Production of xylitol by metabolically engineered strains of Bacillus subtilis

Xylitol-phosphate dehydrogenase (XPDH) genes from several Gram-positive bacteria were isolated and expressed in Bacillus subtilis. The substrate specificities of the recombinant XPDH enzymes were compared and it was found that the XPDH enzymes of Lactobacillus rhamnosus and Clostridium difficile had the highest selectivity towards d-xylulose 5-phosphate. Expression of these two XPDH enzymes in d-ribulose and d-xylulose producing B. subtilis strain resulted in strains of B. subtilis capable of converting d-glucose into xylitol at around 23% yield.