Production of xylitol from D-xylose by Candida tropicalis: optimization of production rate.

The effect of culture conditions on xylitol production rate was investigated using Candida tropicalis IFO 0618. From the variance analysis of xylitol production rate, it was found that initial yeast extract concentration was highly significant (99%), while the interaction between D-xylose concentration and aeration rate was significant (95%). These results show the importance of initial yeast extract concentration and of the balance between D-xylose concentration and aeration in the production of xylitol. It was also clearly shown that C. tropicalis needed more yeast extract concentration for efficient xylitol production than for its growth. In order to enhance xylitol production rate, culture conditions were optimized by the Box-Wilson method. In this respect, initial D-xylose concentration, yeast extract concentration, and K(L)a were chosen as the independent factors in 2(3)-factorial experimental design. As the result of experiments, a maximum xylitol production rate of 2.67 g/L . h was obtained when initial D-xylose concentration and yeast extract concentration were 172.0 and 21.0 g/L, respectively, and K(L)a was 451.50 h(-1) by 90% oxygen gas.