食品科学技术学报2018，Vol.36Issue(2)：42-51,10.DOI:10.3969/j.issn.2095-6002.2018.02.006
一株嗜热链球菌乳糖酶的分离纯化及酶学特性研究
Isolation, Purification and Enzyme Characteristics of Lactase Produced by a Streptococcus thermophiles Strain
摘要
Abstract
At present,there is wide application of microbial lactases, and these enzymes are character-ized with rich source of origin, high yield, low production cost, and short production cycle. This study was based on Streptococcus thermophilus GST-6 isolated from traditional dairy products with lactase produ-cing capability. Firstly,key factors that affect lactase production were determined by single factor tests. Then,the fermentation conditions for lactase production by GST-6 were optimized by using the method of response surface analysis. Based on the optimum fermentation conditions, the crude enzyme was pre-pared. After salting out by ammonium sulfate fractionation, the purified lactase was obtained by DEAE-SepHarose fast flow ion-exchange chromatography and SepHadex G-75 gel filtration chromatography. Fur-thermore,the kinetic properties and stability of the enzyme were studied. The results showed that key factors that affected lactase production were pH,inoculation rate and lactose concentration of the culture medium,and these factors had significant interactions. The optimum fermentation conditions of the cul-ture medium were as follows:pH 6.78,inoculation at 1% and lactose concentration of 25.00 g/L. The enzyme activity reached 112.63 U/mL.The characteristics of the enzyme were determined as follows:op-timum saturation ammonium sulfate fractionation by 10% ~50%; maximum hydrolytic activity at pH 6 and temperature 30~40℃,Mn2+could active enzymatic activty while Cu2+could inhibite enzymatic ac-tivity. The enzymatic inhibition by SDS,galactose,and EDTA was a decreasing order. The Kmvalue and Vmaxof this enzyme was 0.27 mmol/L and 2.20 μmol/min.关键词
嗜热链球菌/乳糖酶/优化/发酵/酶学特性Key words
Streptococcus thermophiles/lactase/optimization/fermentation/enzymology characteristics分类
轻工纺织引用本文复制引用
曹永强,余志坚,陈超,张健,杨贞耐..一株嗜热链球菌乳糖酶的分离纯化及酶学特性研究[J].食品科学技术学报,2018,36(2):42-51,10.基金项目
国家自然科学基金面上项目(31571857). （31571857）
