Bile salt tolerance of <Emphasis Type="Italic">Lactococcus lactis</Emphasis> is enhanced by expression of bile salt hydrolase thereby producing less bile acid in the cells期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

Bile salt tolerance of Lactococcus lactis is enhanced by expression of bile salt hydrolase thereby producing less bile acid in the cells

Authors:	Jie Bi Song Liu Guocheng Du Jian Chen

Affiliation:	1.Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology,Jiangnan University,Wuxi,China;2.National Engineering Laboratory for Cereal Fermentation Technology,Jiangnan University,Wuxi,China;3.Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education,Jiangnan University,Wuxi,China

Abstract:	Objectives Changes of bile salt tolerance, morphology and amount of bile acid within cells were studied to evaluate the exact effects of bile salt hydrolase (BSH) on bile salt tolerance of microorganism. Results The effect of BSHs on the bile salt tolerance of Lactococcus lactis was examined by expressing two BSHs (BSH1 and BSH2). Growth of L. lactis expressing BSH1 or BSH2 was better under bile salt stress compared to wild-type L. lactis. As indicated by transmission electron microscopy, bile acids released by the action of BSH induced the formation of micelles around the membrane surface of cells subject to conjugated bile salt stress. A similar micelle containing bile acid was observed in the cytoplasm by liquid chromatography-mass spectrometry. BSH1 produced fewer bile acid micelles in the cytoplasm and achieved better cell growth of L. lactis compared to BSH2. Conclusions Expression of BSH improved bile salt tolerance of L. lactis but excessive production by BSH of bile acid micelles in the cytoplasm inhibited cell growth.

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