2025 AIChE Annual Meeting

Fermentation of Xylitol Using C. Tropicalis

The U.S. Department of Energy recognizes xylitol as a high-value platform chemical with promising routes to bioproduction from underutilized lignocellulosic biomass such as agricultural wastes and residues. Xylitol is a pentose sugar alcohol that can be used as a platform chemical because of its multiple hydroxyl groups, making it a renewable alternative to petrochemical feedstocks used in lactic acid, ethanol, and other chemical production. Xylitol is also used as a low-calorie sweetener and for its anti-cariogenic properties in food and dental products. This work focuses on production of xylitol from xylose and investigating different fermentation conditions to move towards a commercially viable xylitol bioproduction pipeline. Specifically, methods of pH control and initial xylose concentrations were evaluated. Over multiple fermentation trials, the effects of initial xylose concentrations ranging 10 g/L to 50 g/L with and without pH control were investigated. In pH controlled conditions, pH was maintained at or above 6.5 using phosphate-buffered saline (PBS) solution or sodium hydroxide (NaOH). In the 96 hour fermentations, cell growth, pH, and xylose and xylitol concentrations were monitored at frequent time intervals. Visible spectrophotometry at 600 nm, pH probe measurement, and high performance liquid chromatography (HPLC) were used to measure cell growth, pH, and xylose and xylitol concentrations, respectively. The goal of this work was to optimize fermentation conditions to maximize xylitol titers and yields. A maximum titer of ~0.5 g xylitol / g xylose and maximum yield of 45% were achieved. Concurrent and future research includes the separation of xylitol from fermentation broth using ion-exchange chromatography, crystallization, and conversion to other high value chemicals, as well as life cycle and techno-economic analysis of an industrial-scale xylitol biorefinery.