Application of the broad-spectrum bacteriocin enterocin AS-48 to inhibit Bacillus coagulans in canned fruit and vegetable foods

The enterococcal bacteriocin (enterocin) AS-48 is a broad-spectrum cyclic peptide. Enterocin AS-48 was tested against Bacillus coagulans in three vegetable canned foods: tomato paste (pH 4.64), syrup from canned peaches (pH 3.97), and juice from canned pineapple (pH 3.65). When vegetative cells of B. coagulans CECT (Spanish Type Culture Collection) 12 were inoculated in tomato paste supplemented with 6 μg/ml AS-48 and stored at different temperatures, viable cell counts were reduced by approximately 2.37 (4 °C), 4.3 (22 °C) and 3.0 (37 °C) log units within 24 h storage. After 15-days storage, no viable cells were detected in any sample. Strain B. coagulans CECT 561 showed a poor survival in tomato paste, but surviving cells were also killed by AS-48. The bacteriocin was also very active against B. coagulans CECT 12 vegetative cells in juice from canned pineapple stored at 22 °C, and slightly less active in syrup from canned peaches. In food samples supplemented with 1.5% lactic acid, enterocin AS-48 (6 μg/ml) rapidly reduced viable counts of vegetative cells below detection limits within 24 h storage. Addition of glucose and sucrose (10% and 20%) significantly increased bacteriocin activity against vegetative cells of B. coagulans CECT 12. Enterocin AS-48 had no significant effect on B. coagulans CECT 12 spores. However, the combined application of AS-48 and heat (80–95 °C for 5 min) significantly increased the effect of thermal treatments on spores.