Magali Remaud

Characterization of α-(1→3) Branched Oligosaccharides Synthesized by Acceptor Reaction with the Extracellular Glucosyltransferases from L. Mesenteroides NRRL B-742

Abstract The glucosyltransferases from L. mesenteroides are known to catalyze the transfer of the D-glucosyl group of sucrose onto sugars, now commonly named acceptors. We investigated in the present work, the acceptor reaction catalyzed by the extracellular glucosyltransferases from L. mesenteroides NRRL B-742. The enzymes of the culture supernatant, purified by aqueous two-phase partition between dextran and polyethylene glycol solutions, were found to efficiently transfer the glucose moiety of sucrose onto maltose acceptor. By increasing the sucrose/maltose ratio (S/M), it was possible to catalyze the synthesis of oligosaccharides of increasing degree of polymerisation (d.p.). For an S/M ratio of 7, both linear oligosaccharides (only composed of α-(1→6) linkages and a maltose residue at the reducing end) and branched oligosaccharides were produced. A glucanase treatment permitted isolation of the branched products which were then analyzed by carbon 13 NMR spectroscopy. The chemical shifts arising from ...

Novel enzymatic synthesis of oligosaccharides

Abstract Industrial applications of enzyme catalysts are mostly hydrolysis reactions. But increasing attention is given to enzymatic synthesis reactions. The possibility of obtaining efficient synthesis reactions without involving costly cofactors is illustrated by examples taken in the field of oligosaccharide production. Three main approaches are considered: reversion of hydrolysis reactions, by shifting the position of the reaction equilibrium, “transhydrolytic”; reactions, using the transferase activity of hydrolytic enzymes, transfer reactions, catalyzed by transferase enzymes. The respective advantages and drawbacks of these three approaches are compared. The oligosaccharides thus obtained are of interest in different fields of application: food and feed ingredients, pharmaceutical and immunological products, cosmetic additives, for example.

Molecular Weight Characterization and Structural Properties of Controlled Molecular Weight Dextrans Synthesized by Acceptor Reaction using Highly Purified Dextransucrase

ABSTRACT Controlled molecular weight dextrans were synthesized using a highly purified dextransucrase from Leuconostoc mesenteroides NRRL B-512F in a multi-step process. Maltose was used as acceptor for the first reaction step. The purified product obtained at a given reaction step was used as acceptor for the next reaction step. Dextrans of molecular weights ranging from 1,000 to 100,000 were thus obtained with a good yield (80 %). After purification, the molecular weight distribution of the products was characterized using size exclusion chromatography coupled with low angle laser light scattering (LALLS). Polydispersity of the products was shown to be similar to that of commerical dextrans. 13C NMR spectra and enzymatic hydrolysis data are consistent with the fact that the enzymatically synthesized dextrans are essentially composed of α(1->6) linkages. It was observed that controlled molecular weight dextrans were less branched than commercial products obtained by acidic hydrolysis of high molecular we...