Determination of the effect of the bacteriocin enterocin AS-48 on the microbial loads and bacterial diversity of blueberries

Fresh fruits have been involved in transmission of foodborne pathogens. In the present work, five different batches of blueberries were used. One aliquot from each batch was washed with sterile saline solution (SSS) and the other one with a solution of the circular bacteriocin enterocin AS-48 in SSS. Then, the surface microbiota of controls and bacteriocin-treated samples was recovered and used for microbiota analyses, both using viable counts and high-throughput amplicon sequencing. Total aerobic mesophilic loads ranged from 2.70 to 4.09 log CFU/g in most of the samples. Only two samples yielded detectable viable counts on selective media (Enterobacteriaceae, presumptive Salmonella and coliforms), with values ranging from 2.84 to 3.81 log CFU/g. The bacteriocin treatment reduced viable cell counts of total aerobic mesophiles to a range of 1.40–1.88 log CFU/g. No viable cells were detected on selective media. Amplicon sequencing indicated large batch-to-batch variations in the surface microbiota of blueberries and also an effect of the bacteriocin treatment on microbiota composition.