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Based on the principle of cascade reaction, a fusion enzyme of dextransucrase and dextranase was designed without linker to catalyze the production of oligo-dextran with homogeneous molecular weight from sucrose in one catalytic step. Due to the different effects of temperature on the two components of the fusion enzyme, temperature served as the "toggle switch" for the catalytic efficiency of the two-level fusion enzyme, regulating the catalytic products of the fusion enzyme. Under optimal conditions, the fusion enzyme efficiently utilized 100 % of the sucrose, and the yield of oligo-dextran with a homogeneous molecular weight reached 70 %. The product has been purified and characterized. The probiotic potential of the product was evaluated by analyzing the growth of 10 probiotic species. Its cytotoxic and anti-inflammatory activities were also determined. The results showed that the long-chain oligo-dextran in this study had significantly better probiotic potential and anti-inflammatory activity compared to other oligosaccharides. This study provides a strategy for the application of oligo-dextran in the food and pharmaceutical industries., Competing Interests: Declaration of competing interest The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Dextranase is an enzyme that specifically hydrolyzes the α-1, 6 glucoside bond. In order to improve the activity of dextranase from Arthrobacter oxidans KQ11, site-directed mutagenesis was used to modify the amino acids involved in the "tunnel-like binding site". A saturating mutation at position 507 was carried out on this basis. The mutant enzymes A356G, S357W, W507Y, and W507F with improved enzyme activities and catalytic efficiency were successfully obtained. Compared with wild type (WT), W507Y showed the specific activity increasing by 3.00 times, the k cat value increasing by 3.62 times, the K m value decreasing by 54%, and the catalytic efficiency ( k cat / K m ) increasing by 8.98 times. The three-dimensional structure analysis showed that the increase of the number of hydrogen bonds and the distance between "tunnel-like binding sites" were important factors affecting enzyme activity. Compared with WT, W507Y had a shortened distance from the residues on the other side of the "tunnel-like binding site", which made it easier to generate hydrogen binding forces. Accordingly, the substrate hydrolysis and product efflux were accelerated, which dramatically increased the enzyme activity and catalytic efficiency.

A highly sensitive method has been developed for accurately measuring dextranase activity using 3-methyl-2-benzothiazolinone hydrazine. This method is based on the dextran refinement and fast-dissolving approach established in this study, as well as the assay method for enzymatic hydrolysates. The measurement parameters for the reducing sugar ends were optimized by examining the slope, intercept, R 2 , and time stability of the standard curve of glucose solutions containing dextran. Kinetic determination was utilized to optimize enzymatic parameters and validate the method, which was subsequently utilized for the analysis of toothpaste and mouthwash. The findings suggest that the enzymatic hydrolysis follows a zero-order reaction, laying a solid foundation for the end-point assay of dextranase activity. The results demonstrated a linear correlation within the measurement range (0.7-6.5 mU/mL), exhibiting good repeatability, high sensitivity and accuracy. This method outperformed the 3,5-dinitrosalicylic acid method and circumvented potential interference from other components in toothpaste and mouthwash., Competing Interests: Declaration of competing interest The authors declare that they have no known competing ffnancial interests or personal relationships that could have appeared to inffuence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Dextran, an α-glucan mainly composed of (α1 → 6) linkages, has been widely applied in the food, cosmetic, and medicine industries. Dextranase can hydrolyze dextran to synthesize oligodextrans, which show prominent properties and promising applications in the food industry. Dextranases are widely distributed in bacteria, yeasts, and fungus, and classified into glycoside hydrolase (GH) 13, 15, 31, 49, and 66 families according to their sequence similarity, structural features, and reaction types. Dextranase, as a dextran-hydrolyzing enzyme, displays great application potential in the sugar-making, oral health care, medicine, and biotechnology industries. Here we mainly focused on presenting the enzymatic properties, structural features, and versatile (potential) applications of dextranase. To date, seven crystal structures of dextranases from GH 13, 15, 31, 49, and 66 families have been successfully solved. However, their molecular mechanisms for hydrolyzing dextran, especially on the size determinants of the hydrolysates, remain largely unknown. Additionally, the classification, microbial distribution, and immobilization technology of dextranase were also discussed in detail. This review discussed dextranase from different aspects with the ambition to present how they constitute the groundwork for promising future developments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

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 B 2 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 B 2 ) 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., (© 2024. The Author(s).)

Dextranases are hydrolases that exclusively catalyze the disruption of α-1,6 glycosidic bonds. A series of variant enzymes were obtained by comparing the sequences of dextranases from different sources and introducing sequence substitutions. A correlation was found between the number of amino acids in the 397-401 region and the hydrolytic process. When there were no more than 5 amino acids in the 397-401 region, the enzyme first hydrolyzed the dextran T70 to a low molecular weight dextran with a molecular weight of about 5000, then IMOs 1 appeared in the system if the degradation continued, showing a clear sequential relationship. And when there are more than 5 amino acids in the 397-401 region, IMOs were produced at the beginning of hydrolysis and continue to increase throughout the hydrolytic process. At the same time, we investigated the enzymatic properties of the variants and found that the hydrolytic rate of A-Ca was 11 times higher than that of the original enzyme. The proportion of IMOs produced by A-Ca was 80.68%, which was nearly10% higher than the original enzyme, providing a new enzyme for the industrial preparation of IMOs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In this study, an actinomycete was isolated from sea mud. The strain K1 was identified as Saccharomonospora sp. by 16S rDNA. The optimal enzyme production temperature, initial pH, time, and concentration of the inducer of this actinomycete strain K1 were 37 °C, pH 8.5, 72 h, and 2% dextran T20 of medium, respectively. Dextranase from strain K1 exhibited maximum activity at 8.5 pH and 50 °C. The molecular weight of the enzyme was <10 kDa. The metal ions Sr 2+ and K+ enhanced its activity, whereas Fe 3+ and Co 2+ had an opposite effect. In addition, high-performance liquid chromatography showed that dextran was mainly hydrolyzed to isomaltoheptose and isomaltopentaose. Also, it could effectively remove biofilms of Streptococcus mutans . Furthermore, it could be used to prepare porous sweet potato starch. This is the first time a dextranase-producing actinomycete strain was screened from marine samples.

