Antimicrobial activity of grape, apple and pitahaya residue extracts after carbohydrase treatment against food-related bacteria

In this study, antimicrobial, anti-quorum sensing and anti-biofilm forming activities of phenolic-enriched extracts produced by enzyme-assisted extraction from oven-dried and lyophilized black grape (Vitis vinifera x (Vitis labrusca x Vitis riparia)), apple (Malus domestica cv. Jonagold) and yellow pitahaya (Hylocereus megalanthus) residues were investigated. Both disk-diffusion and minimal inhibitory concentration (MIC) assays showed increased antimicrobial capacity for many extracts after the carbohydrase treatments. The lowest MIC (12.5 mg/mL) was found for black grape samples against Bacillus cereus and Bacillus subtilis, and for apple and pitahaya samples against Pseudomonas putida. The percent quorum sensing inhibition effect on Chromobacterium violaceum has varied between 9 and 36%, 15 and 24% and 6 and 23% for black grape, apple and pitahaya extracts, respectively, depending on the enzyme treatment. Pseudomonas aeruginosa, P. putida and Staphylococcus aureus biofilms were the most sensitive to the extracts, while the Salmonella enterica, Listeria monocytogenes and Escherichia coli biofilms were modulated by certain enzyme-free and treated samples. The extracts can be good candidates for the development of natural preservatives