METABOLISM AND ENERGETICS OF LACTOCOCCUS-LACTIS DURING GROWTH IN COMPLEX OR SYNTHETIC MEDIA

When Lactococcus lactis was grown in various complex or synthetic medi a, the fermentation of glucose remained homolactic whatever the medium used, with a global carbon balance of about 87%, Moreover, the nitrog en balance was not equilibrated, indicating that some amino acids led to the production of unknown nitrogen-containing carbon compounds whil e part of the glucose might contribute to anabolic pathways. In minima l medium containing six amino acids, a high concentration of serine wa s deaminated to pyruvate. This did not occur in more complete media, s uggesting the presence of a regulation of this phenomenon by an amino acid, Ammonia produced during serine consumption was partly reconsumed after serine exhaustion. The values for biomass yield and biomass yie ld relative to ATP (Y-ATP), the maximal growth rate, the specific rate of glucose consumption, and the corresponding rate of ATP synthesis a ll increased with the complexity of the medium, amino acid composition having the most pronounced effect. The Y-ATP values were shown to ran ge from 6.6 to 17.6 g of biomass.mol of ATP(-1) on minimal and complex media.