Recovery of hydroxytyrosol a high added value compound through tyrosol conversion by electro-Fenton process

Biomimetic synthesis of hydroxytyrosol from conversion of tyrosol by mimicking tyrosine hydroxylase

Hydroxytyrosol, one of the most powerful natural antioxidants, exhibits certificated benefits for human health. In this study, a biomimetic approach to synthesize hydroxytyrosol from the hydroxylation of tyrosol was established. EDTA-Fe²⁺ coordination complex served as an active center to simulate tyrosine hydroxylase. H₂O₂ and ascorbic acid were used as oxygen donor and hydrogen donor, respectively. Hydroxy radical and singlet oxygen contributed to active species. The biomimetic system displayed analogous component, structure, and activity with TyrH. Hydroxytyrosol titer of 21.59 mM, and productivity of 9985.92 mg·L^-1·h^-1 was achieved with 100 mM tyrosol as substrate. The proposed approach provided efficient and convenient route to quickly produce high amount of hydroxytyrosol.

Valorization of an Underutilized Waste from Olive Oil Production by Recovery of Hydroxytyrosol

Hydroxytyrosol (HT) is one of the most powerful natural antioxidants, mainly contained in olive oil and its by-products. Here, a procedure for the preparation of an HT-enriched sample is described. An acidic aqueous extract (pH 1.25) from Olive Oil Dregs (OOD), a by-product from oil mills, was prepared by incubation at 37 °C for 1 h. The total phenolic content and HT amount were 6.24 ± 0.10 mg gallic acid equivalent/g OOD and 532.98 ± 5.78 μg/g OOD, respectively. Amberlite XAD16N and XAD7HP resins were used for the recovery of HT from the raw extract. Several elution conditions were tested with both resins, and elution with 25% ethanol provided the highest HT recovery (92.50% from XAD7HP). Antioxidant activities were assessed in the pool containing the highest quantity of HT. The results were compared with those of the raw extract. Ferric reducing antioxidant power values were comparable (95.71 ± 2.50 and 96.64 ± 13.47 μg ascorbic acid equivalent/mg for HT-enriched pool and raw extract, respectively), while the radical scavenging activity was higher for the pool (92.83% ± 0.44 and 44.12% ± 1.82, respectively). The results reported here demonstrate that HT can be recovered with a high yield from OOD, providing a preparation with high radical scavenging power. In addition, it is proved that this by-product, poorly considered up to now, can be usefully exploited.

Production of biologically active hydroxytyrosol rich extract via catalytic conversion of tyrosol

An effective and economical process was established to produce hydroxytyrosol, a naturally occurring orthodiphenolic antioxidant molecule found in olive oil from its monophenolic precursor tyrosol. The approach proposed in the present work presents an environment-friendly method based on wet hydrogen peroxide catalytic oxidation with montmorillonite KSF as an inexpensive and environmentally benign solid acid at room temperature. The influence of the principal operating parameters including concentration of tyrosol, H₂O₂, and catalyst used were studied. The antioxidant activity was realized by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. High antioxidant activity was detected according to the high hydroxytyrosol production (IC₅₀ = 0.7 μg mL⁻¹). The bactericidal and fungicidal properties of hydroxytyrosol rich extract were investigated using the NCCLS broth dilution and EN 1276 standard methods. Positive bactericidal and fungicidal effects of concentrations ranging between 1–0.5 g L⁻¹ and 4–2 g L⁻¹ were obtained.

An effective and economical process was established to produce hydroxytyrosol, a natural antioxidant molecule.

A rapid and efficient removal approach for degradation of metformin in pharmaceutical wastewater using electro-Fenton process; optimization by response surface methodology

Presence of emerging contaminants such as pharmaceutical products in aquatic environments has received high concern due to their undesirable effect on wildlife and human health. Current work deals with developing a treatment model based on the electro- Fenton (EF) process for efficient removal of metformin (MET) from an aqueous medium. The obtained experimental results revealed that over the reaction time of 10 min and solution pH of 3, the maximum removal efficiency of 98.57% is achieved where the value of MET initial concentration, current density, and H₂O₂ dosage is set at 10 mg.L^-1, 6 mA.cm^-2, and 250 μL.L^-1, respectively, which is in satisfactory agreement with the predicted removal efficiency of 98.6% with the desirability of 0.99. The presence of radical scavengers throughout the mineralization of MET under the EF process revealed that the generation of ^•OH radicals, as the main oxidative species, controlled the degradation mechanism. The obtained kinetics data best fitted to the first order kinetic model with the rate constant of 0.4224 min^-1 (R² = 0.9940). The developed treatment process under response surface methodology (RSM) was employed for modeling the obtained experimental data and successfully applied for efficient removal of the MET contaminant from pharmaceutical wastewater as an adequate and cost-effective approach.

Enhanced Electricity Generation and H2O2 Production in a Photocatalytic Fuel Cell and Fenton Hybrid System Assisted with Reverse Electrodialysis

A novel integrating system coupled with photocatalytic fuel cell and Fenton system assisted by reverse electrodialysis (PREC) is proposed. The results demonstrate that H₂O₂ concentration increased continuously in the reaction process to finally reach 960 mg/L and the current became stable at around 5.2 mA. The salinity-driven potential derived from the high concentration and low concentration cells in the hybrid system was 0.72 and 0.90 V respectively, at the salinity ratio of 50 and 100. The hybrid system has an energy recovery of 16%, a cathodic efficiency of 51%, and the maximum power of 76 W/m² at a salinity ratio of 50, with a 100 Ω external resistance. It is proved that PREC-Fenton possessed great potential in industrial wastewater treatment.

Removal of tyrosol from water by adsorption on carbonaceous materials and electrochemical advanced oxidation processes

This work compares the ability of physical and chemical treatments, namely adsorption and electrochemical advanced oxidation processes, to remove tyrosol from aqueous medium. Adsorption on graphene nanoplatelets (GNPs) performed much better than that with a graphite intercalation compound. Adsorption isotherms were found to follow the Freundlich model (R² = 0.96), which is characteristic of a chemisorption process. Successful electrochemical regeneration enables 5 successive adsorption/regeneration cycles before corrosion of GNPs occurs. Other typical aromatic contaminants that may coexist with tyrosol can be also adsorbed on GNPs. Percentage of regeneration efficiency of GNPs showed a higher affinity towards Lewis acids group compounds and a lower one towards Lewis base. The treatment of 100 mL of 0.723 mM tyrosol solutions in non-chlorinated and chlorinated matrices at pH 3.0 was carried out by electrochemical oxidation with electrogenerated H₂O₂ (EO-H₂O₂), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF). Trials were made with a BDD anode and an air-diffusion cathode at 10-30 mA cm^-2. Hydroxyl radicals formed at the anode from water oxidation and/or in the bulk from Fenton's reaction between added Fe²⁺ and generated H₂O₂, along with active chlorine produced in chlorinated medium, were the main oxidants. Tyrosol concentration always decayed following a pseudo-first-order kinetics and its mineralization rose as EO-H₂O₂ < EF < PEF, more rapidly in the chlorinated matrix. The potent photolysis of intermediates under UVA radiation explained the almost total mineralization achieved by PEF in the latter medium. The effect of current density and tyrosol content on the performance of all processes was examined.