Bacteriocins are bactericidal proteins produced by bacteria. The lactic acid bacteria (LAB) are generally regarded as safe microorganisms and thus bacteriocins produced by them can be used to control the growth of spoilage and pathogenic microorganisms in food products during their production and storage. Nisin, a bacteriocin produced by Lactococcus lactis, is approved by the U.S. Food and Drug Administration as a food preservative, and is commercially available in a purified powdered form.

Our long-range goal is to use bacteriocins from LAB as biopreservatives in food products. The objective of the study was to determine the effectiveness of nisin in controlling the growth of E. sakazakii. Sixty-nine strains of E. sakazakii were screened for sensitivity to nisin (500 IU/ml) using the agar-well-diffusion method. Inhibition zones in the confluent growth of E. sakazakii were measured. Micrococcus luteus was used as a positive control. Five strains of E. sakazakii were identified as being sensitive to nisin.

Our current investigation deals with the effectiveness of nisin in powdered infant formula challenged with select strains of E. sakazakii.