Sustainable Bioconversion of Cashew Apple Bagasse Hemicellulosic Hydrolysate into Xylose Reductase and Xylitol by Candida tropicalis ATCC 750: Impact of Aeration and Fluid Dynamics

This study aimed to evaluate the production of xylose reductase (XR), an enzyme responsible for converting xylose into xylitol, by Candida tropicalis ATCC 750 using hemicellulosic hydrolysate from cashew apple bagasse (CABHM) as a low-cost carbon source. The effects of temperature, aeration, and fluid dynamics on XR biosynthesis were also investigated. The highest XR production (1.53 U mL−1) was achieved at 30 °C, with 8.3 g·L−1 of xylitol produced by the yeast under microaerobic conditions, demonstrating that aeration and fluid dynamics are important factors in this process. Cellular metabolism and enzyme production decreased at temperatures above 35 °C. The maximum enzymatic activity was observed at pH 7.0 and 50 °C. XR is a heterodimeric protein with a molecular mass of approximately 30 kDa. These results indicate that CABHM is a promising substrate for XR production by C. tropicalis, contributing to the development of enzymatic bioprocesses for xylitol production from lignocellulosic biomass. This study also demonstrates the potential of agro-industrial residues as sustainable feedstocks in biorefineries, aligning with the principles of a circular bioeconomy.