In Vitro Assays to Evaluate the Effects of Mango By-Product Polyphenolic Extracts Against Bacterial Species Associated with Food Spoilage and Human Diseases and the Relationship with Their Genotypes

Mangifera indica L. by-products obtained by three extraction methods from three cultivars (Keitt, Sensation and Gomera-3) were tested for their antibacterial properties against 20 bacterial species. These species were selected based on their relevance to winemaking processes (Acetobacter, Gluconobacter and Gluconacetobacter), fermented meat products (Staphylococcus) and human diseases (Pseudomonas, Escherichia, Shigella and Klebsiella). All mango by-product extracts showed antimicrobial activity in agar diffusion and broth microdilution experiments. However, differences in antimicrobial activity against acetic acid bacteria were detected between the peel extracts obtained from the two extraction processes. Furthermore, a wide range of minimum inhibitory concentration (MIC) data were found; Staphylococcus spp. (10 species) showed MICs between 1.0–240 mgGAE/mL and Acetobacter spp. (4 species) showed MICs between 1.7 and 200 mgGAE/mL. The most sensitive bacteria belonged to the staphylococcal species (MIC: 1 mgGAE/mL) and the most resistant was Gluconacetobacter saccharivorans (MIC > 400 mgGAE/mL). In general, there was no significant correlation between the phenolic compounds identified and the MIC values. The minimum bactericidal concentration (MBC) revealed that the mango extracts had a bacteriostatic effect. A simple and reliable method for the determination of MIC and MBC in microdilution assays with acetic acid bacteria was described. These results highlight the antibacterial properties of mango by-products against species associated with food spoilage microorganisms and human diseases.