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 0.1 U/mL), five sucrose concentrations (20, 50, 100,200 and 1000 mM), and two temperatures (20 degrees C and 30 degrees C) were studied. The highest amount of enzyme (50 U/mL), with the lowest concentration of sucrose (20 mM), and the lower temperature of 20 degrees C gave the lowest number-average molecular weight (MWn) of 20,630 Da, respectively. As the sucrose concentration was increased, 50 mM, 100 mM, and 200 mM, the MWn was 49,240 Da, 63,350 Da, and 126,720 Da, respectively. The next enzyme concentration (10 U/mL) gave a similar upward trend, starting at 73,130 Da and ending at 237,870 Da at 20 degrees C and 130,040 Da and ending at 415,770 Da at 30 degrees C. The upward trend continued for the 1.0 and 0.1 U/mL enzyme concentrations. An increase in the temperature had the overall effect of increasing the MWn for each decreasing concentration of enzyme and increasing concentration of sucrose. For 0.1 U/mL and 1000 mM sucrose at 30 degrees C, the MWn was 1,645,700 Da. 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. (C) 2010 Elsevier Ltd. All rights reserved.