Nelson Durán

Potential applications of oxidative enzymes and phenoloxidase-like compounds in wastewater and soil treatment: a review

A number of oxidative enzymes from bacteria, fungi and plants have been reported to play an important role in numerous waste treatment applications. Peroxidases and/or phenoloxidases can act on specific recalcitrant pollutants by precipitation or transforming to other products and permitting a better final treatment of the waste. Improvement in the useful life and thereby a reduction in treatment cost has been accomplished through enzyme immobilization. Horseradish peroxidase, lignin peroxidase and manganese peroxidase mineralize a variety of recalcitrant aromatic compounds. Immobilization of these enzymes on porous ceramic supports or resins did not adversely affect their stability and showed a good potential for degradation of environment persistent aromatics. Tyrosinase, which catalyzes the hydroxylation of phenols and dehydrogenation of o-diphenols, in an immobilized form exerted an excellent phenol removal. Laccase is capable of eliminating the phenols through polymerization process, however, the presence of mediator such as ABTS and HBT degraded phenol by oxidative process. Many applications with oxidative enzymes and plant materials in effluent as in soil remediation will be discussed.

Applications of laccases and tyrosinases (phenoloxidases) immobilized on different supports: a review

This review summarizes all the research efforts that have been spent to immobilize laccase and tyrosinase for various applications, including synthetic and analytical purposes, bioremediation, wastewater treatment, and must and wine stabilization. All immobilization procedures used in these areas are discussed. Considerations on the efficacy of immobilized copper oxidases and products, in addition to their kinetic parameters are also discussed. The available data indicate that the immobilization of laccase into cationic polymer cross-linked with epichlorohydrin appears to be a promising procedure for industrial applications. The development of laccase and tyrosinase-based biosensors to monitor a wide range of compounds appears to be at a mature stage of technology.

Mechanistic aspects of biosynthesis of silver nanoparticles by several Fusarium oxysporum strains

Extracellular production of metal nanoparticles by several strains of the fungus Fusarium oxysporum was carried out. It was found that aqueous silver ions when exposed to several Fusarium oxysporum strains are reduced in solution, thereby leading to the formation of silver hydrosol. The silver nanoparticles were in the range of 20–50 nm in dimensions. The reduction of the metal ions occurs by a nitrate-dependent reductase and a shuttle quinone extracellular process. The potentialities of this nanotechnological design based in fugal biosynthesis of nanoparticles for several technical applications are important, including their high potential as antibacterial material.

Semiconductor-assisted photocatalytic degradation of reactive dyes in aqueous solution.

This work reports the semiconductor-assisted photochemical degradation of reactive dyes. In an oxygenated-UV-ZnO system almost total decolorization of Remazol Brilliant Blue R, Remazol Black B, Reactive Blue 221 and Reactive Blue 222 was observed in reaction times of about 60 min. Extending the photochemical treatment up to 120 min, mineralization higher than 80% for all the dyes was observed. During the same period, the residual acute toxicity was significantly reduced only for Remazol Black B. A systematic optimization study carried out by factorial design showed that for the reactive dyes tested, the ZnO semiconductor exhibits a better efficiency than that observed with anatase TiO2. A synergistic effect in the coupled TiO2-ZnO system was not observed.

Nanotoxicity of Graphene and Graphene Oxide

Graphene and its derivatives are promising candidates for important biomedical applications because of their versatility. The prospective use of graphene-based materials in a biological context requires a detailed comprehension of the toxicity of these materials. Moreover, due to the expanding applications of nanotechnology, human and environmental exposures to graphene-based nanomaterials are likely to increase in the future. Because of the potential risk factors associated with the manufacture and use of graphene-related materials, the number of nanotoxicological studies of these compounds has been increasing rapidly in the past decade. These studies have researched the effects of the nanostructural/biological interactions on different organizational levels of the living system, from biomolecules to animals. This review discusses recent results based on in vitro and in vivo cytotoxicity and genotoxicity studies of graphene-related materials and critically examines the methodologies employed to evaluate their toxicities. The environmental impact from the manipulation and application of graphene materials is also reported and discussed. Finally, this review presents mechanistic aspects of graphene toxicity in biological systems. More detailed studies aiming to investigate the toxicity of graphene-based materials and to properly associate the biological phenomenon with their chemical, structural, and morphological variations that result from several synthetic and processing possibilities are needed. Knowledge about graphene-based materials could ensure the safe application of this versatile material. Consequently, the focus of this review is to provide a source of inspiration for new nanotoxicological approaches for graphene-based materials.

