PRODUCTION OF XYLITOL FROM D-XYLOSE BY DEBARYOMYCES-HANSENII

Xylitol, a naturally occurring five-carbon sugar alcohol, can be produ ced from D-xylose through microbial hydrogenation. Xylitol has found i ncreasing use in the food industries, especially in confectionary. It is the only so-called ''second-generation polyol sweeteners'' that is allowed to have the specific health claims in some world markets. In t his study, the effect of cell density on the xylitol production by the yeast Debaryomyces hansenii NRRL Y-7426 from D-xylose under microaero bic conditions was examined. The rate of xylitol production increased with increasing yeast cell density to 3 g/L. Beyond this amount there was no increase in the xylitol production with increasing cell density . The optimal pH range for xylitol production was between 4.5 and 5.5. The optimal temperature was between 28 and 37 degrees C, and the opti mal shaking speed was 300 rpm. The rate of xylitol production increase d linearly with increasing initial xylose concentration. A high concen tration of xylose (279 g/L) was converted rapidly and efficiently to p roduce xylitol with a product concentration of 221 g/L was reached aft er 48 h of incubation under optimum conditions.