Galacto-oligosaccharide synthesis from lactose solution or skim milk using the β-galactosidase from Bacillus circulans

Biochemical characterization of a novel C-terminally truncated β-galactosidase from Paenibacillus antarcticus with high transglycosylation activity

The transgalactosylase activity of β-galactosidases offers a convenient and promising strategy for conversion of lactose into high-value oligosaccharides, such as galacto-oligosaccharides (GOS) and human milk oligosaccharides (HMOs). In this study, we cloned and biochemically characterized a novel C-terminally truncated β-galactosidase (PaBgal2A-D) from Paenibacillus antarcticus with high transglycosylation activity. PaBgal2A-D is a member of glycoside hydrolase (GH) family 2. The optimal pH and temperature of PaBgal2A-D were determined to be pH 6.5 and 50°C, respectively. It was relatively stable within pH 5.0-8.0 and up to 50°C. PaBgal2A-D showed high transglycosylation activity for GOS synthesis, and the maximum yield of 50.8% (wt/wt) was obtained in 2 h. Moreover, PaBgal2A-D could synthesize lacto-N-neotetraose (LNnT) using lactose and lacto-N-triose II (LNT2), with a conversion rate of 16.4%. This study demonstrated that PaBgal2A-D could be a promising tool to prepare GOS and LNnT.

Cyclic Production of Galacto-Oligosaccharides through Ultrafiltration-Assisted Enzyme Recovery

Galacto-oligosaccharides (GOS) are prebiotics manufactured enzymatically from lactose as substrate. The growing GOS market facilitates the valorization of dairy by-products which represent cheap and abundant sources of lactose. Large-scale GOS production typically employs soluble enzymes in batch reactors that are commonly associated with low enzyme usability and, therefore, high operational expenditures. In this study, we investigate the possibility of recovering enzymes by ultrafiltration (UF) and reusing them in repeated reaction steps. The proposed process scheme included 24 h batch reaction steps with Biolacta N5, a commercial enzyme preparation of Bacillus circulans origin. The reaction steps were followed by UF steps to separate the carbohydrate products from the enzymes by applying a volume concentration factor of 8.6. Then, the collected biocatalysts were reused for repeated cycles by adding fresh lactose. Enzyme losses were quantified with a direct method by analyzing the underlying relationship between reaction rates and enzyme dosage obtained from additional experiments conducted with known enzyme loads. Within five cycles, the enzyme activity declined gradually from 923 to 8307 U·kg−1, and the half-life was estimated as ca. 15.3 h. The outcomes of this study may serve as a basis for further optimization of the reported process scheme with enhanced enzyme usability.

In Vitro Production of Galactooligosaccharides by a Novel β-Galactosidase of Lactobacillus bulgaricus

β-galactosidase is an enzyme with dual activity and important industrial application. As a hydrolase, the enzyme eliminates lactose in milk, while as a trans-galactosidase it produces prebiotic galactooligosaccharides (GOS) with various degrees of polymerization (DP). The aim of the present study is the molecular characterization of β-galactosidase from a Bulgarian isolate, Lactobacillus delbrueckii subsp. bulgaricus 43. The sequencing of the β-gal gene showed that it encodes a new enzyme with 21 amino acid replacements compared to all other β-galactosidases of this species. The molecular model revealed that the new β-galactosidase acts as a tetramer. The amino acids D207, H386, N464, E465, Y510, E532, H535, W562, N593, and W980 form the catalytic center and interact with Mg²⁺ ions and substrate. The β-gal gene was cloned into a vector allowing heterologous expression of E. coli BL21(DE3) with high efficiency, as the crude enzyme reached 3015 U/mL of the culture or 2011 U/mg of protein. The enzyme's temperature optimum at 55 °C, a pH optimum of 6.5, and a positive influence of Mg²⁺, Mn²⁺, and Ca²⁺ on its activity were observed. From lactose, β-Gal produced a large amount of GOS with DP3 containing β-(1→3) and β-(1→4) linkages, as the latter bond is particularly atypical for the L. bulgaricus enzymes. DP3-GOS formation was positively affected by high lactose concentrations. The process of lactose conversion was rapid, with a 34% yield of DP3-GOS in 6 h, and complete degradation of 200 g/L of lactose for 12 h. On the other hand, the enzyme was quite stable at 55 °C and retained about 20% of its activity after 24 h of incubation at this temperature. These properties expand our horizons as regards the use of β-galactosidases in industrial processes for the production of lactose-free milk and GOS-enriched foods.

