A combination of mild chemical pre-treatment and enzymatic hydrolysis efficiently produces xylooligosaccharides from sugarcane bagasse

Abstract

Xylooligosaccharides (XOS) are emerging as highly effective but expensive products in the global prebiotics market. The need for biomass pretreatment and the low efficiency of subsequent enzymatic hydrolyses limit XOS yield from lignocellulosic biomass. In this study, a sequential three-step process of mild chemical pretreatment of sugarcane bagasse (SB) with potassium hydroxide followed by pretreatment with phosphoric acid and then hydrolysis with endo-xylanase was developed for producing XOS. The novel process resulted in a maximum XOS (xylobiose [X2]–xylotetraose [X4]) yield of 58.7 g XOS/100 g SB xylan. Mass balance analysis of SB revealed that the maximum yield of XOS was 7.15 g per 100 g raw SB, which is among the highest XOS yield values from SB reported in the literature. Moreover, physical and chemical evidence confirmed that the pretreatment processes removed most of lignin and modified the side chains of xylan. Highly crystalline cellulose tightly wrapped around the remaining SB xylan impeded the accessibility of xylan to xylanase. This strategy provides an alternative option to achieve the release of XOS from SB that is cost effective and environmentally friendly. • A mild KOH–H 3 PO 4 -combined pretreatment for SB was firstly developed. • XOS yield from SB xylan with 58.73% was achieved. • High yield of XOS of 7.15 g was produced from 100 g raw SB. • Pretreatment slightly modified side chains of SB xylan and removed most of lignin. • Highly crystalline cellulose wrapped the remaining xylan after xylanase hydrolysis.