Azo dye biotransformation mediated by AQS immobilized on activated carbon cloth in the presence of microbial inhibitors.

In this work, anthraquinone-2-sulfonate (AQS) was covalently immobilized onto activated carbon cloth (ACC), to be used as redox mediator for the reductive decolorization of reactive red 2 (RR2) by an anaerobic consortium. The immobilization of AQS improved the capacity of ACC to transfer electrons, evidenced by an increment of 3.29-fold in the extent of RR2 decolorization in absence of inhibitors, compared to incubations lacking AQS. Experiments conducted in the presence of vancomycin, an inhibitor of acidogenic bacteria, and with 2-bromoethane sulfonic acid (BES), an inhibitor of methanogenic archaea, revealed that acidogenic bacteria are the main responsible for RR2 biotransformation mediated by immobilized AQS. Nonetheless, the results also suggest that some methanogens are able to maintain their capacity to use immobilized AQS as an electron acceptor to sustain the decolorization process, even in the presence of BES.

Application of redox mediators in bioelectrochemical systems.

Redox mediators (RM) are natural or artificial compounds used by microorganisms as electron acceptors and electron donors during electron transfer. Evidence collected in the last years indicates that the application of RM in bioelectrochemical systems (BES) enhanced the electron transfer from microorganisms to anodes and from cathodes to microorganisms. This review summarizes the results of using soluble or immobilized RM in BES to produce electricity and for the treatment of contaminants from wastewater effluents. In addition, future research focused on biohydrogen production, recovery or removal metals, and the use of humic substances (HS) extracted from natural environment is proposed.

AQDS immobilized solid-phase redox mediators and their role during bioelectricity generation and RR2 decolorization in air-cathode single-chamber microbial fuel cells.

The application of immobilized redox mediators (RMs) in microbial fuel cells (MFCs) is an emerging technology for electricity generation with simultaneous azo dye decolorization due to facilitated electrons transfer from bacteria to anodes and azo dyes. The use of immobilized RMs avoids the requirement of their continuous dosing in MFCs, which has been the main limitation for practical applications. Two strategies of anthraquinones-2,6-disulphonic salt (AQDS) immobilization, AQDS immobilized with polyvinyl alcohol particles and AQDS immobilized on anodes by electropolymerization, were evaluated and compared to achieve simultaneous reactive red 2 (RR2) dye reduction and bioelectricity generation. The AQDS immobilized by electropolymerization showed the highest power density (816±2mW/m2) and extent of RR2 decolorization (89±0.6%). This power density is one of the highest values yet achieved in the presence of a recalcitrant pollutant, suggesting that immobilization was important for enabling current generation in the presence of RR2.

Quinone-functionalized activated carbon improves the reduction of congo red coupled to the removal of p-cresol in a UASB reactor.

In this research was immobilized anthraquinone-2-sulfonate (AQS) on granular activated carbon (GAC) to evaluate its capacity to reduce congo red (CR) in batch reactor and continuous UASB reactors. The removal of p-cresol coupled to the reduction of CR was also evaluated. Results show that the immobilization of AQS on GAC (GAC-AQS) achieved 0.469mmol/g, improving 2.85-times the electron-transferring capacity compared to unmodified GAC. In batch, incubations with GAC-AQS achieved a rate of decolorization of 2.64-fold higher than the observed with GAC. Decolorization efficiencies in UASB reactor with GAC-AQS were 83.9, 82, and 79.9% for periods I, II, and III; these values were 14.9-22.8% higher than the obtained by reactor with unmodified GAC using glucose as energy source. In the fourth period, glucose and p-cresol were simultaneously fed, increasing the decolorization efficiency to 87% for GAC-AQS and 72% for GAC. Finally, reactors efficiency decreased when p-cresol was the only energy source, but systems gradually recovered the decolorization efficiency up to 84% (GAC-AQS) and 71% (GAC) after 250 d. This study demonstrates the longest and efficient continuous UASB reactor operation for the reduction of electron-accepting contaminant in presence of quinone-functionalized GAC, but also using a recalcitrant pollutant as electron donor.

Efficient anaerobic treatment of synthetic textile wastewater in a UASB reactor with granular sludge enriched with humic acids supported on alumina nanoparticles.

A novel technique to co-immobilize humus-reducing microorganisms and humic substances (HS), supported on γ-Al2O3 nanoparticles (NP), by a granulation process in an upflow anaerobic sludge bed (UASB) reactor is reported in the present work. Larger granules (predominantly between 1 and 1.7 mm) were produced using NP coated with HS compared to those obtained with uncoated NP (mostly between 0.25 and 0.5 mm). The HS-enriched granular biomass was then tested for its capacity to achieve the reductive decolorization of the recalcitrant azo dye, reactive red 2 (RR2), in the same UASB reactor operated with a hydraulic residence time of 12 h and with glucose as electron donor. HS-enriched granules achieved higher decolorization and COD removal efficiencies, as compared to the control reactor operated in the absence of HS, in long term operation and applying high concentrations of RR2 (40-400 mg/L). This co-immobilizing technique could be attractive for its application in UASB reactors for the reductive biotransformation of several contaminants, such as nitroaromatics, poly-halogenated compounds, metalloids, among others.

