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

摘要

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 dextram (HMWD) (>10~6 Da) with a concomitant increase in low-molecular weight dextran (LMWD) (<10~5 Da).At 0.1 Msucrose,pH 5.5 and 28deg C 99.8% of the dextran had a MW>10~6 Da and at 4.0 M sucrose 69.9% had a MW <10~5 Da and 30.1% had a MW>10~6 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 effedct on the size of the dextran which was >10~6 Da but it had a significant effect on the degree of branching which was 4.8% at 4 deg C and increased to 14.7% at 45 deg 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.