Aerobic biodegradation of monobranched aliphatic alcohol polyethoxylates

Aerobic biodegradation of the 2-butyl-octyl alcohol polyethoxylate (2Bu-C(8 )AE) was investigated under laboratory standardized conditions (Organizatio n for Economic Cooperation and Development 301E and 310B screening test pro tocols) to study the effect of the 2-alkyl chain length on the biodegradati on mechanism of monobranched alcohol polyethoxylates (AEs). The 2Bu-C(8)AE was compared with linear and monobranched AEs with short 2-alkyl chains, wh ich were simultaneously tested under the same inoculum conditions. The meta bolites identified and the primary biodegradation rate constants obtained i ndicate that the alkyl chain length of the 2-alkyl substituent is the facto r governing the biodegradation pathway of monobranched AEs. Short 2-alkyl s ubstituents (i.e., methyl and ethyl groups) allow the central cleavage mech anism to occur, which leads to the formation of polyethylene glycols, where as AEs with longer alkyl substituents, such as the 2Bu-C(8)AE, biodegrade t hrough hydrolytic oxidation of the alkyl and polyethoxylic chains, which le ads to formation of AE metabolites with carboxylic groups on both the hydro phobic and hydrophilic moieties.