Dextranase is a type of hydrolase that is responsible for catalyzing the breakdown of high-molecular-weight dextran into low-molecular-weight polysaccharides. This process is called dextranolysis. A select group of bacteria and fungi, including yeasts and likely certain complex eukaryotes, produce dextranase enzymes as extracellular enzymes that are released into the environment. These enzymes join dextran's α-1,6 glycosidic bonds to make glucose, exodextranases, or isomalto-oligosaccharides (endodextranases). Dextranase is an enzyme that has a wide variety of applications, some of which include the sugar business, the production of human plasma replacements, the treatment of dental plaque and its protection, and the creation of human plasma replacements. Because of this, the quantity of studies carried out on worldwide has steadily increased over the course of the past couple of decades. The major focus of this study is on the most current advancements in the production, administration, and properties of microbial dextranases. This will be done throughout the entirety of the review., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

The high-degree polymerization of isomaltooligosaccharide (IMO) not only effectively promotes the growth and reproduction of Bifidobacterium in the human body but also renders it resistant to rapid degradation by gastric acid and can stimulate insulin secretion. In this study, we chose the engineered strain expressed dextranase (PsDex1711) as the research model and used the AutoDock vina molecular docking technique to dock IMO4, IMO5, and IMO6 with it to obtain mutation sites, and then studied the potential effect of key amino acids in this enzyme on its hydrolysate composition and enzymatic properties by site-directed mutagenesis method. It was found that the yield of IMO4 increased significantly to 62.32% by the mutant enzyme H373A. Saturation mutation depicted that the yield of IMO4 increased to 69.81% by the mutant enzyme H373R, and its neighboring site S374R IMO4 yield was augmented to 64.31%. Analysis of the enzymatic properties of the mutant enzyme revealed that the optimum temperature of H373R decreased from 30 °C to 20 °C, and more than 70% of the enzyme activity was maintained under alkaline conditions. The double-site saturation mutation results showed that the mutant enzyme H373R/N445Y IMO4 yield increased to 68.57%. The results suggest that the 373 sites with basic non-polar amino acids, such as arginine and histidine, affect the catalytic properties of the enzyme. The findings provide an important theoretical basis for the future marketable production of IMO4 and analysis of the structure of dextranase.

Dextran, a renewable hydrophilic polysaccharide, is nontoxic, highly stable but intrinsically biodegradable. The α-1, 6 glycosidic bonds in dextran are attacked by dextranase (E.C. 3.2.1.11) which is an inducible enzyme. Dextranase finds many applications such as, in sugar industry, in the production of human plasma substitutes, and for the treatment and prevention of dental plaque. Currently, dextranases are obtained from terrestrial fungi which have longer duration for production but not very tolerant to environmental conditions and have safety concerns. Marine bacteria have been proposed as an alternative source of these enzymes and can provide prospects to overcome these issues. Indeed, marine bacterial dextranases are reportedly more effective and suitable for dental caries prevention and treatment. Here, we focused on properties of dextran, properties of dextran-hydrolyzing enzymes, particularly from marine sources and the biochemical features of these enzymes. Lastly the potential use of these marine bacterial dextranase to remove dental plaque has been discussed. The review covers dextranase-producing bacteria isolated from shrimp, fish, algae, sea slit, and sea water, as well as from macro- and micro fungi and other microorganisms. It is common knowledge that dextranase is used in the sugar industry; produced as a result of hydrolysis by dextranase and have prebiotic properties which influence the consistency and texture of food products. In medicine, dextranases are used to make blood substitutes. In addition, dextranase is used to produce low molecular weight dextran and cytotoxic dextran. Furthermore, dextranase is used to enhance antibiotic activity in endocarditis. It has been established that dextranase from marine bacteria is the most preferable for removing plaque, as it has a high enzymatic activity. This study lays the groundwork for the future design and development of different oral care products, based on enzymes derived from marine bacteria.

The enzyme dextranase is widely used in the sugar and food industries, as well as in the medical field. Most land-derived dextranases are produced by fungi and have the disadvantages of long production cycles, low tolerance to environmental conditions, and low safety. The use of marine bacteria to produce dextranases may overcome these problems. In this study, a dextranase-producing bacterium was isolated from the Rizhao seacoast of Shandong, China. The bacterium, denoted as PX02, was identified as Cellulosimicrobium sp. and its growing conditions and the production and properties of its dextranase were investigated. The dextranase had a molecular weight of approximately 40 kDa, maximum activity at 40°C and pH 7.5, with a stability range of up to 45°C and pH 7.0-9.0. High-performance liquid chromatography showed that the dextranase hydrolyzed dextranT20 to isomaltotriose, maltopentaose, and isomaltooligosaccharides. Hydrolysis by dextranase produced excellent antioxidant effects, suggesting its potential use in the health food industry. Investigation of the action of the dextranase on Streptococcus mutans biofilm and scanning electron microscopy showed that it to be effective both for removing and inhibiting the formation of biofilms, suggesting its potential application in the dental industry., (© 2021 Wiley-VCH GmbH.)

An enzymatic membrane reactor (EMR) with immobilized dextranase provides an excellent opportunity for tailoring the molecular weight (Mw) of oligodextran to significantly improve product quality. However, a highly efficient EMR for oligodextran production is still lacking and the effect of enzyme immobilization strategy on dextranase hydrolysis behavior has not been studied yet. In this work, a functional layer of polydopamine (PDA) or nanoparticles made of tannic acid (TA) and hydrolysable 3-amino-propyltriethoxysilane (APTES) was first coated on commercial membranes. Then cross-linked dextranase or non-cross-linked dextranase was loaded onto the modified membranes using incubation mode or fouling-induced mode. The fouling-induced mode was a promising enzyme immobilization strategy on the membrane surface due to its higher enzyme loading and activity. Moreover, unlike the non-cross-linked dextranase that exhibited a normal endo-hydrolysis pattern, we surprisingly found that the cross-linked dextranase loaded on the PDA modified surface exerted an exo-hydrolysis pattern, possibly due to mass transfer limitations. Such alteration of hydrolysis pattern has rarely been reported before. Based on the hydrolysis behavior of the immobilized dextranase in different EMRs, we propose potential applications for the oligodextran products. This study presents a unique perspective on the relation between the enzyme immobilization process and the immobilized enzyme hydrolysis behavior, and thus opens up a variety of possibilities for the design of a high-performance EMR., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

We prepared a high-molecular-weight modified dextrin (MWS-1000) from a partial hydrolysate of waxy corn starch with a weight average molecular weight of 1 × 106 (WS-1000) using Paenibacillus alginolyticus PP710 α-glucosyltransferase. The gel permeation chromatography showed that the weight average molecular weight of MWS-1000 was almost the same as that of WS-1000. The side chain lengths of WS-1000 and MWS-1000 after isomaltodextranase digestion were also shown to be similar to each other by high-performance anion exchange chromatography with pulsed amperometric detection. Since MWS-1000 confirmed the presence of α-1,6 bonds by enzyme digestibility, methylation, and 1H-NMR analyses, it was presumed that the structure of MWS-1000 was based on the introduction of α-1,6 glucosyl residues at the nonreducing ends of the partial hydrolysate of waxy corn starch. Furthermore, the MWS-1000 solution was not retrograded even during refrigerated storage or after repeated freeze-thaw cycles., (© The Author(s) 2021. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

