Adsorption of Direct Blue 78 using chitosan and cyclodextrins as adsorbents

The dyeing industry is one of the most polluting in the world. The adsorption of dyes by polymeric matrixes can be used to minimize the discharge of dyes into the environment. In the present study, chitosan-NaOH and β-cyclodextrin-epichlorohydrin polymers were used to remove the dye Direct Blue 78 from a wastewater model. To understand the adsorption behavior of Direct Blue 78 onto the polymers, adsorption rate and maximum adsorption capacity were calculated using kinetic tests and isotherm curves respectively. The kinetic data and mechanism of the adsorption process were analyzed by three models and the equilibrium data by three adsorption isotherms; also the different thermodynamic parameters were calculated. Results showed that the adsorption process follows pseudo-second-order kinetics in both polymers and the Langmuir isotherm best-fitted data for chitosan-NaOH polymer and the Freundlich isotherm for the β-CDs-EPI polymer. The adsorption process is exothermic in both cases and spontaneous for the β-CDs-EPI polymer to a certain temperature and not spontaneous for the chitosan-NaOH polymer and β-CDs-EPI polymer at higher temperatures. The complementary action of an advanced oxidation process eliminated >99% of the dye from water. The coupled process seems to be suitable for reducing the environmental impact of the dyeing industry.Ciencias de la Alimentació

Stability of microencapsulated strawberry flavour by spray drying, freeze drying and fluid bed

The main goal of this paper was to study the stability of a microencapsulated strawberry flavour using different encapsulating agents and drying techniques: spray drying, freeze drying and fluid bed. According to the quantification of volatile compounds, the blend MDs/Hi-Cap (9/1) at a fixed concentration of CDs (1.7%) was the most appropriate for microencapsulating the strawberry flavour. The best drying yield was observed in the case of freeze drying. In the case of the moisture content, spray drying samples presented the lowest values, followed by freeze drying and fluid bed. The study of stability at different temperatures and times revealed that the presence of CDs in the blend enabled a higher presence of volatile compounds in the powder than in its absence. Microphotographs showed smooth spherical particles in the case of spray drying, whereas the structure of the powder was amorphous, like glass, with freeze drying and irregular in the case of fluid bed.Ciencias de la Alimentació

Complexation of resveratrol by native and modified cyclodextrins: Determination of complexation constant by enzymatic, solubility and fluorimetric assays

The complexation of resveratrol with native a-, b- and c-cyclodextrins (CDs) and modified CDs (hydroxypropyl-b-(HP-b-CDs), maltosyl-b-(G2-b-CDs), methyl-b-, carboxymethyl-b- and acetyl-b-cyclodextrins) was studied, and the complexation constants (Kc) were compared. The complexation constant between resveratrol and each type of CD was calculated using three different methods: enzymatic, solubility and fluorimetric. The Kc values obtained showed that HP-b-CDs with their very high Kc of 18,048 ± 625 M 1, were the most effective for complexing resveratrol. Moreover, comparison of the results obtained by the three methods revealed that the fluorimetric method undervalued the Kc between resveratrol and all cyclodextrins, while the enzymatic and solubility methods were more precise for calculating the Kc between resveratrol and CDs, as demonstrated by the cyclodextrin-assay.This work was partially supported by Fundación Séneca (03025/PPC/05) and Ministerio de Educación y Ciencia (AGL2006-08702/ALI). C.L.A. is a holder of a research grant from the Programa Nacional de Formación de Personal Investigador (FPI), Ministerio de Educación y Ciencia (Spain) (BES-2007-16082).Ciencias de la Alimentació

Effect of HP-b-cyclodextrins complexation on the antioxidant activity of flavonols

The beneficial effects from phenolic compounds have been attributed to their antioxidant activity. Differences in the chemical structure of flavonols and their degree of substitution will influence phenoxyl radical stability and, thereby, their antioxidant properties. Cyclodextrins (CDs) can be used as a flavonol complexation agent, since they act as a substrate reservoir in a dose-controlled manner. In the present paper, the effect of complexing flavonols, kaempferol, quercetin and myricetin with HP-b-CDs on their antioxidant capacity is studied by means of the oxygen radical absorbance capacity-fluorescein (ORAC-FL) assay. This complexation phenomenon increased the antioxidant activity of the three flavonols, which reached a maximum level when each flavonol had been complexed in the hydrophobic cavity of CDs. The antioxidant activity increased because of the flavonol was protected against rapid oxidation by free radicals.Ciencias de la Alimentació

