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In order to study the synthesis of dextran in Lactobacillus and to analyze its structure, in this study, the dextransucrase DsrB was ligated with the Lactococcus lactis expression vector pNZ8148 plasmid vector with SP45 secretion signal peptide, and electrotransferred into L. lactis NZ9000 for heterologous expression. The polysaccharide solution was obtained through a series of steps including alcohol precipitation, protein removal by trichloroacetic acid, secondary alcohol precipitation, dialysis and purification. The composition of monosaccharides was detected by high performance liquid chromatography (HPLC). The molecular weight of dextran was determined by high-performance size exclusion chromatography (HPSEC). The structure of polysaccharides was analyzed by fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM), and the surface characteristics of polysaccharides were observed. The results showed that dextransucrase was expressed in lactic acid bacteria, and the glucan yield was 10.54 g/L at a sucrose concentration of 10%. The monosaccharide composition showed that it contained only one monosaccharide, glucose. The molecular weight of the extracellular polysaccharide was determined to be 2.4×106 Da. The combination of FT-IR and NMR indicated that the extracellular polysaccharide synthesized in vitro contained only the α-(1,6) glycosidic bond, and SEM indicated that the surface of the extracellular polysaccharide showed a porous structure. The heterologous expression in lactic acid bacteria realized the food-grade production of dextran and would provide a theoretical basis for the application of dextran in food.

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Dextransucrases play a crucial role in the production of dextran from economical sucrose; therefore, there is a pressing demand to explore novel dextransucrases with better performance. This study characterized a dextransucrase enzyme, LmDexA, which was identified from the Leuconostoc mesenteroides NN710. This bacterium was isolated from the soil of growing dragon fruit in Guangxi province, China. We successfully constructed six different N-terminal truncated variants through sequential analysis. Additionally, a truncated variant, ΔN190LmDexA, was constructed by removing the 190 amino acids fragment from the N-terminal. This truncated variant was then successfully expressed heterologously in Escherichia coli and purified. The purified ΔN190LmDexA demonstrated optimal hydrolysis activity at a pH of 5.6 and a temperature of 30 °C. Its maximum specific activity was measured to be 126.13 U/mg, with a Km of 13.7 mM. Results demonstrated a significant improvement in the heterologous expression level and total enzyme activity of ΔN190LmDexA. ΔN190LmDexA exhibited both hydrolytic and transsaccharolytic enzymatic activities. When sucrose was used as the substrate, it primarily produced high-molecular-weight dextran (>400 kDa). However, upon the addition of maltose as a receptor, it resulted in the production of a significant amount of oligosaccharides. Our results can provide valuable information for enhancing the characteristics of recombinant dextransucrase and potentially converting sucrose into high-value-added dextran and oligosaccharides. [ABSTRACT FROM AUTHOR]

Six lactic acid bacteria (LAB) isolated from Algerian sheep’s milk, traditional butter, date palm sap and barley, which produce dextran, mannitol, oligosaccharides and vitamin B2 have been characterized. They were identified as Leuconostoc mesenteroides (A4X, Z36P, B12 and O9) and Liquorilactobacillus mali (BR201 and FR123). Their exopolysaccharides synthesized from sucrose by dextransucrase (Dsr) were characterized as dextrans with (1,6)-d-glucopyranose units in the main backbone and branched at positions O-4, O-2 and/or O-3, with d-glucopyranose units in the side chain. A4X was the best dextran producer (4.5 g/L), while the other strains synthesized 2.1–2.7 g/L. Zymograms revealed that L. mali strains have a single Dsr with a molecular weight (Mw) of ~ 145 kDa, while the Lc. mesenteroides possess one or two enzymes with 170–211 kDa Mw. As far as we know, this is the first detection of L. mali Dsr. Analysis of metabolic fluxes from sucrose revealed that the six LAB produced mannitol (~ 12 g/L). The co-addition of maltose–sucrose resulted in the production of panose (up to 37.53 mM), an oligosaccharide known for its prebiotic effect. A4X, Z36P and B12 showed dextranase hydrolytic enzymatic activity and were able to produce another trisaccharide, maltotriose, which is the first instance of a dextranase activity encoded by Lc. mesenteroides strains. Furthermore, B12 and O9 grew in the absence of riboflavin (vitamin B2) and synthesized this vitamin, in a defined medium at the level of ~ 220 μg/L. Therefore, these LAB, especially Lc. mesenteroides B12, are good candidates for the development of new fermented food biofortified with functional compounds. [ABSTRACT FROM AUTHOR]

Background: Dextransucrase is an enzyme synthesized by many bacterial genera, which catalyzes the hydrolysis of sucrose to produce dextran, a polysaccharide with a wide range of medical, pharmaceutical, and industrial applications. The study aimed at isolating Lactobacillus species from the human vagina, assessing the production of dextransucrase, and determining the optimal growth conditions. Methods: A total of 53 bacterial samples were isolated from the reproductive tract of healthy women. Out of these 53 samples, 21 isolates of Lactobacillus spp. were obtained. Dextransucrase production was assessed using both the mucoid and spectrophotometric techniques. The effects of natural carbon, nitrogen sources, concentrations of nitrogen, protein, and sucrose, inoculum size, pH, temperature, and incubation time were evaluated to determine the optimal conditions. Results: The findings showing that Lactobacillus acidophilus isolates produced more dextransucrase than isolates of Lactobacillus plantarum, with Lactobacillus acidophilus V19 being the strongest producer isolate due to its highest specific activity. The best conditions for producing dextransucrase were to use a dextransucrase production medium that underwent incubation at 37°C for 48 hours at pH 5.5, with a concentration of 6% sucrose, and 4% inoculum size. The most efficient source of nitrogen was 6% beef extract, and the best source of carbon was dates. At this point, the dextransucrase activity was at its highest. Conclusion: The findings of the study revealed that the optimal conditions for dextransucrase production are a pH of 5.5, 4% inoculum size, 6% dates extract as a carbon source, 6% beef extract as a nitrogen source, and 48 hours of incubation at 37°C. [ABSTRACT FROM AUTHOR]