The mature basal stipe of mushroom Coprinopsis cinerea loses wall extensibility. We found that an endo-β-1,3-glucanase ENG from C. cinerea could restore mature basal stipe wall extensibility via pretreatment such that the ENG-pretreated basal stipe walls could be induced to extend by chitinase ChiIII. ENG pretreatment released glucose, laminaribiose, and 3-O-D-gentiobiose-D-glucose from the basal stipe walls, consistent with ENG-digested products of β-1,6-branched β-1,3-glucan. Different effects of endo-β-1,3-glucanase ENG and exo-β-1,3-glucanase EXG pretreatment on the structure, amount and ratio (β-1,3-glucoside bonds to β-1,6-glucoside bonds) of products from the basal stipe and the apical stipe cell walls, respectively, and on the cell wall extensibility and the cell wall ultra-architecture of the basal stipes were analyzed. All results demonstrate that the more accumulation and cross-linkage of β-1,6-branched β-1,3-glucan with wall maturation lead to loss of wall extensibility of the basal stipe regions compared to the apical stipe cell walls., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Dextranase catalyzes the degradation of the substrate dextran, which is a component of plaque biofilm. This enzyme is involved in antiplaque accumulation, which can prevent dental caries. The activity of crude dextranase from Penicillium roquefortii TISTR 3511 was assessed, and the maximum value (7.61 unit/g) was obtained at 37 °C and pH 6. The Plackett-Burman design was used to obtain significant factors for enhancing fungal dextranase production, and three influencing factors were found: Dextran, yeast extract concentration and inoculum age. Subsequently, the significant factors were optimized with the Box-Behnken design, and the most suitable condition for dextranase activity at 30.24 unit/g was achieved with 80 g/L dextran, 30 g/L yeast extract and five day- old inoculum. The use of 0.85% alginate beads for encapsulation exhibited maximum dextranase activity at 25.18 unit/g beads, and this activity was stable in toothpaste for three months of testing. This study explored the potential production of fungal dextranase under optimal conditions and its encapsulation using alginate for the possibility of applying encapsulated dextranase as an additive in toothpaste products for preventing dental caries.

Inspired by the compartmentalized structure of cells, self-regulating responsive hollow microcapsules are highly desirable for the modulation of enzymatic reactions. Here, we report a strategy to fabricate gold nanorod embedded proteinosomes by covalently grafting gold nanorods onto the surface of proteinosomes. The excellent photothermal conversion efficiency of the embedded gold nanorod and the thermal phase transition of the grafted PNIPAAm allow the constructed hybrid proteinosomes to show reversible contraction behaviors triggered by near-infrared light with the molecular weight cutoff of the membrane decreased to ca. 50 kDa, and importantly, the contraction frequency of the constructed proteinosomes could be as fast as 1 min and last for at least 15 cycles. Subsequently, the effective encapsulation of three cascade enzymes into the proteinosomes realizes the construction of a near-infrared responsive microreactor that allows control of the cascade reaction by near-infrared illumination, thereby enabling reversible on and off of the enzymatic reaction. Such microcapsule-based reactors demonstrate the potential to alter the membrane molecular weight cutoff, and it is believed that the development of such responsive microcapsules will have great potential for studying cellular responses and provide a platform for future applications in biosensing and drug delivery.

Co-immobilization is a groundbreaking technique for enzymatic catalysis, sometimes strategic, as for dextransucrase and dextranase. In this approach, dextranase hydrolytic action removes the dextran layer that covers dextransucrase reactive groups, improving the immobilization. Another advantage is the synergic effect of the two enzymes towards prebiotic oligosaccharides production. Thus, both enzymes were co-immobilized onto the heterobifunctional support Amino-Epoxy-Glyoxyl-Agarose (AMEG) and the ion exchanger support monoaminoethyl-N-ethyl-agarose (Manae) at pH 5.2 and 10, followed or not by glutaraldehyde treatment. This work is the first attempt to immobilize dextransucrase under alkaline conditions. The immobilized dextransucrase on AMEG support at pH 10 (12.78 ± 0.70 U/g) presents a similar activity of the biocatalyst produced at pH 5.2 (14.95 ± 0.82 U/g). The activity of dextranase immobilized onto Manae was 5-fold higher than the obtained onto AMEG support. However, the operational stability test showed that the biocatalyst produced on AMEG at pH 5.2 kept >60% of both enzyme activities for five batches. The glutaraldehyde treatment was not worthwhile to improve the operational stability of this biocatalyst., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Glycoside hydrolase family (GH) 31 contains a large variety of enzymes, but the major members are enzymes that act on relatively small oligosaccharides such as α-glucosidase. Here, we determined the crystal structure of Flavobacterium johnsoniae dextranase (FjDex31A), an enzyme from F. johnsoniae that hydrolyzes a polysaccharide, dextran. FjDex31A is composed of four domains: an N-terminal domain, a catalytic domain, a proximal C-terminal domain, and a distal C-terminal domain, as observed in typical GH31 enzymes. However, the architecture of active site residues in FjDex31A, other than subsite -1, is markedly different from that of other GH31 enzymes. The FjDex31A structure in complex with isomaltotriose shows that Gly273 and Tyr524, both of which interact with an α-glucose residue at subsite -2, as well as Trp376 and Leu308-cisGln309, are especially unique to FjDex31A. Site-directed mutagenesis of Gly273 and Tyr524 resulted in a decrease in the hydrolysis of polysaccharides dextran and pullulan, as well as that of the disaccharide isomaltose. These results suggest that, regardless of the length of sugar chains of the substrates, binding of FjDex31A to the substrates at subsite -2 is likely to be important for its activity. DATABASE: Structural data are available in the Protein Data Bank under the accession numbers 6JR6, 6JR7, and 6JR8., (© 2019 Federation of European Biochemical Societies.)

Dextranase, a hydrolase that specifically hydrolyzes α-1,6-glucosidic bonds, has been used in the pharmaceutical, food, and biotechnology industries. In this study, the strain of Catenovulum agarivorans MNH15 was screened from marine samples. When the temperature, initial pH, NaCl concentration, and inducer concentration were 30 °C, 8.0, 5 g/L, and 8 g/L, respectively, it yielded more dextranase. The molecular weight of the dextranase was approximately 110 kDa. The maximum enzyme activity was achieved at 40 °C and a pH of 8.0. The enzyme was stable at 30 °C and a pH of 5-9. The metal ion Sr 2+ enhanced its activity, whereas NH 4+ , Co 2+ , Cu 2+ , and Li + had the opposite effect. The dextranase effectively inhibited the formation of biofilm by Streptococcus mutans . Moreover, sodium fluoride, xylitol, and sodium benzoate, all used in dental care products, had no significant effect on dextranase activity. In addition, high-performance liquid chromatography (HPLC) showed that dextran was mainly hydrolyzed to glucose, maltose, and maltoheptaose. The results indicated that dextranase has high application potential in dental products such as toothpaste and mouthwash., Competing Interests: The authors confirm that there is no conflict of interests regarding this paper.

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.