Identification and Characterization of a Novel Cold-Adapted GH15 Family Trehalase from the Psychrotolerant Microbacterium phyllosphaerae LW106

Psychrophiles inhabiting various cold environments are regarded as having evolved diverse physiological and molecular strategies, such as the accumulation of trehalose to alleviate cold stress. To investigate the possible contributions of trehalose metabolism-related enzymes to cold-adaption in psychrotrophic bacteria and enrich the resource bank of trehalose hydrolysis enzymes, a novel cold-adapted GH15 GA-like trehalase (MpTre15A) from psychrotolerant Microbacteriumphyllosphaerae LW106 isolated from glacier sediments was cloned and characterized. The recombinant MpTre15A from M. phyllosphaerae LW106 was expressed and purified in Escherichia coli BL21(DE3). The purified MpTre15A functioned as a hexamer and displayed maximal activity at pH 5.0 and 50 °C. Substrate specificity assay proved MpTre15A only showed hydrolytic activity toward α,α-trehalose. Site-directed mutation verified the key catalytic sites of Glu392 and Glu557 in MpTre15A. The kcat and kcat/Km values of MpTre15A at 4 °C (104.50 s−1 and 1.6 s−1 mM−1, respectively) were comparable to those observed for thermophilic GH15 trehalases at 50 °C, revealing its typical cold-adaptability. MpTre15A showed a trehalose conversion rate of 100% and 99.4% after 10 min and 15 min of incubation at 50 °C and 37 °C, respectively. In conclusion, this novel cold-adapted α,α-trehalase MpTre15A showed potential application for developing therapeutic enzymes, enzyme-based biosensors, and enzyme additives in the fermentation industry.

Effect of process parameters on the β-galactosidase hydrolysis of lactose and galactooligosaccharide formation in concentrated skim milk

The study aimed at evaluation of β-galactosidase activity for lactose hydrolysis (DH) and galactooligosaccharide (GOS) formation at 7 °C. β-galactosidase derived from K. lactis was more effective than B. lichenformis for DH and GOS formation in 16% lactose solution. β-galactosidase from K. lactis exhibited 96.61% DH and 7.28% GOS production after 12 h of reaction and hence was utilized for lactose hydrolysis in concentrated skim milk (40% total solids). Use of 9.53 U/mL enzyme resulted in significantly high DH (97.06%) after 12 h with 4.90 g/L of residual lactose. However, maximum GOS formation of 12.01% with 94.74% DH was obtained after 4 h. Further increase in reaction time up to 12 h resulted in breakdown of tri and tetrasaccharide GOS, thereby, reducing GOS content. Hence, reaction time of 12 h was finalized to obtain maximum DH along with additional benefit of GOS formation.

β-Galactosidase from Kluyveromyces lactis: Characterization, production, immobilization and applications - A review

A review on the enzyme β-galactosidase from Kluyveromyces lactis is presented, from the perspective of its structure and mechanisms of action, the main catalyzed reactions, the key factors influencing its activity, and selectivity, as well as the main techniques used for improving the biocatalyst functionality. Particular attention was given to the discussion of hydrolysis, transglycosylation, and galactosylation reactions, which are commonly mediated by this enzyme. In addition, the products generated from these processes were highlighted. Finally, biocatalyst improvement techniques are also discussed, such as enzyme immobilization and protein engineering. On these topics, the most recent immobilization strategies are presented, emphasizing processes that not only allow the recovery of the biocatalyst but also deliver enzymes that show better resistance to high temperatures, chemicals, and inhibitors. In addition, genetic engineering techniques to improve the catalytic properties of the β-galactosidases were reported. This review gathers information to allow the development of biocatalysts based on the β-galactosidase enzyme from K. lactis, aiming to improve existing bioprocesses or develop new ones.