Exploration of biodiversity led towards the development of commercially important biological metabolites. This study focus on the molecular characterization of dextransucrase biosynthezing lactic acid bacterial strain, L. mesenteroides KIBGE-IB40. Fermentation system was designed to optimize the crucial production parameters of the biosynthesis of dextransucrase by L. mesenteroides. Data acquired from the experimental analysis revealed a significant increase of about 1.69-fold in enzyme titer from 67.13 DSU/ml to 114.04 DSU/ml. The optimum fermentation conditions were found to be fermentation time, 18 hours; fermentation temperature, 25°C; fermentation pH, 7.5. Structural analysis of purified dextran was performed. The morphological analysis of dextran by SEM revealed a porous structure of the polysaccharide. FTIR analysis demonstrates the functional group analysis of the polymer. The significant increase in dextransucrase yield demonstrates the crucial impact of fermentation conditions on the metabolic properties of microbial cells. The obtained results demonstrate a practical approach for the commercial application of L. mesenteroides KIBGE-IB40 dextransucrase in food and other industrial sectors. [ABSTRACT FROM AUTHOR]

Dextransucrases play a crucial role in the production of dextran from economical sucrose; therefore, there is a pressing demand to explore novel dextransucrases with better performance. This study characterized a dextransucrase enzyme, LmDexA, which was identified from the Leuconostoc mesenteroides NN710. This bacterium was isolated from the soil of growing dragon fruit in Guangxi province, China. We successfully constructed six different N-terminal truncated variants through sequential analysis. Additionally, a truncated variant, ΔN190LmDexA, was constructed by removing the 190 amino acids fragment from the N-terminal. This truncated variant was then successfully expressed heterologously in Escherichia coli and purified. The purified ΔN190LmDexA demonstrated optimal hydrolysis activity at a pH of 5.6 and a temperature of 30 °C. Its maximum specific activity was measured to be 126.13 U/mg, with a Km of 13.7 mM. Results demonstrated a significant improvement in the heterologous expression level and total enzyme activity of ΔN190LmDexA. ΔN190LmDexA exhibited both hydrolytic and transsaccharolytic enzymatic activities. When sucrose was used as the substrate, it primarily produced high-molecular-weight dextran (>400 kDa). However, upon the addition of maltose as a receptor, it resulted in the production of a significant amount of oligosaccharides. Our results can provide valuable information for enhancing the characteristics of recombinant dextransucrase and potentially converting sucrose into high-value-added dextran and oligosaccharides.

Statistical approaches have been established for optimizing fermentation practices and because of encouraging outcomes of these methods, several industries are harmonising in using them for maximum productivity of biological metabolites. Statistical methods are feasible and reliable in performing experiments and analysing results as compared to conventional bioprocessing methodologies. Similarly, strain improvement is also a significant strategy. In the current study, combinatorial approach that involves combining of classical mutagenesis and statistical optimization is attempted to scale-up productivity levels of dextransucrase. Enzyme productivity increased 2.56-fold as compared to wild-type. Plackett-Burman design revealed fermentation temperature, sucrose and peptone concentrations as significant factors. Response surface methodology further enhanced enzyme yield from 29.2 DSU ml−1 to 96.9 DSU ml−1. Overall results revealed remarkable improvement in dextransucrase yield (8.5-fold) depicting significance of currently designed combinatorial approaches. Dextran was produced after this statistically proven approach and based on its structural features its diversified applications are suggested.

Consumers often seek healthier options but still desire the familiar eating experience of traditional dairy. Incorporating exopolysaccharide (EPS)-producing cultures into fermented plant-based milk alternatives (PBMAs) offers a promising approach to improving the textural quality of these products. For this, it is essential that the EPS-producing cultures are able to produce EPS in the plant-based substrate. The present study screened 593 plant-derived lactic acid bacteria (LAB) for their ability to produce EPS on a soy milk agar medium. Fifteen LAB isolates (eight Weissella spp. and seven Leuconostoc spp.) exhibited high EPS production. One of the strongest EPS producers was a Weissella confusa strain, and genome sequencing revealed the presence of two potential related EPS genes. To identify the key gene responsible for EPS production in soy milk, 70,000 colonies were screened on soy milk agar and a spontaneous EPS-defective mutant was isolated. The mutant (W. confusa dsr1) had a mutation in a putative dextransucrase gene, which could encode the enzyme catalysing the transfer of glucose from sucrose into a growing chain of dextran. The mutation introduced a premature stop codon, disrupting the enzyme production. Another mutant (W. confusa sac) found during this screen had impaired acidification and growth in soy milk, which was linked to a mutation in the sucrose metabolism gene cluster. Soy milk fermentations using the W. confusa wild-type or sac mutant, significantly increased water holding capacity and viscosity. This suggests their potential to enhance EPS production in fermented PBMAs, bringing their texture closer to that of traditional dairy. [Display omitted] • 593 plant-isolated LAB were screened for exopolysaccharide production in soymilk. • Weissella spp. were the best EPS producers in soymilk medium. • Soymilk fermented with W. confusa 36 had increased viscosity and water holding capacity. • Spontaneous dsr gene mutant of W. confusa 36 was unable to change the soymilk texture. • A W. confusa mutant defective in sucrose metabolism still produced EPS. [ABSTRACT FROM AUTHOR]

Stirred soy yogurt as a dairy alternative is widely accepted among consumers, but its poor stability has been an urgent problem. We found that Leuconostoc mesenteroides Lm10 produced dextran reduced water mobility and improved the water holding capacity of stirred soy yogurt, especially with over 4 % sucrose added which could completely prevent whey separation. With the increase of dextran content, the particle size of stirred soy yogurt was significantly decreased, accompanied by the improvement of viscoelastic behaviors and resistance to deformation. Moreover, dextran had a stronger ability to maintain the stability of stirred soy yogurt in comparison with gelatin, xanthan and carrageenan during cold storage. The structure-function attributes of this dextran were also revealed. Dextransucrase Gtf1674 was responsible for synthesizing dextran during soy yogurt fermentation. The produced dextran was mainly composed of α-1,6 glycosidic linkages with a low-branched degree and high molecular weight. After stirring, the dextran entangled with soy protein and formed small aggregates with a dense gel structure and small pores, causing them prone to binding with water and reducing the syneresis. This study suggested the benefits of dextran produced by Leuc. mesenteroides Lm10 in stirred soy yogurt, and facilitated developing the "clean label" plant-derived products. [Display omitted] [ABSTRACT FROM AUTHOR]

