Energetic analysis of cultures of Lactobacillus delbrueckii subsp bulgaricus:: identification of the type of control between catabolism and anabolism

Growth and energetic parameters of Lactobacillus delbrueckii subsp. bulgaricus were measured during Cultures in synthetic medium, at pH regulated at 6.4 and at free pH. These data enabled the actual biomass yield relative to ATP and the maintenance coefficient to be calculated, and the type of control between catabolism and anabolism to be identified. The Cultures of L. delbrueckii subsp. bulgaricus at pH 6.4 or at a non-regulated pH were characterized by a concomitant and early decrease in both catabolism and anabolism. At a regulated pH, the growth decrease seems to be due to the accumulation of toxic compounds, acting oil anabolic reactions. This inhibition led to a decrease in the catabolic flux, albeit to a lower extent than the anabolic flux. In this condition, the culture was characterized by an excess of energy. On the contrary, at free pH, the lactic acid production led to a pH decrease responsible for the slowing-down of the catabolic flux. At the same time, maintaining the internal pH in the acidified medium wits more energy-consuming. The consequence of both the decrease in the glycolytic flux and the increase in the energy consumption led to an energy limitation of growth, as shown by the lower value of the maintenance coefficient.