초록
<P><B>Abstract</B></P><P>Two acidic β-glucosidases (βGI and βGII) from the brown rot fungus <I>Fomitopsis palustris</I> were purified to homogeneity by several chromatographic steps. βGI and βGII had molecular weights of 130 and 213kDa, respectively, and exhibited optimum activity at pH 2.5 and 55°C. The <I>K</I><SUB><I>m</I></SUB> values of βGI and βGII for <I>p</I>-nitrophenyl-β-<SMALL>D</SMALL>-glucopyranoside were 0.706 and 0.971mM, 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, <I>F. palustris</I> was able to produce ethanol when cultured on medium containing 20g/l of glucose, mannose, cellobiose, and maltose, in which the maximum ethanol concentrations measured were 9.2, 8.7, 9.0, and 8.9g/l, corresponding to 90.2%, 85.3%, 88.2%, and 87.3% of the theoretical yield, respectively. These findings suggest that <I>F. palustris</I> 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.</P>