Leuconostoc citreum JZ-002 was extracted from artisanal orange wine. This strain was used to synthesize dextran with a purification extraction of 27.9 g/L. The resulting dextran had a molecular weight of 2.45 × 106 Da. A significant portion, amounting to 64 % of the structure, is constituted by the main chain, with α-(1,6) glycosidic bonds acting as the linkages. In contrast, the branched chain, comprising 34 % of the entire molecule, is characterized by the presence of α-(1,3) glycosidic bonds. The dextransucrase DsrB, believed to be accountable for the formation of the dextran backbone, was successfully cloned into the pET-28a-AcmA vector. The recombinant expression of the enzyme was achieved. Purified recombinant enzymes and immobilized in a single go using the gram-positive enhancer matrix (GEM). The maximum yield of dextran produced by suchimmobilized enzyme was 191.9 g/L. The composition featured a dextran connected via α-(1,6) glycosidic linkages. Molecular weight controlled synthesis was achieved with sucrose concentrations of 100–2000 mM and enzyme concentrations of 320–1280 U. The Mw of the synthesized dextran extended from 4680 to 1,320,000 Da. By controlling the ratio between enzyme concentration and sucrose concentration, dextrans with diverse Mw can be enzymatically generated. [Display omitted] • Cloning of a dextransucrase gene from Leuconostoc citreum. • Maximum dextran production of 191.9 g/L for recombinant dextransucrase. • Dextran produced by dextransucrase contains α-(1,6) glycosidic bonds. • Application of different ratios of enzyme concentration and sucrose concentration for controlled synthesis of dextran of different molecular weights. [ABSTRACT FROM AUTHOR]

Statistical approaches have been established for optimizing fermentation practices and because of encouraging outcomes of these methods, several industries are harmonising in using them for maximum productivity of biological metabolites. Statistical methods are feasible and reliable in performing experiments and analysing results as compared to conventional bioprocessing methodologies. Similarly, strain improvement is also a significant strategy. In the current study, combinatorial approach that involves combining of classical mutagenesis and statistical optimization is attempted to scale-up productivity levels of dextransucrase. Enzyme productivity increased 2.56-fold as compared to wild-type. Plackett-Burman design revealed fermentation temperature, sucrose and peptone concentrations as significant factors. Response surface methodology further enhanced enzyme yield from 29.2 DSU ml−1 to 96.9 DSU ml−1. Overall results revealed remarkable improvement in dextransucrase yield (8.5-fold) depicting significance of currently designed combinatorial approaches. Dextran was produced after this statistically proven approach and based on its structural features its diversified applications are suggested. [ABSTRACT FROM AUTHOR]

Iron dextran is a common anti-anemia drug, and it requires low molar mass dextran as substrate. In this work, we selected 11 amino acid residues in domain A/B of DSR-MΔ2 within a 5-angstrom distance from sucrose for site-directed mutagenesis by molecular docking. Mutation of Q634 did not affect the enzyme catalytic activity, but showed an obvious impact on the ratio of low molecular weight dextran (L-dextran, 3,000–5,000 Da) and relatively higher molecular weight dextran (H-dextran, around 10,000 Da). L-dextran was the main product synthesized by DSR-MΔ2 Q634A, and its average molecular weight was 3,951 Da with a polydispersity index

Abstract Background Dextransucrases are extracellular enzymes, which catalyze the formation of α-1→6-linked glucose polymers from sucrose. These enzymes are exclusively expressed by lactic acid bacteria, which commonly acidify the extracellular environment due to their physiology. Dextransucrases are thus confronted with steadily changing reaction conditions in regards to the environmental pH, which can further affect the amount of released dextransucrases. In this work, we studied the effect of the environmental pH on the release, the productivity and the product specificity of the dextransucrase expressed by Lactobacillus (L.) hordei TMW 1.1822. Dextransucrases were recovered as crude extracts at pH 3.5–pH 6.5 and then again used to produce dextrans at these pH values. The respectively produced dextran amounts and sizes were determined and the obtained results finally systematically correlated. Results Maximum dextran amounts were produced at pH 4.0 and pH 4.5, while the productivity of the dextransucrases significantly decreased at pH 3.5 and pH 6.5. The distribution of dextran amounts produced at different pH most likely reflects the pH dependent activity of the dextransucrases released by L. hordei, since different transglycosylation rates were determined at different pH using the same dextransucrase amounts. Moreover, similar hydrolysis activities were detected at all tested conditions despite significant losses of transglycosylation activities indicating initial hydrolysis prior to transglycosylation reactions. The molar masses and rms radii of dextrans increased up to pH 5.5 independently of the stability of the enzyme. The gelling properties of dextrans produced at pH 4.0 and pH 5.5 were different. Conclusions The presented methodological approach allows the controlled production of dextrans with varying properties and could be transferred and adapted to other microbes for systematic studies on the release and functionality of native sucrases or other extracellular enzymes.

Plant polyphenols have been extensively studied for their chemopreventive properties for human health. Dextransucrase plays an essential role in synthesizing exopolysaccharides from its exclusive substrate sucrose in Streptococcus mutans. In the present study, the effect of polyphenols gallic acid and tannic acid was investigated on the dextransucrase activity. The enzyme was purified by ethanol precipitation followed by column chromatography by Sephadex G-200 gel chromatography, followed by PEG-400 treatment. The purified enzyme exhibited 52 fold enrichment with 17.5% yield and specific activity of 3.54 Units/mg protein. On SDS-PAGE enzyme protein gave a single band with a molecular weight of 160 kDa. Dextransucrase activity was inhibited 80–90% by 0.04 mM tannic acid (TA) or 0.4 mM gallic acid (GA) suggesting that tannic acid has 10- fold more inhibitory potential than gallic acid on the activity of dextransucrase. CD/ORD studies revealed modifications in the tertiary structure of enzyme protein in presence of tannic acid and gallic acid, which were further confirmed by fluorescence spectra of the protein in presence of tannic acid. These results suggest that inhibition of dextransucrase activity in S. mutans by polyphenols may have potential applications in the prevention and control of dental caries.

