Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A cold-active beta-galactosidase of Antarctic marine bacterium Pseudoalteromonas sp. 22b was synthesized by an Escherichia coli transformant harboring its gene and immobilized on glutaraldehyde-treated chitosan beads. Unlike the soluble enzyme the immobilized preparation was not inhibited by glucose, its apparent optimum temperature for activity was 10 degrees C higher (50 vs. 40 degrees C, respectively), optimum pH range was wider (pH 6-9 and 6-8, respectively) and stability at 50 degrees C was increased whilst its pH-stability remained unchanged. Soluble and immobilized preparations of Antarctic beta-galactosidase were active and stable in a broad range of NaCl concentrations (up to 3 M) and affected neither by calcium ions nor by galactose. The activity of immobilized beta-galactosidase was maintained for at least 40 days of continuous lactose hydrolysis at 15 degrees C and its shelf life at 4 degrees C exceeded 12 months. Lactose content in milk was reduced by more than 90% over a temperature range of 4-30 degrees C in continuous and batch systems employing the immobilized enzyme.
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PMID:Immobilized preparation of cold-adapted and halotolerant Antarctic beta-galactosidase as a highly stable catalyst in lactose hydrolysis. 1705 85

Galacto-oligosaccharides, complex mixtures of various sugars, are produced by transgalactosylation from lactose using beta-galactosidase and are of great interest for food and feed applications because of their prebiotic properties. Most galacto-oligosaccharide preparations currently available in the market contain a significant amount of monosaccharides and lactose. The mixture of galacto-oligosaccharides (GalOS) in this study produced from lactose using recombinant beta-galactosidase from Lactobacillus reuteri contains 48% monosaccharides, 26.5% lactose and 25.5% GalOS. To remove efficiently both monosaccharides and lactose from this GalOS mixture containing significant amounts of prebiotic non-lactose disaccharides, a biocatalytic approach coupled with subsequent chromatographic steps was used. Lactose was first oxidised to lactobionic acid using fungal cellobiose dehydrogenases, and then lactobionic acid and monosaccharides were removed by ion-exchange and size-exclusion chromatography. Two different cellobiose dehydrogenases (CDH), originating from Sclerotium rolfsii and Myriococcum thermophilum, were compared with respect to their applicability for this process. CDH from S. rolfsii showed higher specificity for the substrate lactose, and only few other components of the GalOS mixture were oxidised during prolonged incubation. Since these sugars were only converted once lactose oxidation was almost complete, careful control of the CDH-catalysed reaction will significantly reduce the undesired oxidation, and hence subsequent removal, of any GalOS components. Removal of ions and monosaccharides by the chromatographic steps gave an essentially pure GalOS product, containing less than 0.3% lactose and monosaccharides, in a yield of 60.3%.
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PMID:Production of lactose-free galacto-oligosaccharide mixtures: comparison of two cellobiose dehydrogenases for the selective oxidation of lactose to lactobionic acid. 1835 95

A locally isolated thermophile, Geobacillus sp. SAB-40, producing thermostable extracellular amylase constitutively and an induced intracellular beta-galactosidase was characterized and identified based on 16S rRNA sequencing. A phylogenetic analysis then revealed its closeness to Geobacillus stearothermophilus. To evaluate the effect of the culture conditions on the coproduction of both enzymes by G. stearothermophilus SAB-40, a Plackett-Burman fractional factorial design was applied to determine the impact of twenty variables. Among the tested variables, CaCl2, the incubation time, MgSO4.7H2O, and tryptone were found to be the most significant for encouraging amylase production. Lactose was found to promote beta-galactosidase production, whereas starch had a significantly negative effect on lactase production. Based on a statistical analysis, a preoptimized medium attained the maximum production of amylase and beta-galactosidase at 23.29 U/ml/min and 12,958 U/mg biomass, respectively, which was 3- and 2-fold higher than the yield of amylase and lactase obtained with the basal medium, respectively.
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PMID:Coproduction of thermostable amylase and beta-galactosidase enzymes by Geobacillus stearothermophilus SAB-40: aplication of Plackett-Burman design to evaluate culture requirements affecting enzyme production. 1846 63

