Isolation and Characterization of Psychrotolerant Serratia Quinivorans Strains Secreting β-D-galactosidase (original) (raw)

adapted and extracellular β-D-galactosidase (EC 3.2.1.23) with high specific activity has potential in food industry. Two psychrophlic bacterial isolates (A5-2 and B8) were screened from soil collected from permanent glaciers of Himachal Pradesh, India. Both A5-2 and B8 isolates showed growth between 4-25℃, but not at temperature higher than 30℃, hence classified as psychrotolerants. Biochemical characteristics and 16S rDNA sequencing identified the isolates as Serratia quinivorans A5-2 and Serratia quinivorans B8, and deposited in NCBI GenBank under accesion numbers KJ 176660 and KJ 176661, respectively. The cold active, extracellular β-D-galactosidase activity of A5-2 isolate was three fold higher compared to its intracellular activity. Comparatively, the B8 bacterial showed negligible intracellular activity, and its extracellular activity was two folds higher as compared to that of A5-2 isolate. Interestingly, growth and β-D-galactosidase activity of A5-2 was enhanced in lactose supplemented medium;whereas, growth of B8 isolate was unaffected and its β-D-galactosidase activity was enhanced when grown in lactose supplemented medium. β-D-galactosidase activity was also increased, when the isolates were grown in galactose supplementation medium, but decreased when grown in the presence of glucose. The presence of milk sugars like lactose, glucose, or galactose, or the milk metal ions, namely Ca 2+ and Na + ions did not inhibit the activity of β-D-galactosidase.

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