title: Characterization of two acidic β-glucosidases and ethanol fermentation in the brown rot fungus Fomitopsis palustris.
abstract: Two acidic β-glucosidases (βGI and βGII) from the brown rot fungus Fomitopsis palustris were purified to homogeneity by several chromatographic steps. βGI and βGII had molecular weights of 130 and 213 kDa, respectively, and exhibited optimum activity at pH 2.5 and 55°C. The K(m) values of βGI and βGII for p-nitrophenyl-β-d-glucopyranoside were 0.706 and 0.971 mM, respectively. Although the effect of metal ions and inhibitors differed between the two enzymes, both β-glucosidases exhibited preferential glucose release during hydrolysis of cello-oligosaccharides, indicating that βGI and βGII 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 β-glucosidase enzymes effective at low pH, but also to function as a biocatalyst, which may be suitable for the conversion of lignocellulosic materials into ethanol.
authors: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama, Tottori 680-8552, Japan. okamoto@bio.tottori-u.ac.jp
authors: Kenji
authors: K
authors: Okamoto
authors: Yuko
authors: Y
authors: Sugita
authors: Natsumi
authors: N
authors: Nishikori
authors: Yasuyuki
authors: Y
authors: Nitta
authors: Hideshi
authors: H
authors: Yanase
mesh_terms: D001709:Biotechnology / Q000379:methods*; D002475:Cellobiose / Q000378:metabolism; D055453:Coriolaceae / Q000145:classification / Q000201:enzymology*; D003470:Culture Media; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D005962:Glucosylceramidase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008970:Molecular Weight; D009844:Oligosaccharides / Q000378:metabolism; D013696:Temperature
chemical_list: D003470:Culture Media; D009844:Oligosaccharides; D002475:Cellobiose; D000431:Ethanol; D005962:Glucosylceramidase; D005947:Glucose