Evaluation of hydrothermal and alkaline pretreatment routes for xylooligosaccharides production from sugar cane bagasse using different combinations of recombinant enzymes

Abstract

Xylan is the most abundant constituent of hemicellulose fraction of lignocellulosic biomass. Short xylooligosaccharides (XOS), obtained via xylan hydrolysis, have well-known prebiotic and antioxidant properties that are beneficial for human and animal health. In this study, two alternative pretreatment strategies (alkali and hydrothermal) and three different enzymes were applied for enzymatic XOS production from sugarcane bagasse. The enzymatic hydrolysis was performed with nine different combinations of recombinant endo-xylanases from GH11 and GH10 families and GH11 xylobiohydrolase. Hydrothermal pretreatment followed by optimized enzymatic hydrolysis yielded up to 96 ± 1 mg of XOS per gram of initial biomass, whereas enzymatic hydrolysis of alkali-pretreated sugarcane bagasse rendered around 47.6 ± 0.2 mg/g. For both alkali and hydrothermal routes, the maximum yields of short-length XOS were obtained using the GH10 xylanase alone. Furthermore, differences in XOS profiles obtained by controlled mixtures of the enzymes have been evaluated. For both routes, the best yields of short-length XOS were obtained using the GH10 xylanase alone, which is consistent with the notion that sugarcane xylan substitutions partially hinder GH11 xylanase activity. The results presented here show that a green and cost-effective hydrothermal pretreatment path for xylooligosaccharides production, rendered considerably better XOS yields.