L-cystine produced by the fermentation with Escherichia coli K12 DSM 34232

In the current application an authorisation is sought under Article 4(1) for L-cystine produced by the fermentation with Escherichia coli K12 DSM 34232, under the category/functional group 3(c) “nutritional additives”/“amino acids, their salts and analogues”, and 2(b) “sensory additives”/”flavouring compounds” 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 a minimum of L-cystine content of 98.0 % (w/w, based on dry matter).
The feed additive is intended to be added to feed through premixtures or directly into compound feed (including complimentary feed) and water for drinking. The current authorisation specifies only the maximum limit of 25 mg L-cystine / kg compound feed when used as a sensory additive / flavouring compound.
For the determination of cystine in the feed additive and premixtures the Applicant proposed the EN ISO 17180 method based on ion-exchange chromatography (IEC) coupled to post-column derivatisation and optical (visible – VIS or fluorescence – FLD) detection. The EURL recommended the latter method for the determination of cystine in the feed additive and premixtures in the frame of the previous dossier for very similar product and considers that these recommendations are valid also in frame of the current evaluation.
For the determination of cystine in premixtures and compound feed the Applicant proposed the ring-trial validated European Union (EU) method, based on ion-exchange chromatography (IEC) coupled to post-column derivatisation and optical (VIS) detection, which is dedicated for the determination of free and of total (peptide bound and free) amino acids (cystine plus cysteine) in premixtures and compound feed. The method is described in Commission Regulation (EC) No 152/2009.
The EU method was further ring-trial validated for amino acids (among them cystine plus cysteine), resulting in the equivalent EN ISO 13903 method, which is listed in the above-mentioned Regulation. The following performance characteristics from the two ring-trial validation studies were reported for the determination of total cystine (plus cysteine) in animal feedingstuffs: a relative standard deviation for repeatability (RSD_r) ranging from 1.7 to 4.6 % and a relative standard deviation for reproducibility ranging from 8.8 to 19.0 %.
For the determination of cystine in water the Applicant proposed the EN ISO 13903 method, which is equivalent to the above-mentioned EU method and presented acceptable applicability data, thus demonstrating the fitness-for-purpose of the methods. Additionally, for the identification of L-cystine in the feed additive the Applicant proposed “L-cystine monograph” of the Food Chemical Codex (FCC).
Based on the performance characteristics and available data the EURL recommends for official control: (i) the “L-cystine monograph” of the Food Chemical Codex (FCC) for the identification of L-cystine in the feed additive; (ii) the EN ISO 17180 method based on ion-exchange chromatography coupled with optical (visible or fluorescence) (IEC-VIS/FLD) detection, for the determination of cystine in the feed additive and premixtures; (iii) the ring-trial validated EU method (or equivalent EN ISO 13903 method) based on IEC-VIS for the determination of cystine in premixtures and compound feed (for compound feed only when used as nutritional additives); and iv) the EU method (or equivalent EN ISO 13903 method) based on IEC-VIS for the determination of cystine in water.
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.