A quantitative method for assessing bacteriocins and other food antimicrobials by automated turbidometry

Automated turbidometry was used in assessing the antimicrobial efficacy of bacteriocin-like inhibitors produced by Pediococcus damnosus and Pediococcus pentosaceus. Four bacterial strains, i.e., Pseudomonas aeruginosa, Pseudomonas fragi, Salmonella enteritidis and Salmonella infantis were used as the test organisms. The growth of the test organisms was kinetically monitored throughout the incubation period and various growth curve parameters were used as quantitative indicators of growth inhibition. The results obtained in this study showed that a kinetic method based on automated turbidometry provides a sophisticated tool for the determination of bacteriocin activity. A number of growth curve parameters were applicable for the quantification of inhibitory effects. Regression analysis showed that the linear relationship between the level values and the log CFU counts was in most cases highly significant. However, the area value after 24 h appeared to describe most effectively the overall inhibitory effects since all the other growth curve parameters were simple end-point values giving information solely at a single point of time. Futhermore, the area reduction rate shown by the subsequent serial dilutions of the antimicrobials tested appeared to provide additional data on their antibacterial potency.