| Summary: | 碩士 === 大同工學院 === 化學工程研究所 === 86 === A fungus strain E-189 that produces cellobiose oxidase was isolated from soil and identified as Torula herbarum. E-189 was cultured in wheat bran medium for 5 to 7 days and the cellobiose oxidase was then extracted with phosphate buffer.The cellobiose oxidase was purified to homogeneity from crude extract of wheat bran culture by a series of purification steps, namely, ammonium sulfate fractionation, Fractogel DEAE-650M column, Toyopearl Phenyl-650M column, Fractogel TSK HW-55 column and Ultragel hydroxyapatite column. The specific activity of purified enzyme was identified to be 7.8 units per mg protein.The molecular weight of enzyme was determined by 12% SDS-PAGE and Sephadex S-300 to be about 120kDa and is composed of a dimer molecular. The enzyme activity is stable from pH4 to 9 and with an optimal value at the pH 6. The optimal reaction temperature for this enzyme was found to be 50oC, however, it was also stable under 60oC.Based on the absorption spectrum data, the enzyme is classified as a flavoprotein. Its activity was inhibited when modified with tetranitromethane (TNM), even in the presence of substrate. We suggested that there might be a tyrosine residue involved in the catalytic process. The enzyme was found also inhibited by the sodium azide which may block the electron transport system of the enzyme.This identified enzyme has substrate specificity to both cellobiose and cello-oligosaccharide.
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