## Other Maintenance Quantities

Microorganisms require Gibbs energy for maintenance. This is obtained by catabolizing the required amount of electron donor mD. It is then obvious that other quantities, such as electron acceptor, heat, Gibbs energy, oxidized electron donor, and reduced electron acceptor, are also involved in maintenance, to catabolize the mD electron donor. These maintenance-related quantities are directly obtained from the stoichiometry of the catabolic reaction (Example 3b).

EXAMPLE 3b

Calculating other maintenance rates using the catabolic reaction

In Example 3a it was found that mD = 0.02 C-mol glucose/C-mol biomass/h.

In the growth system being considered, the catabolic reaction is the aerobic oxidation of glucose according to

+ 2,843 kJ Gibbs energy

Using the stoichiometry of this catabolic reaction and the known mD, it is now easy to calculate the other maintenance rates:

maintenance glucose mD = 0.02 C-mol glucose/C-mol Xh

= 0.02/6 mol glucose/C-mol biomass/h maintenance oxygen mA = - x 6 mol O2/C-mol biomass/h