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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

A study dating back to 1981 is available in which the biodegradability of isoleucine was tested according to the Offhaus method. In this study 19% degradation was found after 5 days, and the COD/BOD5 ratio was determined to be 5.3. These results indicate that L-isoleucine will undergo rapid biological degradation.

The inhibition study showed negligible and decreasing disturbance of degradation of 1%.

Based on the observed respiration activity, the degradation should take place undisturbed, even at higher concentrations and especially after certain adaptation.

A second study on the biodegradability of L-isoleucine is available. In this study dating back to 1969, the ability of activated sludges from 3 municipal waste treatment plants to oxidise amino acids was investigared. The activated sludge (concentration 2500 mg/L) was exposed to L-isoleucine at a concentration of 500 mg/L. The biodegradation was assessed during 24h by measurement of the O2 consumption using Warburg flasks. The average biodegradation (as % of theoretical oxygen demand) over the 3 activated sludges was 14.8 %.

As the results available from the two biodegradation studies on L-isoleucine are not directly comparable to the CLP criteria for biodegradation, additionally a read-across to L-valine was considered to further support the conclusion on this endpoint.

Read-across to the test results available for structural analogue L-valine is deemed justified based on a comparison of the main factors driving environmental toxicity: pH, water solubility, log Kow and chemical reactivity (functional groups).

- both are essential amino acids that are in the zwitterion state at physiological pH

- the chemical structure differs only in that L-isoleucine has one extra methylene group in the aliphatic side chain

- the pKa values of the α-COOH group is very similar: 2.36 for ILE, 2.32 for VAL

- the pKa values of the α-NH2 group is very similar: 9.60 for ILE, 9.62 for VAL

- the substances both have a high water solubility: 34 - 41 g/L for ILE, 58 g/L for VAL

- the substances both have a low log Kow value: -1.72 for ILE (experimental value obtained from EpiSuite's WSKOW model database), -2.08 for VAL (calculated by EpiWin QSAR)

As the chemical structure and reactivity, and the water solubility, low Kow and pKa values of L-isoleucine and L-valine are almost identical, it can be concluded that read-across for aquatic toxicity information between those 2 substances is acceptable.

The tests available for L-valine are carried out according to OECD guidelines and reveal that the substance is readily biodegradable within 28 days. As a consequence, it can be concluded that L-isoleucine will also be readily biodegradable.