title: Preliminary kinetic characterization of xylose reductase and xylitol dehydrogenase extracted from Candida guilliermondii FTI 20037 cultivated in sugarcane bagasse hydrolysate for xylitol production.
abstract: Candida guilliermondii FTI 20037 was cultured in sugarcane bagasse hydrolysate supplemented with 2.0 g/L of (NH4)2SO4, 0.1 g/L of CaCl2 x 2H2O, and 20.0 g/L of rice bran at 35 degrees C; pH 4.0; agitation of 300 rpm; and aeration 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 aeration of 0.4 vvm. Under this condition, the xylitol dehydrogenase (XD) activity was low. The apparent K(M) for XR and XD against substrates and cofactors were as follows: for XR, 6.4 x 10(-2)M (xylose) and 9.5 x 10(-3) mM (NADPH); 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 in which the reaction rate is half of the Vmax, some interference on the overall xylitol production by the yeast could be expected.
authors.affiliation: Department of Biochemical and Pharmaceutical Technology, Faculty of Pharmacy, University of São Paulo, SP, Brazil.
authors.forename: L
authors.initials: L
authors.lastname: Sene
authors.forename: M G
authors.initials: MG
authors.lastname: Felipe
authors.forename: S S
authors.initials: SS
authors.lastname: Silva
authors.forename: M
authors.initials: M
authors.lastname: Vitolo
mesh_terms: D000388:Air; D000449:Aldehyde Reductase / Q000302:isolation & purification / Q000378:metabolism*; D027461:Beta vulgaris; D018533:Biomass; D002175:Candida / Q000201:enzymology* / Q000254:growth & development; D050542:D-Xylulose Reductase; D004795:Enzyme Stability; D005285:Fermentation; D005511:Food Handling; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D007700:Kinetics; D013401:Sugar Alcohol Dehydrogenases / Q000302:isolation & purification / Q000378:metabolism*; D013696:Temperature; D014993:Xylitol / Q000096:biosynthesis*
chemical_list: D007220:Industrial Waste; D013401:Sugar Alcohol Dehydrogenases; D000449:Aldehyde Reductase; D050542:D-Xylulose Reductase; D014993:Xylitol