Kinetics of biodegradation of free gossypol by Candida tropicalis in solid-state fermentation

Abstract

In the present work experiments were carried out to study the effect of free gossypol on the growth of Candida tropicalis ZAU-1, evaluate its ability in biodegrading free gossypol, analyze the time course of solid-state fermentation, and model the microbial growth by determining the kinetics of dry matter weight loss, total carbohydrate concentration and the free gossypol content during solid-state fermentation. Results showed that the biomass in inorganic salts glucose medium were unaffected by free gossypol at 500 and 1000 mg/l levels, compared with the control group ( p > 0.05); degradation of free gossypol reached 95.12% and 94.12%, respectively. A logistic equation ( R 2 = 0.9922), describing the growth model of C. tropicalis ZAU-1 was obtained, with the maximum values of u m and X m at 0.0970 h −1 and 21.8631% of dry matter weight loss, respectively. A good-fit curvilinear regression model was achieved to describe the change pattern of total carbohydrate concentration ( R 2 = 0.9910), and the biodegradation pattern of free gossypol ( R 2 = 0.9825). These models could be used to predict the fermentation course by C. tropicalis ZAU-1 under solid-state fermentation.