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L-tryptophan produced by fermentation with Escherichia coli CGMCC 7.460



Publication date
11 September 2023 (Last updated on: 12 December 2023)
Joint Research Centre


In the current application an authorisation is sought under Article 4(1) for L-tryptophan produced by fermentation with Escherichia coli CGMCC 7.460, under the category/functional group 3 (c) 'nutritional additives'/'amino acids, their salts and analogues', according to Annex I of Regulation (EC) No 1831/2003. The authorisation is sought for all animal species.
According to the Applicant, the feed additive contains L-tryptophan with a minimum purity of 98 % (w/w). The feed additive is intended to be added directly to compound feed or through premixtures. The Applicant did not propose a minimum or maximum L-tryptophan content in compound feed.
For the determination of tryptophan in the feed additive and premixtures the Applicant proposed the ring-trial validated EN ISO 17180 method, however the scope of the proposed method does not include the target amino acid (tryptophan). Furthermore, the EURL is aware of another ring-trial validated EN ISO 13904 method based on high performance liquid chromatography with fluorescence detection (HPLC-FLD) which is specifically dedicated for the determination of free tryptophan in commercial products and premixtures (containing more than 2 % (w/w) of tryptophan) and for the determination of free and total tryptophan in compound feed.
For the determination of tryptophan in compound feed the Applicant submitted a ring-trial validated European Union (EU) method, applicable for the determination of the free (synthetic and natural) and total (peptide-bound and free) amino acid using an HPLC method with fluorescence detection (FLD). The method does not distinguish between the amino acid enantiomers.
Based on the performance characteristics available, the EURL recommends for official control the above mentioned two ring-trial validated methods based on HPLC-FLD to determine tryptophan in the feed additive, premixtures and/or compound feed.
In addition, for the identification of the feed additive the EURL recommends the "L-tryptophan monograph" of the Food Chemical Codex (FCC), where different tests including one based on optical rotation for enantiomer-specific identification are described.
Further testing or validation of the methods to be performed through the consortium of National Reference Laboratories as specified by Article 10 (Commission Regulation (EC) No 378/2005, as last amended by Regulation (EU) 2015/1761) is not considered necessary.