Effect of pH on xylitol production by Candida species from a prairie cordgrass hydrolysate.

Using hydrolysates of the North American prairie grass prairie cordgrass buffered at pH 4.5, 5.0, 5.5 or 6.0, xylitol production, xylitol yield, cell biomass production and productivity were investigated for three strains of yeast Candida. Of the three strains, the highest xylitol concentration of 20.19 g xylitol (g xylose consumed)-1 and yield of 0.89 g xylitol (g xylose consumed)-1 were produced by Candida mogi ATCC 18364 when grown for 120 h at 30° C on the pH 5.5-buffered hydrolysate-containing medium. The highest biomass level being 7.7 g cells (kg biomass)-1 was observed to be synthesized by Candida guilliermondii ATCC 201935 after 120 h of growth at 30° C on a pH 5.5-buffered hydrolysate-containing medium. The highest xylitol specific productivity of 0.73 g xylitol (g cells h)-1 was determined for C. guilliermondii ATCC 20216 after 120 h of growth at 30°C on a pH 5.0-buffered hydrolysate-containing medium. Xylitol production and yield by the three Candida strains was higher on prairie cordgrass than what was previously observed for the same strains after 120 h at 30° C when another North American prairie grass big bluestem served as the plant biomass hydrolysate indicating that prairie cordgrass may be a superior plant biomass substrate.