Paenibacillus sp. 598K produces cycloisomaltooligosaccharides (CIs) in culture from dextran and starch. CIs are cyclic oligosaccharides consisting of seven or more α-(1 → 6)-linked-D-glucose residues. The extracellular enzyme CI glucanotransferase (PsCITase), which is the member of glycoside hydrolase family 66, catalyzes the final stage of CI production and produces mainly cycloisomaltoheptaose. We have discovered a novel intracellular CI-degrading dextranase (PsDEX598) from Paenibacillus sp. 598K. The 69.7-kDa recombinant PsDEX598 does not digest isomaltotetraose or shorter isomaltooligosaccharides, but digests longer ones of at least up to isomaltoheptaose. It also digests oligoCIs of cycloisomaltoheptaose, cycloisomaltooctaose, and cycloisomaltononaose better than it does with megaloCIs of cycloisomaltodecaose, cycloisomaltoundecaose, and cycloisomaltododecaose, as well as an α-(1 → 6)-D-glucan of dextran 40. PsDEX598 is produced intracellularly when culture medium is supplemented with cycloisomaltoheptaose or dextran, but not with isomaltooligosaccharides (a mixture of isomaltose, isomaltotriose, and panose), starch, or glucose. The whole genomic DNA sequence of the strain 598K implies that it harbors two genes for enzymes belonging to glycoside hydrolase family 66 (PsCITase and PsDEX598), and PsDEX598 is the only dextranase in the strain. PsDEX598 does not have any carbohydrate-binding modules (CBMs) and has a low similarity (< 30%) with other family 66 dextranases, and the catalytic amino acids of this enzyme are predicted to be Asp191, Asp303, and Glu368. The strain Paenibacillus sp. 598K appears to take up CI-7, so these findings indicate that this bacterium can degrade CIs using a dextranase within the cells and so utilize them as a carbon source for growth.

The crystal structure of Dextranase from the marine bacterium Arthrobacter oxidans KQ11 (Aodex) was determined at a resolution of 1.4 Å. The crystal structure of the conserved Aodex fragment (Ala52-Thr638) consisted of an N-terminal domain N and a C-terminal domain C. The N-terminal domain N was identified as a β-sandwich, connected to a right-handed parallel β-helix at the C-terminus. Sequence comparisons, cavity regions, and key residues of the catalytic domain analysis all suggested that the Aodex was an inverting enzyme, and the catalytic acid and base were Asp439 and Asp420, respectively. Asp440 was not a general base in the Aodex catalytic domain, and Asp396 in Dex49A may not be a general base in the catalytic domain. The thermostability of the S357F mutant using semirational design based on B-factors was clearly better than that of wild-type Aodex. This process may promote the aromatic-aromatic interactions that increase the thermostability of mutant Phe357.

The dexA gene encoding Penicillium funiculosum dextranase (GenBank accession MH581385) belonging to family 49 of glycoside hydrolases (GH49) was cloned and heterologously expressed in two recipient strains, P. canescens RN3-11-7 and P. verruculosum B1-537. Crude enzyme preparations with the recombinant dextranase content of 8-36% of the total secreted protein were obtained on the basis of new Penicillium strains. Both recombinant forms of the dextranase were isolated in a homogeneous state using chromatographic techniques. The purified enzymes displayed very similar properties, that is, pI 4.55, activity optima at pH 4.5-5.0 and 55-60 °C and a melting temperature of 60.7-60.9 °C. They were characterized by similar specific activities (1020-1340 U/mg) against dextrans with a mean molecular mass of 20, 70 and 500 kDa, as well as similar kinetic parameters in the hydrolysis of 70 kDa dextran (K m  = 1.10-1.11 g/L, k cat  = 640-680 s -1 ). However, the recombinant dextranases expressed in P. canescens and P. verruculosum had different molecular masses according to the data of SDS-PAGE (∼63 and ∼60 kDa, respectively); this was the result of different N-glycosylation patterns as MALDI-TOF mass spectrometry analysis showed. The main products of dextran hydrolysis at its initial phase were isomaltooligosaccharides, while after the prolonged time (24 h) the reaction system contained isomaltose and glucose as the major products and minor amounts of other oligosaccharides., (Copyright © 2018 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

Objective: We aimed to identify new high-yield dextranase strains and study the catalytic potential of dextranase from the strain in industrial applications., Results: Dextranase-producing strains were screened from soil samples, and a potential strain was identified as Chaetomium globosum according to its phenotype, biochemical characteristics, and rDNA analysis. Crude dextranase was purified to reach 10.97-fold specific activity and 18.7% recovery. The molecular weight of the enzyme was 53 kDa with an optimum temperature and pH of 60 °C and 5.5, respectively. Enzyme activity was stable at pH 4.0-7.0 and displayed sufficient thermal stability at temperatures < 50 °C. Mn 2+ (10 mM) enhanced dextranase activity by 134.44%. The enzyme was identified as an endodextranase. It displayed very high hydrolytic affinity toward high-molecular weight dextran T2000, reaching 97.9% hydrolysis within 15 min at 2 U/mL., Conclusion: Collectively, these results suggest that Chaetomium globosum shows higher production and specificity of dextranase than that from other reported strains. These findings may offer new insights into the potential of dextranase in the sugar, medical, and food industries.

Application of biocatalytic membrane is promising in food, pharmaceutical, and water treatment industries, whereas enzyme immobilization is the key step of biocatalytic membrane preparation. Thus, how to minimize the negative effect of immobilization on enzyme performance is required to answer. In this work, we proposed a platform for biocatalytic membrane preparation and immobilization mechanism investigation based on polydopamine (PDA) coating, which was demonstrated by immobilizing five commonly used enzymes (laccase, glucose oxidase, lipase, pepsin, and dextranase) on three commercially available membranes via three immobilization mechanisms (electrostatic attraction, covalent bonding, and hydrophobic adsorption), respectively. By examining the enzyme loading, activity, and kinetics under different immobilization mechanisms, we found that except for dextranase, enzyme immobilization via electrostatic attraction retained the most activity, whereas covalent bonding and hydrophobic adsorption were detrimental to enzyme conformation. Enzyme immobilization via covalent bonding ensured a high enzyme loading, and hydrophobic adsorption was only suitable for lipase and dextranase immobilization. Moreover, the properties of functional groups around the enzyme active center should be considered for the selection of suitable immobilization strategy (i.e., avoid covering the active center by membrane carrier). This work not only established a versatile platform for biocatalytic membrane preparation but also provided a novel methodology to evaluate the effect of immobilization mechanisms on enzyme performance.