The heterodisaccharide lactose (1,4-O-beta-D-galactopyranosyl-D-glucose) induces cellulase formation in the ascomycete Hypocrea jecorina (= Trichoderma reesei). Lactose assimilation is slow, and the assimilation of its beta-D-galactose moiety depends mainly on the operation of a recently described reductive pathway and depends less on the Leloir pathway, which accepts only alpha-D-galactose. We therefore reasoned whether galactomutarotase [aldose 1-epimerase (AEP)] activity might limit lactose assimilation and thus influence cellulase formation. We identified three putative AEP-encoding genes (aep1, aep2, aep3) in H. jecorina, of which two encoded intracellular protein (AEP1 and AEP2) and one encoded an extracellular protein (AEP3). Although all three were transcribed, only the aep3 transcript was detected on lactose. However, no mutarotase activity was detected in the mycelia, their cell walls, or the extracellular medium during growth on lactose. Therefore, the effect of galactomutarotase activity on lactose assimilation was studied with H. jecorina strains expressing the C-terminal galactose mutarotase part of the Saccharomyces cerevisiae Gal10. These strains showed increased growth on lactose in a gene copy number-dependent manner, although their formation of extracellular beta-galactosidase activity and transcription of the genes encoding the first steps in the Leloir and the reductive pathway was similar to the parental strain QM9414. Cellulase gene transcription on lactose dramatically decreased in these strains, but remained unaffected during growth on cellulose. Our data show that cellulase induction in H. jecorina by lactose requires the beta-anomer of D-galactose and reveal the lack of mutarotase activity during growth on lactose as an important key for cellulase formation on this sugar.
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PMID:Lack of aldose 1-epimerase in Hypocrea jecorina (anamorph Trichoderma reesei): a key to cellulase gene expression on lactose. 1848 Feb 50

The hydrolysis of lactose by immobilized beta-galactosidase was studied in a continuous-flow capillary bed reactor operating at 30 degrees C. Solutions containing 50, 100, and 150 g lactose and 0.5 g sodium acetate/L were fed to the reactor. Lactose conversions ranging from 24% to greater than 99% were achieved at reactor space times ranging from 0.06 to 6.3 min. These conversion data were successfully modeled in terms of a plug flow reactor model and a form of Michaelis-Menten kinetics which included competitive inhibition by both the alpha and beta forms of galactose.
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PMID:Lactose hydrolysis by immobilized beta-galactosidase in capillary bed reactor. 1858 25

The effect of reduced oxygen supply on the production of a recombinant protein (plasmid-encoded beta-galactosidase) was investigated in Escherichia coli. A novel modified bubble tank reactor was used to provide a direct comparison between immobilized and suspended cells in identical environments except for the immobilization matrix. Decreased oxygen supply led to increased beta-galactosidase synthesis by both immobilized and suspended cells. Immobilized cells produced similar amounts of beta-galactosidase as the suspended cells. Lactose consumption and acetate production, on a per cell basis, were significantly higher in immobilized cells, suggesting that immobilized cells utilized fermentative metabolism. However, a transport analysis of the immobilized cell system showed that immobilized cells were not subject to either external or internal mass transfer gradients.
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PMID:Effect of oxygen supply on metabolism of immobilized and suspended Escherichia coli. 1862 36

Lactose and glucose concentrations were determined simultaneously by using a measuring-cell containing lactose and glucose electrodes made by mixing beta-galactosidase/glucose oxidase and glucose oxidase, respectively, with carbon paste. The glucose electrode responds to glucose alone, while the lactose electrode measures the sum of glucose and lactose. Lactose concentration was calculated by subtracting the glucose concentration from the reading of the lactose electrode. The present dual-working electrode system permitted the determination of lactose and glucose concentrations simultaneously from a single measurement over a linear range of 0.1-2.5 mM. Furthermore, it enabled the determination of lactose concentration in milk in the presence of glucose to be carried out more precisely and with a higher degree of sensitivity than the conventional calorimetric method.
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PMID:Simultaneous determination of lactose and glucose in milk using two working enzyme electrodes. 1896 8

Lactose has been hydrolyzed using covalently immobilized beta-galactosidase on thermally stable carrageenan coated with chitosan (hydrogel). The hydrogel's mode of interaction was proven by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and Schiff's base formation. The DSC thermogram proved the formation of a strong polyelectrolyte complex between carrageenan and chitosan followed by glutaraldehyde as they formed one single peak. The modification of carrageenan improved the gel's thermal stability in solutions from 35 degrees C to 95 degrees C. The hydrogel has been proven to be efficient for beta-galactosidase immobilization where 11 U/g wet gel was immobilized with 50% enzyme loading capacity. Activity and stability of free and immobilized beta-galactosidase towards pH and temperature showed marked shifts in their optimum pH from 4.5-5 to 5-5.5 and temperature from 50 degrees C to 45-55 degrees C after immobilization, which reveals higher catalytic activity and reasonable stability at wider pHs and temperatures. The apparent K(m) of the immobilized enzyme increased from 13.2 to 125 mM, whereas the V(max) increased from 3.2 to 6.6 micromol/min compared to the free enzyme, respectively. The free and immobilized enzymes showed lactose conversion of 87% and 70% at 7 h, respectively. The operational stability showed 97% retention of the enzyme activity after 15 uses, which demonstrates that the covalently immobilized enzyme is unlikely to leach. The new carrier could be suitable for immobilization of other industrial enzymes.
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PMID:Lactose hydrolysis by beta-galactosidase covalently immobilized to thermally stable biopolymers. 1908 62


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