Sweet sorghum with sugar-rich stalks is considered a potential bioenergy crop. In this study, the sucrose in stalk juice was transformed into oligosaccharides by employing microbial and enzymatic methods. The maximum oligosaccharide yield of 10–14 g L−1 was obtained from 20 g L−1 sucrose in the sweet sorghum juice, representing conversion of about 82%–87% sucrose. The caloric value of the modified sweet sorghum juice was reduced by more than 50%. The probiotic bacteria exhibited a noteworthy growth profile in the modified sweet sorghum juice enriched with the non-digestible oligosaccharides. The antioxidative properties of the sweet sorghum stalk juice were not altered in the bioprocessed juice. The modified juice did not show any significant change in sensory properties after sucrose to oligosaccharide transformation. Furthermore, the oligosaccharides in the juice exhibited tolerance to heat exposure and, therefore, is feasible for food processing applications. The results suggested sweet sorghum as low-cost biomass for the development of plant-based functional products. [ABSTRACT FROM AUTHOR]

Dextransucrases released by certain lactic acid bacteria form glucose polymers with predominantly α-1,6-linkages and may be exploited biotechnologically for the tailored production of polysaccharides with application potential. Despite releasing two closely related dextransucrases, previous studies showed that water kefir borne Liquorilactobacillus (L.) hordei TMW 1.1822 and L. nagelii TMW 1.1827 produce different amounts of polysaccharides with distinct particle sizes (molecular weight and radius of gyration) and molecular architectures. To investigate where these differences originate and thus to provide deeper insights into the functionally diverse nature of polysaccharide formation during water kefir fermentation, we constructed two variants of the L. nagelii dextransucrase—a full-length enzyme and a truncated variant, devoid of a C-terminal glucan-binding domain that reflects the domain architecture of the L. hordei dextransucrase—and applied them at various enzyme concentrations to form dextran over 24 h. The full-length enzyme exhibited a high activity, forming constant amounts of dextran until a four-fold dilution, whereas the truncated variant showed a gradual decrease in activity and dextran formation at an increasing dilution. The application of the full-length enzyme resulted in higher average particle sizes compared to the truncated variant. However, the dilution of the enzyme extracts also led to a slight increase in the average particle size in both enzymes. Neither the domain architecture nor the enzyme concentration had an impact on the structural architecture of the dextrans. The presented results thus suggest that the comparatively higher processivity of the L. nagelii dextransucrase is predominantly caused by the additional C-terminal glucan-binding domain, which is absent in the L. hordei dextransucrase. The average particle size may be influenced, to some extent, by the applied reaction conditions, whereas the structural architecture of the dextrans is most likely caused by differences in the amino acid sequence of the catalytic domain.

The properties of the glucopolymer dextran are versatile and linked to its molecular size, structure, branching, and secondary structure. However, suited strategies to control and exploit the variable structures of dextrans are scarce. The aim of this study was to delineate structural and functional differences of dextrans, which were produced in buffers at different conditions using the native dextransucrase released by Liquorilactobacillus (L.) hordei TMW 1.1822. Rheological measurements revealed that dextran produced at pH 4.0 (MW = 1.1 * 108 Da) exhibited the properties of a viscoelastic fluid up to concentrations of 10% (w/v). By contrast, dextran produced at pH 5.5 (MW = 1.86 * 108 Da) was gel-forming already at 7.5% (w/v). As both dextrans exhibited comparable molecular structures, the molecular weight primarily influenced their rheological properties. The addition of maltose to the production assays caused the formation of the trisaccharide panose instead of dextran. Moreover, pre-cultures of L. hordei TMW 1.1822 grown without sucrose were substantial for recovery of higher dextran yields, since the cells stored the constitutively expressed dextransucrase intracellularly, until sucrose became available. These findings can be exploited for the controlled recovery of functionally diverse dextrans and oligosaccharides by the use of one dextransucrase type. [ABSTRACT FROM AUTHOR]

Non-digestible oligosaccharides have wide food industrial applications as dietary fibers and prebiotics. The aim of this study is to realize the effective biosynthesis of isomalto-oligosaccharides (IMOs) and reduce the production of by-product dextran. In the presence of acceptors improved the dextransucrase reaction shifting to oligosaccharides formation but a number of by-products dextran appeared. Maltose acceptor performed stronger inhibition behaviors in dextran synthesis than lactose and glucose acceptor due to its higher efficiencies. Acceptors had no influence on the structure of by-product dextran which mainly composed of α-(1,6)-glycosidic linkages and low α-(1,3)-glycosidic branch. In addition, the Mw and contents of IMOs and oligodextrans synthesized by dual-enzyme were hard to control. Addition of maltose acceptor in the dual-enzyme reaction, the adequate dextranase preferentially degraded dextran than the acceptor products to yield the IMOs. Results indicated that the combined use of the dual-enzyme and the maltose acceptor is a simple and effective method to promote the high-quality of functional IMOs. • Non-digestible oligosaccharides catalyzed by different acceptors reaction system were investigated. • Various carbohydrate acceptors had no influence on the molecular weight and structure of by-product dextran but on yield. • The dextranase preferred to degrade by-product dextran than the maltose acceptor products (IMOs). • The combined use of the dual-enzyme and the maltose acceptor was an effective method to promote the quality of IMOs. [ABSTRACT FROM AUTHOR]

Streptococcus mutans is a common principal causative agent of dental caries. In this communication, we describe that the antibodies raised against purified dextransucrase effectively inhibited the growth of S. mutans. The purified enzyme showed 58-fold enrichment, 17.5% yield and a specific activity of 3.96 units/mg protein. Purified IgG fraction of the antibody showed significant affinity with the antigenic protein. Immunotritation of the enzyme with dextransucrase antibody showed a gradual increase in inhibition of dextransucrase activity. The growth of S. mutans was also inhibited by 85% in the presence of 28 μg of IgG fraction of the antibody. Antibodies also impaired glucosyltransferase activity (72.8%) and biofilm formation by 92.6% in S. mutans. Western blot analysis revealed no cross reactivity with the various tissues of mice, rat, rabbit and humans. Dot blot analysis showed little reactivity with Lactobacillus acidophilus and Staphylococcus aureus and there was no reactivity with other bacterial strains like Enterococcus faecalis, Escherichia coli and Salmonella typhimurium. These findings suggest that antibody raised against dextransucrase exhibit inhibitory effects on the growth of S. mutans and biofilm formation with no reactivity with various mammalian tissues, thus it could be an effective anticariogenic agent. [ABSTRACT FROM AUTHOR]

