Kinetics of Xylitol Fermentation by Candida guilliermondii Grown on Rice Straw Hemicellulosic Hydrolysate

Abstract

The fermentation kinetics for the conversion of rice straw hemicellulosic hydrolysate to xylitol by the yeast Candida guilliermondii was evaluated under batch conditions. The fermentation was accomplished in a 1 L working volume stirred-tank reactor with aeration of 1.3 vvm and agitation of 300 rpm (kLa = 15/h). The maximum specific rate of xylitol formation (0.12 g/g) was achieved when the specific growth rate was lowered to 1/5 of its highest value. From analysis of the fermentation kinetics, a linear correlation between specific growth rate (μx) and specific rate of xylitol formation (qp ) was evident. Based on the Gaden model, this bioprocess was classified as growth-associated production and the relationship between μx and qp can be described by the equation qp = 6.31 μx.