Use of Bacteriocins to Improve Cheese Quality and Safety

Abstract

The objectives of this project were to generate, characterise and exploit a range of novel bacteriocin producing starter cultures to improve both the safety and the quality of fermented dairy foods.

The main conclusions were as follows:

Lacticin 3147 is a broad spectrum bacteriocin which inhibits a wide range of Gram-positive bacteria including lactobacilli, clostridia and Listeria. The bacteriocin has been purified by chromatographic procedures and has been shown to be composed of two peptides, both of which are required for biological activity. The mechanism of action of lacticin 3147 has been elucidated. The entire plasmid encoding lacticin 3147 has been sequenced and the bacteriocin in distinct from any previously characterised lactococcal bacteriocin. The Food Grade introduction of the bacteriocin genes into cheese starters was carried out. Lacticin 3147 producing starters have been used to control the pathogen Listeria monocytogenes on the surface of mould ripened cheese. Lacticin 3147 producing starters have been used to control the non-starter lactic acid bacteria complement in Cheddar cheese during the ripening process. A novel starter system using a bacteriocin (lactococcin)- producing adjunct has been designed which gives increased cell lysis during Cheddar cheese manufacture while ensuring that efficient acid production is not compromised. In summary these studies have found that naturally occurring antimicrobials such as bacteriocins have a wide range of applications in the food industry for improving both the quality and safety of fermented dairy products.