Leucrose is a sucrose isomer which has an α-1,5-linkage, and slowly hydrolyzed to glucose and fructose by small intestinal α-glucosidases. Leucrose can be produced by an isomerization reaction of dextransucrase on a sucrose substrate. In this study, the recombinant dextransucrase from Streptococcus mutans (SmDS) was applied to optimize the reaction conditions for leucrose production. With a substrate mixture of 0.5 M sucrose + 1.0 M fructose, the greatest yield (ca. 24.5%) of leucrose was obtained by SmDS treatment at 30 °C for 120 h. When preadipocyte 3T3-L1 cells were treated with leucrose, this disaccharide inhibited intracellular lipid accumulation in a dose-dependent manner and significantly suppressed mRNA levels of major adipogenic genes, including CCAT/enhancer-binding protein α (C/EBPα), peroxisome proliferator-activated receptor-γ (PPARγ), fatty acid synthase (FAS), and sterol regulatory element-binding protein-1C (SREBP-1C). Phosphorylation of PI3 kinase/Akt/mTOR was also reduced with leucrose treatment. These results suggest that leucrose has a potential in regulating adipogenesis.

Abstract Gallic acid glycoside was enzymatically synthesized by using dextransucrase and sucrose from gallic acid. After purification by butanol partitioning and preparative HPLC, gallic acid glucoside was detected at m/z 355 (C13, H16, O10, Na)+ by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The yield of gallic acid glucoside was found to be 35.7% (114 mM) by response surface methodology using a reaction mixture of 319 mM gallic acid, 355 mM sucrose, and 930 mU/mL dextransucrase. The gallic acid glucoside obtained showed 31% higher anti-lipid peroxidation and stronger inhibition (Ki = 1.23 mM) against tyrosinase than that shown by gallic acid (Ki = 1.98 mM). In UVB-irradiated human fibroblast cells, gallic acid glucoside lowered matrix metalloproteinase-1 levels and increased the collagen content, which was indicative of a stronger anti-aging effect than that of gallic acid or arbutin. These results indicated that gallic acid glucoside is likely a superior cosmetic ingredient with skin-whitening and anti-aging functions.

Dextran is a long chain of carbohydrate polymers synthesized by dextransucrase enzyme with sucrose as a substrate. The physical, chemical conditions, temperature, and the concentration of sucrose in the isolate bacterial growth media play an important role in dextransucrase production. This study aims to isolate and characterize the dextransucrase producing bacteria. The bacteria were isolated from sugar cane. TBT 3.2 Isolate which had the highest viscosity (1.48 cP) and crude dextran (7.87 g/L) production was selected. TBT 3.2 Isolate was identified as Paenibacillus polymyxa with 99% similar identity. The Paenibacillus polymyxa TBT 3.2 was characterized based on their ability to produce dextran and cell number. The bacteria had the optimum growth conditions on the media for producing dextran at pH 7, temperature 30°C, and concentration of 20% sucrose. The highest dextransucrase activity and the highest specific activity were obtained after 25 minutes of incubation, with the activities of 29.41 mU/mL and 0.46 U/mg. Based on the results of this study, the Paenibacillus polymyxa TBT 3.2 can be used as a dextran producing bacteria.

Purified Acetobacter tropicalis dextransucrase was immobilized in different matrices viz. calcium-alginate, κ-carrageenan, agar, agarose and polyacrylamide. Calcium-alginate was proved to be superior to the other matrices for immobilization of dextransucrase enzyme. Standardization of immobilization conditions in calcium-alginate resulted in 99.5% relative activity of dextransucrase. This is the first report with such a large amount of relative activity as compared to the previous reports. The immobilized enzyme retained activity for 11 batch reactions without a decrease in activity which suggested that enzyme can be used repetitively for 11 cycles. The dextransucrase was also characterized, which revealed that enzyme worked best at pH 5.5 and 37 °C for 30 min in both the free as well as immobilized state. Calcium-alginate immobilized dextransucrase of A. tropicalis showed the Km and Vmax values of 29 mM and 5000 U/mg, respectively. Free and immobilized enzyme produced 5.7 mg/mL and 2.6 mg/mL of dextran in 2 L bench scale fermenter under optimum reaction conditions. This immobilization method is very unconventional for purified large molecular weight dextran-free dextransucrase of A. tropicalis as this method is used usually for cells. Such reports on entrapment of purified enzyme are rarely documented. [ABSTRACT FROM AUTHOR]

The genes for dextransucrase and dextranase were cloned from the genomic regions of Leuconostoc mesenteroides MTCC 10508 and Streptococcus mutans MTCC 497, respectively. Heterologous expression of genes was performed in Escherichia coli. The purified enzyme fractions were entrapped in the alginate–pectin beads. A high immobilization yield of dextransucrase (~ 96%), and dextranase (~ 85%) was achieved. Alginate–pectin immobilization did not affect the optimum temperature and pH of the enzymes; rather, the thermal tolerance and storage stability of the enzymes was improved. The repetitive batch experiments suggested substantially good operational stability of the co-immobilized enzyme system. The synergistic catalytic reactions of alginate–pectin co-entrapped enzyme system were able to produce 7–10 g L−1 oligosaccharides of a high degree of polymerization (DP 3–9) from sucrose (~ 20 g L−1) containing feedstocks, e.g., table sugar and cane molasses. The alginate–pectin-based co-immobilized enzyme system is a useful catalytic tool to bioprocess the agro-industrial bio-resource for the production of prebiotic biomolecules. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Agarose-Epoxy support was produced and characterized. • Dextransucrase and dextranase were co-immobilized onto the agarose-epoxy support. • The results were compared to the obtained with Eupergit CM. • The AGE-DS-DN0.5 synthesized oligosaccharides degree of polymerization up to 5. • The infrared spectrum showed that Eupergit CM has others reactive groups besides epoxy. Abstract The best support reported for dextransucrase (DS) and dextranase (DN) immobilization was Eupergit C, but this carrier was discontinued and is no longer available in the market. Thus, epoxy-agarose support is suggested as an alternative to co-immobilize DS from Leuconostoc mesenteroides B-512F and DN from Chaetomium erraticum. The co-immobilization approach improved DS performance, compared to immobilized DS, due to the removal of the dextran layer accumulated on DS by DN, and enhanced both enzymes catalytic activities under a wide range of pH and temperature. Since DS and DN have the same optimum pH and temperature, the co-immobilization was done in a single step. The EPA-DS-DN0.5 (co-immobilized DS (26.16 UI) and DN (2.76 UI) in epoxy-agarose) showed the highest recovered activity (59.54%). The biocatalyst was stable at 4 °C, retaining above 70% of activity for 60 days and was efficient producing oligosaccharides, yielding 12.68 ± 0.09 g/L of oligosaccharides with a degree of polymerization up to 5. [ABSTRACT FROM AUTHOR]

