The three terms: Cooxidation, Cometabolism and fortuitous oxidation are all used to describe the oxidation and degradation of non-growth substrates by microbes. Cooxidation was originally described by Foster(1962) as the phenomenon whereby the actively growing microbes oxidize a compound, but do not utilize either carbon or energy derived from the oxidation.
Cometabolism is defined as the biological transformation of a compound which is unable to support cell replication in the requisite presence of another transformable cosubstrate, thereby clearly differentiating it from fortuitous metabolic events, that result from non-specific monooxygenase activity. It also seems possible that in some cases of cometabolism energy derived from the oxidation of the non-growth substrate can be utilized to fix carbon from the growth substrate. The capacity for cometabolism and fortuitous activity seems to occur most frequently in hydro-carbon utilizing bacteria.
In sewage and wastewater treatment processes, biotransformation of pollutants in the absence of bacterial growth also occurs as a result of the activities of the endoenzymes present i dead(non-viable) bacteria as discussed by Jones(1975) and as a result of exoenzymes excreted by viable bacteria, but the magnitude of such effects has yet to be defined.