2020年2月24日，据欧盟食品安全局（EFSA）消息，应欧盟委员会要求，欧盟动物饲料添加剂和产品（FEEDAP）研究小组就一种L-色氨酸（L-tryptophan）作为所有动物品种的饲料和饮用水的营养添加剂发表科学意见。

　　

　　

　　据了解，这种L-色氨酸是由转基因大肠杆菌菌株CGMCC 7.267发酵产生。经过评估，小组认为，这种添加剂对消费者和环境是安全的。由于缺乏数据，专家小组无法得出添加剂对皮肤和眼睛有刺激性或对皮肤有致敏性的结论。部分原文报道如下：

　　

　　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.