聚氨酯固定化热带假丝酵母发酵木糖醇

Polyurethane Foam Immobilization of Candida tropicalis for Xylitol Production

摘要:

固定在多孔聚氨酯载体中的热带假丝酵母(Candida tropicalis), 可有效地利用玉米芯半纤维素水解液生产木糖醇。在摇瓶条件下, 采用分批发酵方式, 确立了适宜的发酵工艺参数为: 接种量7%, 聚氨酯加入量1.0 g/100 mL, 温度30°C, 初始pH值6.0, 分段改变摇床转速进行溶氧调节, 其中0~24 h 为200 r/min; 24 h~46 h为140 r/min。聚氨酯固定化提高了菌体对发酵抑制物的耐受力, 固定化细胞密度高, 发酵性能稳定, 发酵产率和体积生产速率都有所提高。水解液未经脱色与离子交换便可转化成木糖醇, 大幅降低了成本, 显示了良好的应用前景。固定化细胞连续重复进行12批次21 d的发酵, 木糖醇得率平均为67.6%, 体积生产速率平均为1.92 g/(L·h)。

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).