Enzymatic Hydrolysis Applied to Banana Pseudostem Biomass Compared to Solubilized Xylan for Xylooligosaccharides Production with High Substrate Concentration

Abstract

Xylan is a polysaccharide present in lignocellulosic biomass, which is obtained in large quantities as agricultural and agroindustrial waste. In this study, xylooligosaccharides (XOS) were produced by the enzymatic hydrolysis of xylan, using biomass itself or solubilized xylan as substrate. In addition, enzymatic hydrolysis of solubilized xylan was performed with two cycles in a higher volume and higher substrate concentrations. XOS and xylan molecular weight were evaluated. After partial delignification, the hemicellulose in the material increased by 6 percentual points due to the lignin removal. Milling and partial delignification of biomass helped to improve the enzymatic hydrolysis since conversion went up by 47.13% after the use of both strategies together. Regarding the solubilized xylan enzymatic hydrolysis, the increase of substrate concentration led to a decrease in the yield of around 13%; however, the amount of XOS produced went from 14.68 g/L to 50.40 g/L. The hydrolysis 2nd cycle led to an increase of only around 10% conversion for all substrate concentrations. After hydrolysis, the molecular weight of the xylan decreased, as did the polydispersity. However, after the second hydrolysis cycle, both the molecular weight and polydispersity increased, since probably the enzyme acted in the easing xylan fraction and the remaining complex substrate limited enzyme action. Comparatively, the enzymatic hydrolysis of solubilized xylan resulted in a higher yield and concentration than enzymatic hydrolysis of the partial delignified biomass.