Nanoparticle-based amplification for sensitive detection of β-galactosidase activity in fruits

Development of fast and sensitive assays for enzyme activity detection has received a great deal of attention because of the wide spread applications in measurements of numerous clinical, food and environmental processes. Herein, a novel amplification approach to enhance the sensitivity of colorimetric assays for detection of β-galactosidase (β-Gal) activity is proposed. β-Gal detection is important in biomedical applications and in food industry, where it is associated with the ripening process of fruits. The method is based on the use of multivalent cerium oxide nanoparticles (CeNPs) which catalyze the oxidation of 4-aminophenol (4-AP) produced in the hydrolysis process of the 4-aminophenyl-β-d-galactopyranoside substrate (4-APG) by β-Gal, thus enhancing detection sensitivity of β-Gal in the visible range. The developed assay is highly sensitive and easy to use. Using the optimized procedure, a limit of detection of 0.06 mU/mL was obtained with a linearity range up to 2.0 mU/mL. The feasibility of the method was demonstrated for detection of β-Gal activity in fruits and the results were compared with the conventional assay, providing over a 30-fold amplification as compared to a commercially available β-Gal protocol. The advantage of the presented assay is its biocatalytic event amplified by a secondary reaction, which enables much more sensitive detection of the enzymatic product. The sensing platform can be applied broadly to a variety of applications that rely on β-Gal activity measurements.

β-galactosidase GALA from Bacillus circulans with high transgalactosylation activity

β-galactosidase catalyzes lactose hydrolysis and transfers reactions to produce prebiotics such as galacto-oligosaccharides (GOS) with potential applications in the food industry and pharmaceuticals. However, there is still a need for improved transgalactosylation activity of β-galactosidases and reaction conditions of GOS production in order to maximize GOS output and reduce production costs. In this study, a β-galactosidase gene, galA, from Bacillus circulans was expressed in Pichia pastoris, which not only hydrolyzed lactose but also had strong transgalactosylation activity to produce GOS. Response surface methodology was adopted to investigate the effects of temperature, enzyme concentration, pH, initial lactose concentration, and reaction time on the production of GOS and optimize the reaction conditions for GOS. The optimal pH for the enzyme was 6.0 and remained stable under neutral and basic conditions. Meanwhile, GALA showed most activity at 50°C and retained considerable activity at a lower temperature 30–40°C, indicating this enzyme could work under mild conditions. The enzyme concentration and temperature were found to be the critical parameters affecting the transgalactosylation activity. Response surface methodology showed that the optimal enzyme concentration, initial lactose concentration, temperature, pH, and reaction time were 3.03 U/mL, 500 g/L, 30°C, 5.08, and 4 h, respectively. Under such conditions, the maximum yield of GOS was 252.8 g/L, accounting for approximately 50.56% of the total sugar. This yield can be considered relatively high compared to those obtained from other sources of β-galactosidases, implying a great potential for GALA in the industrial production and application of GOS.

Optimization and comparison of the production of galactooligosaccharides using free or immobilized Aspergillus oryzae β-galactosidase, followed by purification using silica gel

The aim of this study was to optimize and compare the production of galactooligosaccharides (GOSs) by free and cotton cloth-immobilized Aspergillus oryzae β-galactosidase, and perform economical evaluation of production of GOSs (100%) between them. Using the response surface method, the optimal reaction time (3.9 h), initial lactose concentration (57.13%), and enzyme to lactose ratio (44.81 U/g) were obtained for the free enzyme, which provided a GOSs yield of 32.62%. For the immobilized enzyme, the optimal yield of GOSs (32.48%) was obtained under reaction time (3.09 h), initial lactose concentration (52.74%), and temperature (50.0 ℃). And it showed desirable reusability during five successive enzymatic reactions. The recovery rate of GOSs (100%) is 65% using silica gel filtration chromatography. The economical evaluation showed almost no difference in the manufacturing cost for the GOSs (100%) between these two systems, and that the recovery rate had a great impact on the cost.

