Grapefruit and lemon pectin obtained from the respective waste citrus peels via hydrodynamic cavitation in water only are powerful, broad-scope antimicrobial alternatives to antibiotics against Gram-negative and -positive pathogens. Dubbed IntegroPectin, these pectic polymers functionalized with citrus flavonoids and terpenes show superior antimicrobial activity when compared to commercial citrus pectin. Similarly to commercial pectin, lemon IntegroPectin determined ca. 3 log reduction of Staphylococcus aureus cells, while an enhanced activity of commercial citrus pectin was detected in the case of Pseudomonas aeruginosa cells with a minimal bactericidal concentration (MBC) of 15 mg mL-1. Although grapefruit and lemon IntegroPectin share equal MBC in the case of P. aeruginosa cells, grapefruit IntegroPectin shows boosted activity upon exposure of S. aureus cells with a 40 mg mL-1 biopolymer concentration being sufficient to achieve complete killing of the bacterial cells. Insight on the mechanism of action of these biocompatible antimicrobials and their effect on bacterial cells, at the morphological level, were obtained indirectly through Fourier Transform Infrared spectroscopy and directly through scanning electron microscopy. In the era of antimicrobial resistance, these results are of great societal and sanitary relevance as they open new avenues to develop innovative antimicrobials for the treatment of polymicrobial infections unlikely to develop drug resistance.

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