Increase of Xylitol Productivity by Cell-Recycle Fermentation of Candida tropicalis Using Submerged Membrane Bioreactor(BIOCHEMICAL ENGINEERING)

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Candida tropicalis, an osmophilic strain isolated from honeycomb, produced xylitol at a maximal volumetric productivity of 3.5g l^<-1> h^<-1> from an initial xylose concentration of 200g l^<-1>. Even at a very high xylose concentration, e.g., 350g l^<-1>, this strain produced xylitol at a moderate rate of 2.07g l^<-1> h^<-1>. In a fed-batch fermentation of xylose and glucose, 260g l^<-1> xylose was added, and the xylitol production was 234g l^<-1> for 48h, corresponding to a rate of 4.88g 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 180g l^<-1>, 19.5h, 8.5g 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 12g 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.
公益社団法人日本生物工学会の論文
2006-01-25