Modulating the Synthesis of Dextran with the Acceptor Reaction Using Native and Encapsulated Dextransucrases
Arantza Gómez de Segura, Miguel Alcalde, Nieves López-Cortés, Francisco J. Plou and Antonio Ballesteros*
Departamento de Biocatálisis, Instituto de Catálisis y Petroleoquímica, CSIC, Cantoblanco, Marie Curie 2, E-28049 Madrid, Spain
Article history:
Received July 29, 2004
Accepted November 22, 2004
Key words:
glucosyltransferases, immobilization, dextran, acceptor, prebiotics
Summary:
Dextransucrases are glucansucrases with broad applications in the food, cosmetics and pharmaceutical industries. Using sucrose as the glucosyl donor, they synthesize both high molecular weight (HMW) dextrans and potential prebiotic oligosaccharides. The process selectivity can be modulated by varying the reaction conditions. When no other molecule is present in the reaction, only dextrans are synthesized. In the presence of methyl α-D-glucopyranoside, the synthesis of methyl polyglucosides takes place, diminishing the transfer of glucose molecules to form dextran. In this work, the formation of HMW soluble dextran and methyl polyglucosides was studied with dextransucrases from Leuconostoc mesenteroides, strains B-512F and B-1299. The amount of dextran formed with dextransucrase B-512F was reduced up to 4 % with respect to the control in absence of acceptor, using a mass ratio of sucrose:methyl α-D-glucopyranoside of 1:4. The encapsulation in alginate retains the dextran inside the beads, causing a distortion of the biocatalyst and finally releasing the polysaccharides into the reaction medium.
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