Dextrans biosynthesis

This type of polysaccharide elongation mechanism is known as an insertion mechanism in which the monomer residue or repeating unit is apparently inserted between the reducing end of the polysaccharide chain and a lipid pyrophosphate coenzyme carrier or an enzyme-protein carrier. Actually, it is not a real insertion, but rather the transfer of the polysaccharide chain from one carrier to the carbohydrate moiety of a monomer or repeating unit attached to another carrier (see Figs. 10.12A section 10.12 on dextran biosynthesis). 

Several types of enzymatic reactions were studied during the last decade for the biosynthesis of dextran. Reports on the application of chromatographic reactors for an enzyme catalyzed reaction were first demonstrated in the late 1980s [171, 172]. 

Several types of reaction may be carried out in a chromatographic reactor. The reaction can be chemical or biochemical, taking place on the stationary phase, in the mobile phase, or both. The stationary phase must be chosen to have a good retention (affinity) for at least one component of the reaction system, and in some cases it has to act as a catalyst or catalyst support. Chromatographic reactors are particularly suited to enzyme-catalysed reactions such as the inversion of sucrose and biosynthesis of dextran, to various... 

Biosynthesis of dextran polymer 81 Chromatographic pulse reactor... 

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. 

Biosynthesis to obtain dextran with controlled and reproducible molecular structure and molecular weight... 

Flavonoids, biosynthesis of, 268 Flow birefringence, studies on dextran, 349... 

Vanillin, biosynthesis of, 268 Vi Antigen, 335 Viscose process, 95 Viscosity, of dextran solutions, 350 effects of structure on, 350... 

Most microbial exopolysaccharides are apparently synthesized in-tracellularly. However, with various Leuconostoc, Streptococcus, and Bacillus species, such exopolysaccharides as dextran and levan can be formed by adding proper substrates that do not penetrate the cell membrane.216,217 Surprisingly little information is available about the biosynthesis of biopolymers of commercial value. However, as most of them are probably formed intracellularly, the process by which substrates enter microbial cells, where they are modified by various enzymic reactions and finally excreted in polymerized form into the medium, bears attention. Even with a lack of complete biosynthetic information, the results of research on related micro-organisms may be extrapolated to form a reasonable hypothesis for the biosynthesis of polysaccharides. 

Neely, W. Brock, Dextran Structure and Synthesis, 15, 341 — 369 Neely, W. Brock, Infrared Spectra of Carbohydrates, 12, 13 — 33 Neuberg, Carl, Biochemical Reductions at the Expense of Sugars, 4, 75—117 Neufeld, Elizabeth F., and Hassid, W. Z., Biosynthesis of Saccharides from Glycopyranosyl Esters of Nucleotides ( Sugar Nucleotides ), 18, 309 - 356... 

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