The food enzyme is a β-galactosidase (β-D-galactoside galactohydrolase; EC 18.104.22.168) produced with the genetically modified Escherichia coli strain NCIMB 30325 by Clasado Ingredients Ltd. The β-galactosidase encoding gene is introduced into the recipient strain of E. coli using a self-replicating plasmid which also contains a gene, which confers resistance to an antibiotic listed as a critically important antimicrobial. This gene was detected in the food enzyme. The absence of viable cells of the production strain in the food enzyme was not demonstrated. The food enzyme is intended to be used only for the production of a mixture of galacto-oligosaccharides (GOS). Genotoxicity tests did not raise a safety concern. Subchronic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level at the highest dose tested of 900 mg total organic solids (TOS)/kg body weight (bw) per day. Similarity of the amino acid sequence to those of known allergens was searched and no match was found. The Panel considered that under the intended conditions of use the risk for allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood is considered low. Given the risk associated with the presence of antibiotic resistance gene in the food enzyme and the lack of data showing the absence of viable cells, the Panel concludes that the use of β-galactosidase produced with the genetically modified E. coli NCIMB 30325 cannot be considered safe.