The Michaelis constants ratio for two substrates with a series of fungal (mould and yeast) β-galactosidases

Anthocyanins degradation mediated by β-glycosidase contributes to the color loss during alcoholic fermentation in a structure-dependent manner

Anthocyanins deteriorate during fermentation to varying degrees depending on the structure of the anthocyanin, thus affecting the sensory quality of the wine, and the degradation of anthocyanins is closely associated with the β-glycosidase. In this study, the alcoholic fermentation systems containing cyanidin-3-O-glucoside (C3G), peonidin-3-O-glucoside (Pn3G), delphinidin-3-O-glucoside (D3G), petunidin-3-O-glucoside (Pt3G), and malvidin-3-O-glucoside (M3G) incubated for eight days. Our results indicated that the color of the systems containing different anthocyanins saw significant and dissimilar changes during fermentation, in relation to anthocyanin degradation. The five anthocyanins showed varying degradation degrees, which are relevant to theβ-glycosidase produced by yeast. Enzyme kinetics and molecular docking analysis showed the affinity between anthocyanins and β-glucosidase: C3G < M3G < Pn3G < Pt3G < D3G. This study demonstrated that β-glycosidase had distinct effects on anthocyanins with diverse structures, resulting in different color changes in fermentation systems. It provided a potential strategy for sensory quality improvement during the fermentation of fruit wines rich in anthocyanins.

Cloning, expression and structural stability of a cold-adapted β-galactosidase from Rahnella sp. R3

A novel gene was isolated for the first time from a psychrophilic gram-negative bacterium Rahnella sp. R3. The gene encoded a cold-adapted β-galactosidase (R-β-Gal). Recombinant R-β-Gal was expressed in Escherichia coli BL21 (DE3), purified and characterized. R-β-gal belongs to the glycosyl hydrolase family 42. Circular dichroism spectrometry of the structural stability of R-β-Gal with respect to temperature indicated that the secondary structures of the enzyme were stable to 45°C. In solution, the enzyme was a homo-trimer and was active at temperatures as low as 4°C. The enzyme did not require the presence of metal ions to be active, but Mg(2+), Mn(2+), and Ca(2+) enhanced its activity slightly, whereas Fe(3+), Zn(2+) and Al(3+) appeared to inactive it. The purified enzyme displayed K(m) values of 6.5 mM for ONPG and 2.2mM for lactose at 4°C. These values were lower than the corresponding K(m)s reported for other cold-adapted β-Gals.

Cloning, purification, and characterization of β-galactosidase from Bacillus licheniformis DSM 13

The gene encoding homodimeric β-galactosidase (lacA) from Bacillus licheniformis DSM 13 was cloned and overexpressed in Escherichia coli, and the resulting recombinant enzyme was characterized in detail. The optimum temperature and pH of the enzyme, for both o-nitrophenyl-β-D: -galactoside (oNPG) and lactose hydrolysis, were 50°C and 6.5, respectively. The recombinant enzyme is stable in the range of pH 5 to 9 at 37°C and over a wide range of temperatures (4-42°C) at pH 6.5 for up to 1 month. The K(m) values of LacA for lactose and oNPG are 169 and 13.7 mM, respectively, and it is strongly inhibited by the hydrolysis products, i.e., glucose and galactose. The monovalent ions Na(+) and K(+) in the concentration range of 1-100 mM as well as the divalent metal cations Mg²(+), Mn²(+), and Ca²(+) at a concentration of 1 mM slightly activate enzyme activity. This enzyme can be beneficial for application in lactose hydrolysis especially at elevated temperatures due to its pronounced temperature stability; however, the transgalactosylation potential of this enzyme for the production of galacto-oligosaccharides (GOS) from lactose was low, with only 12% GOS (w/w) of total sugars obtained when the initial lactose concentration was 200 g/L.

beta-Galactosidase from Lactobacillus plantarum WCFS1: biochemical characterization and formation of prebiotic galacto-oligosaccharides

