Co-production of xylanase and xylooligosaccharides from lignocellulosic agricultural wastes

Lignocellulosic biomass including agricultural residues and by-products, and woody biomass are produced\udworldwide in large amounts every year. With the exception of limited-usage areas, these materials are\udregarded as waste. Therefore, renewable lignocellulosic biomass is gaining considerable attention\udbecause of its potential for use in the production of biofuels and other value-added products. In this\udstudy, the co-production of two value-added products, xylanase (enzyme) and xylooligosaccharides\ud(XO), was investigated by utilizing lignocellulosic biomass residues within a multi-product biorefinery\udframework. Box–Behnken design-based response surface methodology was employed to optimize\udculture parameters for xylanase production from a thermophilic fungus, Scytalidium thermophilum, and\udthe enzyme was biochemically characterized. Optimized media conditions resulted in an approximately\ud2-fold increase in xylanase activity compared to the initial conditions. Crude enzyme solution was\udcapable of producing XO from the hemicellulosic fraction of various biomass residues. The highest\udhemicellulose extraction yield was achieved from corn cob (37.7 1.5%), followed by wheat bran (26.6 \ud0.8%) and cotton stalks (22.2 0.6%). The highest reducing end concentration was obtained from\udsunflower seed shell (4.89 0.02 mg mL 1), followed by sunflower stalks (4.41 0.03 mg mL 1) and\udcorn cob (3.49 0.09 mg mL 1). Accordingly, corn cob yielded the highest XO production (172.1 mg XO\udper g raw biomass residue) with the main products of xylose (X1) and xylobiose (X2). In terms of the\udhemicellulosic fraction, beechwood had the maximum XO yield with 793 mg XO per g hemicellulose.\udSunflower seed shell hydrolysis yielded mainly X1 and xylotetrose (X4) without X2 and xylotriose (X3).\udAfter 1 h of reaction time, X2 and higher sugars were obtained from the commercial beechwood xylan,\udwhile only X1 and X4 were obtained after 6 h. Xylose-free xylobiose was obtained from sugar beet\udbagasse and wheat bran, which are regarded as potential XO sources because XO with degrees of\udpolymerization from 2–4 are preferred in food applications and XO without xylose are important in the\udfood industry from a prebiotic point of view