Xylanases from alkalophilic thermophilic Bacillus spp. W1 and W2 were purified and characterized. The xylanases from the two strains were fractionated into two active components (I and II) by DEAE-Toyopearl 650M chromatography. Components I from the two strains had similar properties: optimum pH, 6.0; optimum temperature, 65°C; isoelectric point, pH 8.5 and 8.3; molecular weight, 21, 500 and 22, 500; and Michaelis constant, 4.5 and 4.0mg-xylan/ml. Components II from the two strains also had similar properties: optimum pH, 7.0-9.0 and 7.0-9.5; optimum temperature, 70°C; isoelectric point, pH 3.6 and 3.7; molecular weight, 49, 500 and 50, 000; and Michaelis constant, 0.95 and 0.57mg-xylan/ml. The activities of components I and II were inhibited by Hg⁺⁺ and Cu⁺⁺. Components I hydrolyzed xylan to yield xylobiose and higher oligomers, but components II produced xylose other than xylobiose and xylooligomers.

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