National Institute of Research and Physico and Chemical Analysis

Amara C., El Mahdi A., Medimagh R., Khwaldia K.

Cellulose is one of the most interesting bioresources owing to its abundance, renewability, and biodegradability. Nanocellulose (NC), which can be isolated from natural cellulosic sources or synthesized by bacteria, has gained much research focus in recent years thanks to its non toxicity, recyclability, biodegradability, and reinforcing capability. The outstanding physical and mechanical properties of NC including high elastic modulus, high surface area, high strength, and high gas barrier properties have prompted its use in biomedical, cosmetic, electronics, and food packaging industries. In this review, we focus on NC sources, extraction methods, and use for the development of sustainable packaging materials. The processing methods of NC-based composites films, the effect of NC incorporation on the properties of packaging films, and health-related issues are discussed.

Mazouz Z., Mokni M., Fourati N., Zerrouki C., Barbault F., Seydou M., Kalfat R., Yaakoubi N., Omezzine A., Bouslema A., Othmane A.

Rapid and accurate detection of proteins in biological fluids is increasingly required in the biomedical environment. Actually, it is performed with conventional techniques, which are generally run by robotized platforms at centralized laboratories. In this work, molecular dynamics calculations and an experimental procedure were conducted to set up electrochemical sensors based on polypyrrol (PPy) molecular imprinted polymers (MIP) for proteins detection. Here, prostate-specific antigen (PSA) was selected as a template model. Computational calculations indicate that for any PPy conformation and any amino-acid location in the protein, PSA molecules remain strongly inserted in the PPy polymer without biological alterations. One from possible orientations, appeared to be most probable as it presents the lowest absorption energy (-363 kcal mol-1) and largest contact area (4034.1 Å2). The device was then elaborated by in situ electropolymerization of PPy films. MIP's thickness and extraction duration were optimized by chronoamperometry. Square wave voltammetry technique was investigated for PSA detection in standard solution in the concentration range of 3x10 -8 ng.ml-1- 300 ng ml-1. According to the Hill equation, the equilibrium dissociation constant Kdbetween PSA and its imprint was estimated at Kd = (1.02 ± 0.54) × 10-14 M, confirming the strong binding between the designed MIP and the protein as predicted by the computational study. PSA concentration values directly measured in 35 human serum samples were found closely correlated to those measured by the ELISA technique. The promising fast and low-cost sensor might be used successfully for proteins detection at low concentrations with high selectivity and reproducibility.

Tahari N., de Hoyos-Martinez P.L., Izaguirre N., Houwaida N., Abderrabba M., Ayadi S., Labidi J.

A series of novel chitosan/tannin/montmorillonite (Cs/Tn/MMT) films were synthesised by loading different (from 0.2 to 0.5 wt%) and MMT (from 0.5 to 1.5 wt%) ratios, to be used as promising low-cost biosorbents for methyl orange (MO) removal from aqueous media. The prepared films were characterised using different techniques such as x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), water contact angle, optical properties, colourimetric measurement, porosity, swelling and thickness. The effects of various parameters, i.e. initial MO concentration, adsorbent dose, pH and temperature, were studied. The Cs/Tn0.2/MMT1 film showed a high removal efficiency of 95.62% and maximum adsorption capacity of 57.37 mg/g under the optimum adsorption conditions (initial methyl orange concentration 60 mg/L, pH 7 and 25 °C). The adsorption kinetic followed the pseudo second order kinetic model and the experimental data were a good fit for the Langmuir isotherm indicating a homogeneous and monolayer adsorption process. The thermodynamic parameters suggested physical adsorption and exothermic behaviour. Consequently, Cs/Tn/MMT films showed effective potential for the uptake of anionic dyes.

Andrade M.A., Barbosa C.H., Shah M.A., Ahmad N., Vilarinho F., Khwaldia K., Silva A.S., Ramos F.

Citrus production produces about 15 million tons of by-products/waste worldwide every year. Due to their high content of bioactive compounds, several extraction techniques can be applied to obtain extracts rich in valuable compounds and further application into food applications. Distillation and solvent extraction continues to be the most used and applied extraction techniques, followed by newer techniques such as microwave-assisted extraction and pulsed electric field extraction. Although the composition of these extracts and essential oils directly depends on the edaphoclimatic conditions to which the fruit/plant was exposed, the main active compounds are D-limonene, carotenoids, and carbohydrates. Pectin, one of the most abundant carbohydrates present in Citrus peels, can be used as a biodegradable polymer to develop new food packaging, and the extracted bioactive compounds can be easily added directly or indirectly to foods to increase their shelf-life. One of the applications is their incorporation in active food packaging for microbiological and/or oxidation inhibition, prolonging foods’ shelf-life and, consequently, contributing to reducing food spoilage. This review highlights some of the most used and effective extraction techniques and the application of the obtained essential oils and extracts directly or indirectly (through active packaging) to foods.

