Production of xylitol in cell recycle fermentations of Candida tropicalis

Xylitol was produced a in two-substrate, batch fermentation with cell recyc ling of Candida tropicalis ATCC 13803. A series of cell-recycle experiments showed that the feeding of xylose, glucose and yeast extract in the xylito l production phase was most effective in enhancing xylitol productivity. Th e optimized cell recycle fermentation resulted in 0.82 g xylitol/g xylose y ield, 4.94 g xylitol l(-1) h(-1) productivity, and final xylitol concentrat ion of 189 g l(-1). These results were 1.3 times higher in volumetric xylit ol productivity and 2.2 times higher in final product concentration compare d with the corresponding values of the optimized two-substrate batch cultur e.