Potential applications of laccase in the food industry

Abstract Laccase is a widely studied enzyme because of its potential use in several areas such as textile, paper and pulp industries. This review presents the potential application of this enzyme in the food industry. Laccase can be used in bioremediation, beverage (wine, fruit juice and beer) processing, ascorbic acid determination, sugar beet pectin gelation, baking, and as biosensor and to improve food sensory parameters. Laccase could increase productivity, efficiency and quality of food products without a costly investment and has the advantage of being a mild technology.

Phenolic compounds and total antioxidant potential of commercial wines

Abstract Growing evidence of the role of free radicals and antioxidants in health and ageing has focussed great interest on these compounds. The relationship between the total antioxidant potential and the phenolic content of commercial wines was evaluated. A close relationship between total phenolic content and total antioxidant potential for all wines was observed. Capillary zone electrophoresis showed that, in red wines, gallic acid was the highest of the phenolic acids and (+)-catechin and (−)-epicatechin were the next most abundant phenolics. Also, these compounds were strictly correlated with the total antioxidant potential of wines. Total antioxidant potential, by bleaching of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cations, using gallic acid as standard, could be a practical and simple measurement to evaluate the characteristics of different wines. Furthermore, capillary electrophoresis is a powerful and high-performing tool for evaluating principal antioxidant wine components.

NOVAS TENDÊNCIAS NO TRATAMENTO DE EFLUENTES TÊXTEIS

Textile effluents, when not correctly treated, cause a high impact to the environment. The main recalcitrant compounds present in textile effluent are represented by the synthetic dyes, used during the fibber dying process. Among others, the azo dyes are considered the most harmful due to its mutagenic and carcinogenic character. In the present work we reported a revision study on the new tendencies for remediation of textile effluents, mainly to degrade the recalcitrant compounds. For this purpose, chemical, physical, photochemical, biological and combined processes were investigated.

Silver nanoparticles: a brief review of cytotoxicity and genotoxicity of chemically and biogenically synthesized nanoparticles.

In recent years interest in silver nanoparticles and their applications has increased mainly because of the important antimicrobial activities of these nanomaterials, allowing their use in several industrial sectors. However, together with these applications, there is increasing concerning related to the biological impacts of the use of silver nanoparticles on a large scale, and the possible risks to the environment and health. In this scenario, some recent studies have been published based on the investigation of potential inflammatory effects and diverse cellular impacts of silver nanoparticles. Another important issue related to nanoparticle toxicity in biological media is the capacity for increased damage to the genetic material, since nanoparticles are able to cross cell membranes and reach the cellular nucleus. In this regard, there is increasing interest in the analysis of potential nanoparticle genotoxicity, including the effects of different nanoparticle sizes and methods of synthesis. However, little is known about the genotoxicity of different silver nanoparticles and their effects on the DNA of organisms; thus further studies in this field are required. This mini‐review aims to present and to discuss recent publications related to genotoxicity and the cytotoxicity of silver nanoparticles in order to better understand the possible applications of these nanomaterials in a safe manner. This present work concludes that biogenic silver nanoparticles are generally less cyto/genotoxic in vivo compared with chemically synthesized nanoparticles. Furthermore, human cells were found to have a greater resistance to the toxic effects of silver nanoparticles in comparison with other organisms. Copyright

Mechanistic aspects in the biogenic synthesis of extracellular metal nanoparticles by peptides, bacteria, fungi, and plants

Metal nanoparticles have been studied and applied in many areas including the biomedical, agricultural, electronic fields, etc. Several products of colloidal silver are already on the market. Research on new, eco-friendly and cheaper methods has been initiated. Biological production of metal nanoparticles has been studied by many researchers due to the convenience of the method that produces small particles stabilized by protein. However, the mechanism involved in this production has not yet been elucidated although hypothetical mechanisms have been proposed in the literature. Thus, this review discusses the various mechanisms provided for the biological synthesis of metal nanoparticles by peptides, bacteria, fungi, and plants. One thing that is clear is that the mechanistic aspects in some of the biological systems need more detailed studies.