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In order to assess the biotic degradation, the results from a test performed with Coco dipropylene triamines(C8-18dipropylene triamine;CAS#: 91771-18-5)was read across. The read across is based on the following justification:

N-alkyl dipropylene triamines are surfactants chemically characterized by a either a coco-alkyl(C8-18), Tallow-alkyl (C12-18), Decyl (C10), or Oleyl (C18) chain linked to one of the primary nitrogen atoms (Triameen C, Triameen T and Triameen OV) or the secondary amine (Triameen YT) of dipropylenetriamine (N-(3-aminopropyl)-1,3-propanediamine (idealized)). Biodegradation of surfactants refer to the reduction in complexity of the chemical through metabolic activity of microorganisms. If a surfactant is to serve as a carbon and energy source for aerobic microorganisms then it has to be converted into a form that can enter the central metabolism of microorganisms. Normally this involves converting the surfactant into one, or more, low molecular weight intermediates of the tricarboxylic acid (TCA) cycle or compounds that feed into it. Many of these conversions are described in pathways for surfactants (Steber and Berger, 1995; White, 1993; van Ginkel, 2007). Although micro-organisms capable of degrading surfactants are immensely diverse, the central metabolism (b-oxidation and TCA cycle) is remarkably similar. Kluyver and Donker (1926) first described this similarity known as the unity of biochemistry. This unity is the key to justification of the use of read-across of biodegradability test results.

N-alkyl dipropylene triamines, acetates are salts of positively charged fatty amine derivatives and a negatively loaded acetate ion. Dissolution and dissociation of the salts lead to equilibrium in aqueous solutions so the fatty amine derivative will reach essentially the same state

regardless of the counter ion in the product (present or absent). Counter ions do therefore not influence the biodegradation of the N-alkyl dipropylene triamines. Acetate used as reference compound is degraded within 14 days in ready biodegradability tests. Salts of fatty amine

derivatives with acetic acid are therefore readily biodegradable when the fatty amine derivative is readily biodegradable.

Mineralisation of other fatty amine derivatives has been studied in detail. These studies imply that complete mineralisation of fatty amine derivatives is achieved by consortia of alkyl chain utilizing and hydrophilic moiety degrading microorganisms (van Ginkel 1996). Most surfactant-degrading consortia interact commensalistically through production and release of the hydrophilic part of the molecule by alkyl chain degrading bacteria. Another organism utilizes the hydrophilic moiety released as growth substrate.

The most plausible biodegradation pathway of N-alkyl dipropylene triamine is an attack on the hydrophobic part of the molecule followed by the degradation of dipropylenetriamine. The alkyl chain is degraded through the b-oxidation cycle. In each cycle, the alkyl chain is progressively shortened by two carbons yielding one molecule of acetyl-CoA. The acetyl-CoA generated in b-oxidation enters the TCA cycle, where it is further oxidised to carbon dioxide and water. A single micro-organism can degrade both saturated and unsaturated chains with varying chain lengths. The alkyl chains are therefore completely degraded by micro-organisms with comparable potential. The hydrophilic moiety, dipropylenetriamine is metabolised through ß-alanine, which also feeds into the TCA cycle (Large, 1992). Dipropylene triamine (N-(3-aminopropyl)-1,3-propanediamine) is readily biodegradable (van Ginkel et al, 2010; Rothkopf and bartha, 1984). N-alkyl dipropylene triamines, acetates base on the biodegradation pathways of all moeities, are therefore completely (ultimately) biodegradable.

Triamine Y12D (dodecyldipropylenetriamine) is biodegraded 79% at day 28 in the Closed Bottle test, and should therefore be classified as readily biodegradable (Garttener and van Ginkel, 2003).However, in most standard ready biodegradability tests with N-alkyl dipropylene triamines biodegradation percentages of less than 60% were found at day 28. Use of silica gel resulted in a biodegradation percentage of 75 % for Coco dipropylene triamine(C8-18dipropylene triamine)at day 28 in a Closed Bottle test inoculated with river water (van Ginkel et al, 2009; van Ginkel, 2009). The silica gel prevents inhibition of growth of the competent microorganisms due to toxicity of these surfactants. Based on the broad substrate specificity of microorganisms degrading N-alkyl dipropylene triamines, acetates with respect to the alkyl chain length it is unlikely that the biodegradability of these surfactants differs significantly with varying alkyl chain lengths. Biocidal effects explain negative results obtained in ready biodegradability tests. Closed Bottle tests with silica gel do probably not lead to false negative results and thus to a fair interpretation of the biodegradability. The adequate ready biodegradability test results obtained with two N-alkyl dipropylene triamines and the scientific evidence that consortia of micro-organisms (acetate-, dipropylenetriamine- and alkyl-utilizing) through a joint biodegradation pathway degrade all N alkyl dipropylene triamines lead to the conclusion that all N-alkyl dipropylene triamines are readily biodegradable.

 

References

 

·        NS Battersby, L Kravetz and JP Salanitro (2000) Proceedings 5th World Surfactant Congress. Federchimica,,, 1397–1407

·        ICM Garttener, CG van Ginkel (2003) Biodegradability of triameen Y12D in the Closed Bottle test. CGS-ENV F02026

·        CG van Ginkel (1996) Complete degradation of xenobiotic surfactants by consortia of aerobic microorganisms. Biodegradation 7 151-164

·        CG van Ginkel (2007) Handbook of Cleaning Agents/Decontamination of Surfaces. Eds I Johansson and P Somasundaran, Elsevier Amsterdam TheVolume 2 pp 655-694

·        CG van Ginkel (2009) Evaluation of the biodegradability of Trameen C using the semi-continuous activated sludge (SCAS) and Closed Bottle tests. Doc no 2.3390.236

·        CG van Ginkel (2009) Bidodegradability of cocodipropylene triamine (CAS 91771-18-5) in the Closed Bottle test. Doc. No. 2.390.262

·        AJ Kluyver and HJL Donker (1926) Chemie der Zelle und Gewebe, 13: 134‑190

·        PJ Large (1992) Enzymes and pathways of polyamine breakdown in microorganisms FEMS Microbiol Rev 88 249-262.

·        J Steber and H Berger (1995) Biodegradability of surfactants. Eds DR Karsa and MR Porter Blackie A&P London, England, 134-182

·        GF White (1993) Pesticide Science, 37: 159-166

·        GS Rothkopf and R Bartha (1984) Structure-Biodegradability correlation among xenobiotic industrial amines. JAOCS 61 977-980.