Development of efficient cellulolytic enzyme display on the cell surface of the yeast Saccharomyces cerevisiae

Abstract

Sugar-rich effluent from prehydrolysis of eucalyptus wood (prehydrolysate) is an abundant byproduct of paper and pulp industries. It can be used as a resource for xylose production and biorefinery. However, it is mostly concentrated and burned for energy production. In this paper, a commercial xylanase was applied to examine the feasibility of enzymatic treatment of the prehydrolysate. The xylanase efficiently hydrolyzed the xylooligosaccharides in the prehydrolysate to xylose. The optimal hydrolysis conditions were determined to be at pH 5.0, a temperature of 50 °C, a concentration of xylooligosaccharides at 23.46 g/L, and xylanase loading of 75 U/g xylooligosaccharides. Using the aforementioned reaction conditions, xylooligosaccharides in the prehydrolysate were completely hydrolyzed within 24 h. The total xylose concentration reached 50.41 g/L. The xylose was recovered by active carbon decolorization, ion exchange chromatography, desalination, and crystallization, which produced crystal xylose with a 97% purity at a 35% recovery rate. The results demonstrated that xylanase is an efficient and ecofriendly tool for eucalyptus pulping prehydrolysate. Moreover, the prehydrolysate from hardwood pulp industry can serve as an abundant and low cost resource for industrial xylose production.