Abstract
Lactococcus lactis IL1403 is a Gram‐positive bacterium of great biotechnological interest for food grade applications. Its use is however hampered by the difficulty to efficiently transform this strain. We here describe a detailed, optimized electrotransformation protocol which yields a transformation efficiency of 106 cfu/μg of DNA with the two E. coli Gram‐positive shuttle vectors pC3 and pVA838. The utility of the protocol was demonstrated by the generation of single‐ and double‐knock‐out mutants by homologous recombination.