Xylose reductase activity in Debaryomyces hansenii UFV-170 cultivated in semi-synthetic medium and cotton husk hemicellulose hydrolyzate.
To develop a new enzymatic xylose-to-xylitol conversion, deeper knowledge on the regulation of xylose reductase (XR) is needed. To this purpose, a new strain of Debaryomyces hansenii (UFV-170), which proved a promising xylitol producer, was cultivated in semi-synthetic media containing different carbon sources, specifically three aldo-hexoses (D-glucose, D-galactose and D-mannose), a keto-hexose (D-fructose), a keto-pentose (D-xylose), three aldo-pentoses (D-arabinose, L-arabinose and D-ribose), three disaccharides (maltose, lactose and sucrose) and a pentitol (xylitol). The best substrate was lactose on which cell concentration reached about 20 g l(-1) dry weight (DW), while the highest specific growth rates (0.58-0.61 h(-1)) were detected on lactose, D-mannose, D-glucose and D-galactose. The highest specific activity of XR (0.24 U mg(-1)) was obtained in raw extracts of cells grown on D-xylose and harvested in the stationary growth phase. When grown on cotton husk hemicellulose hydrolyzates, cells exhibited XR activities five to seven times higher than on semi-synthetic media.
Sampaio
Fábio Coelho
FC
Food Technology Department, Federal University of Viçosa, Viçosa, Minas Gerais 36571-000, Brazil.
de Faria
Janaína Teles
JT
Coimbra
Jane Sélia R
JS
Lopes Passos
Flávia M
FM
Converti
Attilio
A
Minin
Luis Antônio
LA
D000449:Aldehyde Reductase / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D003470:Culture Media; D055165:Debaryomyces / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism*; D005285:Fermentation; D005524:Food Technology; D003368:Gossypium / Q000737:chemistry; D006868:Hydrolysis; D007700:Kinetics; D011134:Polysaccharides / Q000378:metabolism*; D013379:Substrate Specificity; D014993:Xylitol / Q000096:biosynthesis; D014994:Xylose / Q000378:metabolism
D003470:Culture Media; D011134:Polysaccharides; C007916:hemicellulose; D014994:Xylose; D000449:Aldehyde Reductase; D014993:Xylitol