does not encompass all forms of fermentation. For example, propionate fermentation which uses H₂ as an electron donor, or the second step of butyrate fermentation where CO₂ can act as an electron acceptor. Thus, it is simplest to use this definition while acknowledging that protons can also be used as electron donors and CO₂ as acceptors.

In 1876, before the discovery of anaerobic respiration, Louis Pasteur described it as "la vie sans air" (life without air). It