Purpose: To determine if spoilage organisms have the ability to degrade purified leucocin A and decrease the inhibitory effect against L. monocytogenes.
Methods: A number of spoilage organisms, including Brochothrix thermosphacta, were screened for their ability to degrade leucocin A in vitro. Leucocin A was either partially or fully purified by column chromatography and HPLC. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to confirm the presence of leucocin A. Antimicrobial activity was confirmed by spot-on-lawn assay against Carnobacterium divergens UAL9. To confirm degradation in food, hot dogs with 1 mM leucocin A were co-inoculated with B. thermosphacta or C. divergens and L. monocytogenes, vacuum packaged and stored at 7°C for 2 weeks prior to sampling for antimicrobial activity and peptide degradation via mass spectrometry.
Results: After either partial or complete purification, activity was detected against C. divergens UAL9 and MALDI-TOF confirmed the presence of the leucocin A with a mass of 3930 Da. When partially purified leucocin A was combined with a culture of B. thermosphacta, no activity was detected against C. divergens, but the positive control did provide activity. Similar results were found on hot dogs.
Significance: This research suggested that degradation of bacteriocins by spoilage organisms may be a concern for the application to control the growth of pathogens in food.