β-Galactosidase-Producing Isolates in Mucoromycota: Screening, Enzyme Production, and Applications for Functional Oligosaccharide Synthesis

β-Galactosidases of Mucoromycota are rarely studied, although this group of filamentous fungi is an excellent source of many industrial enzymes. In this study, 99 isolates from the genera Lichtheimia, Mortierella, Mucor, Rhizomucor, Rhizopus and Umbelopsis, were screened for their β-galactosidase activity using a chromogenic agar approach. Ten isolates from the best producers were selected, and the activity was further investigated in submerged (SmF) and solid-state (SSF) fermentation systems containing lactose and/or wheat bran substrates as enzyme production inducers. Wheat bran proved to be efficient for the enzyme production under both SmF and SSF conditions, giving maximum specific activity yields from 32 to 12,064 U/mg protein and from 783 to 22,720 U/mg protein, respectively. Oligosaccharide synthesis tests revealed the suitability of crude β-galactosidases from Lichtheimia ramosa Szeged Microbiological Collection (SZMC) 11360 and Rhizomucor pusillus SZMC 11025 to catalyze transgalactosylation reactions. In addition, the crude enzyme extracts had transfructosylation activity, resulting in the formation of fructo-oligosaccharide molecules in a sucrose-containing environment. The maximal oligosaccharide concentration varied between 0.0158 and 2.236 g/L depending on the crude enzyme and the initial material. Some oligosaccharide-enriched mixtures supported the growth of probiotics, indicating the potential of the studied enzyme extracts in future prebiotic synthesis processes.

Yarrowia lipolytica as an emerging biotechnological chassis for functional sugars biosynthesis

Functional sugars have unique structural and physiological characteristics with applied perspectives for modern biomedical and biotechnological sectors, such as biomedicine, pharmaceutical, cosmeceuticals, green chemistry, and agro-food. They can also be used as starting matrices to produce biologically active metabolites of interests. Though numerous chemical synthesis routes have been proposed and deployed for the synthesis of rare sugars, however, many of them are limited and economically incompetent because of expensive raw starting feedstocks. Whereas, the biosynthesis by enzymatic means are often associated with high catalyst costs and low space-time yields. Microbial production of rare sugars via green routes using bio-renewable resources offers noteworthy solutions to overcome the aforementioned limitations of synthetic and enzymatic synthesis routes. From the microbial-based synthesis perspective, the lipogenic yeast Yarrowia lipolytica is rapidly evolving as the most prevalent and unique "non-model organism" in the bio-production arena. Due to high flux tendency through the tri-carboxylic acid cycle intermediates and precursors such as acetyl-CoA and malonyl-CoA, this yeast has been widely investigated to meet the increasing demand of industrially relevant fine chemicals, including functional sugars. Incredible interest in Y. lipolytica originates from its robust tolerance to unstable pH, salt levels, and organic compounds, which subsequently enable easy bioprocess optimization. Meaningfully, GRAS (generally recognized as safe) status creates Y. lipolytica as an attractive and environmentally friendly microbial host for the manufacturing of nutraceuticals, fermented food, and dietary supplements. In this review, we highlight the recent and state-of-the-art research progress on Y. lipolytica as a host to synthesize bio-based compounds of interest beyond the realm of well-known fatty acid production. The unique physicochemical properties, biotechnological applications, and biosynthesis of an array of value-added functional sugars including erythritol, threitol, fructooligosaccharides, galactooligosaccharides, isomalto-oligosaccharides, isomaltulose, trehalose, erythrulose, xylitol, and mannitol using sustainable carbon sources are thoroughly vetted. Finally, we conclude with perspectives that would be helpful to engineer Y. lipolytica in greening the twenty-first century biomedical and biotechnological sectors of the modern world.

