THE DEFINITION OF ENERGETIC GROWTH EFFICIENCIES FOR AEROBIC AND ANAEROBIC MICROBIAL-GROWTH AND THEIR DETERMINATION BY CALORIMETRY AND BY OTHER MEANS

Several possible definitions for energetic growth efficiency are revie wed. Although definitions based on a simple comparison of inflowing an d outflowing energy suffer from shortcomings, they are the only ones t hat can be related to the respective energy dissipation in a unique wa y, even in cases with complex growth stoichiometry. It is therefore po ssible to determine the enthalpic growth efficiency in a very simple w ay by calorimetry. In completely aerobic growth, the result is also vi rtually equal to the free energy efficiency. In mixed respiro-fermenta tive growth, the two efficiencies are different and the free energy ef ficiency must be computed based on detailed knowledge of the growth st oichiometry. In aerobic, mixed, and anaerobic growth of Kluyveromyces fragilis yeast, the free energy efficiency remained constant at about 60%.