A new batch calorimeter for aerobic growth studies

A microcalorimeter for aerobic growth studies, derived from a Tian Calvet differential apparatus, was successfully constructed. The calorimetric vessel was a short cylinder, which permitted a good exchange between the surface area and the gas phase. The time constant of the calorimeter was 3.6 min and the sensitivity 234 V/W. The thermochemical aspect of the aerobic growth of Escherichia coli on succinate, acetate, and glucose was investigated. This analysis revealed that the contribution of biosynthetic reactions varied with the substrate used and strongly influenced the heat evolution. The experimental metabolic enthalpy change was in good agreement with the predicted value for succinate and glucose growth. To explain the discrepancy between the two values observed for acetate growth we suggest that acetate metabolism may generate a by-product which was not further oxidized.