An integrated and scalable biorefinery approach for producing high purity xylo-oligosaccharides from prehydrolysis liquor

Pre-hydrolysis liquor (PHL), a by-product of the kraft pulping process, contains abundant dissolved hemicellulose (mainly includes xylose, xylo-oligosaccharides (XOS), and xylan). Biorefinery of XOS from the PHL using an efficient and time-saving strategy remains a long-standing challenge. Herein, a sustainable and scalable biorefinery approach including sequential calcium hydroxide (CH) pretreatment, laccase assisted xylanase (LX) treatment, and activated carbon (AC) adsorption was proposed for producing XOS with high purity. CH pretreatment effectively enhanced xylanase hydrolysis efficiency by removing the acetyl side chains of xylan, converting approximately 86 % xylan to XOS. LX synergistic treatment outperformed single laccase and xylanase treatments, which could simultaneously remove lignin and concentrate XOS without catalytic efficiency loss. Overall, 91.5 % lignin and 100 % furfural were removed, and 87.9 % xylosugars were recovered. XOS content was significantly increased by 27.6 %, resulted in a considerable increase in XOS purity from 42.0 % to 75.2 %. The purified XOS contained a small amount of side chains (4-O-methyl-D-glucuronic acids and acetyls) and lignin carbohydrate complex (PhGlc3). This work demonstrates an efficient, eco-friendly, and time-saving strategy to prepare high purity XOS and provides theoretical guidance for purifying XOS from PHL via enzyme-based biorefining process. • XOS with high purity was obtained from PHL via biochemical process. • CH pretreatment enhanced xylanase hydrolysis, converting ∼86 % of xylan to XOS. • LX synergistic treatment outperformed single laccase and xylanase treatments. • 91.5 % lignin and 100 % furfural removal, and 27.6 % XOS increase were achieved.