Effect of the incorporation of β-galactosidase in the GOS production during manufacture of soft cheese

Galactooligosaccharides (GOS) are non-digestible oligosaccharides with recognized prebiotic role. The present study aims to evaluate a β-galactosidase from K. lactis during soft cheese making and to analyse the impact on carbohydrates metabolism, proteolysis, and volatile compounds production, physicochemical and microbiological characteristics of the product. The enzyme was added to cheese milk (fluid milk plus whey powder) before (40 min.) or simultaneously of the starter addition (Ep and E treatments, respectively); cheese without enzyme addition was also made (C treatment). Also, we characterized fresh and soft commercial cheeses from the point of view of carbohydrate fraction, highlighting GOS, and organic acid profiles. The inclusion of the enzyme in soft cheese making produced a delay in reaching the target pH (~5.2). Carbohydrate fermentation profiles differed among treatments during cheese making and ripening. GOS were only detected in Ep and E cheeses (0.88 and 0.51 g/100 g, respectively). Lactose content was lower, and glucose and galactose levels were higher in E and Ep than C. No differences in physicochemical and microbial composition and organic acids profiles among samples were observed. Bioformation of volatile compounds belonging to the chemical families of aldehydes, ketones, alcohols, esters and acids, was not substantially affected by the modification in the carbohydrate profile. GOS were not detected in any of the commercial cheeses; great variations in the carbohydrate contents and organic acids were found. The results obtained demonstrate the feasibility of obtaining cheeses with GOS. Although the GOS values achieved are not adequate enough for the desired effect, the proposed technological approach turned out to be satisfying and original. Cheeses with prebiotic fiber are not still widespread in the market.

Technical integrative approaches to cheese whey valorization towards sustainable environment

Whey, a byproduct of cheese production, is often treated as an industrial dairy waste. A large volume of this product is disposed of annually due to inadequate bioconversion approaches. With its high pollutant load, disposal without pretreatment has raised a lot of environmental concerns alerting the need to seek optimal methods for adequately extracting and utilizing its organic content. In recent years, several techniques for whey valorization have emerged which may serve as interventionary measures against its environmental effects after disposal. In this review, we discuss five major approaches, by which whey can be converted into eco-friendly products, to significantly cut whey wastage. The approaches to whey valorization are therefore examined under the following perspectives: whey as a raw material for the production of bioethanol and prebiotic oligosaccharides via β-galactosidase and microbe catalyzed reactions, for the production of refined lactose as an excipient for pharmaceutical purposes, and the clinical significance of whey hydrolysates and their antifungal activity in food processing.

Selective Synthesis of Galactooligosaccharides Containing β(1→3) Linkages with β-Galactosidase from Bifidobacterium bifidum (Saphera)

The transglycosylation activity of a novel commercial β-galactosidase from Bifidobacterium bifidum (Saphera) was evaluated. The optimal conditions for the operation of this enzyme, measured with o-nitrophenyl-β-d-galactopyranoside, were 40 °C and pH around 6.0. Although at low lactose concentrations the property of this enzyme was basically hydrolytic, an increase of lactose concentration to 400 g/L resulted in a significant formation (107.2 g/L, 27% yield) of prebiotic galactooligosaccharides (GOS). The maximum amount of GOS was obtained at a lactose conversion of approximately 90%, which contrasts with other β-galactosidases, for which the highest GOS yield is achieved at 40-50% lactose conversion. Using high-performance anion-exchange chromatography with pulsed amperometric detection, semipreparative high-performance liquid chromatography-hydrophilic interaction liquid chromatography, mass spectrometry, and 1D and 2D NMR, we determined the structure of most of the GOS synthesized by this enzyme. The main identified products were Gal-β(1→3)-Gal-β(1→4)-Glc (3'-O-β-galactosyl-lactose), Gal-β(1→6)-Glc (allolactose), Gal-β(1→3)-Glc (3-galactosyl-glucose), Gal-β(1→3)-Gal (3-galactobiose), and the tetrasaccharide Gal-β(1→3)-Gal-β(1→3)-Gal-β(1→4)-Glc. In general, B. bifidum β-galactosidase showed a tendency to form β(1→3) linkages followed by β(1→6) and more scarcely β(1→4).

