A levansucrase from Leuconostoc mesenteroides NTM048 was cloned and expressed and its enzymatic product was characterized. The fructansucrase gene from Leuconostoc mesenteroides was cloned and expressed in Escherichia coli. The recombinant enzyme was purified as a single protein and its properties investigated. The polymer produced by the recombinant enzyme was identified as levan by various means including TLC and NMRs, and the enzyme was identified as a GH68 levansucrase. The enzyme was optimal at pH 5.5-6 and 30 A degrees C, and its activity was stimulated by Ca2+. The levan produced by this strain induced IgA production in mice. Leuconostoc mesenteroides, a probiotic strain, possessed levansucrase which catalyzed the produced levan that had immunomodulating activity.