Factors affecting the production of L-xylulose by resting cells of recombinant Escherichia coli.

Factors affecting the production of the rare sugar L-xylulose from xylitol using resting cells were investigated. An E. coli BPT228 strain that recombinantly expresses a gene for xylitol dehydrogenase was used in the experiments. The ratio of xylitol to L-xylulose was three times lower in the cytoplasm than in the medium. The effects of pH, temperature, shaking speed, and initial xylitol concentration on L-xylulose production were investigated in shaking flasks using statistical experimental design methods. The highest production rates were found at high shaking speed and at high temperature (over 44 degrees C). The optimal pH for both productivity and conversion was between 7.5 and 8.0, and the optimal xylitol concentration was in the range 250-350 g l(-1). A specific productivity of 1.09 +/- 0.10 g g(-1) h(-1) was achieved in a bioreactor. The response surface model based on the data from the shake flask experiments predicted the operation of the process in a bioreactor with reasonable accuracy.