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The production of dextransucrase (DS) by Leuconostoc mesenteroides T3, novel isolate from water kefir grain, was studied and optimized. Bacterial supernatant reached activity of 3.1 U/ml when the culture was grown at 23 C and under static culture condition using classical Tsuchiya medium for DS production. The increase of sucrose concentration to 7% led to an increase of DS activity by 52% compared to the control. Medium with 2% beef extract and 1% yeast extract resulted in 4.52 U/ml, which was 47% higher than in the control (with 2% yeast extract). Finally, the increase of K2HPO4 concentration from 2 to 3% resulted in the increased enzyme activity by 28%. Enzyme purified by polyethylene glycol 400 fractionation displayed maximum activity at 30°C and pH 5.4. Zymogram analysis confirmed the presence of DS of approximately 180 kDa. The addition of divalent cations Ca2+, Mg2+, Fe2+ and Co2+ led to a minor increase of DS activity, while the addition of Mn2+ was the most prominent with 73% increase. These findings classify dextransucrase from Leuconostoc mesenteroides T3 as promising candidate for production of dextran, which has numerous applications in various industries. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 31035]

Liquorilactobacillus (L.) hordei (formerly Lactobacillus hordei) is one of the dominating lactic acid bacteria within the water kefir consortium, being highly adapted to survive in this environment, while producing high molecular weight dextrans from sucrose. In this work, we extensively studied the physiological response of L. hordei TMW 1.1822 to sucrose compared to glucose, applying label-free, quantitative proteomics of cell lysates and exoproteomes. This revealed the differential expression of 53 proteins within cellular proteomes, mostly associated with carbohydrate uptake and metabolism. Supported by growth experiments, this suggests that L. hordei TMW 1.1822 favors fructose over other sugars. The dextransucrase was expressed irrespectively of the present carbon source, while it was significantly more released in the presence of sucrose (log2FC = 3.09), being among the most abundant proteins within exoproteomes of sucrose-treated cells. Still, L. hordei TMW 1.1822 expressed other sucrose active enzymes, predictively competing with the dextransucrase reaction. While osmolysis appeared to be unlikely, sucrose led to increased release of a multitude of cytoplasmic proteins, suggesting that biofilm formation in L. hordei is not only composed of a polysaccharide matrix but is also of proteinaceous nature. Therefore, our study highlights the intrinsic adaptation of water kefir-borne L. hordei to sucrose-rich habitats and provides fundamental knowledge for its use as a starter culture in plant-based food fermentations with in situ dextran formation.

A study of modulation of the reactions catalyzed by dextransucrase from Leuconostoc mesenteroides Lm 28 strain in the presence of triterpenoid ursolic acid was carried out. This compound showed concentration dependent inhibition of the studied dextransucrase and Ki = 1.9 mM, which is about 5 times higher than Ki value of the known glucansucrase inhibitor acarbose. Ursolic acid affected significantly the acceptor reactions catalyzed by Lm 28 dextransucrase in the presence of maltose and sucrose to maltose ratio 2. Increasing concentrations of ursolic acid shifted concentration and degree of polymerization (DP) distribution of the synthesized glucooligosaccharides (GOS) to acceptor products with DP ≤ 5. The oligosaccharide synthesis scheme applied in this study is a promising approach for production of GOS with controlled length of the chain.

The incorporation of probiotic bacteria to food products is restricted by their instability, so microencapsulation could provide them better protection during storage and gastrointestinal digestion. In this study Bifidobacterium animalis subsp. lactis INL1 was microencapsulated by spray drying using whey proteins isolate (WPI) and dextrans (DX of 6, 70 and 450 kDa) conjugates obtained by Maillard reaction as wall materials. The stability during storage time and temperature, the viability after simulated gastrointestinal digestion and the antioxidant capacity of the microcapsules were assayed. The cell viability was negatively affected by the gastrointestinal digestion and also over the storage time (12 months). Conjugate with DX 6 kDa was the most stable system at 25 °C and showed improved antioxidant capacity whit ABTS + technique; meanwhile with OH technique no differences were found among the samples. Free cells also showed antioxidant activity in all their fractions analyzed using the same techniques. [ABSTRACT FROM AUTHOR]

A continuous synthesis process for the production of oligodextrans from sucrose by using dextransucrase and dextranase in a recycle ultrafiltration membrane bioreactor was developed. During continuous oligodextrans synthesis, changes in weight-average molecular weight (Mw) and polydispersity index (D value) in the second feed tank (i) were monitored by high-performance gel permeation chromatography. Mw decreased with increasing reaction time, resulting in an increasingly homologous solution of low Mw oligodextrans (approximately 1 × 104 Da). The D value of the oligodextrans produced was nearly 1.0. In addition, the polymer degradation model well described the kinetics of Mw changes in oligodextrans. Results showed that recycle membrane bioreactor coupled with dextransucrase and dextranase is a simple and effective method that can be used to produce and improve the quality of oligodextrans. [ABSTRACT FROM AUTHOR]

The formation of HoPS and oligosaccharides in sourdough fermentation improves bread quality but is dependent on the expression of glycansucrases by lactic acid bacteria. Data on the expression of dextransucrases by Weissella spp., however, are limited. This study therefore aimed to assess dextansucrase expression in W . cibaria 10 M, focusing on the effect of temperature. The effect of temperature on growth, oligosaccharide and dextran synthesis by W . cibaria 10 M was determined and the expression and activity of cell-associated dextransucrase from W . cibaria 10 M were investigated. The oligosaccharides profiles were measured by thin layer chromatography and high performance anion exchange chromatography coupled to pulsed amperometric detection. Dextran formation was quantified by size exclusion chromatography. W . cibaria grew fastest at 30 °C but oligosaccharide formation was highest at 20 °C or less. Dextransucrase expression as measured by reverse transcription quantitative PCR, SDS-PAGE, and activity of cell-associated dextransucrase were maximal at 15 °C. Cold shift incubation, characterized by incubation at 30 °C to obtain biomass, followed by shift to 6 °C to induce dextransucrase expression, supported high dextransucrase activity in laboratory media. Cold shift fermentation of wheat and sorghum sourdoughs supplemented with 15 or 30% sucrose increased the yields of oligosaccharides, and resulted in formation of 16 and 12 g/kg dextran in wheat and sorghum sourdoughs, respectively. Dextran formation was decreased in favour of oligosaccharide formation when doughs were supplemented with maltose. In conclusion, cold shift fermentation of sourdough with W . cibaria supports high dextran yields or formation of oligosaccharides without excess acidification. [ABSTRACT FROM AUTHOR]

