Study on the Purification of β-mannanase Produced from Aspergillus niger and Its Enzymatic Properties

[Objective] The study aimed to separate and purify β-mannanase produced by A.niger with solid state fermentation and study the enzymatic properties of β-mannanase.[Method] Crude enzyme liquid was prepared with solid state fermentation.β-mannanase was separated and purified from the crude enzyme liquid by(NH4)2SO4 segmentation precipitation,acetone precipitation,and Sephadex gel chromatography,resp.,and its purity was detected by PAGE.Enzymatic properties of purified β-mannanase were measured.[Result] The specific activity of β-mannanase could be increased to 1 180.9 U/mg through(NH4)2SO4 precipitation with saturation of 40%～90%;that could be increased to 1 847.0 U/mg through acetone precipitation with the volume ratio of 1.0∶1.0-1.6∶1.0;and finally,that could be increased to 7 950.4 U/mg and the purification fold was 8.67 through gel chromatography.It showed one single band on PAGE gel,which was purified β-mannanase. [Conclusion] The optimum pH value of purified β-mannanase had the enzymatic properties as follows: the optimum pH value of 4.2,the optimum reaction temperature of 60 ℃ and the michaelis constant Km of 2.67 mg/ml.