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Enzyme and Microbial Technology 48 (2011) 359–364

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Enzyme and Microbial Technology
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Characterizationof two acidic -glucosidases and ethanol fermentation in the brown rot fungus Fomitopsis palustris
Kenji Okamoto ∗ , Yuko Sugita, Natsumi Nishikori, Yasuyuki Nitta, Hideshi Yanase
Department ofChemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama, Tottori 680-8552, Japan

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Two acidic -glucosidases ( GI andGII) from the brown rot fungus Fomitopsis palustris were purified to homogeneity by several chromatographic steps. GI and GII had molecular weights of 130 and 213 kDa, respectively, and exhibited optimumactivity at pH 2.5 and 55 ◦ C. The Km values of GI and GII for pnitrophenyl- -d-glucopyranoside were 0.706 and 0.971 mM, respectively. Although the effect of metal ions and inhibitors differedbetween the two enzymes, both -glucosidases exhibited preferential glucose release during hydrolysis of cello-oligosaccharides, indicating that GI and GII possess effective exo-type activities. Notably,F. palustris was able to produce ethanol when cultured on medium containing 20 g/l of glucose, mannose, cellobiose, and maltose, in which the maximum ethanol concentrations measured were 9.2, 8.7,9.0, and 8.9 g/l, corresponding to 90.2%, 85.3%, 88.2%, and 87.3% of the theoretical yield, respectively. These findings suggest that F. palustris has the ability not only to secrete -glucosidase enzymeseffective at low pH, but also to function as a biocatalyst, which may be suitable for the conversion of lignocellulosic materials into ethanol. © 2010 Elsevier Inc. All rights reserved.

Articlehistory: Received 24 July 2010 Received in revised form 17 December 2010 Accepted 20 December 2010 Keywords: -Glucosidase Purification Ethanol Fermentation Brown rot fungus Fomitopsis palustris