This paper examines a new dextransucrase (DS) purification process of the extracellular enzyme (EC 2.4.1.5) produced by Leuconostoc mesenteroides IBUN 91.2.98. The enzyme was purified using a methodology which combines the immobilization of the enzyme in the produced biopolymer dextran, followed by a concentration step by ultrafiltration, using a membrane with a pore size of 300kDa and subsequent hydrolysis of dextran by action of a dextranase and finally enzyme purification by anion exchange chromatography. The obtained enzyme has a purification factor of 118 and a yield of 26% from the initial extract. The purified dextransucrase has a specific activity of 335.1U/mg, electrophoretic analysis shows absence of subunits, and a molecular weight of 170.1kDa, a Vmax of 28.1U/ml and a Km of 48mM. Optimal conditions of pH, temperature and substrate concentration were 5, 30°C and 584mM sucrose respectively in a ratio of 0.4U/mole of substrate. The produced dextran has a molecular size of 800-1000kDa. Both the hydrolytic and transference activity are inhibited by Fe +3 (96.5%) and Al +3 (99.1%), whereas Mg +2 and K produce activation of 36.7% and 27.2%, respectively., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Dextransucrase from Leuconostoc mesenteroides NRRL B-512F was subjected to immobilization and co-immobilization with dextranase from Chaetomium erraticum. Immobilization has enhanced the operational and storage stability of dextransucrase. Two hundred milligrammes (2.4 IU/mg) of alginate beads (immobilized and co-immobilized) were found to be optimum for the production of gluco-oligosaccharides (GOS) in orange juice with a high degree of polymerization. The pulp of the orange juice did not interfere in the reaction. In the batch process, co-immobilized dextransucrase (41 g/L) produced a significantly higher amount of GOS than immobilized dextransucrase (37 g/L). Alginate entrapment enhanced the thermal stability of dextransucrase for up to 3 days in orange juice at 30 °C. The production of GOS in semi-continuous process was 39 g/L in co-immobilized dextransucrase and 33 g/L in immobilized dextransucrase. Thus, immobilization technology offers a great scope in terms of reusability and efficient production of a value added functional health drink.

Dextranase is a unique biocatalyst that has high specificity and stereo-selectivity towards a complex biopolymer known as dextran. Dextranase has wide industrial application, but most of the time harsh environmental conditions adversely affect the functionality and stability of the enzyme. To overcome this issue, a covalent cross-linking immobilization method was adapted in the current study utilizing a nontoxic and biocompatible matrix known as chitosan. Chitosan hydrogel microspheres were synthesized using chitosan which exhibited noteworthy physical and mechanical strength. After treatment with glutaraldehyde, chitosan hydrogel microspheres were used for immobilization of dextranase. The kinetic characteristics of immobilized dextranase were compared with that of the soluble enzyme. A shift in optimum pH and temperature from 7.0 to 7.5 and 50 to 60 °C was observed after immobilization, respectively. Recycling efficiency, thermal stability, and activation energy distinctly improved after immobilization, whereas anchoring of substrate at the active site of the soluble dextranase exhibited an increase in K m with no change in V max after crosslinking. This technique involves the reduction in the size of carrier molecules (microspheres) that provide a larger surface area for improved immobilization efficiency. Therefore, it is concluded that increased stability and reusability of this immobilized biocatalyst makes it a promising aspirant for the utilization at commercial level.

Dental plaque is a biofilm of water-soluble and water-insoluble polysaccharides, produced primarily by Streptococcus mutans. Dextranase can inhibit biofilm formation. Here, a dextranase gene from the marine microorganism Arthrobacter oxydans KQ11-1 is described, and cloned and expressed using E. coli DH5α competent cells. The recombinant enzyme was then purified and its properties were characterized. The optimal temperature and pH were determined to be 60°C and 6.5, respectively. High-performance liquid chromatography data show that the final hydrolysis products were glucose, maltose, maltotriose, and maltotetraose. Thus, dextranase can inhibit the adhesive ability of S. mutans. The minimum biofilm inhibition and reduction concentrations (MBIC 50 and MBRC 50 ) of dextranase were 2 U ml -1 and 5 U ml -1 , respectively. Scanning electron microscopy and confocal laser scanning microscope (CLSM) observations confirmed that dextranase inhibited biofilm formation and removed previously formed biofilms.

A novel endodextranase isolated from Paenibacillus sp. was found to produce isomaltotetraose and small amounts of cycloisomaltooligosaccharides with a degree of polymerization of 7-14 from dextran. To determine the active site, the enzyme was modified with 1-ethyl-3-[3- (dimethylamino)-propyl]-carbodiimide (EDC) and α-epoxyalkyl α-glucosides (EAGs), an affinity labeling reagent. The inactivation followed pseudo first-order kinetics. Kinetic analysis and chemical modification using EDC and EAGs indicated that carboxyl groups are essential for the enzymatic activity. Three Asp and one Glu residues were identified as candidate catalytic amino acids, since these residues are completely conserved across the GH family of 66 enzymes. Replacement of Asp189, Asp340, or Glu412 completely abolished the enzyme activity, indicating that these residues are essential for catalytic activity.

Objective: We aimed to express and characterize biochemical properties of Chi92, a chitinase from Aeromonas veronii B565, and study its potential application as aquafeed supplement., Methods: The chitinase gene chi92 was cloned from A. veronii strain B565 and expressed in Pichia pastoris GS115. The recombinant chitinase (Chi92) was purified and characterized. Chi92 was supplemented in diets containing P. pastoris powder and fed to zebrafish for 14 days. By comparing with the control group, effect of Chi92 supplementation on growth, feed utilization, microvilli morphology, and disease resistance was investigated., Results: The complete gene sequence encoded a polypeptide with 864 amino acids. Chi92 exhibited optimal activity at pH 6.0 and 40℃, and was resistant to proteases and not substantially inhibited by metal ions. Chi92 had high chitinase activity (69.4 U/mL). The specific activity was 809.2 U/mg and 235.6 U/mg on colloidal chitin and β-1,3-1,4-glucan, respectively. Thin-layer chromatography and electrospray ionization-coupled mass spectrometry revealed that N-diacetylglucosamine was the dominant product of Chi92 when colloidal chitin was used as substrate. Moreover, Chi92 showed advantages over other chitinases for degradation of yeast cell wall. Supplementation of Chi92 in diet containing yeast product significantly improved the intestine microvilli length and density of zebrafish after two weeks of feeding. Marginally improved growth performance, feed utilization, as well as disease resistance were also observed in the Chi92 supplement group., Conclusion: The pH stability, resistance against metal ions/chemical reagents/proteases, and high yeast cell wall degradation activity of Chi92 suggest its potential use as feed additive enzyme for warm water aquaculture.

Objective: We attempted to obtain a fungus producing thermotolerant dextranase by screening samples from soil., Methods: The fungus producing thermotolerant dextranase was isolated and screened by auxotrophic medium, combined with Pour Plate method and Flat Transparent Circle method. The strain was identified by its colony, cell morphology and cultural characteristics, as well as ITS rDNA sequence analysis. The dextranase produced by the strain was characterized., Results: We obtained the strain DG001 producing thermotolerant dextranase, which was identified as Paecilomyces lilacinus. The optimum catalytic conditions for the dextranase were 55℃, pH 5.0, and the optimum substrate concentration was 5% dextran T70. The dextranase was stable below 60℃ and between pH 4.0 and 7.0. Urea, Mn2+ and Mg2+ could increase enzyme activity, and the low concentration of Mn2+ and Urea could increase enzyme activity to 116.91% and 110.14% respectively, whereas Cu2+ had a strong inhibitory effect on the dextranase. The dextranase, identified as endo-dextranase, hydrolyzed dextran T2000 with main products as isomalt and isomaltotriose. The enzyme-substrate affinity increased with the increasing substrate molecular weight., Conclusion: Strain DG001 producing thermotolerant dextranase was obtained through successful screening, bearing a high activity in a wide temperature range and a good thermal stability. This enzyme shows a promising prospect of application in sugar industry and in the preparation of different molecular weight dextran.

