Safety and efficacy of l-tryptophan produced by fermentation using Escherichia coli CGMCC 7.267 for all animal species

EFSA FEEDAP Panel, Lieve Herman

Research output: Contribution to journalA2: International peer reviewed article (not A1-type)peer-review


Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on l-tryptophan produced by fermentation with a genetically modified strain of Escherichia coli CGMCC 7.267 when used as a nutritional additive in feed and water for drinking for all animal species and categories. The production strain E. coli CGMCC 7.267 is safe for the production of l-tryptophan. No viable cells or DNA of the production strain were detected in the additive under assessment. The use of l-tryptophan produced using E. coli CGMCC 7.267 in supplementing feed to compensate for tryptophan deficiency in feedingstuffs is safe for non-ruminant target species. However, excess doses would create amino acid imbalances with negative consequences on animal performance. The use of unprotected l-tryptophan in feed poses safety concerns for ruminants. The use of l-tryptophan produced by fermentation with E. coli CGMCC 7.267 in animal nutrition is considered safe for the consumers and for the environment. The endotoxin activity in the product and its dusting potential indicate an inhalation risk for the user. In the absence of data, the FEEDAP Panel cannot conclude on the potential of the additive to be irritant to skin and eyes or to be a skin sensitiser. The additive l-tryptophan produced using E. coli CGMCC 7.267 is regarded as an effective source of the amino acid l-tryptophan. In order to be as efficacious in ruminants as in non-ruminants, it should be protected from ruminal degradation.
Original languageEnglish
JournalEFSA Journal
Issue number2
Pages (from-to)e06013
Number of pages17
Publication statusPublished - Feb-2020


  • Escherichia coli
  • L-tryptophan
  • amino acid
  • efficacy
  • nutritional additive
  • safety

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