Use of Lemon Peel Extract as Antimicrobial Supported on Eco-friendly Polyvinyl Alcohol/Polydimethylsiloxane Sponges

Abstract

Prevention of biofilm formation is essential for water treatment and industrial processes. Although there are different agents capable to inhibit bacteria proliferation, the use of natural, and in particular obtained from waste, is highly desirable in the green chemistry paradigm. The objective of this work is to obtain eco-friendly sponges that can be used to prevent biofilm formation by the action of a natural antimicrobial agent. Polyvinylalcohol (PVA) sponges were prepared by freeze-drying using malic and citric acid as green crosslinkers. Aqueous lemon peel extract was used as antimicrobial agent for PVA dissolution. Some sponges were coated with polydimethylsiloxane (PDMS) in order to increase the stability in aqueous media and provide flexibility. Sponges were characterized by ATR-FTIR, TGA, DSC, nitrogen adsorption isotherms and SEM. Water contact angles and swelling degrees of all the prepared sponges were measured. Kinetic release measurements of the yellow pigment, present in the lemon extract, were analyzed under different pH and ionic strength conditions. The obtained sponges were incubated for 24 h at room temperature with Pseudomonas protegens. The surface of the sponges after incubation was characterized by Raman spectroscopy and observed at the microscope to determine the presence of biofilm. UV–Vis spectrophotometry with crystal violet were employed to quantify biofilm formation and optical density at 600 nm was measured in the liquid media to determine the bacterial cell concentration. Sponges show high mechanical and chemical resistance and incorporation of lemon extract prevent biofilm formation as high as 70% with respect to sponges without the extract.