产木聚糖酶白地霉培养特性及部分纯化的酶学特性

本文对白地霉Ref1的培养特性、产酶条件和酶学特性进行了初步研究。结果表明:该菌为低温型菌株,其最佳生长条件为pH6、20℃和酵母膏作为氮源;最佳产酶条件为pH3-7、15℃及以酵母膏氮源;条件优化后产酶可达118.7U/mL,可溶蛋白含量可达到60μg/mL,酶溶液的比活可达到1250U/mg蛋白质;该木聚糖酶的最适反应温度和pH分别为50℃和5,金属离子Mg2+、Na+和8mmol/L的Fe2+、Cu2+、Zn2+等对木聚糖酶的活性有抑制作用,而Ca2+、4mmol/L的Fe2+、Cu2+、Zn2+和8mmol/L的Mn2+等对该酶反应则有促进作用;该木聚糖酶在保温2h后在15-40℃范围内能保持80%以上的酶活性,在50℃时能保持68%的酶活性;用lineweaver-Burk作图法(双倒数作图法)求得该酶的最大反应速度Vmax和Km值分别为163.38mmol/mg/min和0.75mg/mL。

Growth conditions and xylanase property of Geotrichum candidum

The characteristics of culture, xylanase producing condition and characteristics of enzyme of Geotrichum candidum Ref1 were studied. The result showed that Ref1 was a psychrophile, and the best growing conditions were pH 6, 20℃ and yeast extract as nitrogen source while the best xylanase producing conditions were pH 3-7, 15℃ and yeast extract as nitrogen source. Xylanase activity of optimized Ref1 reached 118.7U/mL and soluble protein 60μg/mL; the specific activity of the crude enzyme was 1250U/mg protein. The xylanase has an optimal activity at 50 ℃ and pH 5.0, and the relative enzyme activity remains 80% while keeping at the temperatures of 15-40℃. Mg2+, Na+ and 8mmol/L Fe2+, Cu2+, Zn2+ were strong inhibitors, while Ca2+ , 4mmol/L Fe2+, Cu2+, Zn2+ and 8mmol/L Mn2+ were stimulators of the enzyme. The maximum velocity of reaction and the Km of the xylanase were 163.38mmol/mg/min and 0.75mg/mL, respectively.