Juliana Arriel Torres

Immobilized soybean hull peroxidase for the oxidation of phenolic compounds in coffee processing wastewater.

Chitosan beads were prepared, using glutaraldehyde as a crosslinking agent for the immobilization of soybean hull peroxidase (SBP). The activity of free and immobilized SBP was studied. The optimum pH was 6.0 for both the free and immobilized enzyme; however, enzyme activity became more dependent on the temperature after immobilization. This study evaluated the potential use of immobilized and free enzyme in the oxidation of caffeic acid, of synthetic phenolic solution (SPS) and of total phenolic compounds in coffee processing wastewater (CPW). Some factors, such as reaction time, amount of H2O2 and caffeic acid were evaluated, in order to determine the optimum conditions for enzyme performance. Both enzymes showed a potential in the removal of caffeic acid, SPS and CPW, and immobilized SBP had the highest oxidation performance. The immobilized enzyme showed a potential of 50% in the oxidation of caffeic acid after 4 consecutive cycles.

Descoloração de corantes industriais e efluentes têxteis simulados por peroxidase de nabo ( Brassica campestre )

The removal of important textile dyes by turnip peroxidase (TNP) was evaluated. The textile effluents besides the residual dyes contain also chemical auxiliaries such as salts, dispersing and wetting agents. The effect of these was evaluated in the removal of the dyes reactive blue 21 and reactive blue 19 by TNP in synthetic effluents. A decrease of the efficency decolorization was observed. The action of the enzyme on colour removal of dye mixture was equivalent to the dyes alone. The chemical demand of oxygen in the effluent after enzymatic treatment had a significant increase in relation to the untreated effluent.

Immobilization of soybean peroxidase on silica-coated magnetic particles: a magnetically recoverable biocatalyst for pollutant removal

In this work we investigated the enzymatic degradation of ferulic acid, a model pollutant, by free and immobilized soybean peroxidase. With the aim of developing greener catalysts, we proposed the synthesis of a magnetic catalyst prepared via immobilization of soybean peroxidase onto a magnetic nanosupport by covalent attachment. The immobilization of soybean peroxidase was carried out using magnetite nanoparticles modified with amino groups as support. The magnetite particles were characterized before and after chemical modification by XRD, SEM and TEM analysis. The characterization data indicated that the Fe3O4–SiO2 nanoparticles were successfully synthetized. The high immobilization yield was obtained in only 1 hour of reaction (89.23%). The resulting nanobiocatalyst (enzyme load 5.25 U) was able to remove 99.67 ± 0.10% of ferulic acid in comparison to 57.67 ± 0.27% for free enzyme under the same reaction conditions. The immobilized peroxidase could easily be separated under a magnetic field and reused. On the basis of these results, we concluded that the prepared magnetic nanoparticles can be considered a high-performance nanocatalyst for environmental remediation.

Combined experimental and theoretical study on the removal of pollutant compounds by peroxidases: affinity and reactivity toward a bioremediation catalyst

Water pollution is a significant and growing problem throughout the world, especially in developing countries. In order to minimize environmental problems, catalysts have increasingly been designed to remove pollutants from the water. In an attempt to innovate by the creation of new low-cost alternatives to efficiently remove pollutants, the enzymatic treatment has been intensely studied for this purpose. Reactions catalyzed by enzymes are able to perform specific treatments, commonly with high rates of the final products. With this, the enzyme, peroxidase, is a promising candidate as a bioremediation catalyst. The efficiency of oxidoreductive enzymes, such as horseradish peroxidase (HRP) and soybean peroxidase (SP) have been studied, given that their performance depends on the substrate. In this investigation, experimental techniques and theoretical calculations have been employed in order to investigate the oxidative process for the ferulic acid and bromophenol blue dyes, performed by HRP and SP. Both enzymes showed a comparable behavior with respect to ferulic acid substrate. On the other hand, by utilizing bromophenol blue dye as a substrate, the behavior of the employed catalysts was significantly different. Experimental data have shown that HRP was more active toward bromophenol blue when compared to ferulic acid, being more rapidly degraded by the HRP enzyme. This tendency was confirmed by our theoretical docking, PM6 semi-empirical method, and DFT calculation results, in which the interaction, binding energies, and transition states were determined.

Enzymatic oxidation of phenolic compounds in coffee processing wastewater

Peroxidases can be used in the treatment of wastewater containing phenolic compounds. The effluent from the wet processing of coffee fruits contains high content of these pollutants and although some studies propose treatments for this wastewater, none targets specifically the removal of these recalcitrant compounds. This study evaluates the potential use of different peroxidase sources in the oxidation of caffeic acid and of total phenolic compounds in coffee processing wastewater (CPW). The identification and quantification of phenolic compounds in CPW was performed and caffeic acid was found to be the major phenolic compound. Some factors, such as reaction time, pH, amount of H2O2 and enzyme were evaluated, in order to determine the optimum conditions for the enzyme performance for maximum oxidation of caffeic acid. The turnip peroxidase (TPE) proved efficient in the removal of caffeic acid, reaching an oxidation of 51.05% in just 15 minutes of reaction. However, in the bioremediation of the CPW, the horseradish peroxidase (HRP) was more efficient with 32.70%±0.16 of oxidation, followed by TPE with 18.25%±0.11. The treatment proposed in this work has potential as a complementary technology, since the efficiency of the existing process is intimately conditioned to the presence of these pollutants.

