Production of galactooligosaccharides from lactose using a beta-glucosidase from Thermus sp. Z-1

Immunomodulation by Human Milk Oligosaccharides: The Potential Role in Prevention of Allergic Diseases

The prevalence and incidence of allergic diseases is rising and these diseases have become the most common chronic diseases during childhood in Westernized countries. Early life forms a critical window predisposing for health or disease. Therefore, this can also be a window of opportunity for allergy prevention. Postnatally the gut needs to mature, and the microbiome is built which further drives the training of infant's immune system. Immunomodulatory components in breastmilk protect the infant in this crucial period by; providing nutrients that contain substrates for the microbiome, supporting intestinal barrier function, protecting against pathogenic infections, enhancing immune development and facilitating immune tolerance. The presence of a diverse human milk oligosaccharide (HMOS) mixture, containing several types of functional groups, points to engagement in several mechanisms related to immune and microbiome maturation in the infant's gastrointestinal tract. In recent years, several pathways impacted by HMOS have been elucidated, including their capacity to; fortify the microbiome composition, enhance production of short chain fatty acids, bind directly to pathogens and interact directly with the intestinal epithelium and immune cells. The exact mechanisms underlying the immune protective effects have not been fully elucidated yet. We hypothesize that HMOS may be involved in and can be utilized to provide protection from developing allergic diseases at a young age. In this review, we highlight several pathways involved in the immunomodulatory effects of HMOS and the potential role in prevention of allergic diseases. Recent studies have proposed possible mechanisms through which HMOS may contribute, either directly or indirectly, via microbiome modification, to induce oral tolerance. Future research should focus on the identification of specific pathways by which individual HMOS structures exert protective actions and thereby contribute to the capacity of the authentic HMOS mixture in early life allergy prevention.

Enzymatic generation of lactulose in sweet and acid whey: Optimization of feed composition and structural elucidation of 1-lactulose

Prebiotics are rising in interest in commercial scale productions due to increasing health awareness of consumers. Under bio-economic aspects, sweet and acid whey provide a suitable feed medium for the enzymatic generation of prebiotic lactulose. Since whey has a broad variation in composition, the influence of the feed composition on the concentration of generated lactulose was investigated. The influence of lactose and fructose concentration as well as enzymatic activity of two commercially available β-galactosidases were investigated. The results were evaluated via response surface analysis with a quadratic model containing pairwise interaction terms. The optimal feed composition yielding a theoretical maximal amount of lactulose was determined as 1.28 or 0.74 mol/kg fructose and 0.17 or 0.19 mol/kg lactose with an enzymatic activity of 2.0 or 2.8 μkat/kg for acid (pH 4.4) or sweet (pH 6.6) whey. Furthermore, the major reaction product was isolated and subsequently, the structural identity was elucidated and verified via extensive NMR analysis.

Rational mutagenesis by engineering disulphide bonds improves Kluyveromyces lactis beta-galactosidase for high-temperature industrial applications

Kluyveromyces lactis β-galactosidase (Kl-β-Gal) is one of the most important enzymes in the dairy industry. The poor stability of this enzyme limits its use in the synthesis of galactooligosaccharides (GOS) and other applications requiring high operational temperature. To obtain thermoresistant variants, a rational mutagenesis strategy by introducing disulphide bonds in the interface between the enzyme subunits was used. Two improved mutants, R116C/T270C and R116C/T270C/G818C, had increased half-lives at 45 °C compared to Kl-β-Gal (2.2 and 6.8 fold increases, respectively). Likewise, Tm values of R116C/T270C and R116C/T270C/G818C were 2.4 and 8.5 °C, respectively, higher than Kl-β-Gal Tm. Enrichment in enzymatically active oligomeric forms in these mutant variants also increased their catalytic efficiency, due to the reinforcement of the interface contacts. In this way, using an artificial substrate (p-nitrophenyl-β-D-galactopyranoside), the Vmax values of the mutants were ~1.4 (R116C/T270C) and 2 (R116C/T270C/G818C) fold higher than that of native Kl-β-Gal. Using the natural substrate (lactose) the Vmax for R116C/T270C/G818C almost doubled the Vmax for Kl-β-Gal. Validation of these mutant variants of the enzyme for their use in applications that depend on prolonged incubations at high temperatures was achieved at the laboratory scale by monitoring their catalytic activity in GOS synthesis.