Humus-reducing microorganisms and their valuable contribution in environmental processes.

Humus constitutes a very abundant class of organic compounds that are chemically heterogeneous and widely distributed in terrestrial and aquatic environments. Evidence accumulated during the last decades indicating that humic substances play relevant roles on the transport, fate, and redox conversion of organic and inorganic compounds both in chemically and microbially driven reactions. The present review underlines the contribution of humus-reducing microorganisms in relevant environmental processes such as biodegradation of recalcitrant pollutants and mitigation of greenhouse gases emission in anoxic ecosystems, redox conversion of industrial contaminants in anaerobic wastewater treatment systems, and on the microbial production of nanocatalysts and alternative energy sources.

Immobilized humic substances as redox mediator for the simultaneous removal of phenol and Reactive Red 2 in a UASB reactor.

The present study reports a novel treatment concept combining the redox-mediating capacity of immobilized humic substances with the biodegrading activity of anaerobic sludge for the simultaneous removal of two representative pollutants of textile wastewaters (e.g., phenol and Reactive Red 2 (RR2)) in a high-rate anaerobic reactor. The use of immobilized humic substances (1 g total organic carbon (TOC) L(-1), supported on an anion exchange resin) in an upflow anaerobic sludge blanket (UASB) reactor increased the decolorization efficiency of RR2 (~90 %), extent of phenol oxidation (~75 %), and stability as compared to a control UASB reactor operated without immobilized humic substances, which collapsed after 120 days of dye introduction (50-100 mg L(-1)). Increase in the concentration of immobilized humic substances (2 g TOC L(-1)) further enhanced the stability and efficiency of the UASB reactor. Detection of aniline in the effluent as RR2 reduction product confirmed that reduction of RR2 was the major mechanism of dye removal. This is the first demonstration of immobilized humic substances serving as effective redox mediators for the removal of recalcitrant pollutants from wastewater in a high-rate anaerobic bioreactor. The novel treatment concept could also be applicable to remove a wide variety of contaminants susceptible to redox conversion, which are commonly found in different industrial sectors.

Kinetics during the redox biotransformation of pollutants mediated by immobilized and soluble humic acids.

The aim of this study was to elucidate the kinetic constraints during the redox biotransformation of the azo dye, Reactive Red 2 (RR2), and carbon tetrachloride (CT) mediated by soluble humic acids (HAs) and immobilized humic acids (HAi), as well as by the quinoid model compounds, anthraquinone-2,6-disulfonate (AQDS) and 1,2-naphthoquinone-4-sulfonate (NQS). The microbial reduction of both HAs and HAi by anaerobic granular sludge (AGS) was the rate-limiting step during decolorization of RR2 since the reduction of RR2 by reduced HAi proceeded at more than three orders of magnitute faster than the electron-transferring rate observed during the microbial reduction of HAi by AGS. Similarly, the reduction of RR2 by reduced AQDS proceeded 1.6- and 1.9-fold faster than the microbial reduction of AQDS by AGS when this redox mediator (RM) was supplied in soluble and immobilized form, respectively. In contrast, the reduction of NQS by AGS occurred 1.6- and 19.2-fold faster than the chemical reduction of RR2 by reduced NQS when this RM was supplied in soluble and immobilized form, respectively. The microbial reduction of HAs and HAi by a humus-reducing consortium proceeded 1,400- and 790-fold faster than the transfer of electrons from reduced HAs and HAi, respectively, to achieve the reductive dechlorination of CT to chloroform. Overall, the present study provides elucidation on the rate-limiting steps involved in the redox biotransformation of priority pollutants mediated by both HAs and HAi and offers technical suggestions to overcome the kinetic restrictions identified in the redox reactions evaluated.

Simultaneous biodegradation of phenol and carbon tetrachloride mediated by humic acids.

The capacity of an anaerobic sediment to achieve the simultaneous biodegradation of phenol and carbon tetrachloride (CT) was evaluated, using humic acids (HA) as redox mediator. The presence of HA in sediment incubations increased the rate of biodegradation of phenol and the rate of dehalogenation (2.5-fold) of CT compared to controls lacking HA. Further experiments revealed that the electron-accepting capacity of HA derived from different organic-rich environments was not associated with their reducing capacity to achieve CT dechlorination. The collected kinetic data suggest that the reduction of CT by reduced HA was the rate-limiting step during the simultaneous biodegradation of phenol and CT. To our knowledge, the present study constitutes the first demonstration of the simultaneous biodegradation of two priority pollutants mediated by HA.

