The reduction of xylose to xylitol by Candida guilliermondii and Candida parapsilosis: Incidence of oxygen and pH

Summary The ability of C. guilliermondii and C. parapsilosis to ferment xylose to xylitol was evaluated under different oxygen transfer rates in order to enhance the xylitol yield. In C. guilliermondii, a maximal xylitol yield of 0.66 g/g was obtained when oxygen transfer rate was 2.2 mmol/l.h. Optimal conditions to produce xylitol by C. parapsilosis (0.75 g/g) arose from cultures at pH 4.75 with 0.4 mmoles of oxygen/l.h. The response of the yeasts to anaerobic conditions has shown that oxygen was required for xylose metabolism.Nomenclature max maximum specific growth rate (per hour) - qSmax maximum specific rate of xylose consumption (g xylose per g dry biomass per hour) - qpmax maximum specific productivity of xylitol (g xylitol per g dry biomass per hour) - Qp average volumetric productivity of xylitol (g xylitol per liter per hour) - Y_P/S xylitol yield (g xylitol per g substrate utilized) - Y_P'/S glycerol yield (g glycerol per g substrate utilized) - Y_X/S biomass yield (g dry biomass per g substrate utilized)