Synthesis of methyl α-d-glucooligosaccharides by entrapped dextransucrase from Leuconostoc mesenteroides B-1299

The synthesis of methyl α-d-glucooligosaccharides, using sucrose as glucosyl donor and methyl α-d-glucopyranoside as acceptor, was studied with dextransucrase from Leuconostoc mesenteroides NRRL B-1299. The enzyme was immobilized by entrapment in alginate. By NMR and mass spectrometry we identified three homologous series (S1–S3) of methyl α-d-glucooligosaccharides. Series S2 and S3 were characterized by the presence of α(1 → 2) linkages, in combination with α(1 → 6) bonds. Two parameters, sucrose to acceptor concentration ratio (S/A) and the total sugar concentration (TSC) determined the yield of methyl α-d-glucooligosaccharides. The maximum concentration achieved of the first acceptor product, methyl α-d-isomaltoside, was 65 mM using a S/A 1:4 and a TSC of 336 g l−1. When increasing temperature, a shift of selectivity towards compounds containing α(1 → 2) bonds was observed. The formation of leucrose as a side process was very significant (reaching values of 32 g l−1) at high sucrose concentrations.