In this article we will discuss about the fermentation of pyruvate to acetate to show oxidation-reduction balance.
The oxidation-reduction reactions in any fermentation must be balanced. The total number of electrons in the products on the right side of the equation must balance the number in the substrates on the left side of the equation. To show oxidation-reduction balance the fermentation of pyruvate to acetate is taken, for instance (Fig. 26.4).
Many a number of anaerobic bacteria produce acetate from pyruvate as one of the products of fermentation. The key high energy organic intermediate product in this fermentation is acetyl- CoA, which then is converted to acetyl phosphate. The high energy phosphate group of acetyl phosphate is subsequently transferred to adenosine diphosphate (ADP) by acetate kinase via substrate- level phosphorylation, yielding to ATP and acetate.
The excess electrons released during this conversion are utilized in the production of molecular hydrogen (H2) in which the protons (H+) derived from water serve as electron acceptors.
Hydrogen (H2) production is generally associated with ferredoxin, a very low potential electron carrier, which transfers electrons to H with the help of hydrogenase. In conditions where hydrogen production does not take place, the excess electrons are used to make a more reduced end product.