Soares Mateus A.R., Pena A., Sendón R., Almeida C., Nieto G.A., Khwaldia K., Sanches Silva A.

Food processing is fundamental to extend the shelf-life of food products. During the processing, several parts of food are wasted. FAO indicated that about one-third of the world's food production for human consumption was lost or wasted, and food waste is an environmental, economic, and social problem. Fruits and vegetables are the food groups with the highest amount of food waste, both in food processing and in consumption stage. However, those by-products constitute a potential source of bioactive compounds, with powerful biological activities. This paper carries out a comprehensive review of the scientific literature, on the main active compounds of some fruits and vegetable by-products, their biological activities, and potential uses. This study highlights the importance of food safety assessment of by-products to ensure human health. The cherry, plum, date and artichoke by-products presented high antioxidant and antimicrobial activity, which makes them sustainable natural high-added value compounds to be reincorporated into the food supply chain, to improve functionality as well as to extend the shelf-life of food products, within the framework of the circular economy.

Lo M., Ktari N., Gningue-Sall D., Madani A., Aaron S.E., Aaron J., Mekhalif Z., Delhalle J., Chehimi M.M.

The last two decades have witnessed attractive, innovative aspects of conductive polymers (CPs) in monitoring environmental pollution. In this regard, CP-based electrode materials were designed for the selective recognition of heavy metal ions in the environment (e.g. waste, river or tap water) or in simulated polluted environmental samples. In this review, the emphasis is on polypyrrole (PPy), an interesting electrosensing electrode material for heavy metals due to its facile preparation, versatile chemistry and physicochemical features. Indeed, health issues raised by metal ion pollutants require an urgent holistic approach for environmental problem solving. In this review, we will summarize the existing knowledge on the use of PPy as electrode material for the detection of heavy metals. We will report strategies of preparation of polypyrrole that exhibit selectivity towards heavy metal ions: (i) choice of dopant, (ii) functionalization of polymer backbone by chelatant groups, and (iii) preparation of ion imprinted polypyrrole. It is clear from this review that dopants could act as chelatant of metal ions and increase the selectivity. Such improvement could also be achieved by copolymerization of pyrrole with pyrrole-bearing chelatant groups (e.g. EDTA-like) or finally by the imprinting technique. The latter imparts artificial receptor sites for the recognition of metal ions combining the shape of the receptor site within the polypyrrole matrix that fit in well with the size of the metal ion, on the one hand, and the receptor site–ion interactions, on the other hand. Regardless, the method employed to design polypyrrole sensing layers for heavy metal nanostructuration seems to definitely improve the sensitivity of polypyrrole-based sensor devices. The review finishes by concluding remarks and indication of possible challenging new directions exploring polypyrrole in tracking occurrence of heavy metal ions in the environment.

Khwaldia K., Attour N., Matthes J., Beck L., Schmid M.

Among the most important agro-industrial activities in the Mediterranean basin, olive oil production has a high impact on the economy of many Mediterranean countries. However, olive oil extraction generates huge quantities of byproducts, including leaves, pomace residues, stones and wastewater, which have severe environmental impacts mainly because of their phytotoxicity and great organic content. Olive oil byproducts are regarded as inexpensive and abundant raw materials rich in bioactive compounds with high and varied health-related activities. Several phenolic compounds and terpenoids were recovered from olive byproducts using different conventional and advanced extraction methods due to their potential to be used in food, packaging, pharmaceutical, and cosmetic industries. Recently, the use of olive byproducts and their functional compounds to enhance the functional properties of packaging systems was investigated as a sustainable strategy for food preservation, fostering the sustainability of the olive-oil chain, and promoting circular economy. In this framework, the main goals of this review are to summarize the main bioactive compounds in olive byproducts, to review the main advancements in their extraction, purification, and characterization, and finally to discuss their applications in food packaging systems as well as safety-related aspects.

Mahouachi L., Rastogi T., Palm W., Ghorbel-Abid I., Ben Hassen Chehimi D., Kümmerer K.

