SPECIES-INDEPENDENT MAINTENANCE ENERGY AND NATURAL-POPULATION SIZES

A general strategy to estimate the size of an active microbial communi ty based on catabolic rates was developed. Tijhuis et al. (Biotechnol. Bioeng. 42, 1993, 509-519) calculated from chemostat experiments main tenance energy consumption rates by multiplication of the maintenance substrate consumption rate with the standard free energy of the catabo lic reaction. They showed that the maintenance energy can generally be described as species-independent by an Arrhenius equation. In the pre sent communication, it is shown that the theory is applicable for diff erent microbial culture systems. For a given environmental situation, the maximal microbial population size is obtained when the free energy conserved is consumed solely for maintenance of the cell. The free en ergy conservation rate per volume together with the species-independen t description of maintenance energy enables calculations of the maxima l population size corresponding to a catabolic rate and of maintenance substrate consumption rates for microbial cultures.