期刊
JOURNAL OF DAIRY SCIENCE
卷 101, 期 8, 页码 6946-6954出版社
ELSEVIER SCIENCE INC
DOI: 10.3168/jds.2018-14605
关键词
beta-galactosidase; Erwinia; isolation and purification; enzymatic characteristics
资金
- National Science and Technology Support Program of China (Beijing) [2015BAD17B02]
- National Natural Science Foundation of China (Beijing) [31000752]
- Jiangsu Overseas Research & Training Program for University Prominent Young & Middle-aged Teachers and Presidents (Nanjing, China)
beta-Galactosidases are widely used in industry for elimination of lactose from milk products. A new beta-galactosidase was obtained from bacterial strain Erwinia sp. E602, newly isolated in northeast China. The enzyme was purified with the methods of ammonium sulfate fractionation, ion exchange, and gel filtration chromatography for further study of the enzymatic characteristics. The purified enzyme had a molecular weight of near 110 kDa. The optimum reaction temperature and pH of this enzyme was determined to be 40 degrees C and 7.0, respectively, indicating that this enzyme was a mesophilic neutral beta-galactosidase. Furthermore, the enzyme retained near 10% of the activity at 0 degrees C, which also suggested its cold-adapted property. Kinetics of the beta-galactosidase was studied, and the Km (Michaelis constant) and Vmax (maximum enzymatic reaction rate) of this enzyme were 0.21 mmol/L and 263.16 mu mol/mg per minute, respectively. The effects of metal ions on the enzymatic activity and the lactose hydrolysis efficiency in milk, as well as its trans-glycosylation activity, were studied in this work. The beta-galactosidase coding gene was cloned to be a 3-kb length fragment, which shared at most 81% of identity with the published sequences in NCBI Blast database (https://blast.ncbi.nlm.nih.gov). Results in this work suggested it is a new beta-galactosidase and it has potential to be used in dairy and food processing.
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