Analysis of the dextranase activity produced by an oral strain of Bacteroides ochraceus

Dextran-Coated Zinc-Doped Hydroxyapatite for Biomedical Applications

Dextran-coated zinc-doped hydroxyapatite (ZnHApD) was synthesized by an adapted sol-gel method. The stability of ZnHApD nanoparticles in an aqueous solution was analyzed using ultrasonic measurements. The analysis of the evolution in time of the attenuation for each of the frequencies was performed. The X-ray diffraction (XRD) investigations exhibited that no impurity was found. The morphology, size and size distribution of the ZnHApD sample was investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The TEM and SEM results showed that the ZnHApD particles have an ellipsoidal shape and a narrow distribution of sizes. The cell growth and toxicity of HEK-293 cells were investigated on the ZnHApD solution for four different concentrations and analyzed after 24 and 48 h. The ZnHApD solution presented a non-toxic activity against HEK-293 cells for all analyzed concentrations. The antibacterial assay revealed that all the tested microorganisms were inhibited by the ZnHApD dispersion after 24 and 48 h of incubation. It was observed that the effect of the ZnHApD solution on bacteria growth depended on the bacterial strain. The Porphyromonas gingivalis ATCC 33277 bacterial strain was the most sensitive, as a growth inhibition in the presence of 0.075 μg/mL ZnHApD in the culture medium was observed.

Effect of cross-linking on the physicochemical and in vitro properties of pullulan/dextran microbeads

Hydrogels are very promising for tissue engineering as they provide scaffolds and a suitable microenvironment to control cell behavior and tissue regeneration. We used a patented method to obtain beads of pullulan/dextran cross-linked with sodium trimetaphosphate (STMP), that were already described for in vivo bone repair. The aim of this study was to provide a comparative analysis of microbeads made of polysaccharides prepared using three different STMP feeding ratio of 1.5, 2.25 or 3 % w/w. The morphology, swelling and biodegradability of these structures were assessed. Mesenchymal stem cells were also seeded to evaluate the cell organization onto the beads. We found that the amount of phosphorus resulting from the cross-linking was proportional to the introduced STMP concentration. An increase of cross-linking decreased the in vitro enzymatic degradability, and also decreased the swelling in PBS or water. The microstructures observed by SEM and confocal microscopy indicated that homogeneous spherical microbeads were obtained, except for the lower cross-linking ratio where the shapes were altered. Beads hydrated in PBS exhibited a mean diameter ranging from 400 to 550 µm with the decrease of STMP ratio. Cells adhered to the surface of microbeads even in the absence of protein coating. Cell viability studies revealed an increase in cell numbers over two weeks for the highest cross-linked beads, whereas the two lowest STMP concentrations induced a decrease of cell viability. Overall, this study demonstrated that pullulan/dextran hydrogels can be designed as microbeads with adjustable physicochemical and biological properties to fulfill requirements for tissue engineering approaches.

Enzymes in therapy of biofilm-related oral diseases

Biofilm-related infections of the oral cavity, including dental caries and periodontitis, represent the most prevalent health problems. For years, the treatment thereof was largely based on antibacterial chemical agents. Recently, however, there has been growing interest in the application of more preventive and minimally invasive biotechnological methods. This review focuses on the potential applications of enzymes in the treatment and prevention of oral diseases. Dental plaque is a microbial community that develops on the tooth surface, embedded in a matrix of extracellular polymeric substances of bacterial and host origin. Both cariogenic microorganisms and the key components of oral biofilm matrix may be the targets of the enzymes. Oxidative salivary enzymes inhibit or limit the growth of oral pathogens, thereby supporting the natural host defense system; polysaccharide hydrolases (mutanases and dextranases) degrade important carbohydrate components of the biofilm matrix, whereas proteases disrupt bacterial adhesion to oral surfaces or affect cell-cell interactions. The efficiency of the enzymes in in vitro and in vivo studies, advantages and limitations, as well as future perspectives for improving the enzymatic strategy are discussed.

