Control of Clostridium botulinum by bacteriocins and characterization of nisin action during spore-to-cell transformation

Bacteriocins from lactic acid bacteria (LAB) can serve as a natural preservative to control foodborne pathogens in minimally processed foods. For effective biocontrol, type of bacteriocin, level of application, and stage of application against target pathogen, such as Clostridium botulinum in this study, are the some of the factors need to be optimized. The purposes of this study were; (1) to determine the most effective bacteriocin against C. botulinum, (2) to verify the effect of bacteriocin in a food system, (3) to monitor the germination of C. botulinum spores after heat treatment and in the presence of bacteriocin, and (4) to define the function of bacteriocin at different stages of spore-to cell transformation.; Culture supernatant of a nisin producing bacterium was more effective against C. botulinum than that of pediocin PO2 or lacidin A producer. Commercial nisin (50–250 μg/g potatoes), was a very effective bactericidal agent against C. botulinum in roasted potatoes packaged under modified atmosphere (100% N₂ or 20% CO₂ : 80% N₂).; Nisin was added at various stages of spore-to-vegetative cell transformation and changes in sensitivity to the bacteriocin were observed. Nisin was bactericidal against vegetative cells, but was sporostatic against spores of C. botulinum under the same concentration. The degree of bactericidal and sporostatic action of nisin was dependent on the concentration of nisin used. Nisin activated spores during heat treatment, and the effect of nisin on the activation stage was greater under low pH conditions. Nisin, on the other hand, delayed germination of activated spores when it was added after heat treatment. In addition, outgrowth of germinated spores was prevented for 20 days when nisin was added after the germination stage.; Findings from this study indicate that LAB bacteriocins may be effective biocontrol agents against C. botulinum in ready-to-eat refrigerated foods such as roasted potatoes. In addition, it is suggested that the bacteriocin application time is important for the effective control of spores during the heating process of foods. It may be possible to apply nisin at the stage of processing that coincides with the most sensitive stage of spore transformation.