Antimicrobial Activity and Phytochemical Profiling of Natural Plant Extracts for Biological Control of Wash Water in the Agri-Food Industry

Water used in cleaning processes within the agri-food industry can be a vector for post-harvest contaminants, thus contributing to cross-contamination. The contamination risk is increased when water is not replaced between batches or when disinfection protocols are insufficient. Given the increasing focus in recent years on the potential of natural, non-invasive plant extracts to combat a variety of pathogens, including multidrug-resistant bacteria, environmental strains, and clinical isolates, this study aimed to evaluate the antibacterial activity of selected water-ethanol plant extracts against six opportunistic pathogens isolated from wash water in the agri-food industry, along with chromatographic analyses of the selected extracts. Plant extracts were obtained from the fruits, leaves, shoots, roots, and bark of 13 species. Antibacterial activity was assessed using the well diffusion method. The results indicated that antimicrobial activity was exhibited by six extracts: Tilia cordata Mill., Camellia sinensis, Quercus robur L., Betula pendula Roth, Rubus idaeus L., and Salix alba L. The extracts showed strain-dependent antimicrobial activity, with C. sinensis and R. idaeus up to 4.0 mm and 8.0 mm inhibition zones, respectively. P. aeruginosa and E. faecalis were the most susceptible strains, demonstrating the largest inhibition zones. In contrast, P. vulgaris and K. oxytoca were more resistant. The efficacy of the most active extracts can be linked to the presence of phytochemicals identified via GC-MS, including epicatechin, shikimic acid, quinic acid, gallic acid, and caffeine. These metabolites are known to interfere with bacterial cell structures and metabolic pathways. These studies may serve as a preliminary step toward the development of non-invasive water treatment methods for wash water.