L-tryptophan produced with Escherichia coli CGMCC 7.593

In the current application an authorisation is sought under Article 4(1) for L-tryptophan produced by fermentation with Escherichia Coli CGMCC 7.593, 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 98.5 % (w/w based on dry matter). The feed additive is intended to be added directly to compound feed or through premixtures, complementary feed or water for drinking. However, the Applicant did not propose a minimum or maximum tryptophan content in compound feed or in water for drinking. 

For the identification of L-tryptophan in 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 an enantiomer-specific identification are described. 

For the determination of tryptophan in the feed additive and premixtures the Applicant proposed the ring-trial validated method EN ISO 13904 based on high performance liquid chromatography (HPLC) with fluorescence detection (FLD) which is dedicated for the determination of free tryptophan in commercial products and premixtures and for the determination of free and total tryptophan in compound feed. This method is listed in Regulation (EC) No 152/2009. 

For the determination of tryptophan in compound feed the Applicant proposed the ring-trial validated European Union (EU) method based on HPLC-FLD, which is described in Commission Regulation (EC) No 152/2009. The method is applicable for the determination of free (synthetic and natural) and total (peptide-bound and free) tryptophan in feed and it does not distinguish between the amino acid enantiomers. 

The Applicant did not propose any method for the determination of tryptophan in water for drinking. However, in the frame of the stability studies the Applicant presented experimental data in water for drinking obtained analysing tryptophan with the European Union (EU) method based on HPLC-FLD. 

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, compound feed and water for drinking. 

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, and its further relevant amendments) is not considered necessary.