Interference in the production of bacterial virulence factors by olive oil processing waste

The reuse of agricultural waste is essential to mitigate environmental pollution problems. Consequently, this work focused on the valorization of the most extensive olive processing residue, alperujo, in terms of its ability to interfere with the virulence processes of Pseudomonas aeruginosa and Staphylococcus aureus contaminating food and reference strains. The activity of alperujo extracts of different polarities on virulence factors producing bacteria, and its relationship with antioxidant capacity and polyphenolic content was comparatively evaluated. The results indicated that the polar extracts significantly reduced the biofilm formed by both bacteria. They were also able to act against a previously formed biofilm by reducing its biomass and the cells’ metabolism. Ethanolic extracts, rich in polyphenolic compounds, exhibited antioxidant capacity and Quorum sensing (QS) inhibitory activity against Chromobacterium violaceum. Additionally, they limited the spread of P. aeruginosa by restricting swarming and swimming movements. They also interfere in other QS controlled phenotypes like elastase and pyocyanin. The antipathogenic ability of the polar extracts could be mainly due to the synergistic effect of several phenolic compounds identified by LC–MS/MS analysis, such as luteolin, vanillic acid hexoside, oleuropein and derivates, quinic acid, apigenin, among others. As a result, this study contributes to the developing of sustainable strategies to revalorize a polluting waste into a value-added byproduct that could be used in the food and sanitary industries.