GLUTATHIONE CONTENT OF LACTIC-ACID BACTERIA

The quantity of intracellular total thiol groups and glutathione was analyzed in a variety of lactic acid bacteria. The concentration of thiol groups (.7 to 81 nmol/mg of protein) and glutathione (6 to 51 nmol/mg of protein) varied widely. Concentrations were highest in strains of Lactococcus lactis ssp. cremoris and Streptococcus thermophilus, followed by Leuconostoc mesenteroides ssp. cremoris. Glutathione was not detected in Lactococcus lactis ssp. lactis, micrococci, pediococci, and lactobacilli (except Lactobacillus helveticus CNRZ 32) cultures. The effect of several growth conditions on total thiol groups and glutathione content was studied with L. lactis ssp. cremoris Z8. During growth in Elliker broth, glutathione concentration increased during exponential growth; in M17 broth, intracellular concentrations of glutathione did not vary as a function of growth phase, and lower concentrations were detected. Aeration resulted in a temporarily increased accumulation of glutathione. When cultures were grown in milk, the highest concentrations of thiol groups and glutathione occurred during the stationary phase. Supplementation of milk with glutathione or the precursor amino acids of glutathione resulted in increased intracellular glutathione.