The sensitivity of nisin to proteolytical breakdown in intestinal environment was studied in an ex vivo model using jejunal chyme from fistulated dogs. Sixty six percentage of the added nisin retained induction activity after 30 min incubation in jejunal chyme, indicating that nisin has potential to be used as an inducing agent in in situ delivery systems of bioactive peptides and proteins by genetically modified bacteria in the intestine.