A thermodynamic framework has been provided for the description of maintenance requirements of microorganisms. The central parameter is the biomass specific Gibbs energy consumption for maintenance, m(E) (kJ/C-mol biomass . h). A large set of data has been used including (i) a large range of different organisms (bacteria, yeasts, plant cells), (ii) mixed cultures, (iii) heterotrophic and autotrophic growth, (iv) growth under aerobic and anaerobic conditions, and (v) a large temperature range (5-75 degrees C). It appears that only the temperature has a major influence, with an energy of activation of 69 kJ/mol. Different electron donors or electron acceptors only show a very minor influence on m(E). On the basis of the data set, temperature correlations of m(E) have been derived for aerobic and anaerobic growth. The generalized concept for maintenance Gibbs energy is used to establish a correlation which allows the estimation of the biomass yield on electron donor as a function of C-source, electron donor, electron acceptor, N source, growth rate, and temperature. The advantage of using the m(E) parameter over other maintenance-related parameters (like mu(e), m(O2), m(D), gamma(D)m(D)) is discussed.
(c) 1993 John Wiley & Sons, Inc.