Biodegradability of ethoxylated fatty amines: detoxification through a central fission of these surfactants.

Non-ionic surfactants are initially degraded by a central fission of the molecule or by the oxidation of the far end of the polyoxyethylene (EO) chain. Alcohol ethoxylates are metabolized via a central fission, whereas alkylphenol ethoxylates are degraded by a stepwise shortening of the polyoxyethylene moiety. The biodegradation curves of ethoxylated fatty amines suggest a 'rapid' mineralization via an oxidation of the alkyl chain. The intermediates formed, viz., secondary ethoxylated amines, are 'slowly' biodegraded. This 'total' mineralization of the ethoxylated fatty amines was demonstrated in 'prolonged' Closed-Bottle tests. Decisive evidence for a central fission of ethoxylated fatty amines was obtained in a pure culture study. An isolated Pseudomonas sp. cleaved the C(alkyl)-N bond of octadecyl-bis(2-hydroxyethyl) amine and utilized the alkyl chain as sole carbon and energy source. Biodegradation products of both alcohol ethoxylates and ethoxylated fatty amines, formed through a central fission of the molecule, are non-toxic.