title: Xylose reductase and xylitol dehydrogenase activities of Candida guilliermondii as a function of different treatments of sugarcane bagasse hemicellulosic hydrolysate employing experimental design.
abstract: The sugarcane bagasse hydrolysate, which is rich in xylose, can be used as culture medium for Candida guilliermondii in xylitol production. However, the hydrolysate obtained from bagasse by acid hydrolysis at 120 degrees C for 20 min has by-products (acetic acid and furfural, among others), which are toxic to the yeast over certain concentrations. So, the hydrolysate must be pretreated before using in fermentation. The pretreatment variables considered were: adsorption time (15,37.5, and 60 min), type of acid used (H2So4 and H3Po4), hydrolysate concentration (original, twofold, and fourfold concentrated), and active charcoal (0.5, 1.75 and 3.0%). The suitability of the pretreatment was followed by measuring the xylose reductase (XR) and xylitol dehydrogenase (XD) activity of yeast grown in each treated hydrolysate. The response surface methodology (2(4) full factorial design with a centered face) indicated that the hydrolysate might be concentrated fourfold and the pH adjusted to 7.0 with CaO, followed by reduction to 5.5 with H3PO4. After that it was treated with active charcoal (3.0%) by 60 min. This pretreated hydrolysate attained the high XR/XD ratio of 4.5.
authors.affiliation: Department of Biochemical and Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, University of São Paulo, SP, Brazil.
authors.forename: Lourdes A
authors.initials: LA
authors.lastname: Alves
authors.forename: Michele
authors.initials: M
authors.lastname: Vitolo
authors.forename: Maria das Graças A
authors.initials: Md
authors.lastname: Felipe
authors.forename: João Batista
authors.initials: JB
authors.lastname: de Almeida e Silva
mesh_terms: D000449:Aldehyde Reductase / Q000378:metabolism*; D002175:Candida / Q000187:drug effects / Q000201:enzymology*; D002482:Cellulose / Q000494:pharmacology*; D050542:D-Xylulose Reductase; D006868:Hydrolysis; D011134:Polysaccharides / Q000494:pharmacology*; D031786:Saccharum; D013401:Sugar Alcohol Dehydrogenases / Q000378:metabolism*
chemical_list: D011134:Polysaccharides; C007916:hemicellulose; D002482:Cellulose; C027433:bagasse; D013401:Sugar Alcohol Dehydrogenases; D000449:Aldehyde Reductase; D050542:D-Xylulose Reductase