Leuconostoc mesenteroides, dextran

A new chapter in the chemistry of dextrans was opened by the discovery that certain of these contained a-(i ->-3 ->6) branch points. Barker, Bourne, Bruce and Stacey found 24-dimethyl-D-glucose among the hydrolysis products of the methyl ether of a Betacoccus arabinosaceous dextran. The disaccharide nigerose was also detected in the hydrolysis products of the dextran itself. Abdel-Akher, Hamilton, Montgomery and Smith reported the application, to a certain Leuconostoc mesenteroides dextran, of a new procedure for structural determination. This involved periodate oxidation References p. 259... 

Leuconostoc mesenteroides dextrans have acquired considerable importance during recent years following the discovery that, when suitably degraded, they can be used as a substitute for blood plasma. Dextran sulphate is also used as a blood anticoagulant. Other ethers and esters of dextran find widespread applications in industry. 

Sucrose is subjected to the action of the bacterium Leuconostoc mesenteroides B 512 and the crude, high-molecular weight dextran thus formed is hydrolyzed and fractionated to an average molecular weight of about 40,000 as measured by light-scattering techniques. 

Homopolysaccharides are synthesised by relatively few spedfic enzymes and are not constructed from subunits. The commerdally important homo polymer dextran is synthesised extracellularly by the enzyme dextransucrase. In Leuconostoc mesenteroides the enzyme is induced by the substrate sucrose. This is deaved to release free fructose and link the glucose to the redudng end of the acceptor dextran chain, which is bound to the enzyme. The product from this bacterium is composed almost exdusively of... 

A) dextran (95% a-1- 6 linkages and 5% a-1- 3 branch linkages) S3mthesized by Leuconostoc mesenteroides B-512F dextansucrase ... 

This degradation has also been applied151 to the dextran produced by Leuconostoc mesenteroides NRRL B-512, which is composed of (1 — 6)-linked a-D-glycopyranose residues, about 5% of which carry a side chain linked to 0-3 (partial structure 87). Tritylation of... 

Smith, E. E. 1970. Biosynthetic relation between the soluble and insoluble dextrans produced by Leuconostoc mesenteroides NRRL B-1229. FEBS Lett. 12, 33-37. 

The number of enzymes responsible for the formation of polysaccharides from sucrose is also restricted. The two best known enzymes that form polysaccharides from sucrose are the dextran, synthesized by the microorganism Leuconostoc mesenteroides (8) and related organisms, and the levan, produced from the same substrate by Acetobacter levanicum (9) and other species. 

Xanthan gum, dextran Xanthomonas campestris, Leuconostoc mesenteroides Food, pharmaceutical, textile industries, useful for thickening, stiffening and setting properties... 

Leuconostoc mesenteroides and Leuconostoc ssp. are found in fermented foods of plant origin [11]. The occurrence of these bacteria in sugar refineries is responsible for problems in filtration processes because of increased viscosity by the presence of soluble dextran [12,13]. Furthermore, dextran retards the rate of crystallisation of sucrose and adversely affects the crystal shape. The occurrence of dextran in the matrix of dental plaque results from certain Streptococcus strains [14]. The principle organism, Streptococcus mutans, is able to produce water-soluble glucan (named dextran) and water-insoluble... 

The majority of dextrans in nature are produced extracellularly via dextran-sucrase from sucrose by several lactic acid bacteria, principally Leuconostoc and Streptococcus species [13]. Dextran is also synthesised by dextrinase of different Gluconobacter species [56]. Referring to this enzyme, fermentation of maltodextrins leads to a- —4) branched dextrans with comparatively lower Mw. However, dextransucrase from Leuconostoc mesenteroid.es NRRL B-512F has attracted most interest because of commercial use. 

Dextran is a unique polysaccharide because of its structure (only glucose units), purity, defined branching pattern depending on the microbial sources and defined molecular weight. Today, it is produced on a commercial scale resulting from optimised biotechnological processes for the biosynthesis of dextran using preferably Leuconostoc mesenteroides. 

Synthesis of Branch Linkages in Leuconostoc mesenteroides B-512F Dextran... 159... 

Dextran Acetobacter spp. Leuconostoc mesenteroides Plastic flow as source for utilizing dextran derivatives for pharmaceutical purposes... 

Kim D, Robyt JF, Lee SY, Lee JH, Kim YM (2003) Dextran molecular size and degree of branching as a function of sucrose concentration, pH, and temperature of reaction of Leuconostoc mesenteroides B-512FMCM dextransucrase. Carbohydr Res 338 1183-1189... 

Figure 1 shows tablets (300 mg) of native dextran obtained from Leuconostoc mesenteroides B-512F (Sigma) with a 10% water (w/w) punch in an eccentric machine (Manesty) at 15 kN with tablet side (flat-flace diameter) 10mm. Axial displacement of water was observed according to the change in color. 

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