Worldwide, the aquatic environment is contaminated by micro-pollutants, such as ingredients of personal care products, pesticides and pharmaceuticals. This contamination is one of the major environmental issues of global concern. Adsorption is one of approach, which has been most extensively discussed within recent years for the reduction of the input of micro-pollutants into the environment. In the present study, the natural clay classified as Na-montmorillonite, was characterized and tested for its potential to remove four model compounds representing different polarity and ionizability: i) diatrizoic acid (DAT), ii) iopamidol (IOP), iii) metformin (MTF), and iv) carbamazepine (CBZ). The adsorption efficiency of clay was evaluated by initial compound concentration, effect of pH, contact time and temperature. The results indicated that clay was able to remove the pharmaceuticals from aqueous medium with an efficiency of 70% for CBZ and MTF. In contrast, clay showed a lower removal of 30% for DAT and no removal for IOP. The results indicate that clay could rapidly and efficiently reduce the concentration of CBZ and MTF, which could provide a solution to remove some substances, without undesirable by-product generation. However, this study clearly demonstrated that removal rates strongly depend on the compound. Albeit chemical structure may play a role for the different degree of removal, this study could not completely explain the sorption mechanism between sorbent-sorbate interactions.

Derbali M., Othmani A., Kouass S., Touati F., Dhaouadi H.

Effect of interfering species on response currents of H 2 O 2 electrohemical sensor based on the BiVO 4 /TiO 2 nanocomposite electrode in saturated N 2 0.1 M NaOH solution at 0.5 V. • BiVO 4 /TiO 2 nanocomposites electrode is tested as an electrochemical sensor for sensitively detecting H 2 O 2 . • The synergic effect between TiO 2 and BiVO 4 improve the H 2 O 2 sensing performance of BiVO 4 /TiO 2 . • Long term stability and fast response of the BiVO 4 /TiO 2 composite electrode was investigated by CV . This study reports the synthesis of the BiVO 4 /TiO 2 nanocomposite in optimized conditions using the hydrothermal route. By varying many experimental parameters such as the temperature, the hydrothermal reaction time, the pH of the solution and the surfactant’s nature, we have successfully obtained BiVO 4 (monoclinic)/TiO 2 (anatase) nanomaterials with different morphologies. These materials were characterized by X-ray powder Diffraction (XRD), Infrared Spectroscopy (IR) and Scanning Electron Microscopy (SEM). The as-prepared nanocomposites were employed to manufacture hybrid electrode sensors to detect H 2 O 2 . The BiVO 4 /TiO 2 nanocomposite was deposited on nickel foam which acts as the working electrode. The response to hydrogen peroxide on the formed electrode was examined using cyclic voltammetry and amperometry techniques. Due to the synergic effect and the nanometric character of the BiVO 4 /TiO 2 nanocomposite, the synthesized sensor shows an enhanced electrochemical sensing performance. Under optimal conditions, the H 2 O 2 sensing tests indicate that the as-prepared BiVO 4 /TiO 2 electrochemical sensor exhibits a low detection limit (5 μM), a high sensitivity (3014 μA/mM), which is two times larger than that of BiVO 4 and TiO 2 , a large linear range (5–400 μM), and long-term stability. Finally, the practical applications of the BiVO 4 /TiO 2 electrochemical sensor were also evaluated by analyzing H 2 O 2 in the presence of common interfering species such as uric acid, ascorbic acid, vitamin-B12, glycine, asparagine, glucose, urea, KNO 3 , NaNO 3 and NaCl. The as-obtained results confirm the high selectivity towards H 2 O 2 of the BiVO 4 /TiO 2 electrode. These results could open the route for potential applications of the BiVO 4 /TiO 2 -based sensor in many fields such as: biomedicine, environmental detection, electrochemical sensing and pharmaceutical analysis.

Gharbi C., Louis H., Amodu I.O., Benjamin I., Fujita W., Ben Nasr C., Khedhiri L.

Present study focuses on the synthesis, crystal structure analysis,density functional theory (DFT), and the potential of 1-(2,5-dimethyphenyl) piperazine tetrachlorocobaltate hydrate (C12H20N2) CoCl4·H2O as adsorbent material for small moleculesas: CO2, H2CO, H2S, NH3, and NO2 gas.To gain insight into the geometrical properties, Infrared spectrum, and the intermolecular interactions within the crystal structure, X-ray crystallography, Fourier transform infrared spectroscopy (FT-IR), and Hirshfeld analysis have been carried out.The calculated adsorption energies follow a decreasing pattern of Hybrid-NO2 > Hybrid-NH3 > Hybrid-H2S > Hybrid-H2CO > Hybrid-CO2. It is evident that Hybrid-NO2 reflects the highest adsorption energy of − 0.5235 eV, depicting that the hybrid will better adsorb NO2 gas as compared to other gases. In all cases,the adsorption phenomena are best described as chemisorptions owing to the negative adsorption magnitudes.In furtherance, the magnetic susceptibility measured over a range of 2 – 300 K reveals paramagnetic behavior with weak magnetic interactions between Co(II) ions. At 300 K, theχpTvalue reflects 2.461 emu K mol–1, indicating a spin-orbit coupling contribution to the spin-only value of 1.875 emu K mol–1 expected for Co(II) with 3d7 spin configuration.