Recombinant beta-galactosidase from Lactobacillus plantarum WCFS1, homologously over-expressed in L. plantarum, was purified to apparent homogeneity using p-aminobenzyl 1-thio-beta-d-galactopyranoside affinity chromatography and subsequently characterized. The enzyme is a heterodimer of the LacLM-family type, consisting of a small subunit of 35kDa and a large subunit of 72kDa. The optimum pH for hydrolysis of its preferred substrates o-nitrophenyl-beta-d-galactopyranoside (oNPG) and lactose is 7.5 and 7.0, and optimum temperature for these reactions is 55 and 60 degrees C, respectively. The enzyme is most stable in the pH range of 6.5-8.0. The K(m), k(cat) and k(cat)/K(m) values for oNPG and lactose are 0.9mM, 92s(-1), 130mM(-1)s(-1) and 29mM, 98s(-1), 3.3mM(-1)s(-1), respectively. The L. plantarum beta-galactosidase possesses a high transgalactosylation activity and was used for the synthesis of prebiotic galacto-oligosaccharides (GOS). The resulting GOS mixture was analyzed in detail, and major components were identified by using high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) as well as capillary electrophoresis. The maximal GOS yield was 41% (w/w) of total sugars at 85% lactose conversion (600mM initial lactose concentration). The enzyme showed a strong preference for the formation of beta-(1-->6) linkages in its transgalactosylation mode, while beta-(1-->3)-linked products were formed to a lesser extent, comprising approximately 80% and 9%, respectively, of the newly formed glycosidic linkages in the oligosaccharide mixture at maximum GOS formation. The main individual products formed were beta-d-Galp-(1-->6)-d-Lac, accounting for 34% of total GOS, and beta-d-Galp-(1-->6)-d-Glc, making up 29% of total GOS.

Use of whey permeate for cultivating Ganoderma lucidum mycelia

A novel approach to utilizing whey permeate, the cultivation of mycelia of the edible mushroom Ganoderma lucidum, is introduced. The major objective of this research was to use whey permeate as an alternative growth medium for the cultivation of mycelia of edible mushroom G. lucidum and to find an optimum condition for solid-state cultivation. Response surface analysis was applied to determine the combination of substrate concentration (25 to 45 g of lactose/L), pH (3.5 to 5.5), and temperature (25 to 35 degrees C) resulting in a maximal mycelial growth. The radial extension rates, estimated by measuring the diameters of growing colonies on the Petri dishes, were used as the growth of the mycelia at different conditions. In the model, pH and temperature significantly affected mycelial growth, but lactose concentration did not. The condition predicted to maximize the radial extension rate of 17.6 +/- 0.4 mm/d was determined to be pH 4.4 and temperature 29.4 degrees C. Therefore, the results suggest that whey permeate could be utilized as a growth substrate for the cultivation of mycelia from the edible mushroom G. lucidum, enhancing the use of this by-product by the cheese manufacturing industry.

Purification and characterization of two novel beta-galactosidases from Lactobacillus reuteri

The intracellular beta-galactosidase (beta-gal) enzymes from two strains of Lactobacillus reuteri, L103 and L461, were purified by ammonium sulfate fractionation, hydrophobic interaction, and affinity chromatography. Both enzymes are heterodimers with a molecular mass of 105 kDa, consisting of a 35 kDa subunit and a 72 kDa subunit. Active staining of L. reuteri L103 and L461 beta-gal with 4-methylumbelliferyl beta-d-galactoside showed that the intact enzymes as well as the larger subunits possess beta-galactosidase activity. The isoelectric points of L. reuteri L461 and L103 beta-gal were found to be in the range of 3.8-4.0 and 4.6-4.8, respectively. Both enzymes are most active in the pH range of 6-8; however, they are not stable at pH 8. The L. reuteri beta-galactosidases are activated by various mono- and divalent cations, including Na(+), K(+), and Mn(2+), and are moderately inhibited by their reaction products d-glucose and d-galactose. Because of their origin from beneficial and potentially probiotic lactobacilli, these enzymes could be of interest for the synthesis of prebiotic galacto-oligosaccharides.