Functional Characterization of a New Cold-Adapted β-Galactosidase from an Arctic Fjord Sediment Bacteria Enterobacter ludwigii MCC 3423

• Published in: Catalysis letters 2018-10, Vol.148 (10), p.3223-3235
• Main Authors: Alikunju, Aneesa P., Joy, Susan, Salam, Jaseetha Abdul, Silvester, Reshma, Antony, Ally C., Rahiman, K. M. Mujeeb, Krishnan, K. P., Hatha, A. A. Mohamed
• Format: Article
• Language: English
• Subjects: Bacteria; Calcium ions; Catalysis; Chemistry; Chemistry and Materials Science; Enterobacter cloacae; Enzymes; Fjords; Galactooligosaccharides; Galactose; Galactosidase; Industrial Chemistry/Chemical Engineering; Lactose; Organometallic Chemistry; Physical Chemistry
• ISSN: 1011-372X; 1572-879X
• DOI: 10.1007/s10562-018-2504-3

In the present study, a new cold-adapted β-galactosidase, BgalEL isolated from the fjord sediment bacteria, Enterobacter ludwigii MCC 3423, was purified and characterized. The phylogenetic analysis of partial sequence of bgalEL gene revealed 99% relatedness of the enzyme to Enterobacter cloacae β-galactosidase. BgalEL is a homotetramer with molecular weight 465 kDa composed of ~ 116.42 kDa subunits. The optimal pH range and temperature for maximum hydrolytic activity on ONPG were 7.0–8.0 and 45 °C respectively. BgalEL was stable at pH ranges 6.0–8.0. The K m and V max for BgalEL were recorded as 2.03 mM and 49.3 U mg −1 respectively. The product formation by BgalEL was modelled with various degradation kinetic models and zeroth was found as model was best-fitted model. The kinetic half-life period of ONPG was noted as 9.0 × 10 −4 . The presence of K + , Mg 2+ and Mn 2+ at 10 mM concentrations stimulated BgalEL activity by 31 ± 3.9, 34 ± 1.2 and 42 ± 1.9% respectively. It was interesting to see that BgalEL was least affected by the hydrolytic products, glucose and galactose. Noteworthy, effect of Ca 2+ ions on BgalEL activity was negligible at concentrations of 10 mM. BgalEL hydrolyzed lactose in milk at refrigerated temperature and also displayed transglycosylation potential in the presence of substantial concentrations of lactose at 40 °C. Finally, this is the first report with such a detailed characterization of β-galactosidase enzyme from a gram-negative bacterium isolated from the Arctic region. In light of the above mentioned properties, we thus recommend the enzyme BgalEL for the large scale production lactose free milk for the safe consumption in lactose-intolerance and the prebiotic galactooligosaccharides as supplement for infant food formulas. Graphical Abstract