Microbial dextran-hydrolyzing enzymes: fundamentals and applications

Dextran is a chemically and physically complex polymer, breakdown of which is carried out by a variety of endo- and exodextranases. Enzymes in many groups can be classified as dextranases according to function: such enzymes include dextranhydrolases, glucodextranases, exoisomaltohydrolases, exoisomaltotriohydrases, and branched-dextran exo-1,2-alpha-glucosidases. Cycloisomalto-oligosaccharide glucanotransferase does not formally belong to the dextranases even though its side reaction produces hydrolyzed dextrans. A new classification system for glycosylhydrolases and glycosyltransferases, which is based on amino acid sequence similarities, divides the dextranases into five families. However, this classification is still incomplete since sequence information is missing for many of the enzymes that have been biochemically characterized as dextranases. Dextran-degrading enzymes have been isolated from a wide range of microorganisms. The major characteristics of these enzymes, the methods for analyzing their activities and biological roles, analysis of primary sequence data, and three-dimensional structures of dextranases have been dealt with in this review. Dextranases are promising for future use in various scientific and biotechnological applications.

Characterization of the dextranase purified from Streptococcus mutans Ingbritt

We purified dextranase from the culture supernatant of Streptococcus mutans Ingbritt by procedures including ammonium sulfate precipitation, ion-exchange chromatography, and gel filtration. The molecular weight of the enzyme was estimated as 78 kDa by SDS-PAGE. The enzyme degraded dextran at the optimum pH of 5.5, but not other glucans and fructans at all. Paper chromatographic analysis revealed that the enzyme cleaved dextran by an endo-type mechanism. The enzyme was inhibited by Hg2+, Fe3+, Zn2+, and anionic detergents SDS and deoxycholic acid, but not inhibited by non-ionic detergents Triton X-100, Lubrol PX, Nonidet P-40, and Tween 80. SDS-blue dextran-PAGE analysis of the culture supernatant revealed that the enzyme activity detected in the 96 kDa band shifted gradually to the 78 kDa band during handling the supernatant. This shift was inhibited by phenylmethylsulfonyl fluoride, suggesting that the shift of the molecular size is due to proteolytic degradation of the enzyme by serine protease.

Extracellular dextranase activity produced by human oral strains of the genus Bifidobacterium

Three strains of anaerobic, dextranase-producing, gram-positive, rod-shaped bacteria were isolated from human dental plaque associated with root carious lesions. The isolates produced a molar ratio of acetate to lactate from glucose fermentation ranging from 1.1 to 1.9. Each strain also produced fructose-6-phosphate phosphoketolase. The isolates were identified as belonging to the genus Bifidobacterium, but from their carbohydrate fermentation patterns they did not appear to be strains of Bifidobacterium dentium. These microorganisms fermented high-molecular-weight dextrans. A partial characterization of the dextranase activity was included in this study and revealed an extracellular dextranase with a pH optimum of 7.1. Analysis of the dextran degradation products demonstrated the liberation of saccharides larger than 1 glucose unit. It was concluded that this enzyme used an endohydrolytic mode of dextran cleavage.

Isolation and properties of dextranases from Bacteroides oralis Ig4a

Extracellular dextranases were extracted from a dextran-degrading microorganism, Bacteroides oralis Ig4a, which had been isolated from human dental plaque, and purified. Crude enzyme preparations obtained from a broth culture supernatant by salting out with ammonium sulfate were subjected to column chromatography on DEAE-cellulose and subsequent Bio-Gel p-100, followed by isoelectric focusing. Two kinds of enzyme preparations, Enzymes I and II, with the ability to degrade soluble dextran were obtained. The optimal pHs of Enzymes I and II were 5.5 and 6.8, and the isoelectric points were pH 4.5 and 6.5, respectively. The molecular weights of Enzymes I and II were estimated by SDS-PAGE to be 44,000 and 52,000. Both enzymes were inhibited by Pb2+ and Fe3+, but not by Ca2+, Mg2+, Zn2+, or Fe2+. Neither the presence of EDTA nor iodoacetamide had any appreciable effect on the enzyme activity. The enzyme activity was independent of any of these metal ions. Enzyme I liberated glucose, isomaltose, maltotriose and higher oligosaccharides from dextran. In contrast, Enzyme II liberated only glucose from dextran and was assumed to be an exoglycosidase. Neither of the enzymes degraded modified insoluble glucan, which is a partially oxidized mutan of S. mutans containing predominantly alpha-(1,3) linkages.