Combinatorial effects of bovicin HC5 and epsilon-polylysine against Alicyclobacillus acidoterrestris in orange juice

Abstract

BACKGROUNDAlicyclobacillus acidoterrestris, a spoilage-causing bacterium in fruit juices remains a concern post-pasteurization, making antimicrobial peptides (AMPs) a promising alternative for its control. Bovicin HC5 and epsilon-polylysine were tested for their antimicrobial efficacy against A. acidoterrestris DSMZ 2498 in both AAM broth and orange juice. This study determined the minimum inhibitory concentrations (MICs) and minimum bactericidal concentration (MBC) for epsilon-polylysine and bovicin HC5 against 106 CFU/mL vegetative cells and activated endospores of A. acidoterrestris DSMZ 2498. Their combined effect was also assessed using the checkerboard method. Viable cell counts were measured after 48 hours at 45 {degrees}C, and thermal resistance of endospores was examined after exposure to both AMPs as well as their combinations, by determining the exposure time (in minutes) required to kill 90 % of the initial population at 95 {degrees}C. Finally, atomic force microscopy (AFM) was employed to investigate their impact on the cell structure and morphology of A. acidoterrestris. RESULTSBovicin HC5 and epsilon-polylysine demonstrated antibacterial effects against A. acidoterrestris DSMZ 2498 inoculated in orange juice. The combination of both AMPs exhibited an additive effect, significantly reducing the number of viable cells after a 48-hour incubation at 45 {degrees}C and a 90 % reduction in thermal resistance at 95 {degrees}C. Atomic force microscopy (AFM) revealed structural and morphological changes in A. acidoterrestris cells treated by these AMPs. CONCLUSIONSThe findings in this study revealed the potential application of bovicin HC5 and epsilon-polylysineas natural preservatives in hurdle technologies to control A. acidoterrestris and improve the microbiological stability and safety of fruit juices.