Modeling mixed culture fermentations;: the role of different electron carriers

A recently established mixed culture fermentation ( MCF) model has been modified to account for the role of different electron carriers in the process. The MCF- model predicts the product spectrum as a function of the actual environmental conditions using a thermodynamic optimization criterion while satisfying a number of constraints. Other improvements made to the original model are the inclusion of formate as fermentation end- product, and gas- liquid mass transfer. The model is adequately capable of reproducing experimental results in terms of butyrate and formate versus hydrogen/ carbon dioxide production. The model is not capable of predicting the production of an ethanol/ acetate mixture as measured at higher pH- values, suggesting specific biochemical control. Catabolic acetate production can potentially be explained by anabolic requirements for a specific electron donor like NADH.