Preliminary kinetic characterization of xylose reductase and xylitol dehydrogenase extracted from Candida guilliermondii FTI 20037 cultivated in sugarcane bagasse hydrolysate for xylitol production
L. Sene et al., Preliminary kinetic characterization of xylose reductase and xylitol dehydrogenase extracted from Candida guilliermondii FTI 20037 cultivated in sugarcane bagasse hydrolysate for xylitol production, APPL BIOC B, 91-3, 2001, pp. 671-680
Candida guilliermondii FTI 20037 was cultured in sugarcane bagasse hydrolys
ate supplemented with 2.0g/L of (NH4)(2)SO4, 0.1 g/L of CaCl2 . 2H(2)O, and
20.0 g/L of rice bran at 35 degreesC; pH 4.0; agitation of 300 rpm; and ae
ration of 0.4, 0.6, or 0.8 vvm. The high xylitol production (20.0 g/L) and
xylose reductase (XR) activity (658.8 U/mg of protein) occurred at an aerat
ion of 0.4 vvm. Under this condition, the xylitol dehydrogenase (XD) activi
ty was low. The apparent K-M for XR and XD against substrates and cofactors
were as follows: for XII, 6.4 x 10(-2)M (xylose) and 4.5 x 10(-3) mM (NADP
H); for XD, 1.6 x 10(-1)M (xylitol) and 9.9 x 10(-2) mM (NAD+). Because XR
requires about 10-fold less xylose and cofactor than XD for the condition i
n which the reaction rate is half of the V-max, some interference on the ov
erall xylitol production by the yeast could be expected.