Novel eco-friendly biocatalyst: soybean peroxidase immobilized onto activated carbon obtained from agricultural waste

The immobilization of enzymes is an excellent alternative to overcome the drawbacks of using these biocatalysts in free form. This process plays a significant role in cost-effective recovery, increased catalyst productivity and in simplifying process operations. After the soybean peroxidase (SP) extraction, a residue at high carbon and low ash content is generated. This residue was used as carbonaceous precursor for production of carbon activated (AC) with high surface area (1603 m2 g−1). The AC produced was used as support for SP immobilization. The immobilization of SP was evaluated in different time conditions, enzyme load, pH and temperature. The samples, before and after immobilization, were characterized by thermogravimetric analysis, elemental analysis composition, specific surface area, X-ray powder diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. In addition, repeated applications of immobilized biocatalyst were made in order to evaluate its operational stability and capacity to recover the reaction medium, in which was observed that after a decline in activity from the first to the second cycle, it remained constant until the tenth application. In the context, the process of material obtainment constitutes a clean route for the development of more sustainable biocatalysts capable of applications in various areas.

Evaluation of the protective effect of chemical additives in the oxidation of phenolic compounds catalysed by peroxidase

ABSTRACT The use of oxidoredutive enzymes in removing organic pollutants has been the subject of much research. The oxidation of phenolic compounds in the presence of chemical additives has been the focus of this study. In this investigation, the influence of the additives polyethylene glycol and Triton X-100 was evaluated in the phenol oxidation, caffeic acid, chlorogenic acid and total phenolic compounds present in coffee processing wastewater (CPW) at different pH values, performed by turnip peroxidase and peroxidase extracted from soybean seed hulls. The influence of these additives was observed only in the oxidation of phenol and caffeic acid. In the oxidation of other studied phenolic compounds, the percentage of oxidation remained unchanged in the presence of these chemical additives. In the oxidation of CPW in the presence of additives, no change in the oxidation of phenolic compounds was observed. Although several studies show the importance of evaluating the influence of additives on the behaviour of enzymes, this study found a positive response from the economic point of view for the treatment of real wastewater, since the addition of these substances showed no influence on the oxidation of phenolic compounds, which makes the process less costly.

Soybean peroxidase immobilized on δ-FeOOH as new magnetically recyclable biocatalyst for removal of ferulic acid

A significant enhancement in the catalytic performance due to enzymes immobilization is a great way to enhance the economics of biocatalytic processes. The soybean peroxidase (SP) immobilization under ferroxyte and the ferulic acid removal by the enzyme free and immobilized were investigated. The immobilization via silica-coated ferroxyte nanoparticles was effective, and immobilization yield of 39%. The scanning electron microscopy (SEM) images showed significant changes in the materials morphology. Substantial differences were observed in the particles’ Fourier Transform Infrared (FTIR) spectra. The magnetic catalyst revealed a better performance than the free enzyme in the ferulic acid conversion, presenting a good Vmax/Km ratio when compared with the free enzyme. The reuse evaluated by ten cycles exhibited excellent recycling, remaining constant between the sixth and seventh cycles. The use of magnetic nanocatalyst becomes possible to eliminate the high operational costs, and complicated steps of the conventional enzymatic processes. Thus, a viable industrial route for the use of the enzyme as catalyst is possible.

Experimental and theoretical study on the reactivity of maghemite doped with Cu2+ in oxidation reactions: structural and thermodynamic properties towards a Fenton catalyst

In this work, a polymeric method was used to prepare undoped and Cu-doped iron oxide catalysts for the H2O2 decomposition reaction. These catalysts were characterized by powder X-ray diffractometry (XRD), scanning electronic microscopy (SEM) coupled to an energy dispersive X-ray spectrometer (EDX), and H2-Temperature Programmed Reduction (H2-TPR). The SEM images show an inhomogeneous particle cluster in both samples, tending to decrease in size with Cu-doping. EDX mapping reveals a good dispersion of Cu2+ in the iron oxide. In addition, Rietveld refinement of the XRD patterns reveals that the samples are constituted of hematite and maghemite, but only maghemite has octahedral Fe3+ ions isomorphically replaced by 2 wt% Cu2+. Cu-doping produces an active catalyst for H2O2 decomposition. Tests using phenol show the strong inhibition of H2O2 decomposition by the Cu-doped catalysts, suggesting that H2O2 may be decomposed via a radical mechanism. Furthermore, phenol degradation kinetics confirm that the doping of maghemite with Cu2+ brings about a significant improvement in catalytic activity. Theoretical calculations reveal that Cu-doping in maghemite produces low electronic density sites, favoring the interactions between the surface oxygens of H2O2 and Cu2+, thus improving the catalytic activity. This strategy can be extended to other materials to design active heterogeneous catalysts for environmental purposes.

Obtention of plant peroxidase and its potential for the decolorization of the reactive dye Remazol Turquoise G 133

Peroxidases can be used in the decolorization process. There is a growing interest for new sources of this enzyme and for obtaining economically viable processes. In this work, a low-cost vegetable peroxidase extraction process is proposed; the resulting enzyme is characterized to determine its optimum pH, temperature, and stability conditions, and it is then applied in the decolorization of reactive dye Remazol Turquoise G 133%. The turnip peroxidase (TP) was utilized as an enzymatic source. This enzyme exhibited maximum activity at pH 7.0, and it was active in the temperature range of 30 to 50 °C, which favors its use in industrial processes. Acetone was the most efficient solvent to induce precipitation. The removal of Remazol Turquoise G 133% was 56.0% complete after 50 min, while 41.0% of the same dye was removed with the commercial horseradish peroxidase enzyme in 50 min. TP presents potential as a viable alternative in the decolorization of textile wastewaters.