Xylo-oligosaccharide oriented biorefining of corncob through citric acid/sodium citrate buffer hydrolysis and enzymatic upgrading

Abstract

Selective production of xylo-oligosaccharides (XOS) from corncob is hindered by secondary degradation during acid hydrolysis. Here, a citric acid/sodium citrate (CA/SC) conjugate acid-base system was developed for XOS-oriented fractionation of corncob. Compared with the citric acid hydrolysis, the optimal CA/SC hydrolysis increased the XOS yield from 44.3% to 50.5%, indicating a more favorable hydrolysis environment for XOS accumulation. Subsequent endoxylanase hydrolysis further upgraded residual high-degreesoluble oligomers and increased the XOS yield to 60.2%, with clear enrichment of xylobiose and xylotriose. Meanwhile, the pretreatment selectively removed hemicellulose while largely preserving glucan, producing cellulose-rich solid residues with enhanced enzymatic digestibility. Cellulase hydrolysis of residues gave glucose and xylose yields of 89.5% and 75.5%, respectively. Mass balance based on 1000 g of raw corncob gave 185.4 g XOS, 329.2 g glucose, and a lignin-rich final residue, demonstrating the potential of the CA/SC system for integrated corncob valorization.