RESUMO
Microorganisms capable of producing xylitol from D-arabitol were screened for. Of the 420 strains tested, three bacteria, belonging to the genera Acetobacter and Gluconobacter, produced xylitol from D-arabitol when intact cells were used as the enzyme source. Among them, Gluconobacter oxydans ATCC 621 produced 29.2 g/l xylitol from 52.4 g/l D-arabitol after incubation for 27 h. The production of xylitol was increased by the addition of 5% (v/v) ethanol and 5 g/l D-glucose to the reaction mixture. Under these conditions, 51.4 g/l xylitol was obtained from 52.4 g/l D-arabitol, a yield of 98%, after incubation for 27 h. This conversion consisted of two successive reactions, conversion of D-arabitol to D-xylulose by a membrane-bound D-arabitol dehydrogenase, and conversion of D-xylulose to xylitol by a soluble NAD-dependent xylitol dehydrogenase. Use of disruptants of the membrane-bound alcohol dehydrogenase genes suggested that NADH was generated via NAD-dependent soluble alcohol dehydrogenase.
