Xylitol production on sugarcane biomass hydrolysate by newly identified Candida tropicalis JA2 strain.

Abstract

Xylitol is a building block for a variety of chemical commodities, besides being widely used as a sugar substitute in the food and pharmaceutical industries. The aim of this work was to develop a microbial process for xylitol production using sugarcane bagasse hydrolysate as substrate. In this context, 218 non-Saccharomyces yeast strains were screened by growth on steam-exploded sugarcane bagasse hydrolysate containing a high concentration of acetic acid (8.0g/L). Seven new Candida tropicalis strains were selected and identified, and their ability to produce xylitol on hydrolysate at low pH (4.6) under aerobic conditions was evaluated. The most efficient strain, designated C.tropicalis JA2, was capable of producing xylitol with a yield of 0.47g/g of consumed xylose. To improve xylitol production by C.tropicalis JA2, a series of experimental procedures were employed to optimize pH and temperature conditions, as well as nutrient source, and initial xylose and inoculum concentrations. C.tropicalis JA2 was able to produce 109.5g/L of xylitol with a yield of 0.86g/g of consumed xylose, and with a productivity of 2.81g·L·h, on sugarcane bagasse hydrolysate containing 8.0g/L acetic acid and177 g/L xylose, supplemented with 2.0g/L yeast nitrogen base and 4.0g/L urea. Thus, it was possible to identify a new C.tropicalis strain and to optimize the xylitol production process using sugarcane bagasse hydrolysate as a substrate. The xylitol yield on biomass hydrolysate containing a high concentration of acetic acidobtained in here is among the best reported in the literature.