Kwon Soun-Gyu, Park Seung-Won, Oh Deok-Kun
Department of Bioscience and Biotechnology, Sejong University, 98 Gunja-dong, Gwangin-gu, Seoul 143-747, Korea.
J Biosci Bioeng. 2006 Jan;101(1):13-8. doi: 10.1263/jbb.101.13.
Candida tropicalis, an osmophilic strain isolated from honeycomb, produced xylitol at a maximal volumetric productivity of 3.5 g l(-1) h(-1) from an initial xylose concentration of 200 g l(-1). Even at a very high xylose concentration, e.g., 350 g l(-1), this strain produced xylitol at a moderate rate of 2.07 g l(-1) h(-1). In a fed-batch fermentation of xylose and glucose, 260 g l(-1) xylose was added, and the xylitol production was 234 g l(-1) for 48 h, corresponding to a rate of 4.88 g l(-1) h(-1). To increase xylitol productivity, cells were recycled in a submerged membrane bioreactor with suction pressure and air sparging. For each recycle round in cell-recycle fermentation, the average concentration of xylitol produced, fermentation time, volumetric productivity, and product yield were 180 g l(-1), 19.5 h, 8.5 g l(-1) h(-1), and 85%, respectively. When cell-recycle fermentation was started with the cell mass concentrated twofold after batch fermentation and performed for 10 recycle rounds, we achieved a very high productivity of 12 g l(-1) h(-1). The productivity and total amount of xylitol in cell-recycle fermentation were 3.4- and 11.0-fold higher than those in batch fermentation, respectively.
热带假丝酵母是从蜂巢中分离出的嗜渗菌株，在初始木糖浓度为200 g l⁻¹的条件下，木糖醇的最大体积生产率为3.5 g l⁻¹ h⁻¹。即使在非常高的木糖浓度下，例如350 g l⁻¹，该菌株仍以2.07 g l⁻¹ h⁻¹的适中速率生产木糖醇。在木糖和葡萄糖的补料分批发酵中，添加了260 g l⁻¹的木糖，48小时内木糖醇产量为234 g l⁻¹，对应速率为4.88 g l⁻¹ h⁻¹。为提高木糖醇生产率，细胞在具有抽吸压力和空气鼓泡的浸没式膜生物反应器中进行循环。在细胞循环发酵的每个循环周期中，木糖醇的平均产生浓度、发酵时间、体积生产率和产物得率分别为180 g l⁻¹、19.5小时、8.5 g l⁻¹ h⁻¹和85%。当细胞循环发酵以分批发酵后浓缩两倍的细胞量开始，并进行10个循环周期时，我们实现了12 g l⁻¹ h⁻¹的非常高的生产率。细胞循环发酵中木糖醇的生产率和总量分别比分批发酵高3.4倍和11.0倍。