A novel process for the production of high-purity galactooligosaccharides (GOS) using consortium of microbes

Galactooligosaccharides (GOS) are nondigestible dietary fibers which have a beneficial effect on human health by promoting the growth of probiotic bacteria in the gut. In addition, other health benefits have been reported from oligosaccharides consumption such as stimulation of intestinal mobility, colon cancer prevention, mineral absorption as well as protection against certain pathogenic bacterial infections. The goal of this research was to develop an efficient biotransformation system using a consortium of microbes for the production of ≥85% pure GOS and reusing the cell biomass in repeated cycles of biotransformation. Production of GOS by lactose transgalactosylation using whole cells of Sporobolomyces singularis MTCC 5491 as a source of β-galactosidase and monosaccharides utilization by yeast isolate (NUTIDY007) were studied. For increasing the purity of GOS, growth and bioconversion parameters on the transgalactosylation by the whole cells were investigated. Further, continuous production of GOS was studied in a reactor with microfiltration membrane system. A maximum GOS purity of 42% was achieved using single culture of S. singularis. Under optimized conditions, single culture of S. singularis produced a maximum of 56% pure GOS. Addition of second culture to the reaction mixture for utilization of glucose significantly increased the GOS purity from 56% to ≥85%. The product consisted of tri- to penta-galactooligosaccharides. Trisaccharides were the main component of the reaction mixture. A maximum productivity of 10.9 g/L/hr was obtained under the optimum conditions.

Structural Dissection of the Active Site of Thermotoga maritima β-Galactosidase Identifies Key Residues for Transglycosylating Activity

Glycoside hydrolases, specifically β-galactosidases, can be used to synthesize galacto-oligosaccharides (GOS) due to the transglycosylating (secondary) activity of these enzymes. Site-directed mutagenesis of a thermoresistant β-galactosidase from Thermotoga maritima has been carried out to study the structural basis of transgalactosylation and to obtain enzymatic variants with better performance for GOS biosynthesis. Rational design of mutations was based on homologous sequence analysis and structural modeling. Analysis of mutant enzymes indicated that residue W959, or an alternative aromatic residue at this position, is critical for the synthesis of β-3'-galactosyl-lactose, the major GOS obtained with the wild-type enzyme. Mutants W959A and W959C, but not W959F, showed an 80% reduced synthesis of this GOS. Other substitutions, N574S, N574A, and F571L, increased the synthesis of β-3'-galactosyl-lactose about 40%. Double mutants F571L/N574S and F571L/N574A showed an increase of about 2-fold.

Production of β-galactosidase from streptococcus thermophilus for galactooligosaccharides synthesis

Efficiency of different methods for disruption of Streptococcus thermophilus cells, isolated from different dairy products, to release β-galactosidase and synthesis of GOS by extracted enzyme using whey supplemented with different concentrations of lactose as a substrate was studied. Unlike most other studies on GOS synthesis which used only one method of cell disruption and only few microbial strains, we compared five different cell disruption methods and used 30 strains of S. thermophilus in order to find out the most effective method and efficient strain for production of β-galactosidase. Appreciable amount of GOS (53.45 gL(-1)) was synthesized at a lactose concentration of 30 %, using enzyme (10 U mL(-1) of reaction medium), extracted from S. thermophilus within a very short incubation time of 5 h at a temperature of 40 °C and pH 6.8. S. thermophilus is heavily employed in the preparation of fermented dairy products but this study extends the use of this organism for the production of GOS, a potential prebiotic.

Immobilization of thermostable β-galactosidase on epoxy support and its use for lactose hydrolysis and galactooligosaccharides biosynthesis

Thermoresistant, recombinant β-galactosidase from Thermotoga maritima was purified and immobilized on the surface of epoxy-coated magnetic beads. The enzyme, which has hexameric quaternary structure as shown by gel filtration chromatography, attaches to the resin through multiple covalent linkages that involve different subunits. The bound enzyme shows higher stability than the free form. The immobilized enzyme showed to be efficient for the hydrolysis of lactose and the biosynthesis of galactooligosaccharides (GOS). The chemical structure of synthesized GOS has been determined by NMR revealing that the main product was β-3′-galactosyl lactose. Although β-galactosidases from different sources have been used for the same purposes, the distinct advantage of the methodology described in this communication is that the enzyme can be easily produced, purified and immobilized in large quantities.

Production, health aspects and potential food uses of dairy prebiotic galactooligosaccharides

Galactooligosaccharides are sugars composed of 3-10 molecules of galactose and glucose via a transgalactosylation reaction mediated by the enzyme β-galactosidase. Prebiotics are non-digestible food ingredients that pass through the upper digestive system relatively intact and ferment in the lower colon, producing short-chain fatty acids that support the growth of supplemented or indigenous colonic microbiota. Galactooligosaccharides and other prebiotic ingredients are increasingly being recognized as useful dietary tools for the modulation of the colonic microflora toward a healthy balance. Galactooligosaccharides compare well to other oligosaccharides in terms of their prebiotic, immunomodulation, and functional properties in foods. This review elucidates the galactooligosaccharide production process from refined lactose and/or cheese whey permeates, galactooligosaccharide market share and economic value, their health properties, and potential food applications.

