Xylitol biosynthesis and process scale-up from wheat straw hemicellulosic hydrolysate using Candida tropicalis

Abstract

Due to growing applications of xylitol in pharma and food industries, process development for xylitol biosynthesis from lignocellulosic biomass seems to be a promising strategy. The present study focuses on the process development for facilitating efficient xylose to xylitol bioconversion from wheat straw hemicellulosic hydrolysate using Candida tropicalis ATCC 13803. A methodical attempt to scale up the fermentation bioprocess is demonstrated by maintaining a constant volumetric mass transfer coefficient (kLa) in bioreactors of various scales. Xylitol productivity of 1.47 and 0.58 g/Lh and yield of 1.58 and 0.74 g/g, respectively, were achieved from xylose-rich hydrolysate (41.49 g/L xylose) and synthetic xylose (40.69 g/L) in a 0.5 L bioreactor at an optimum kLa of 0.74 min-1 and 0.68 min-1, respectively. Further, scale-up in 1 L bioreactor using optimum kLa resulted in xylitol productivity (g/Lh) and yield (g/g) of 1.49 & 0.58; 1.57 & 0.74, respectively, from hydrolysate and synthetic xylose. Moreover, scale-up in a 5 L bioreactor using optimum kLa resulted in xylitol yield and productivity of 0.74 g/g and 1.55 g/Lh from synthetic xylose. The successful bioprocess scale-up studies highlight the relevance of lignocellulosic biomass’s valorization to high-valued xylitol.