Li Yin, Hugenholtz Jeroen, Abee Tjakko, Molenaar Douwe
Wageningen Centre for Food Sciences, NIZO Food Research, 6710 BA Ede, The Netherlands.
Appl Environ Microbiol. 2003 Oct;69(10):5739-45. doi: 10.1128/AEM.69.10.5739-5745.2003.
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 approximately 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.
在M17培养基中生长的几种乳酸乳球菌菌株中发现了谷胱甘肽。这些菌株均不能合成谷胱甘肽。在化学成分确定的培养基中，当向培养基中添加该化合物时，乳酸乳球菌乳脂亚种SK11菌株能够积累高达约60 mM的谷胱甘肽。与没有细胞内谷胱甘肽的细胞相比，在添加了谷胱甘肽的化学成分确定的培养基中生长的SK11菌株的稳定期细胞对H2O2处理的抗性显著增加（抗性增加高达五倍）。在所测试的16株乳酸乳球菌中，发现对H2O2处理的抗性取决于谷胱甘肽的积累。我们提出，通过摄取谷胱甘肽，乳酸乳球菌可能会激活稳定期细胞中的谷胱甘肽-谷胱甘肽过氧化物酶-谷胱甘肽还原酶系统，该系统催化H2O2的还原。在大多数乳酸乳球菌菌株中都可检测到还原氧化型谷胱甘肽的谷胱甘肽还原酶，但不同菌株的活性差异很大。一般来说，乳酸乳球菌乳酸亚种的谷胱甘肽还原酶活性高于乳酸乳球菌乳脂亚种，并且当菌株在有氧条件下生长时，活性要高得多。此外，在SK11菌株中可检测到谷胱甘肽过氧化物酶，当该生物体在有氧条件下生长时，其水平比在厌氧条件下生长时高五倍。因此，乳酸乳球菌中谷胱甘肽的存在可能导致在储存条件下具有更高的稳定性以及接种后更快的生长，这是成功的发酵剂培养物的两个重要特性。