Síntese de galacto-oligossacarídeos a partir de lactose usando β-galactosidase comercial de Kluyveromyces lactis

O objetivo deste trabalho foi estudar a influência de parâmetros reacionais na obtenção via enzimática de galacto-oligossacarídeos (GOS), utilizando-se a enzima comercial β-galactosidase de Kluyveromyces lactis (Lactozym® 3000 L), tendo como substrato a lactose. Foi proposto um planejamento experimental 2³, verificando a influência da temperatura (30 a 40 °C), da concentração de lactose (200 a 400 mg.mL-1) e da concentração de enzima (5 a 10 U.mL-1) no desempenho da reação enzimática. Os ensaios foram conduzidos a 180 rpm e pH 7,0 (tampão fosfato de sódio 0,1 M). A enzima Lactozym® 3000 L apresentou atividade de transgalactosilação, tendo sido atingido rendimento do processo igual a 41,9% e concentração de GOS de 167,5 mg.mL-1 no sistema reacional composto por 400 mg.mL-1 de lactose e 5 U.mL-1 de enzima a 30 °C em 14 h de reação. Nessa condição, a conversão de lactose foi de 65,0%. Maior concentração de lactose foi favorável ao mecanismo de transgalactosilação, enquanto que, em menores concentrações, o mecanismo hidrolítico predominou.

BbgIV Is an Important Bifidobacterium β-Galactosidase for the Synthesis of Prebiotic Galactooligosaccharides at High Temperatures

The individual contributions of four β-galactosidases present in Bifidobacterium bifidum NCIMB 41171 toward galactooligosaccharide (GOS) synthesis were investigated. Although the β-galactosidase activity of the whole cells significantly decreased as a function of temperature (40-75 °C), GOS yield was at its maximum at 65 °C. Native-PAGE of the whole cells showed that the contributions of BbgIII and BbgIV to GOS synthesis increased as the temperature increased. Moreover, BbgIII and BbgIV were found to be more temperature stable and to produce a higher GOS yield than BbgI and BbgII, when used in their free form. The GOS yield using BbgIV was 54.8% (percent of total carbohydrates) and 63.9% (percent lactose converted to GOS) at 65 °C from 43% w/w lactose. It was shown that BbgIV is the most important β-galactosidase in B. bifidum NCIMB 41171 and can be used for GOS synthesis at elevated temperatures.

Effect of the substrate concentration and water activity on the yield and rate of the transfer reaction of β-galactosidase from Bacillus circulans

Prebiotic galactosyl oligosaccharides (GOS) are produced from lactose by the enzyme β-galactosidase. It is widely reported that the highest GOS levels are achieved when the initial lactose concentration is as high as possible; however, little evidence has been presented to explain this phenomenon. Using a system composed of the commercial β-galactosidase derived from Bacillus circulans known as Biolacta FN5, lactose and sucrose, the relative contribution of water activity, and substrate availability were assessed. Oligosaccharide levels did not appear to be affected by changes in water activity between 1.0 and 0.77 at a constant lactose concentration. The maximum oligosaccharide concentration increased at higher initial concentrations of lactose and sucrose, while initial reaction rates for transfer increased but remained constant for hydrolysis. This suggests that the high oligosaccharide levels achieved at the raised initial saccharide concentration are due to increases in reactions that form oligosaccharides rather than decreases in concurrent reactions, which degrade oligosaccharides. There were different effects from changing the initial concentration of lactose compared to sucrose, suggesting that the ability of lactose to act as a donor saccharide may be more important for increasing maximum oligosaccharide concentrations than the combined ability of both saccharides to act as galactosyl acceptors.

