Enhancement of xylitol productivity and yield using a xylitol dehydrogenase gene-disrupted mutant of Candida tropicalis under fully aerobic conditions.

The effects of glycerol and the oxygen transfer rate on the xylitol production rate by a xylitol dehydrogenase gene (XYL2)-disrupted mutant of Candida tropicalis were investigated. The mutant produced xylitol near the almost yield of 100% from D: -xylose using glycerol as a co-substrate for cell growth and NADPH regeneration: 50 g D: -xylose l(-1) was completely converted into xylitol when at least 20 g glycerol l(-1) was used as a co-substrate. The xylitol production rate increased with the O(2) transfer rate until saturation and it was not necessary to control the dissolved O(2) tension precisely. Under the optimum conditions, the volumetric productivity and xylitol yield were 3.2 g l(-1) h(-1) and 97% (w/w), respectively.