Citrus Water-Extracts Obtained by Microwave-Assisted and Conventional Methods: Antimicrobial and Antibiofilm Activity Evaluation.

Citrus pomace is a huge agro-food industrial waste mostly composed of peels. Owing to its high content of compounds beneficial to humans (e.g., flavonoids, phenol-like acids, and terpenoids), citrus waste is increasingly used to produce valuable supplements, fragrance, or antimicrobials. Sustainable and efficient extraction strategies by solvent-free techniques for environmentally-friendly good practices should be desirable. In this work, both conventional extraction methods using hot water (HWE) and microwave-assisted extraction (MAE) were used to obtain water extracts. The antimicrobial and antibiofilm activity of water extracts of three citrus peels (orange, lemon, and citron) against ten different sanitary relevant bacteria were evaluated. Even though no extract fully inhibited the growth of the target bacteria, these latter (mostly pseudomonads) showed a significant reduction in biofilm biomass. The most active extracts were obtained from orange and lemon peel by using MAE at 100 °C for 8 min. These results showed that citrus peel water infusions by MAE may reduce biofilm formation possibly enhancing the susceptibility of sanitary-related bacteria to disinfection procedures