Preventing microbe colonization on avocado (Persea nubigena var. guatemalensis) through metabiotic treatment, a promising postharvest safety improvement

IntroductionLactic acid bacteria (LAB) produce various metabolites (i.e. metabiotics) with inhibitory capacity towards harmful foodborne pathogens.MethodsThis study aimed to design several antimicrobial formulations based on metabiotics obtained from different native LAB species (Lactobacillus pentosus UTNGt5, Lactococcus lactis UTNGt28, and Weissella cibaria UTNGt21O) and to detect the possible mode of action towards two multidrug resistant Staphylococcus spp. strains isolated from avocado (Persea nubigena var. guatemalensis) fruits. Additionally, the formulation with the highest inhibitory activity was tested ex vitro on avocados at the immature (firm) ripeness stage to evaluate their effect on microorganisms’ growth and fruit quality attributes post-harvest.Results and discussionOut of the top five formulations showing the highest bactericidal effect in vitro at their minimum inhibitory concentration (1 x MIC) on both Staphylococcus spp. targets one candidate annotated P11 (consisting of UTNGt21O and UTNGt28; 1:3, v/v) was selected. Co-cultivation of Staphylococcus strains with P11 formulation results in cell viability reduction by 98%, by impairing the integrity of the cell membrane inducing cytoplasm molecule content leakage, protein profile changes, and finally bacterial death. Even though the total coliforms, Staphylococcus spp., Enterobacter spp., molds, and yeasts counts were not fully eliminated by day 13 of storage, a statistically significant reduction (p