Lactococcus lactis, a spherical-shaped, Gram-positive, catalasenegative
lactic acid bacterium, is widely used as a starter culture
in fermented dairy products [1]. As a probiotic microorganism,
L. lactis is known for its diverse host-beneficial properties such as
immune modulatory effects [2], improvement of digestion [3], and
reduction of antibiotic-associated diarrhea [4] in animals. In addition,
L. lactis has been approved to be used alive as the first
genetically modified organism for clinical trials of human diseases
such as inflammatory bowel diseases [5e8].