Synthesis of New Cyclodextrin-Based Adsorbents to Remove Direct Red 83:1

Two cyclodextrins (CDs), γ– and hydroxypropyl (HP)–γ–CDs were used to synthesize new adsorbents by using epichlorohydrin (EPI) as cross-linking agent in order to remove Direct Red 83:1 (DR) from water. Both polymers were characterized in terms of Fourier spectroscopy, nuclear magnetic resonance, particle size distribution and thermogravimetric analysis. Experimental data for both polymers were well fitted to the pseudo-second order and intraparticle diffusion model, indicating that in the adsorption both chemical and physical interactions are essential in the removal of DR. Three different isotherm models were analyzed, concluding that γ–CDs–EPI followed the Temkin isotherm and HP–γ–CDs-EPI the Freundlich isotherm, these results suggested that the adsorption was happening onto heterogeneous surfaces. The results of the Gibbs free energy showed that the adsorption was spontaneous at room temperature. In order to eliminate the remaining dye after the polymer treatment, and advanced oxidation process (AOP) was considered, achieving more than 90% of removal combining both mechanisms.European project “DYES4EVER” (Use of cyclodextrins for treatment of wastewater in textile industry to recover and reuse textile dyes, LIFE12 ENV/ES/000309) within the LIFE+ 2012 “Environment Policy and Governance project application” program.Ingeniería, Industria y Construcció

The synergistic action of cyclodextrin-based adsorbent and advanced oxidation processes for sulfamethoxazole removal from water

In this work, the removal of sulfamethoxazole from water was studied by adsorption on a cyclodextrin–epichlorohydrin copolymer and through Advanced Oxidation Processes. The adsorption was efficient and fast, requiring only 10 min to reach the equilibrium; it was also highly favored, with adsorption efficiency higher than 80%, at slightly acidic pH and at room temperature. The desorption of sulfamethoxazole was obtained by raising the temperature to 80 °C. The regenerated polymer has been reused multiple times without any loss in performance, allowing a reduction in costs associated with the process. As an alternative method to regenerate the adsorbent material, the photodegradation of sulfamethoxazole adsorbed on the polymer alone and in the presence of TiO2 as a catalyst through continuous irradiation with UV light and Pulsed Light was attempted and studied. For this purpose, polymeric adsorbents containing different amounts of TiO2 were synthesized and tested. The Pulsed Light showed the highest efficiency since it allowed the complete removal of sulfamethoxazole, regardless of the presence of TiO2 which, however, reduces adsorption efficiency of the material. Furthermore, a qualitative assessment of formed pulsed light by-products was also attempted. The remains of SMX in solution were decomposed by Pulsed Light technology and the effect of the presence of hydrogen peroxide on the photodegradation process was also studied. Despite the presence of by-products after Advanced Oxidation Processes, the procedure proposed in this work is effective and easy to apply to water treatment plants, thanks to the use of environmental-friendly adsorbents and light sources

Kinetic characterisation and thermal inactivation study of polyphenol oxidase and peroxidase from table grape (Crimson Seedless)

Polyphenol oxidase (PPO) and peroxidase (POD) were extracted from a table grape (Crimson Seedless) using Triton X-114 and characterized using spectrophotometric methods. Both PPO and POD were activated by acid shock. However, in the presence of the anionic detergent sodium dodecil sulphate (SDS), PPO was activated whereas POD was inactivated. The enzymes were kinetically characterized and both followed Michaelis–Menten kinetics, although with different values of their kinetic parameters. The Vm/Km ratio showed that Crimson Seedless grape PPO presents a similar affinity for 4-tert-butyl-catechol (TBC) whether activated by acid shock (0.018 min1 ) or SDS (0.023 min1 ). With regards to POD, the Km and Vm values for 2,20 -azinobis(3-ethylbenzothiazolinesulphonic acid) (ABTS) were 0.79 mM and 1.20 lM/min, respectively. In the case of H2O2, the Km and Vm value were 0.4 mM and 0.93 lM/min, respectively. PPO and POD showed similar thermostability, losing >90% of relative activity after only 5 min of incubation at 78 C and 75 C, respectively. In addition, PPO´ s activation energy was similar to that obtained for POD (295.5 kJ/mol and 271.9 kJ/mol, respectively).Ciencias de la Alimentació

DYRK1A and Activity-Dependent Neuroprotective Protein Comparative Diagnosis Interest in Cerebrospinal Fluid and Plasma in the Context of Alzheimer-Related Cognitive Impairment in Down Syndrome Patients

