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Applied and Environmental Microbiology, October 2003, p. 5739-5745, Vol. 69, No. 10
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.10.5739-5745.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Glutathione Protects Lactococcus lactis against Oxidative Stress

Yin Li,1,{dagger} Jeroen Hugenholtz,1 Tjakko Abee,2 and Douwe Molenaar1*

Wageningen Centre for Food Sciences, NIZO Food Research, 6710 BA Ede,1 Laboratory of Food Microbiology, Wageningen University, 6703 HD Wageningen, The Netherlands2

Received 21 February 2003/ Accepted 9 July 2003

Glutathione was found in several dairy Lactococcus lactis strains grown in M17 medium. None of these strains was able to synthesize glutathione. In chemically defined medium, L. lactis subsp. cremoris strain SK11 was able to accumulate up to ~60 mM glutathione when this compound was added to the medium. Stationary-phase cells of strain SK11 grown in chemically defined medium supplemented with glutathione showed significantly increased resistance (up to fivefold increased resistance) to treatment with H2O2 compared to the resistance of cells without intracellular glutathione. The resistance to H2O2 treatment was found to be dependent on the accumulation of glutathione in 16 strains of L. lactis tested. We propose that by taking up glutathione, L. lactis might activate a glutathione-glutathione peroxidase-glutathione reductase system in stationary-phase cells, which catalyzes the reduction of H2O2. Glutathione reductase, which reduces oxidized glutathione, was detectable in most strains of L. lactis, but the activities of different strains were very variable. In general, the glutathione reductase activities of L. lactis subsp. lactis are higher than those of L. lactis subsp. cremoris, and the activities were much higher when strains were grown aerobically. In addition, glutathione peroxidase is detectable in strain SK11, and the level was fivefold greater when the organism was grown aerobically than when the organism was grown anaerobically. Therefore, the presence of glutathione in L. lactis could result in greater stability under storage conditions and quicker growth upon inoculation, two important attributes of successful starter cultures.

* Corresponding author. Mailing address: NIZO Food Research, P.O. Box 20, 6710 BA Ede, The Netherlands. Phone: 31-318-659656. Fax: 31-318-650400. E-mail: Douwe.Molenaar{at}nizo.nl.

{dagger} Present address: The Key Laboratory of Industrial Biotechnology, Ministry of Education, Southern Yangtze University, Wuxi 214036, People's Republic of China.

Applied and Environmental Microbiology, October 2003, p. 5739-5745, Vol. 69, No. 10
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.10.5739-5745.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



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