Limitation of Maillard Reactions in Lactose-Reduced UHT Milk via Enzymatic Conversion of Lactose into Galactooligosaccharides during Production

Lactose-hydrolyzed (LH) ultrahigh temperature (UHT) processed milk is more prone to Maillard reactions and formation of advanced glycation end products (AGEs) during processing and storage than conventional (CON) UHT milk because of the presence of free galactose and glucose. Commercially available β-d-galactosidases with transgalactosylating activity can incorporate galactose into galactooligosaccharides (GOSs) and potentially limit Maillard reactions in this lactose-reduced GOS-containing milk. The aim of this study was to examine the extent of Maillard reactions in a lactose-reduced GOS milk compared to LH and CON milk after UHT processing. The GOS milk had significant lower levels of lysine- and arginine-derived AGEs compared to LH milk, while their concentrations were similar to those found in CON milk. The total concentration of measured Arg-derived AGEs was similar to the total concentration of Lys-derived AGEs in the three types of milk, indicating that Arg is an important source of AGEs in milks. Interestingly, the GOS milk generated threefold higher concentrations (up to 330 ± 6 μM) of 3-deoxyglucosone (3-DG, a C6 α-dicarbonyl). These results demonstrate that GOS milk could be a potential alternative for LH milk for lactose-intolerant individuals, although further studies are needed to understand the increased formation of 3-DG in GOS-containing milk.

Interfacial Biocatalytic Performance of Nanofiber-Supported β-Galactosidase for Production of Galacto-Oligosaccharides

Molecular distribution, structural conformation and catalytic activity at the interface between enzyme and its immobilising support are vital in the enzymatic reactions for producing bioproducts. In this study, a nanobiocatalyst assembly, β-galactosidase immobilized on chemically modified electrospun polystyrene nanofibers (PSNF), was synthesized for converting lactose into galacto-oligosaccharides (GOS). Characterization results using scanning electron microscopy (SEM) and fluorescence analysis of fluorescein isothiocyanat (FITC) labelled β-galactosidase revealed homogenous enzyme immobilization, thin layer structural conformation and biochemical functionalities of the nanobiocatalyst assembly. The β-galactosidase/PSNF assembly displayed enhanced enzyme catalytic performance at a residence time of around 1 min in a disc-stacked column reactor. A GOS yield of 41% and a lactose conversion of 88% was achieved at the initial lactose concentration of 300 g/L at this residence time. This system provided a controllable contact time of products and substrates on the nanofiber surface and could be used for products which are sensitive to the duration of nanobiocatalysis.

Inactivation mechanism of E. coli O157:H7 under ultrasonic sterilization

Ultrasonic sterilization (US), as a promising non-thermal sterilization method, exhibits unique superiorities than traditional sterilization methods. In this study, the inactivation mechanism of E. coli O157:H7 under US was investigated in cucumber and bitter gourd vegetable juices. Results revealed that the US treatment showed good antibacterial ability in countering E. coli O157:H7. Through determinations of conductivity and β-galactosidase activity, significant augmentation in membrane permeability of the bacteria was confirmed after the US treatment. The morphologies of the US treated E. coli O157:H7 demonstrated that the integrity of the cell membrane was disrupted by US treatment. SDS-PAGE and LSCM data further proved the disruptive action of US, leading to the leakage of proteins and DNA through the breakage on cell membrane. The decrease of metabolic-related enzyme activity was verified through investigation of bacterial metabolism. The antibacterial mechanism analysis indicated that the US can generate free radicals which resulted in the rise of intracellular oxidative stress, attenuation of energy metabolism and inhibition of hexose monophosphate pathway. As the application verification, the US treatment can cause the deprivation of E. coli O157:H7 cell viability in vegetable juices without obvious impact on the sensory quality.

