Developing applications for lactococcal bacteriocins

While much of the applied research carried out to date with bacteriocins ha s concerned nisin, lactococci produce other bacteriocins with economic pote ntial. An example is the two component bacteriocin lacticin 3147, which is active over a wide pH range and has a broad spectrum of activity against Gr am-positive bacteria. Since the genetic determinants for lacticin 3147 are encoded on a large self-transmissible plasmid, the bacteriocin genes may be conveniently transferred to different lactococcal starters. The resulting food-grade strains can then be used to make a significant impact on the saf ety and quality of a variety of fermented foods, through the inhibition of undesirable microflora. The bacteriocin is heat stable so it can also be us ed as an ingredient in a powdered form such as a spray-dried fermentate. Gi ven the observation that lacticin 3147 is effective at physiological pH, th ere is also considerable potential for biomedical applications. Field trial s have demonstrated its efficacy in the prevention of mastitis infections i n dairy cows. In contrast to lacticin 3147, the lactococcin bacteriocins A, B and M have a narrow spectrum of activity limited to lactococci. Strains which produce these inhibitors can be exploited in the acceleration of chee se ripening by assisting the premature lysis of starter cultures.