Effects of environmental conditions on xylose reductase and xylitol dehydrogenase production by Candida guilliermondii

The effects of environmental conditions, namely initial pH (2.5-7.0) and te mperature (25 and 35 degrees C), on xylose reductase and xylitol dehydrogen ase levels, as well as on xylitol production, were evaluated. Although the fermentative parameter values increased with an increase in pH and temperat ure (the maximum Y-p/s and Q(p) were 0.75 g/g and 0.95 g/[L.h], respectivel y, both attained at pH 6.0/, 35 degrees C),.the highest xylose reductase ac tivities (nearly 900 IU/mg of protein) were observed at an initial pH varyi ng from 4.0 to 6.0. Xylitol dehydrogenase was favored by an increase in bot h initial pH and temperature of the medium. The highest xylitol dehydrogena se specific activity was attained at pH 6.5 and 35 degrees C (577 IU/mg of protein).