Aerobic biodegradation of monobranched aliphatic alcohol polyethoxylates

Abstract

Aerobic biodegradation of the 2-butyl-octyl alcohol polyethoxylate (2Bu-C8AE) was investigated under laboratory standardized conditions (Organization for Economic Cooperation and Development 301E and 310B screening test protocols) to study the effect of the 2-alkyl chain length on the biodegradation mechanism of monobranched alcohol polyethoxylates (AEs). The 2Bu-C8AE was compared with linear and monobranched AEs with short 2-alkyl chains, which were simultaneously tested under the same inoculum conditions. The metabolites identified and the primary biodegradation rate constants obtained indicate that the alkyl chain length of the 2-alkyl substituent is the factor governing the biodegradation pathway of monobranched AEs. Short 2-alkyl substituents (i.e., methyl and ethyl groups) allow the central cleavage mechanism to occur, which leads to the formation of polyethylene glycols, whereas AEs with longer alkyl substituents, such as the 2Bu-C8AE, biodegrade through hydrolytic oxidation of the alkyl and polyethoxylic chains, which leads to formation of AE metabolites with carboxylic groups on both the hydrophobic and hydrophilic moieties

Biodegradation and Ecotoxicity of Branched Alcohol Ethoxylates: Application of the Target Lipid Model and Implications for Environmental Classification

“…Prior reports on highly branched AEO have consistently characterized an inverse relationship between degree of branching and biodegradation rate (Dorn et al, 1993;Kravetz et al, 1991;Marcomini et al, 2000a;Marcomini et al, 2000b;Mausner et al, 1969). It is critical to appreciate that biodegradation screening tests (OECD 301 series) are considered stringent and their interpretation conservative.…”

Aerobic biodegradation of aliphatic polyethoxylates: An 1H‐nuclear magnetic resonance spectroscopy investigation

“…However, additional peaks in the range 4.45 to 4.55 ppm were attributed to (CH 2 ) E adjacent to a carboxyl group and were diagnostic of carboxylated AE or PEGC. The interpretation of the biodegradation profiles obtained by 1 H‐NMR took great advantage from the comparison with the biodegradation time profiles resulting from the liquid chromatography analysis (either HPLC‐FL detection or HPLC‐MS) of samples undergoing biodegradation under the same inoculum condition [7,9]. While liquid chromatography could provide compound‐specific information, 1 H‐NMR recorded the total amount of alkyl and ethoxyl methylene groups belonging to different compounds regardless of which chemical entity they belonged to (i.e.…”

“…By matching the oxo ‐AE time profile with that of Figure 3, the result was that, as previously observed by HPLC [7], a fraction of the β‐alkyl‐substituted oxo ‐AE degraded more slowly mainly through the formation of PEG, that is, through hydrolytic central scission. On the basis of an HPLC study [9], the β‐alkyl side chain must be composed mainly of methyl, ethyl, and propyl groups because the presence of longer substituents would lead to the inhibition of microbial attack of both alkyl and ethoxyl chains [7]. On the other hand, a new set of signals, located between 4.10 and 4.20 ppm in the oxo ‐AE 1 H‐NMR spectrum, was compared to those exhibited by the protons of PEGC and glycolic acid (HO‐CH 2 ‐COOH).…”

“…The results showed that PEG are key intermediates during the biodegradation of both linear and monobranched AE having methyl or ethyl groups as β‐alkyl side chain [7,8]. A further investigation on the effects of the β‐alkyl side chain length demonstrated that a butyl‐substituted aliphatic moiety underwent aerobic biodegradation without PEG formation through hydrolytic oxidation of both alkyl and polyethoxyl chains [9].…”

“…Chem. 21, 2002 A. de Lazzari et al through hydrolytic oxidation of both alkyl and polyethoxyl chains [9].…”