A Sustainable Approach for Xylitol Production from Pistachio Shell using Candida tropicalis

Abstract In this study, first xylose rich hydrolysate was obtained from pistachio shell using microwave-assisted high-pressure CO2/H2O hydrolysis and then xylitol was produced biotechnologically from xylose-rich hydrolysate by Candida tropicalis. The maximum xylose concentration and yield attained were 14.58 ± 0.11 g/L and 62.01 ± 0.92%, respectively. Before the bioconversion process, hydrolysate was detoxified to remove HMF and furfural with activated charcoal. Box Behnken design was implemented to investigate the effect of temperature, pH and aeration rate on xylitol yield during bioconversion in bioreactor. The highest xylitol yield of 0.94 g/g was recorded at 72 h under optimized conditions of 34.5°C, pH 4.5 and 1.2 vvm. Recovery and purification of xylitol from the fermentation medium was achieved using ethanol as an antisolvent. Xylitol was recovered with a yield of 68.4% from culture medium by crystallization. Based on the findings of this study, it is conceivable to propose a sustainable and environmentally friendly process for recovering and purifying xylitol from pistachio shell hydrolysate.