Down syndrome (DS) is a complex genetic condition due to an additional copy of human chromosome 21, which results in the deregulation of many genes. In addition to the intellectual disability associated with DS, adults with DS also have an ultrahigh risk of developing early onset Alzheimer's disease dementia. DYRK1A, a proline-directed serine/threonine kinase, whose gene is located on chromosome 21, has recently emerged as a promising plasma biomarker in patients with sporadic Alzheimer's disease (AD). The protein DYRK1A is truncated in symptomatic AD, the increased truncated form being associated with a decrease in the level of full-length form. Activity-dependent neuroprotective protein (ADNP), a key protein for the brain development, has been demonstrated to be a useful marker for symptomatic AD and disease progression. In this study, we evaluated DYRK1A and ADNP in CSF and plasma of adults with DS and explored the relationship between these proteins. We used mice models to evaluate the effect of DYRK1A overexpression on ADNP levels and then performed a dual-center cross-sectional human study in adults with DS in Barcelona (Spain) and Paris (France). Both cohorts included adults with DS at different stages of the continuum of AD: asymptomatic AD (aDS), prodromal AD (pDS), and AD dementia (dDS). Non-trisomic controls and patients with sporadic AD dementia were included for comparison. Full-form levels of DYRK1A were decreased in plasma and CSF in adults with DS and symptomatic AD (pDS and dDS) compared to aDS, and in patients with sporadic AD compared to controls. On the contrary, the truncated form of DYRK1A was found to increase both in CSF and plasma in adults with DS and symptomatic AD and in patients with sporadic AD with respect to aDS and controls. ADNP levels showed a more complex structure. ADNP levels increased in aDS groups vs. controls, in agreement with the increase in levels found in the brains of mice overexpressing DYRK1A. However, symptomatic individuals had lower levels than aDS individuals. Our results show that the comparison between full-length and truncated-form levels of DYRK1A coupled with ADNP levels could be used in trials targeting pathophysiological mechanisms of dementia in individuals with DS

Effect of temperature, pH, β- and HP-β-CDs on the solubility and stability of flavanones: naringenin and hesperetin

Naringenin and hesperetin are two of the most abundant flavanones found in citrus with beneficial effects on human health. However, their poor water solubility imposes considerable limitations to their use in functional foods or nutraceuticals development. In order to increase their aqueous solubility and find a new stable system, the effect of different factors as temperature, pH or complexation agents as cyclodextrins has been studied. The solubility of both flavanones increased exponentially with temperature (25-90 ºC): 10-fold in the case of naringenin and 20-fold for hesperetin. The solubility of both flavanones also increased with the media pH (3.5-8.5): 314-fold in the case of naringenin and 3.5-fold for hesperetin. Flavanones solubility also increased with β- or HP-β-CDs concentration. By the addition of β-CDs 13 mM naringenin solubility increased 9.3-fold and hesperetin solubility 30-fold. Using HP-β-CDs 100 mM naringenin solubility increased 143-fold and hesperetin 467-fold. In summary, the higher increase in naringenin solubility was reached by increasing pH up 8.5. However, in the case of hesperetin, the higher increase was obtained by complexation with HP-β-CDs 100 mM. Moreover, the presence of CDs, not only increased the aqueous solubility of flavanones, but also improved the stability of hesperetin at pHs 3.5 and 6.5.Ciencias de la Alimentació

Kinetic characterisation and thermal inactivation study of red alga (Mastocarpus stellatus) peroxidase

Peroxidase (POD) was extracted from red alga (Mastocarpus stellatus) using Triton X-114 and characterised by UV-spectrophotometry. Optimum activity using 2,2´ -azinobis(3-ethylbenzothiazolinesulphonic acid) (ABTS) as the H-donor was obtained at pH 5.0. In the presence of the anionic detergent, sodium dodecyl sulphate (SDS), however, POD was inactivated at all the pH values studied and totally inactivated at 1 mM SDS. When the enzyme was kinetically characterised, the KM and Vm values for ABTS were found to be 13 mM and 40 lM/min, respectively. In addition, when the H2O2 concentration was increased, at a fixed concentration of ABTS, the activity was inhibited at the highest H2O2 concentrations. In a study of the effect of several reducing agents, L-cysteine was found to be the most active. A thermal inactivation study showed a first-order inactivation kinetic, and the Arrhenius plot yielded a straight line with a slope equivalent to an activation energy of 121.6 kJ/mol. Significant inactivation occurred at temperatures of >35 C, with >90% of the relative activity being lost after only 5 min of incubation at 48.4 C.Ciencias de la Alimentació