Without internal affiliation

  • Author: Schmidt, Mariane

    University of Copenhagen

  • Author: Stougaard, Peter

    University of Copenhagen

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A novel, cold-active β-galactosidase was isolated from an Arctic Gram-positive bacterium, Alkalilactibacillus ikkense. The corresponding gene was cloned and expressed as an active enzyme in Escherichia coli. Denaturing gel electrophoresis of both the native and the recombinant β-galactosidase showed a monomeric molecular weight of 115-120 kDa. Analysis of the DNA sequence showed sequence similarity to known Glycosyl Hydrolase Family 2 β-galactosidases from the genera Bacillus, Paenibacillus, Geobacillus, and Lactobacillus. The β-galactosidase from this study was purified and shown to be highly active at low temperatures with more than 60% of its maximal activity maintained at 0 °C. The apparent optimal activity was observed at temperatures between 20 °C and 30 °C and at pH 8. The purified recombinant enzyme was stable without stabilizing agents for more than 100 hours at temperatures at and below 10 °C. At temperatures 40 °C and above, the β-galactosidase was irreversibly inactivated within 10 minutes. When lactose was present in substantial amounts, the enzyme displayed transgalactosylation activity. Comparison of the β-galactosidase with a commercially available enzyme showed that the conversion rate of the A. ikkense enzyme was approximately two-fold higher at temperatures between 0 °C and 20 °C.
Keyword: Psychrophilic,β -galactosidase,Alkalilactibacillus,Lactase,Cold-active
Original languageEnglish
JournalEnvironmental Technology
Issue number10
Pages (from-to)1107-1114
StatePublished - 2010
Externally publishedYes
CitationsWeb of Science® Times Cited: 19
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ID: 5561799