Characterization of glucans and glucansucrases from novel Leuconostoc strains (including sp. S-51)

Nine kinds of glucan-producing strains were isolated in their culture supernatant from the lines of a sugar-manufacturing factory. Eight strains produced water-soluble glucan.13C NMR analysis suggested that five out of the nine glucans mainly consisted of 6-Glcp and the other four glucans were branched. Among the 6-Glcp glucan-producing strains, S-51 was selected because it had the highest extracellular glucansucrase activity. S-51 strain was identified as Leuconostoc sp. Only one kind of glucansucrase with a molecular mass of 165 kDa was found in the culture supernatant of strain S-51. Optimum temperature and pH of the S-51 glucansucrase were 35°C and 5.5, respectively. Compared with the B-512F glucansucrase, S-51 glucansucrase has a lower Km value and was slightly more stable at varying pHs and temperatures.