Synthesis of β-Galactooligosaccharides from Lactose Using Microbial β-Galactosidases

  Galactooligosaccharides (GOSs) are nondigestible oligosaccharides and are comprised of 2 to 20 molecules of galactose and 1 molecule of glucose. They are recognized as important prebiotics for their stimulation of the proliferation of intestinal lactic acid bacteria and bifidobacteria. Therefore, they beneficially affect the host by selectively stimulating the growth and/or activity of a limited number of gastrointestinal microbes (probiotics) that confer health benefits. Prebiotics and probiotics have only recently been recognized as contributors to human health. A GOS can be produced by a series of enzymatic reactions catalyzed by β-galactosidase, where the glycosyl group of one or more D-galactosyl units is transferred onto the D-galactose moiety of lactose, in a process known as transgalactosylation. Microbes can be used as a source for the β-galactosidase enzyme or as agents to produce GOS molecules. Commercial β-galactosidase enzymes also do have a great potential for their use in GOS synthesis. These transgalactosyl reactions, which could find useful application in the dairy as well as the larger food industry, have not been fully exploited. A better understanding of the enzyme reaction as well as improved analytical techniques for GOS measurements are important in achieving this worthwhile objective.

Enzymatic production of galactooligosaccharides by beta-galactosidase from Bifidobacterium longum BCRC 15708

The production of galactooligosaccharides (GOSs) by transgalactosylation using beta-galactosidase from Bifidobacterium longum BCRC 15708 was studied. Other than lactose, galactose, and glucose, two types of GOSs, tri- and tetrasaccharides, were formed after beta-galactosidase action on 40% lactose. Trisaccharides were the major type of GOS formed. Generally, an increase of the initial lactose concentration in the reaction mixture resulted in a higher GOS production. A maximum yield of 32.5% (w/w) GOSs could be achieved from 40% lactose solution at 45 degrees C, pH 6.8, when the lactose conversion was 59.4%. The corresponding productivity of GOSs was 13.0 g/(L.h). Transgalactosylation activity of beta-galactosidase from a test organism showed a relatively lower sensitivity toward glucose and galactose than that from other organisms. The addition of 5% or 10% glucose or galactose to the reaction mixture did not significantly (p>0.05) reduce the transgalactosylation reaction of beta-galactosidase.

Characterization of a thermostable recombinant beta-galactosidase from Thermotoga maritima

AIMS

Characterization of a thermostable recombinant beta-galactosidase from Thermotoga maritima for the hydrolysis of lactose and the production of galacto-oligosaccharides.

METHODS AND RESULTS

A putative beta-galactosidase gene of Thermotoga maritima was expressed in Escherichia coli as a carboxyl terminal His-tagged recombinant enzyme. The gene encoded a 1100-amino acid protein with a calculated molecular weight of 129,501. The expressed enzyme was purified by heat treatment, His-tag affinity chromatography, and gel filtration. The optimum temperatures for beta-galactosidase activity were 85 and 80 degrees C with oNPG and lactose, respectively. The optimum pH value was 6.5 for both oNPG and lactose. In thermostability experiments, the enzyme followed first-order kinetics of thermal inactivation and its half-life times at 80 and 90 degrees C were 16 h and 16 min, respectively. Mn2+ was the most effective divalent cation for beta-galactosidase activity on both oNPG and lactose. The Km and Vmax values of the thermostable enzyme for oNPG at 80 degrees C were 0.33 mm and 79.6 micromol oNP min(-1) mg(-1). For lactose, the Km and Vmax values were dependent on substrate concentrations; 1.6 and 63.3 at lower concentrations up to 10 mm of lactose and 27.8 mm and 139 micromol glucose min(-1) mg(-1) at higher concentrations, respectively. The enzyme displayed non-Michaelis-Menten reaction kinetics with substrate activation, which was explained by simultaneous reactions of hydrolysis and transgalactosylation.

CONCLUSIONS

The results suggest that the thermostable enzyme may be suitable for both the hydrolysis of lactose and the production of galacto-oligosaccharides.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings of this work contribute to the knowledge of hydrolysis and transgalactosylation performed by beta-galactosidase of hyperthermophilic bacteria.

Overproduction of Thermus sp. Strain T2 beta-galactosidase in Escherichia coli and preparation by using tailor-made metal chelate supports

A novel thermostable chimeric beta-galactosidase was constructed by fusing a poly-His tag to the N-terminal region of the beta-galactosidase from Thermus sp. strain T2 to facilitate its overexpression in Escherichia coli and its purification by immobilized metal-ion affinity chromatography (IMAC). The poly-His tag fusion did not affect the activation, kinetic parameters, and stability of the beta-galactosidase. Copper-iminodiacetic acid (Cu-IDA) supports enabled the most rapid adsorption of the His-tagged enzyme, favoring multisubunit interactions, but caused deleterious effects on the enzyme stability. To improve the enzyme purification a selective one-point adsorption was achieved by designing tailor-made low-activated Co-IDA or Ni-IDA supports. The new enzyme was not only useful for industrial purposes but also has become an excellent model to study the purification of large multimeric proteins via selective adsorption on tailor-made IMAC supports.