We describe the development of cross-linked enzyme aggregates (CLEA) of dextransucrase of Leuconostoc mesenteroides B-512 F. Treatments of enzyme preparation using dextranase were evaluated varying incubation time to remove the dextran layer involving the enzyme molecule, turning it suitable for immobilization. Results showed 21 days of treatment as the best outcome. Subsequently, we tested different water-miscible organic solvents as precipitants, the reaction and centrifugation times, and the concentration of cross-linker agent (glutaraldehyde) in the preparation of CLEA. Optimal conditions were: the use of isopropanol as solvent, 30 min of centrifugation time, 3 h of cross-linking time, and 100 mM of glutaraldehyde. A central composite design was carried out to optimize conditions to obtain the highest enzymatic activity, testing the pH (3.0–7.0) and temperature (20 °C-60 °C). Results showed that dextransucrase CLEA operate at optimal pH of 3.0 and temperature of 60 °C. The operational stability of the immobilized biocatalyst showed up to 30% of residual activity after 10 cycles of reuse, in a solution of 100 mM of sucrose and 600 mM of maltose. The preparation of dextransucrase CLEA is described for the first time and results suggest that this novel immobilized biocatalyst has potential in many industrial applications. [ABSTRACT FROM AUTHOR]

The current study reported the statistically designed experimental method to enhance the biocatalytic efficacy of dextransucrase from Weissella confusa . Various environmental and nutritional parameters were optimized using multiple responses under submerged fermentation environment. Statistical models were constructed to screen the influence of nine factors on the biocatalysis of dextransucrase. Among them, fermentation time, pH, sucrose and peptone exhibited significant probability ( P  < 0.05) and are considered as substantial constituents in accordance with Plackett-Burman design. Central composite design was further implemented to optimize the levels of selected variables for maximum enzyme yield. The predicted optimum conditions were pH of 7.5 under fermentation time of 8 h with 30.0 g l −1 sucrose and 1.0 g l −1 peptone. The overall enzyme yield increased from 11.4 DSU ml −1 to 52.75 DSU ml −1 with 4.62-fold upsurge after the implementation of the statistical models. Furthermore, SEM analysis showed the biocatalytic conversion of sucrose into highly porous dextran when utilizing dextransucrase. The biopolymer produced under the current optimized model could be utilized as an emulsifying, gelling, stabilizing and thickening agent in food industry. [ABSTRACT FROM AUTHOR]

The TiO 2 based hybrid supports with different functional groups (amino, glutaraldehyde or epoxy) were prepared and their influence on immobilization of dextransucrase (DS) was studied. Novel synthetic route for surface modification of TiO 2 with amino and glutaraldehyde groups was developed taking advantage of charge transfer complex (CTC) formation between surface Ti atoms and salicylate-type of ligand (5‑aminosalicylic acid (5-ASA)). The proposed coordination of 5-ASA to the surface of TiO 2 powder and optical properties of CTC was presented. The pristine TiO 2 and amino functionalized TiO 2 have higher sorption capacity for DS (12.6 and 12.0 mg g −1 , respectively) compared to glutaraldehyde and epoxy activated supports (9.6 and 9.8 mg g −1 , respectively). However, immobilized enzyme to either glutaraldehyde or epoxy functionalized TiO 2 have almost two times higher expressed activities compared to pristine TiO 2 support (258, 235 and 142 IU g −1 , respectively). Thermal stability of enzyme immobilized on glutaraldehyde and epoxy functionalized supports was studied at 40 °C, as well as operational stability under long-run working conditions in repeated cycles. After five cycles, DS imobilized on glutaraldehyde activated support retained almost 70% of its initial expressed activity, while, after five cycles, performance of DS immobilized on epoxy activated support was significantly lower (15%). [ABSTRACT FROM AUTHOR]

Twelve bacterial strains were isolated from beehives of Yemen, Nigerian and Libyan honey bee. All the isolates showed dextransucrase activity with degrees of variation. Esawy-1 recorded the highest activity (10.53) and was identified morphologically and based on 16S rRNA as Enterococcus faecalis . Some isolate safety was assessed such as hemolytic activity and resistance to antibiotic. The isolate showed sensitivity to most tested antibiotic such as levofloxacin, ofloxacin, ciprofloxacin and vancomycin. Also, the hemolytic activity was negative. A 2- level Plackett–Burman design was used to determine the bioprocess parameters that affected dextransucrase productivity. Central composite design was consequently showed 6.70-fold improvement in dextransucrase productivity in compared to the basal medium. Also, the results showed a 96% correlation between sucrose concentration and the amount of dextran yield. FTIR and 1HNMR spectrum confirmed that the formed polysaccharide was dextran comparing to a standard dextran. Enterococcus faecalis Esawy KR758759 dextran showed a fibrinolytic activity matching the standard Hemoclar preparation (40%) while the anticoagulation activity was negative. Also, it recorded a promising prebiotic against Lactobacillus casie (1.82). All previous results recommended the Enterococcus faecalis dextran to be used in food and pharmaceutical fields and paid attention to the honey as a source of potential bacterial dextransucrase. [ABSTRACT FROM AUTHOR]

