Characterization of Thermostable Acidic β-mannanase from Bacillus pumilus XZG33

[Objective]An extracellular acid mannanase from the Bacillus pumilus XZG33 was purified and characterized.[Method]The mannanase of XZG33 strain was purified to homogeneity using precipitation with ammonium sulfate,DEAE-cellulose DE52 ion exchange chromatography and Sephadex G-100 gel filtration,with a 39.7-fold increase in specific activity and 20.2% recovery.The enzyme purified is composed of a single polypeptide chain having an apparent molecular mass of 40.0 kDa as determined by SDS-PAGE and gel filtration through sephadex G-75 column.The optimum pH value and temperature for the mannanase activity were 5.0 and 60 ℃,respectively.The enzyme was stable in the pH value range of 2.0-8.0.It was stable up to 80 ℃.The mannanase was activated by divalent cations such as Ca2+,Mn2+,Mg2+ and Co2+.The mannanase was highly specific towards locust bean gum,but exhibited very low activity towards starch,CMC and birchwood xylan.Apparent Km value of the mannanase for locust bean gum was 4.6 mg/ml.[Conclusion]The thermal and pH stability of the purified β-mannanase from Bacillus pumilus XZG33 make this enzyme attractive for biotechnological applications.