Abstract: Leuconostoc citreum, a Gram-positive lactic acid bacterium isolated from fermented grains and vegetables, can express various enzymes involved in the biosynthesis of different extracellular polysaccharide (EPS). In this study, Leuconostoc citreum BD1707 was cultured in tomato juice. After 24 and 72 h of culture, samples were collected for ammonium sulfate precipitation followed by in situ activity analysis using native-polyacrylamide gel electrophoresis (native-PAGE). The results showed that Leuconostoc citreum BD1707 could secrete three EPS synthases with molecular masses of about 150, 90 and 80 kDa, respectively, which were higher than those of the known levansucrases.

Key words: lactic acid bacteria; Leuconostoc citreum BD1707; extracellular polysaccharides; levansucrase; levan

摘要： 柠檬明串珠菌是一类从发酵谷物和蔬菜中分离出的革兰氏阳性乳酸菌，该类菌株能表达多种胞外多糖合成酶来合成不同类型的胞外多糖。对柠檬明串珠菌BD1707在番茄汁中培养24、72 h的发酵液进行硫酸铵沉淀和非变性聚丙烯酰胺凝胶电泳原位活性测试。结果表明：柠檬明串珠菌BD1707可以分泌分子质量约为150、90、80 kDa 3 种大小的胞外多糖合成酶，单糖分析表明产生的胞外多糖均为果聚糖，与已知的果聚糖蔗糖酶相比，这些酶的分子质量均偏大。

关键词: 乳酸菌；柠檬明串珠菌BD1707；胞外多糖；果聚糖蔗糖酶；果聚糖