Dextran is a bacterial exopolysaccharide (EPS) which has multifarious values in the area of medicine, food and fine chemical industries. It is a linear polymer of glucose joined mainly by a (1 → 6) links and fewer a (1 → 2), a (1 → 3) and/or a (1 → 4) links. Fermentation processes for EPS production are utterly expensive owing to purification costs, giving an advantage to the use of enzymes. Therefore, dextran polymer can be synthesized from sucrose by the action of dextransucrase enzyme which is an extracellular bacterial glucosyltransferase. In the current study, purified dextransucrase from Leuconostoc lactis KU665298 has been immobilized by using various entrapment methods and calcium-alginate was found to be the most suitable matrix for this enzyme immobilization with an immobilization efficiency of 90.7%. Different conditions were standardized for the entrapment of purified dextransucrase from L. lactis in calcium alginate matrix and enzyme was also characterized for various reaction parameters for its utility in dextran production in a laboratory fermenter. The dextran production by calcium-alginate immobilized dextransucrase was found to be 2.02 g/L on dry weight basis after 24 h of incubation. [ABSTRACT FROM AUTHOR]

The potent producer A. tropicalis was isolated and selected on the basis of high dextransucrase activity. Different physicochemical parameters for A. tropicalis dextransucrase production have been optimized. A. tropicalis showed maximum dextransucrase activity (4.58 U/mL) when incubated for 8 h at 25 °C in medium having initial pH 7. The 26 technological combinations were also designed to study the effect of physical and chemical parameters in combination which proved to be very satisfactory on economical point of view. The selected combination gave 21.2 folds increase in dextransucrase activity over the basal medium (0.23 U/mL) and more activity than the medium formed after studying the effect of individual physicochemical parameters. Optimum reaction conditions for maximum dextransucrase activity were found to be 25 mM sodium acetate buffer with pH 5.5, reaction temperature 37 °C and sucrose concentration 2% (w/v). Optimization of reaction conditions resulted in maximum 12.2 U/mL dextransucrase activity. This activity was higher than the activity reported previously for other strains. Crude dextransucrase A. tropicalis showed Km=29.86 mM and Vmax=7.0 U/mL. This is the first report on dextransucrase production by A. tropicalis. [ABSTRACT FROM AUTHOR]

Antiviral efficiency of oxidized dextrans (OD) with different molecular weights and oxidation degree (OD40min, OD70min, OD40max, and OD70 max) was studied in vitro and in vivo. Dextrans OD40max and OD70max prevented the development of the cytopathic effect of influenza A(H1N1)pdm09 virus in more than 50% MDCK cells vs. control (no OD). Four intranasal doses of OD40min, OD40max, and OD70min and one intranasal dose of OD70max before infection of BALB/c mice with A(H1N1)pdm09 influenza virus significantly reduced mortality and prolonged life span in comparison with controls receiving saline. These and our previous data attest to clear-cut preventive effect of OD in influenza infection. [ABSTRACT FROM AUTHOR]

Dextran produced by dextransucrase hold strong potential for industrial applications. The exact determinants of the linkage specificity of glucansucrase enzymes have remained largely unknown. Previous studies have investigated the relationships between structure and linkage specificity of the dextransucrase DSR from Leuconostoc mesenteroides by the site-directed mutagenesis of the catalytic pocket. The glycosidic linkage of dextran produced by mutant enzymes changed slightly by 3% to 20%. The mutagenesis dextransucrases were constructed by inserting an amino acid into a catalytic pocket to investigate the product specificities of dextransucrase thoroughly. The sequence and structural analysis of glycoside-hydrolase family 70 enzymes led to two sequences (Motif II and Motif IV) being targeted, which were inserted by saturation mutagenesis and simultaneously recombined between A552 and V553, D662, and S663. Variants with catalytic activity were screened of the library, which synthesizes high molecular weight α-glucans with different proportions of α(1–4) linkages, which ranges from 0% to 52%. Mutant sequence analysis, biochemical characterization, and molecular modeling studies revealed the mechanism of product specificities. The mutant dextransucrase, which synthesizes hyperbranched dextran, were obtained by the novel mutagenesis method. The different properties of dextran provide the foundation for subsequent studies and application. [ABSTRACT FROM AUTHOR]

Exploration of biodiversity lead towards the discovery of novel exopolysaccharide (EPS) producing microbes that have multiple applications. The safety compatibility status of lactic acid bacteria (LAB) makes it an attractive candidate for the production of EPS in industries. Therefore, new bacterial isolates are continuously being identified from different habitats. Current research was conducted to explore indigenous biodiversity for the production of dextransucrase, which is involved in the synthesis of dextran. Dextran is an EPS which is used in different industries. In this study, thirty-nine LAB were isolated from different food samples. The isolates were identified as genus Leuconostoc , Weissella and Streptococcus based on genotypic and phenotypic characteristics. Screening revealed that only eight isolates can produce dextransucrase in high titres. Fermentation conditions of dextran producing LAB was optimized. The results indicated that Weissella confusa exhibited maximum specific activity (1.50 DSU mg −1 ) in 8 h at 25 °C with pH 7.5. Dextran produced from Weissella proved to be a useful alternative to commercially used dextran produced by Leuconostoc mesenteroides in industries for various applications. [ABSTRACT FROM AUTHOR]

Dextransucrase is the enzyme that catalyzes the synthesis of dextran from sucrose. Though dextran is an unwanted deterioration product in the sugar industry, it is being widely used in medicine, cosmetics, and several food areas. Currently, the natural enzyme activity of dextransucrase is low. Thus, it is of great interest to understand how to improve the dextransucrase activity. In the study, Leuconostoc mesenteroides (L.M.CICC-20724) were cultured in a glucose-based solid medium (glucose was the sole carbon source) and then transferred to a sucrose-based solid medium (sucrose was the sole carbon source) for rejuvenation. It was observed that the dextransucrase production was inhibited when L.M.CICC- 20724 using the glucose-based solid medium. After 3 months of acclimation, the activity of dextransucrase produced by the acclimated L. mesenteroides ( Glu- L.M.) achieved a stable level at approximately 4.20 U/mL. The dextransucrase activity (approximately 1-2 U/mL) increased more than two times with L.M.CICC-20724 in comparision with original one. Dextran products generated from Glu- L.M. and L.M.CICC- 20724 were studied using Fourier transform infrared spectroscopy and results showed that both dextrans had a consistent structural composition. The kinetics of sucrose consumption was studied. Under the condition of 0.5 U/mL dextransucrase activity, the consumption of relative low initial sucrose concentrations (0.1, 0.2 and 0.4 M) more fitted to the first-order reaction kinetics, while the consumption of relative high initial sucrose concentrations (0.6 and 0.8 M) was fitted better to the second-order reaction kinetics. [ABSTRACT FROM AUTHOR]