Improving Galactooligosaccharide Synthesis Efficiency of β-Galactosidase Bgal1-3 by Reshaping the Active Site with an Intelligent Hydrophobic Amino Acid Scanning

There are ongoing interests in improving the galactooligosaccharide (GOS) synthesis efficiency of β-galactosidase by protein engineering. In this study, an intelligent double-hydrophobic amino acid scanning strategy was proposed and employed to target nine residues forming the glycon-binding site (-1 subsite) of β-galactosidase Bgal1-3. Two mutants C510V and H512I with significantly improved GOS synthesis efficiency were obtained. When 40% (w/v) lactose was used as a substrate, Bgal1-3 reached a maximum GOS yield of 45.3% at 16 h, while the mutants reached higher yields in a much shorter time (59.1% at 10 h for C510V, 51.5% at 2 h for H512I). When skim milk was treated with these enzymes, more GOS was produced (19.9 g/L for C510V, 12.7 g/L for H512I) than that for Bgal1-3 (10.3 g/L) at a lactose conversion of 90%. These results validated hydrophobicity scanning as an efficient method to engineer β-galactosidases into promising catalysts for the preparation of GOS and GOS-enriched milk.

Discovery of Novel High-Molecular Weight Oligosaccharides Containing N-Acetylhexosamine in Bovine Colostrum Whey Permeate Hydrolyzed with Aspergillus oryzae β-Galactosidase

Bovine milk oligosaccharides (BMOs) that resemble human milk oligosaccharides are found in whey permeate, indicating that dairy streams can be used as a potential source of bioactive oligosaccharides. Recovery of oligosaccharides from whey permeate is hindered by their low abundance and high concentration of lactose. In the present work, lactose in bovine colostrum whey permeate was hydrolyzed by Aspergillus oryzae β-galactosidase to facilitate subsequent monosaccharide removal by membrane separation. Chromatographic separation coupled with high-resolution mass spectrometry revealed β-galactosidase degradation of several β-linkage-containing BMOs and production of novel oligosaccharides that ranged in size from 5 to 11 monosaccharide units containing several galactose repeating units and N-acetylhexosamine at their reducing ends. Optimization of BMO hydrolysis and separation methodology could generate high amounts of hetero-oligosaccharides for improved recovery of potentially biotherapeutic oligosaccharides.

Inhibition of Maillard Reactions by Replacing Galactose with Galacto-Oligosaccharides in Casein Model Systems

Lactose reduced dairy products are more prone to Maillard reactions due to the presence of reactive monosaccharides. Conventional β-galactosidases, which are used for lactose hydrolysis in lactose-reduced dairy products, will lead to conversion of lactose into glucose and galactose, where especially galactose is very reactive during Maillard reactions. Some β-galactosidases have transgalactosylating activity and will thus convert lactose into galacto-oligosaccharides (GOS) and hereby limit the release of galactose. The aim of this study was to investigate the extent of participation of GOS in Maillard reactions in comparison to lactose, a 50:50 mixture of glucose and galactose, and galactose exclusively in sodium caseinate-based milk-like model systems heated at 130 and 75 °C at pH 6.8. The GOS system exhibited reduced loss of free amino groups; accumulated less furosine and less of the following advanced glycation end products (AGEs): N^ε-carboxyethyl lysine, methylglyoxal-derived hydroimidazolone isomers, glyoxal-derived lysine dimer, and methylglyoxal-derived lysine dimer; and also developed less browning compared to monosaccharide models. However, the GOS-caseinate system accumulated more 3-deoxyglucosone and 3-deoxygalactosone, which resulted in higher concentrations of 5-(hydroxymethyl)furfural and pyrraline. The results indicated that GOS overall participate less readily in Maillard reactions than the monosaccharides investigated but were more prone to degradation to C6 α-dicarbonyls species. Finally, relationship analysis indicated that C6 α-dicarbonyls seemed to primarily increase concentrations of 5-(hydroxymethyl)furfural instead of AGEs. Our results suggest that conversion of lactose into GOS instead of monosaccharides in milk by transgalactosylating β-galactosidases could be a useful strategy for production of lactose-free milk for people with lactose intolerance.

