Biooxidation is oxidation catalyzed by an enzyme or a living biological system, resulting in net electron removal from an organic or inorganic substrate. Oxidases transfer reducing equivalents to molecular oxygen, dehydrogenases transfer them to cofactors such as NAD(P)+, oxygenases incorporate one or both atoms of O₂ into a substrate, and peroxidases use peroxides as electron acceptors ^[1][2]. Whole-cell biooxidation can couple these enzyme reactions to cofactor regeneration and respiratory electron transport, while isolated-enzyme biooxidation contains only the catalytic protein and required cofactors. The class is defined by the biological catalyst and oxidative direction, not by a particular substrate or terminal acceptor. It therefore includes microbial oxidation of inorganic species and selective oxidation of organic functional groups, but excludes abiotic oxidation and biological transformations with no change in substrate oxidation state. Biooxidation is narrower than biotransformation generally and is the oxidative counterpart of enzymatic reduction.