CALORIMETRY AND ENERGETIC EFFICIENCIES IN AEROBIC AND ANAEROBIC MICROBIAL-GROWTH

A simple definition of the energetic growth efficiency both in terms o f enthalpy and free energy is given and discussed. In cultures growing by respiratory catabolism, these efficiencies may conveniently be obs erved on-line by isothermal reaction calorimetry. If the fermentative part of catabolism is important, the free energy growth efficiency mus t be evaluated based on biomass yield measurements. In continuous cult ures of two yeasts, growing by respiration, by pure fermentation, and on a mixed catabolism the efficiency was always between 05 and 0.6 des pite widely varying growth yields.