chemical-mechanical pretreatment for coproduction of xylooligosaccharides, fermentable sugars and porous carbon materials

Abstract

In recent decades, one of the major challenges of biorefinery is the full utilization of lignocellulosic components for coproduction of value-added materials. In this context, we proposed an integrated process of acetic acid (AC) pretreatment, Papir Forsknings Institutet (PFI) refining and enzymatic hydrolysis to coproduce xylooligosaccharides, fermentable sugars and lignin-based porous carbon materials. Results showed AC pretreatment (170 ºC, 60 min, 5 w/v % acetic acid and 5% 2-naphthol addition based on dry mass of biomass) resulted in maximum xylooligosaccharids (XOS) yield of 51.08%. The integrated process of AC pretreatment assisted by 2-naphthol-7-sulfonate addition and PFI post-refining led to cellulose hydrolysis yield of 98.20% and lignin-based porous carbon materials with methylene blue adsorption capacity of up to 749.17 mg/g. Moreover, it was found lignin repolymerization inhibitors (i.e. 2-naphthol, 2-naphthol-7-sulfonate) in acid pretreatment helped increase the specific surface area of substrate and decrease surface lignin coverage, which enhanced cellulose accessibility to cellulase enzymes. Moreover, they enhanced lignin detaching during enzymatic hydrolysis, which reduced cellulase aggregation and promoted the ease of cellulose hydrolysis. Results demonstrated an efficient pretreatment strategy to maximize coproduction of xylooligosaccharids, fermentable sugars and lignin materials from lignocellulosic biomass for full utilization.