Estimation of true growth and product yields in aerobic cultures

The use of stoichiometric relations for the description and analysis of microbial cultures

A general method is described, which enables the derivation of predictive fermentation equations for any microbiological process. The method combines the well-known achievements of the elemental balance approach with microscopic, metabolic balances and biochemical restrictions, using the key intermediates concept. Special attention is paid to the distinction between independent and dependent flow variables of a system. The method is fully illustrated for the very simple example of heterotrophic growth on a single substrate without product formation. Other examples include growth on mixed substrates and the description of catabolic and anabolic product formation.

Available electron and energetic yields in fermentation processes

Microbial growth and product yields have been investigated for several cultures. Available electron and free energy balances may be used to examine the efficiency of microbial energetics. Energetic yields based on free energy analysis were obtained and compared with yields from available electron analysis. Estimates of true growth yields under anaerobic conditions have been obtained using statistical methods and the results were compared with theoretical maximum yields.