The crystal structures of the wild type and catalytic mutant Asp-312→Gly in complex with isomaltohexaose of endo-1,6-dextranase from the thermophilic bacterium Thermoanaerobacter pseudethanolicus (TpDex), belonging to the glycoside hydrolase family 66, were determined. TpDex consists of three structural domains, a catalytic domain comprising an (β/α)8-barrel and two β-domains located at both N- and C-terminal ends. The isomaltohexaose-complex structure demonstrated that the isomaltohexaose molecule was bound across the catalytic site, showing that TpDex had six subsites (-4 to +2) in the catalytic cleft. Marked movement of the Trp-376 side-chain along with loop 6, which was the side wall component of the cleft at subsite +1, was observed to occupy subsite +1, indicating that it might expel the cleaved aglycone subsite after the hydrolysis reaction. Structural comparison with other mesophilic enzymes indicated that several structural features of TpDex, loop deletion, salt bridge and surface-exposed charged residue, may contribute to thermostability., (© The Authors 2015. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.)

Objective of the present investigation was to prepare and evaluate the potential of enteric coated dextran microspheres for colon targeting of 5-fluorouracil (5-FU). Dextran microspheres were prepared by emulsification-crosslinking method and the formulation variables studied included different molecular weights of dextran, drug:polymer ratio, volume of crosslinking agent, stirring speed and time. Enteric coating (Eudragit S-100) of dextran microspheres was performed by oil-in-oil solvent evaporation method using different coat:core ratios (4:1 or 8:1). Uncoated and coated dextran microspheres were characterized by particle size, surface morphology, entrapment efficiency, DSC, in vitro drug release in the presence of dextranase and 2% rat cecal contents. The release study of 5-FU from coated dextran microspheres was pH dependent. No release was observed at acidic pH; however, the drug was released quickly where Eudragit starts solublizing there was continuous release of drug from the microspheres. Organ distribution study was suggested that coated dextran microspheres retard the release of drug in gastric and intestinal pH environment and released of drug from microspheres in colon due to the degradation of dextran by colonic enzymes.

Degradation of high molecular weight dextran for obtaining low molecular weight dextran is based on the hydrolysis using chemical and enzymatic methods. Current research study focused on production, purification and characterization of dextranase from a newly isolated strain of Bacillus licheniformis KIBGE-IB25. Dextranase was purified up to 36 folds with specific activity of 1405 U/mg and molecular weight of 158 kDa. It was found that enzyme performs optimum cleavage of dextran (5000 Da, 0.5%) at 35 °C in 15 min at pH 4.5 with a Km and Vmax of 0.374 mg/ml and 182 μmol/min, respectively. Relative amino acid composition analysis of purified enzyme suggested the presence of higher number of hydrophobic, acidic and glycosylation promoting amino acids. The N-terminal sequence of dextranase KIBGE-IB25 was AYTVTLYLQG. It exhibited distinct amino acid sequence yet shared some inherent characteristics with glycosyl hydrolases (GH) family 49 and also testified the presence of O-glycosylation at N-terminal end., (Copyright © 2015 Elsevier B.V. All rights reserved.)

While phages of lactobacilli are extensively studied with respect to their structure and role in the dairy environment, knowledge about phages in bacteria residing in sourdough fermentation is limited. Based on the previous finding that the Lactobacillus sanfranciscensis phage EV3 carries a putative dextranase gene (dex), we have investigated the distribution of similar dex(+) phages in L. sanfranciscensis, the chance of gene transfer and the properties of the dextranase encoded by phage EV3. L. sanfranciscensis H2A (dex(-)), originally isolated from a wheat sourdough, expressed a Dex(+) phenotype upon infection with EV3. The dextranase gene was isolated from the transductant and heterologously expressed in Escherichia coli. The gene encoded a protein of 801 amino acids with a calculated molecular weight (Mw) of 89.09 kDa and a calculated pI of 5.62. Upon purification aided by a 6-His tag, enzyme kinetic parameters were determined. The Km value was 370 mM, and the Vmax was calculated in about 16 μmol of glucose released from dextran by 1 mg of enzyme in 1 min in a buffer solution at pH 5.0. The optimum conditions were 60 °C and pH 4.5. The enzyme retained its activity for >3h at 60 °C and exhibited only 40% activity at 30 °C; the highest homology of 72% was found to a dextranase gene from Lactobacillus fermentum phage φPYB5. Within 25 L. sanfransiscensis isolates tested, the strain 4B5 carried a similar prophage encoding a dextranase gene. Our data suggest a phage-mediated transfer of dextranase genes in the sourdough environment resulting in superinfection-resistant L. sanfranciscensis Dex(+) strains with a possible ecological advantage in dextran-containing sourdoughs., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Dextranase can degrade dextran polymer into low molecular weight polysaccharide. Dextranase and its hydrolysates are widely used in food, medicine and chemical industries. Studies on dextranase progresses rapidly in recent years. We reviewed literature reports combined with our study about the progress of dextranase and its potential applications in industry. In addition, we addressed hot topics and emphasized on the current research about dextranase, existing problems in domesticstudies and the future research needs needs.

In this study, we have investigated various adding times of dextranase to the dextransucrase system to reveal the synergistic process of dextransucrase and dextranase. Dextranase added into the dextransucrase-sucrose system at different times gave rise to different main dextran products. The results showed that dextranase added into sucrose system at the same time with dextransucrase synthesized low molecular weight (Mw) dextran targeted to 5 kDa, while dextranase added during the reaction process of dextransucrase directionally prepared dextran with medium Mw of 10 kDa and 20 kDa. Fourier-transform infrared (FTIR) spectroscopy and (1)H Nuclear magnetic resonance (NMR) exhibited that the synthesized oligodextrans were mainly composed of α-1,6-glycosidic linkages (dextran 6587 Da, 96.82%; dextran 22,521 Da, 96.03%) and low α-1,3-glycosidic branch. The research established the relationship between the synergistic catalysis of the double enzymatic system and the synthesis of oligodextrans with different Mw., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Endodextranase D8144 from Penicillium sp. (EC 3.2.1.2.) was immobilized on an epoxy-activated monolithic Convective Interaction Media (CIM(®)) disk in order to produce isomaltooligosaccharides (IMOS) from Dextran T40 in a continuous IMmobilized Enzymes Reactor (IMER). Enzymatic parameters and structure of IMOS were studied for free and immobilized enzymes. The immobilization efficiency of endodextranase D8144 was about 15.9% (w/w) and the real specific activity was close to 6.5 U mg enz(-1). The Km values (4.8 ± 0.2 g L(-1)) for free and immobilized enzymes were the same, showing the absence of diffusional limitation. Moreover, specific patterns of DPs (Degrees of Polymerization) distributions were observed during the enzymatic hydrolysis by HPAEC-PAD (High Pressure Anion Exchange Chromatography-Pulsed Amperometric Detection). Thus, sought-after sizes of IMOS (DPs 8-10) were generated all over the hydrolysis. Finally, the results showed the high stability of this IMER since a relative enzymatic activity about 78% was measured after 5400 volumes column., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Factors affecting matrix degradation in protein-loaded microgels were investigated for dextran-based microgels, the sugar-binding protein Concanavalin A (ConA), and the dextran-degrading enzyme Dextranase. For this system, effects of enzyme, protein, and glucose concentrations, as well as pH, were considered. Microgel network degradation was monitored by micromanipulator-assisted light microscopy, whereas enzyme and protein distributions were monitored by confocal microscopy. Results show that Dextranase-mediated microgel degradation increased with increasing enzyme concentration, whereas an increased ConA loading in the dextran microgels caused a concentration-dependent decrease in microgel degradation. In the presence of glucose, competitive release of microgel-bound ConA restored the microgel degradation observed in the absence of ConA. To clarify effects of mass transport limitations, microgel degradation was compared to that of non-cross-linked dextran, demonstrating that ConA limits enzyme substrate access in dextran microgels primarily through pore blocking and induction of pore shrinkage. The experimentally observed effects were qualitatively captured by a modified Michaelis-Menten approach for spherical symmetry, in which network blocking by ConA was included. Taken together, the results demonstrate that matrix degradation of protein-loaded microgels depends sensitively on a number of factors, which need to be considered in the use of microgels in biomedical applications.

