Julie Fouilloux

The goal of this study was to provide antioxidant and antibacterial properties to different types of fabrics via tannic acid (TA) covalent grafting. To that extent, TA was first methacrylated using glycidylmethacrylate. TA derivatives were characterized using infrared spectroscopy and ¹H NMR to assess the degree of acrylation. Antioxidant and antibacterial properties of TA were preserved after chemical modification. The coating process was studied using infrared spectroscopy (IR), weight gain, and radical scavenging activity (RSA) measurements. To covalently bond TA to raw polypropylene (PP) and PP coated with chitosan, photoinduced grafting was performed. The process was optimized and resulted in fabrics with enough tannic acid to provide strong antioxidant activity, with RSA ranging at 95%. The antibacterial activity was assessed against E. coli and S. aureus, the main strains responsible for nosocomial infections. Results revealed a substantial reduction of bacterial contamination for PP samples coated with chitosan, with stronger activity against E. coli, attributed to hydrophobic repellence. This study highlights the benefits of using tannic acid to obtain antioxidant and antibacterial fabrics.

A straightforward and cost-effective way to coat polypropylene fibers, designed for healthcare textiles, was developed through chitosan crosslinking for antibacterial purposes. As polypropylene is an inert material, the goal was to physically trap the inert fibers through a network of crosslinked chitosan or a quaternized derivative (to enhance the antibacterial action). First, chitosan or its quaternized derivative was physically deposited by impregnation or spraying. Then, chitosan was crosslinked in glutaraldehyde solution followed by its quaternized derivative with a diisocyanate. Coated fabrics were characterized by infrared spectroscopy (IR), weight gain measurements, and scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX). This led us to conclude that spraying provides uniform deposition while maintaining the fabric's porosity. Acidic washing allowed us to prove that chitosan and its quaternized derivative were successfully immobilized on the fabric. Biological assays were conducted against two major strains of bacteria responsible for nosocomial infections: Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). Chitosan-crosslinked samples did not show significant antibacterial activity, but the quaternized derivative allowed a significant decrease in S. aureus colonization. This study presents a simple and scalable process to coat inert fabrics with a polymer containing reactive functions potentially available to graft various additional antimicrobial agents.

A green cross-linking and straightforward method to physically trap inert fibers in a network of chitosan was implemented. The cross-linking reaction involved a biosourced and biocompatible cross-linker [tannic acid (TA)] and mild conditions in water (pH = 8.5, O₂ bubbling, 60 °C, 3 h). The steric hindrance of TA led to a low but effective cross-linking rate leaving parts of primary amines of chitosan available for postmodification such as the grafting of quaternary ammoniums for antibacterial purposes. Fabric's coatings were characterized by scanning electron microscopy coupled with energy-dispersive X-ray, infrared spectroscopy, and weight gain measurements. This allowed the optimization of process conditions. No significant antioxidant activity was observed on fabrics coated with chitosan cross-linked with TA, confirming the low cross-linking rate. This low cross-linking rate allowed grafting of quaternary ammoniums for antibacterial purposes, but it is possible to consider grafting other active molecules. Biological assays were conducted on this coating to assess its antibacterial properties. Reduction of bacterial colonization on both Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), two of the major strains responsible for nosocomial infections, confirmed the potential of the coating for antibacterial purposes. This study displays a simple and ecofriendly process to coat inert fabrics with a chitosan network containing reactive functions (primary amines) available for grafting active molecules for various purposes.

Ion-exchange membranes (IEMs) are increasingly used in dialysis and electrodialysis processes for the extraction, fractionation and concentration of valuable components, as well as reagent-free control of liquid media pH in the food industry. Fouling of IEMs is specific compared to that observed in the case of reverse or direct osmosis, ultrafiltration, microfiltration, and other membrane processes. This specificity is determined by the high concentration of fixed groups in IEMs, as well as by the phenomena inherent only in electromembrane processes, i.e., induced by an electric field. This review analyzes modern scientific publications on the effect of foulants (mainly typical for the dairy, wine and fruit juice industries) on the structural, transport, mass transfer, and electrochemical characteristics of cation-exchange and anion-exchange membranes. The relationship between the nature of the foulant and the structure, physicochemical, transport properties and behavior of ion-exchange membranes in an electric field is analyzed using experimental data (ion exchange capacity, water content, conductivity, diffusion permeability, limiting current density, water splitting, electroconvection, etc.) and modern mathematical models. The implications of traditional chemical cleaning are taken into account in this analysis and modern non-destructive membrane cleaning methods are discussed. Finally, challenges for the near future were identified.

Electrodialysis (ED) was first established for water desalination and is still highly recommended in this field for its high water recovery, long lifetime and acceptable electricity consumption. Today, thanks to technological progress in ED processes and the emergence of new ion-exchange membranes (IEMs), ED has been extended to many other applications in the food industry. This expansion of uses has also generated several problems such as IEMs’ lifetime limitation due to different ageing phenomena (because of organic and/or mineral compounds). The current commercial IEMs show excellent performance in ED processes; however, organic foulants such as proteins, surfactants, polyphenols or other natural organic matters can adhere on their surface (especially when using anion-exchange membranes: AEMs) forming a colloid layer or can infiltrate the membrane matrix, which leads to the increase in electrical resistance, resulting in higher energy consumption, lower water recovery, loss of membrane permselectivity and current efficiency as well as lifetime limitation. If these aspects are not sufficiently controlled and mastered, the use and the efficiency of ED processes will be limited since, it will no longer be competitive or profitable compared to other separation methods. In this work we reviewed a significant amount of recent scientific publications, research and reviews studying the phenomena of IEM fouling during the ED process in food industry with a special focus on the last decade. We first classified the different types of fouling according to the most commonly used classifications. Then, the fouling effects, the characterization methods and techniques as well as the different fouling mechanisms and interactions as well as their influence on IEM matrix and fixed groups were presented, analyzed, discussed and illustrated.