Biosynthesis of dextrans with different molecular weights by selecting the concentration of Leuconostoc mesenteroides B-512FMC dextransucrase, the sucrose concentration, and the temperature.

Leuconostoc mesenteroides B-512FMC dextransucrase was found to synthesize dextrans of varying molecular weights by selecting the concentrations of dextransucrase and sucrose, as well as the temperature. Four enzyme concentrations (50, 10, 1.0, and 0.1U/mL), five sucrose concentrations (20, 50, 100, 200 and 1000mM), and two temperatures (20°C and 30°C) were studied. The highest amount of enzyme (50U/mL), with the lowest concentration of sucrose (20mM), and the lower temperature of 20°C gave the lowest number-average molecular weight (MW(n)) of 20,630Da, respectively. As the sucrose concentration was increased, 50mM, 100mM, and 200mM, the MW(n) was 49,240Da, 63,350Da, and 126,720Da, respectively. The next enzyme concentration (10U/mL) gave a similar upward trend, starting at 73,130Da and ending at 237,870Da at 20°C and 130,040Da and ending at 415,770Da at 30°C. The upward trend continued for the 1.0 and 0.1U/mL enzyme concentrations. An increase in the temperature had the overall effect of increasing the MW(n) for each decreasing concentration of enzyme and increasing concentration of sucrose. For 0.1U/mL and 1000mM sucrose at 30°C, the MW(n) was 1,645,700Da. The results of the study show that the molecular weights of the synthesized dextrans were inversely proportional to the concentration of the enzyme and directly proportional to the concentration of sucrose and the temperature. 2010 Elsevier Ltd. All rights reserved.