A novel atmospheric and room-temperature plasma (ARTP) method was used to breed high-yielding mutations of Arthrobacter KQ11. Mutagenesis produced two mutations, 4-1 and 4-13, which increased enzyme activity by 19 and 30%, respectively. Dents on the cell envelope were observed under scanning electron microscopy (SEM). The optimal temperature and pH of the wild strain were 45°C and 5.5 and those of the mutant strains were 45°C, pH 6.0 (4-1) and 50°C, pH 6.0 (4-13). Under optimal enzyme production conditions of the wild and mutant strains, the dextranase activity of 4-13 was 50% higher than that of the wild strain. Through amino acid alignment, several nucleotides of the mutant strains were found to have changed. Experiments performed in vitro suggested that this endo-dextranase may inhibit biofilm formation by Streptococcus mutans., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In this research work, dextranase was immobilized onto calcium alginate beads by the combination of ultrasonic irradiation and high hydrostatic pressure (US/HHP) treatments. Effects of US/HHP treatments on loading efficiency and immobilization yield of dextranase enzyme onto calcium alginate beads were investigated. Furthermore, the activities of immobilized enzymes prepared with and without US/HHP treatments and that prepared with ultrasonic irradiation (US) and high hydrostatic pressure (HHP), as a function of pH, temperature, recyclability and enzyme kinetic parameters, were compared with that for free enzyme. The maximum loading efficiency and the immobilization yield were observed when the immobilized dextranase was prepared with US (40 W at 25 kHz for 15 min) combined with HHP (400 MPa for 15 min), under which the loading efficiency and the immobilization yield increased by 88.92% and 80.86%, respectively, compared to immobilized enzymes prepared without US/HHP treatment. On the other hand, immobilized enzyme prepared with US/HHP treatment showed Vmax, KM, catalytic and specificity constants values higher than that for the immobilized enzyme prepared with HHP treatment, indicated that, this new US/HHP method improved the catalytic kinetics activity of immobilized dextranase at all the reaction conditions studied. Compared to immobilized enzyme prepared either with US or HHP, the immobilized enzymes prepared with US/HHP method exhibited a higher: pH optimum, optimal reaction temperature, thermal stability and recyclability, and lower activation energy, which, illustrating the effectiveness of the US/HHP method. These results indicated that, the combination of US and HHP treatments could be an effective method for improving the immobilization of enzymes in polymers., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Dextranases can hydrolyze dextran deposits and have been used in the sugar industry. Microbial strains which produce dextranases for industrial use are chiefly molds, which present safety issues, and dextranase production from them is impractically long. Thus, marine bacteria to produce dextranases may overcome these problems. Crude dextranase was purified by a combination of ammonium sulfate fractionation and ion-exchange chromatography, and then the enzyme was characterized. The enzyme was 66.2 kDa with an optimal temperature of 50°C and a pH of 7. The enzyme had greater than 60% activity at 60°C for 1h. Moreover, 10mM Co(2+) enhanced dextranase activity (196%), whereas Ni(2+) and Fe(3+) negatively affected activity. 0.02% xylitol and 1% alcohol enhanced activity (132.25% and 110.37%, respectively) whereas 0.05% SDS inhibited activity (14.07%). The thickness of S. mutans and mixed-species oral biofilm decreased from 54,340 nm to 36,670 nm and from 64,260 nm to 43,320 nm, respectively., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Dextran hydrolysis-mediated conversion of polyethylene glycol (PEG)-dextran (DEX) aqueous two-phase system droplets to a single phase was used to directly visualize Dextranase activity. DEX droplets were formed either by manual micropipetting or within a continuous PEG phase by computer controlled actuation of an orifice connecting rounded channels formed by backside diffused light lithography. The time required for the two-phase to one-phase transition was dependent on the Dextranase concentration, pH of the medium, and temperature. The apparent Michaelis constants for Dextranase were estimated based on previously reported catalytic constants, the binodal polymer concentration curves for PEG-DEX phase transition for each temperature, and pH condition. The combination of a microfluidic droplet system and phase transition observation provides a new method for label-free direct measurement of enzyme activity.

Dextranases can hydrolyze dextran, so they are used in the sugar industry to mitigate the milling problems associated with dextran contamination. Few studies have been carried out on the storage stability of dextranase, let alone the dextranase of Arthrobacter oxydans KQ11 isolated from sea mud samples. This study improved the storage stability of dextranase from marine A. oxydans KQ11 by adding enzymatic protective reagents (stabilizer and antiseptic). Initially, the conditions (55 °C and 30 min) for maintaining 50% dextranase activity were obtained. Then, the best stabilizers of dextranase were obtained, namely, glycerol (16%), sodium acetate (18%) and sodium citrate (20%). Results showed that p-hydroxybenzoic acid compound sodium acetate (0.05%), D-sodium isoascorbiate (0.03%), and potassium sorbate (0.05%) were the best antiseptics. Subsequent validation experiment showed that dextranase with enzymatic protective reagents maintained 70.8% and 28.96% activities at the 13th week at 25 and 37 °C, respectively., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Application of environmentally friendly enzymes to remove thin-film composite (TFC) reverse osmosis (RO) membrane biofoulants without changing the physico-chemical properties of the RO surface is a challenging and new concept. Eight enzymes from Novozyme A/S were tested using a commercially available biofouling-resistant TFC polyamide RO membrane (BW30, FilmTech Corporation, Dow Chemical Co.) without filtration in a rotating disk reactor system operated for 58 days. At the end of the operation, the accumulated biofoulants on the TFC RO surfaces were treated with the three best enzymes, Subtilisin protease and lipase; dextranase; and polygalacturonase (PG) based enzymes, at neutral pH (~7) and doses of 50, 100, and 150 ppm. Contact times were 18 and 36 h. Live/dead staining, epifluorescence microscopy measurements, and 5 μm thick cryo-sections of enzyme and physically treated biofouled membranes revealed that Subtilisin protease- and lipase-based enzymes at 100 ppm and 18 h contact time were optimal for removing most of the cells and proteins from the RO surface. Culturable cells inside the biofilm declined by more than five logs even at the lower dose (50 ppm) and shorter incubation period (18 h). Subtilisin protease- and lipase-based enzyme cleaning at 100 ppm and for 18 h contact time restored the hydrophobicity of the TFC RO surface to its virgin condition while physical cleaning alone resulted in a 50° increase in hydrophobicity. Moreover, at this optimum working condition, the Subtilisin protease- and lipase-based enzyme treatment of biofouled RO surface also restored the surface roughness measured with atomic force microscopy and the mass percentage of the chemical compositions on the TFC surface estimated with X-ray photoelectron spectroscopy to its virgin condition. This novel study will encourage the further development and application of enzymes to remove biofoulants on the RO surface without changing its surface properties.

