固定化细胞在三相流化床中发酵生产木糖醇

Xylitol production by immobilized Candida sp. cells in three-phase fluidized-bed bioreactor

为了建立一种成本低、产率高、能连续高效地生产木糖醇的新工艺,研究了固定化假丝酵母(Candidasp.)细胞在三相流化床内分批发酵玉米芯半纤维素水解液生产木糖醇这一工艺过程.适宜的工艺条件为:32℃,起始木糖质量浓度100g/L,固定化细胞与发酵培养基体积比1∶3.8,分段通气:0～24h,0.5L/min;24～80h,0.175L/min.利用固定化细胞重复进行6批发酵,木糖醇得率平均为63.5%.玉米芯半纤维素水解液未经脱色以及离子交换等脱毒处理便可直接有效地转化成木糖醇;三相流化床生物反应器动力消耗少、流化状态稳定均匀.该方法大大降低了原料预处理的成本,发酵结果较好.

In order to develop an efficient continuous process for producing xylitol at low cost and high yield, batch xylitol production on corn cob hemicellulosic hydrolysates carried out in a three-phase fluidized-bed bioreactor using Candida sp. cells immobilized in Ca-alginate beads was investigated. The optimal batch fermentation conditions in the bioreactor were as follows: 32°C, initial xylose concentration of hydrolysates: 100 g/L; volume ratio of immobilized cell to fermentation medium: 1:3.8; aeration rate: 0.5 L/min for the first 24 h, and then 0.175 L/min during 24-80 h. The immobilized cells could be reused successfully in at least 6 batch cycles with average xylitol yield of 63.5% in the bioreactor. The corn cob hemicellulosic hydrolysates could be efficiently converted to xylitol without being decolored or ion-exchanged. The three-phase fluidized-bed bioreactor has good mass transfer ability and low energy requirement for xylitol production. This process can effectively reduce the pretreatment costs and the fermentation results are desirable.