ABSTRACT
Immobilization conditions of Candida tropicalis to be absorbed in polyurethane foam carrier materials were studied on the xylitol production from corn hemicellulosic hydrolysate. Optimum batch-fermentation conditions were as follows: inoculum amount, 7% (volume ratio); polyurethane foam quantity, 1.0 g/100 mL; 30?C; initial pH, 6.0. Shaking speed was divided into two-phase to accommodate the dissolved oxygen, with 200 r/min at 0~24 h and 150 r/min at 24 h~46 h. The immobilized cells on polyurethane foam carrier have high density and good resistance to inhibitors in the hydrolysates. Average xylitol yield and volumetric productivity of polyurethane foam immobilized fermentation were much higher than the fermentation without immobilization. Corn cob hydrolysates can be directly biotransformed to xylitol without decoloration or ion-exchange treatment. This process can effectively reduce production costs, and it shows broad prospects of applications. Average xylitol yield was 67.6% and xylitol volumetric productivity was 1.92 g/(L?h).