Cultural conditions optimization for production of β-galactosidase from Bacillus licheniformis ATCC 12759 under solid-state fermentation

Objective:

The aim of this work was to study the optimal cultivation conditions for β-galactosidase production byBacillus licheniformisATCC 12759.

Materials and methods:

The screening of β-galactosidase production fromB. licheniformisATCC 12759 was performed by solid state fermentation method on media rich with rice bran (RB). Different factors were tested for the optimization of β-galactosidase production.

Results:

Certain fermentation parameters involving incubation time, incubation temperature, inoculum level, moisture content, initial pH, agitation speed, size of fermentation medium and optimum temperature of β-galactosidase activity were studied separately. Maximal amount of β-galactosidase production was obtained when solid-state fermentation (SSF) was carried out using RB, having inoculum level 35%, moisture content of 20%, initial pH 7.5 at 37°C for 48 h.

Conclusion:

Results indicated that optimal fermentation conditions play a key role in the maximum production of β-galactosidase fromB. licheniformisATCC 12759. This study shows the potential of the studied enzymes to be promoting candidates for the degradation of lactose and production of important bioproducts.

Response surface methodology as a tool for modelling galacto-oligosaccharide production

The experiments reported in this research paper describe the effects of β-galactosidase enzyme dose and cheese whey amount, on the maximum concentration and yield of galacto-oligosaccahride (GOS) and reaction time. The experimental plan was based on central composite rotational design (CCRD) and modelled by response surface methodology (RSM). The results indicate that the proposed mathematical models could adequately describe the concentration and yield of GOS and the reaction time within the limits of the factors that are being investigated. The variance analysis shows high values of coefficients of determination (>0·97) while no significant lack of fit was evident. Hence, the models could be employed to select reaction conditions applied in the manufacture of products enriched in bioactive compounds with high value-added.

Biochemical characterization of a novel β-galactosidase from Paenibacillus barengoltzii suitable for lactose hydrolysis and galactooligosaccharides synthesis

A β-galactosidase gene (PbBGal2A) was cloned from Paenibacillus barengoltzii and expressed in Escherichia coli. The in silico analysis of the deduced amino acid sequences revealed that PbBGal2A shared the highest identity of 40% with the characterized glycoside hydrolase (GH) family 2 β-galactosidase from Actinobacillus pleuropneumoniae. The recombinant β-galactosidase (PbBGal2A) was purified with a molecular mass of 124.2kDa on SDS-PAGE. The optimal pH and temperature of PbBGal2A were determined to be pH 7.5 and 45°C, respectively. PbBGal2A was stable within pH 6.0-8.0 and up to 45°C. It completely hydrolyzed the lactose in milk and whey powder solution. In addition, PbBGal2A exhibited high transglycosylation activity and a maximum yield of 47.9% (w/w) for galactooligosaccharides (GOS) production was obtained in 8h at a lactose concentration of 350g/L. These properties make PbBGal2A an ideal candidate for commercial use in the production of lactose-free milk and GOS.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

Production of High Galacto-oligosaccharides by Pectinex Ultra SP-L: Optimization of Reaction Conditions and Immobilization on Glyoxyl-Functionalized Silica

A rational optimization for the synthesis of galacto-oligosaccharides (GOS) from lactose catalyzed by β-galactosidase from Aspergillus aculeatus, included in the commercial product Pectinex Ultra SP-L, has been performed by using experimental design and surface response methodology. This accurate tool optimized empirical production of the most desired high-GOS (tri-GOS and tetra-GOS) up to 16.4% under the following reaction conditions: 59 °C, 4 U/mL free enzyme concentration, pH 6.5, 250 g/L initial lactose concentration, and 20 h of reaction. The statistical analysis revealed temperature and initial lactose concentration as critical parameters. The successful immobilization of the enzyme on a glyoxyl-functionalized porous silica support slightly increased the yield toward high-GOS (17.6%), especially tri-GOS yield (15.3%), under the optimized reaction conditions as compared to the free enzyme. Furthermore, the promotion of the transgalactosylation reaction toward tri-GOS production increased 1.5-fold the productivity of high-GOS as compared to the free enzyme.