Fermentation

Some prokaryotes and eukaryotes use anaerobic respiration in which they can create energy for use in the absence of oxygen.

Acetogenesis is a biological reaction wherein volatile fatty acids are converted into acetic acid, carbon dioxide, and hydrogen.

Fermentation is the process of extracting energy from the oxidation of organic compounds such as carbohydrates.

Syntrophy is the phenomenon where one species lives off the products of another species.