Innovative approaches to nisin production.

Nisin is a bacteriocin produced by Lactococcus lactis that has been approved by the Food Drug Administration for utilization as a GRAS status food additive. Nisin can inhibit spore germination and demonstrates antimicrobial activity against Listeria, Clostridium, Staphylococcus, and Bacillus species. Under some circumstances, it plays an immune modulator role and has a selective cytotoxic effect against cancer cells, although it is notable that the high production cost of nisin-a result of the low nisin production yield of producer strains-is an important factor restricting intensive use. In recent years, production of nisin has been significantly improved through genetic modifications to nisin producer strains and through innovative applications in the fermentation process. Recently, 15,400 IU ml-1 nisin production has been achieved in L. lactis cells following genetic modifications by eliminating the factors that negatively affect nisin biosynthesis or by increasing the cell density of the producing strains in the fermentation medium. In this review, innovative approaches related to cell and fermentation systems aimed at increasing nisin production are discussed and interpreted, with a view to increasing industrial nisin production.