Dextran molecular size and degree of branching as a function of sucrose concentration, pH, and temperature of reaction of Leuconostoc mesenteroides B-512FMCM dextransucrase Original Research Article

Reactions of Leuconostoc mesenteroides B-512FMCM dextransucrase with increasing concentrations of sucrose, from 0.1 to 4.0 M, gave a decreasing amount of high-molecular weight dextran (HMWD) (>106 Da) with a concomitant increase in low-molecular weight dextran (LMWD) (<105 Da). At 0.1 M sucrose, pH 5.5, and 28 °C, 99.8% of the dextran had a MW>106 Da and at 4.0 M sucrose, 69.9% had a MW<105 Da and 30.1% had a MW>106 Da, giving a bimodal distribution. The degree of branching increased from 5% for 0.1 M sucrose to 16.6% for 4.0 M sucrose. The temperature had very little effect on the size of the dextran, which was >106 Da, but it had a significant effect on the degree of branching, which was 4.8% at 4 °C and increased to 14.7% at 45 °C. Both the molecular weight (MW) and the degree of branching were not significantly affected by different pH values between 4.5 and 6.0.