Beta-D-galactosidase from Enterobacter cloacae: production and some physicochemical properties

Production and immobilization of β-galactosidase isolated from Enterobacter aerogenes KCTC2190 by entrapment method using agar-agar organic matrix

In the present study, Enterobacter aerogenes KCTC2190 was isolated from soil around a cattle shed area, which was capable of producing intracellular β-galactosidase. Partially purified β-galactosidase was immobilized by entrapment method in agar-agar gel matrix. Agar-agar entrapped beads were prepared by dropping the enzyme-agar solution to ice-cooled toluene-chloroform ((3:1 (v/v)). 45.88±0.11% activity of partially purified β-galactosidase was retained after immobilization (bead shape). Maximum immobilization yield was observed in the presence of 2.5% agar-agar concentration. After immobilization, optimum temperature required for the enzyme-substrate reaction was shifted from 50 to 60 °C and the optimum reaction time was shifted from 15 to 25 min. The optimum pH for both free and immobilized β-galactosidase was pH 7. Free enzyme showed lower activation energy in comparison with the immobilized one. For free as well as immobilized β-galactosidase thermal deactivation, rate constant (k_d) increased with increasing temperature while the values of decimal reduction time (D-values) and half-lives (t_1/2) decreased. Immobilization process increased the t_1/2 and D-values of β-galactosidase while it decreased the k_d. Thermostability of immobilized β-galactosidase was higher as they showed higher enthalpy (ΔΗ⁰) and Gibb's free energy (ΔG⁰)value than those of the free β-galactosidase. The negative entropy (ΔS⁰) of free and immobilized β-galactosidase established that both were in a more ordered state within the temperature range (50 to 70 °C) studied. Immobilized β-galactosidase was able to retain 51.65±1.61% of its initial activity after 7 batches of enzyme-substrate reaction. Immobilized β-galactosidase showed 78.09±3.69% of its initial activity even after 40 days of storage at 4 °C.

Characterization of three novel β-galactosidases from Akkermansia muciniphila involved in mucin degradation

The gut microbe Akkermansia (A.) muciniphila becomes increasingly important as its prevalence is inversely correlated with different human metabolic disorders and diseases. This organism is a highly potent degrader of intestinal mucins and the hydrolyzed glycan compounds can then serve as carbon sources for the organism itself or other members of the gut microbiota via cross-feeding. Despite its importance for the hosts' health and microbiota composition, exact mucin degrading mechanisms are still mostly unclear. In this study, we identified and characterized three extracellular β-galactosidases (Amuc_0771, Amuc_0824, and Amuc_1666) from A. muciniphila ATCC BAA-835. The substrate spectrum of all three enzymes was analyzed and the results indicated a preference for different galactosidic linkages for each hydrolase. All preferred target structures are prevalent within mucins of the colonic habitat of A. muciniphila. To check a potential function of the enzymes for the degradation of mucosal glycan structures, porcine stomach mucin was applied as a model substrate. In summary, we could confirm the involvement of all three β-galactosidases from A. muciniphila in the complex mucin degradation machinery of this important gut microbe. These findings could contribute to the understanding of the molecular interactions between A. muciniphila and its host on a molecular level.

Screening and Characterization of Cold-Active β-Galactosidase Producing Psychrotrophic Enterobacter ludwigii from the Sediments of Arctic Fjord

Low-temperature-tolerant microorganisms and their cold-active enzymes could be an innovative and invaluable tool in various industrial applications. In the present study, bacterial isolates from the sediment samples of Kongsfjord, Norwegian Arctic, were screened for β-galactosidase production. Among the isolates, KS25, KS85, KS60, and KS92 have shown good potential in β-galactosidase production at 20 °C. 16SrRNA gene sequence analysis revealed the relatedness of the isolates to Enterobacter ludwigii. The optimum growth temperature of the isolate was 25 °C. The isolate exhibited good growth and enzyme production at a temperature range of 15-35 °C, pH 5-10. The isolate preferred yeast extract and lactose for the maximum growth and enzyme production at conditions of pH 7.0, temperature of 25 °C, and agitation speed of 100 rpm. The growth and enzyme production was stimulated by Mn²⁺ and Mg²⁺ and strongly inhibited by Zn²⁺, Ni²⁺, and Cu⁺. β-Galactosidases with high specific activity at low temperatures are very beneficial in food industry to compensate the nutritional problem associated with lactose intolerance. The isolate exhibited a remarkable capability to utilize clarified whey, an industrial pollutant, for good biomass and enzyme yield and hence could be well employed in whey bioremediation.

Crystallization and preliminary X-ray analysis of a cold-active β-galactosidase from the psychrotrophic and halotolerant Planococcus sp. L4

β-Galactosidases catalyze the hydrolysis of a galactosyl moiety from the nonreducing termini of oligosaccharides or from glycosides. A novel GH family 42 cold-active β-galactosidase identified from the psychrotrophic and halotolerant Planococcus sp. L4 (BgaP) was crystallized and a complete data set was collected from a single frozen crystal on an in-house X-ray source. The crystal diffracted to 2.8 Å resolution and belonged to space group P1, with unit-cell parameters a = 104.29, b = 118.12, c = 121.12 Å, α = 62.66, β = 69.48, γ = 70.74°. A likely Matthews coefficient of 2.58 Å(3) Da(-1) and solvent content of 52.32% suggested the presence of six protein subunits in the asymmetric unit.