In our current research work, the effect of combination of ultrasonic irradiation and high hydrostatic pressure (US/HHP) on the enzymatic activity and enzymatic hydrolysis kinetic parameters of dextran catalytic by dextranase were investigated. Furthermore, the effects of US/HHP on the structure of dextranase were also discussed with the aid of fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The maximum hydrolysis of dextran was observed under US (40 W at 25 kHz for 15 min) combined with HHP (400 MPa for 25 min), in which the hydrolysis of dextran increased by 163.79% compared with the routine thermal incubation at 50 °C. Results also showed that, Vmax and KM values, as well as, kcat of dextranase under US/HHP treatment were higher than that under US, HHP and thermal incubation at 50 °C, indicated that, the substrate is converted into the product at an increased rate when compared with the incubation at 50 °C. Compared to the enzymatic reaction under US, HHP, and routine thermal incubation, dextranase enzymatic reaction under US/HHP treatment showed decreases in Ea, ΔG and ΔH, however small increase in ΔS value was observed. In addition, fluorescence and CD spectra reflected that US/HHP treatment had increased the number of tryptophan on dextranase surface with increased α-helix by 19.80% and reduced random coil by 6.94% upon US/HHP-treated dextranase protein compared to the control, which were helpful for the improvement of its activity. These results indicated that, the combination of US and HHP treatments could be an effective method for improving the hydrolysis of dextran in many industrial applications including sugar manufacturing processes., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The graft polymer Dex-g-PSSS was obtained through poly(sodium 4-styrene sulfonate) (PSSS) grafted on dextran(Dex) by using the cerium salt-hydroxyl group redox initiation system. The cross-linked microspheres C(Dex-g-PSSS) were synthesized by suspension polymerization with epichlorohydrin as the cross-linking agent. The chemical structure and physicochemical characteristics of C(Dex-g-PSSS) microspheres were represented by infrared spectroscopy (FTIR), optical microscope, and zeta potential analysis. The aim of the study is to constitute a colon-specific drug delivery system via molecular design, using C(Dex-g-PSSS) microspheres as the drug-carrying material and taking 5-fluorouracil (5-FU) as the model drug. The drug-carrying ability and mechanism of the cross-linked microspheres C(Dex-g-PSSS) for 5-FU were investigated. Finally, in vitro release tests for the drug-carrying microspheres were conducted. The experimental results show that in the medium with pH 2, the cross-linked microspheres C(Dex-g-PSSS) exhibit a strong adsorption ability for 5-FU because of strong electrostatic interactions and have an adsorption capacity of 154 ± 7.5 mg/g, displaying high drug-carrying efficiency. The in vitro release behavior of the drug-carrying microspheres is highly dependent on pH and dextranase. In the medium with pH 2, the drug-carrying microspheres do not release the drug and in the medium with pH 1, they release a little, whereas in the medium with pH 7.4, a sudden delivery phenomenon of the drug will occur, and in the presence of dextranase, a more sudden delivery phenomenon of the drug will occur, displaying an excellent colon-specific drug delivery behavior.

In this research work, dextranase has immobilized onto calcium alginate beads using a novel ultrasound method. The process of immobilization of the enzyme was carried out in a one-step ultrasound process. Effects of ultrasound conditions on loading efficiency and immobilization yield of the enzyme onto calcium alginate beads were investigated. Furthermore, the activity of the free and immobilized enzymes prepared with and without ultrasound treatment, as a function of pH, temperature, recyclability and enzyme kinetic parameters, was compared. The maximum loading efficiency and the immobilization yield were observed when the immobilized dextranase was prepared with an ultrasonic irradiation at 25 kHz, 40 W for 15 min, under which the loading efficiency and the immobilization yield increased by 27.21% and 18.77%, respectively, compared with the immobilized enzymes prepared without ultrasonic irradiation. On the other hand, immobilized enzyme prepared with ultrasonic irradiation showed Vmax and KM value higher than that for the immobilized enzyme prepared without ultrasonic irradiation, likewise, both the catalytic and specificity constants of immobilized enzyme prepared with ultrasonic irradiation were higher than that for immobilized enzyme prepared without ultrasound, indicating that, this new ultrasonic method improved the catalytic kinetics activity of immobilized dextranase at all the reaction conditions studied. Compared with immobilized enzyme prepared without ultrasound treatment, the immobilized enzymes prepared with ultrasound irradiation exhibited: a higher pH optimum, optimal reaction temperature, activation energy, and thermal stability, as well as, a higher recyclability, which, illustrating the effectiveness of the sonochemical method. To the best of our knowledge, this is the first report on the effect of ultrasound treatments on the immobilization of dextranase., (Copyright © 2012 Elsevier B.V. All rights reserved.)

In our current research work, the effect of ultrasound irradiation on the enzymatic activity and enzymatic hydrolysis kinetic parameters of dextran catalysis by dextranase were investigated. Furthermore, the effects of ultrasound irradiation on the structure of dextranase were investigated with the aid of fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The maximum activity of dextranase was observed when the sample was treated with ultrasound at 25 kHz, 40 W for 15 min, under which the enzyme activity increased by 13.43% compared the routine thermal incubation at 50 °C. Experimental Kinetics results, demonstrated that, both the V(max) and K(M) values of dextranase increased with ultrasound-treated compared with the incubation at 50 °C. Likewise, both the catalytic and specificity constants were higher under the effects of an ultrasonic field, indicating that, the substrate is converted into the product at an increased rate when compared with the incubation at 50 °C. On the other hand, fluorescence and CD spectra reflected that the ultrasound irradiation had increased the number of tryptophan on dextranase surface with increased α-helix by 15.74% and reduced random coil by 5.41% upon ultrasound-treated dextranase protein compared to the control, which were helpful for the improvement of its activity., (Copyright © 2012 Elsevier B.V. All rights reserved.)