Bioproduction of Xylitol From Chestnut Shell Hydrolysate: Optimization of Fermentation Parameters

Abstract

In this study, xylitol production of Candida tropicalis M2 was optimized in chestnut shell hemicellulosic hydrolysate. Initial xylose concentration, initial concentration of ammonium chloride which was chosen as a nitrogen source and shaking rate were selected as the independent variables. Modelling the effects of the independent variables on maximum xylitol concentration (Y1), xylitol yield (Y2), maximum xylitol production rate (Y3), percentage of substrate conversion (Y4) and specific product formation rate (Y5) were performed by response surface methodology using central composite design. Variations of the responses with the independent variables were defined by a quadratic model except the Y4. According to ANOVA results, initial concentration of ammonium chloride was found to be the most important parameter. Linear effect of the initial xylose concentration was found as significant for only Y1. The effect of shaking rate was very significant for the Y1 and Y4. By numeric optimization conducted; the conditions with 80 g/L initial xylose concentration, 3.761 g/L initial ammonium chloride concentration and 80 strokes/min of shaking rate were predicted as optimum conditions. In optimum conditions; Y1, Y2, Y3, Y4 and Y5 were obtained as; 24.50 g/L, 31.517%, 0.497 g/L.h, 97.35% and 0.06 g/L.h.N, respectively