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Appl. Environ. Microbiol. doi:10.1128/AEM.02787-06
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Glutathione Protects Lactococcus lactis Against Acid Stress

The Key Laboratory of Industrial Biotechnology, Ministry of Education; School of Biotechnology, Jiangnan University, Wuxi 214122, P. R. China; Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China; Wageningen Centre for Food Sciences, Kluyver Centre for Genomics of Industrial Fermentation, and NIZO Food Research, 6710 BA, Ede, The Netherlands; Laboratory of Tea Biochemistry & Biotechnology, Ministry of Agriculture and Ministry of Education, Anhui Agricultural University, Hefei 230036, P. R. China

^* To whom correspondence should be addressed. Email: yli{at}im.ac.cn. jchen{at}jiangnan.edu.cn.

	Abstract

Previously we have shown that glutathione (GSH) can protect Lactococcus lactis against oxidative stress (Li et al. AEM, 2003, 69: 5739). In the present study we show that the GSH imported by L. lactis ssp. cremoris SK11, or produced by engineered L. lactis ssp. cremoris NZ9000, can protect both strains against a long-term mild acid challenge (pH 4.0) and a short-term severe acid challenge (pH 2.5). This shows for the first time that GSH can protect a Gram-positive bacterium against acid stress. During acid challenge, strain SK11 containing imported GSH and strain NZ9000 containing self-produced GSH exhibited a significantly higher intracellular pH as compared to the control. Furthermore, strain SK11 containing imported GSH had a significantly higher activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as compared to the control. These results suggest that the acid-stress resistance of starter culture can be improved by selecting L. lactis strains capable of producing or importing GSH.