Tert-Butylhydroquinone pretreatment protects kidney from ischemia-reperfusion injury.

BACKGROUND: It is generally accepted that an excessive production of reactive oxygen species plays an important role in acute renal failure secondary to ischemia and reperfusion. tert-Butylhydroquinone (tBHQ) is a well-known antioxidant. In this study, we evaluated whether tBHQ pretreatment prevented renal damage induced by ischemia and reperfusion (I/R). METHODS: Four groups of rats were studied: (a) control-sham (CT), (b) tBHQ-sham (tBHQ), (c) I/R and (d) tBHQ + I/R. Intraperitoneal (i.p.) injections of tBHQ (50 mg/kg) were given to the tBHQ and tBHQ + I/R groups and 3% ethanol/isotonic saline solution to the CT and I/R groups. Animals were killed 24 hours after I/R. RESULTS: tBHQ attenuated I/R-induced renal dysfunction, structural damage, oxidative/nitrosative stress, glutathione depletion and the decrease in several antioxidant enzymes. CONCLUSION: The renoprotective effect of tBHQ on I/R injury was associated with the attenuation in oxidative/nitrosative stress and the preservation of antioxidant enzymes.

Preventive effect of tert-butylhydroquinone on cisplatin-induced nephrotoxicity in rats.

Cis-diamminedichloroplatinum II (CDDP)-induced nephrotoxicity is associated with the overproduction of reactive oxygen species. tert-Butylhydroquinone (tBHQ) is a compound widely used as food antioxidant. The purpose of this study was to investigate the ability of tBHQ to prevent the nephrotoxic effect of CDDP in rats as well as the mechanisms involved. Thirty-six Wistar rats divided in the following groups were used: control, tBHQ (12.5mg/kg), CDDP (7.5mg/kg) and tBHQ+CDDP. Twenty-four h urine was collected at the beginning and at the end of the experiment and the rats were sacrificed 72h after CDDP-administration. Histological studies were performed and markers of renal function and oxidative/nitrosative stress were measured. In addition, the activity of the following antioxidant enzymes was measured: glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione reductase (GR) and glutathione-S-transferase (GST). CDDP-induced renal dysfunction, structural damage and oxidative/nitrosative were prevented by tBHQ. In addition, tBHQ completely prevented the CDDP-induced fall in GPx and GST activities. In conclusion, the present study indicates that the antioxidant activity of tBHQ is associated with its nephroprotective effect against CDDP-induced acute kidney injury in rats.

Renoprotection by alpha-Mangostin is related to the attenuation in renal oxidative/nitrosative stress induced by cisplatin nephrotoxicity.

Cisplatin (CDDP) is a chemotherapeutic agent that produces nephrotoxicity associated with oxidative/nitrosative stress. alpha-Mangostin (alpha-M) is a xanthone extracted from mangosteen with antioxidant and anti-inflammatory properties. The purpose of this study was to evaluate the renoprotective effect of alpha-M on the CDDP-induced nephrotoxicity. alpha-M was administered (12.5 mg/kg/day, i.g.) for 10 days (7 days before and 3 days after CDDP injection). On day 7, rats were treated with a single injection of CDDP (7.5 mg/Kg, i.p.); 3 days after the rats were killed. alpha-M attenuated renal dysfunction, structural damage, oxidative/nitrosative stress, decrease in catalase expression and increase in mRNA levels of tumour necrosis factor alpha and transforming growth factor beta. In conclusion the renoprotective effect of alpha-M on CDDP-induced nephrotoxicity was associated with the attenuation in oxidative/nitrosative stress and inflammatory and fibrotic markers and preservation of catalase activity.

Treatment with pyrrolidine dithiocarbamate improves proteinuria, oxidative stress, and glomerular hypertension in overload proteinuria.

We evaluated whether the blockade of the proinflammatory transcription factor NF-kappaB would modify the oxidative stress, inflammation, and structural and hemodynamic alterations found in the kidney as a result of massive proteinuria. Twenty male Sprague-Dawley rats were injected with 2 g of BSA intraperitoneally daily for 2 wk. Ten of them received in addition the inhibitor of NF-kappaB activation pyrrolidine dithiocarbamate (PDTC; 200 mg.kg(-1).day(-1) sc) and the rest received vehicle. Seven rats that received intraperitoneal saline were used as controls. Glomerular hemodynamics were studied after 14 days. Markers of oxidative stress (NF-kappaB subunit p65+ cells, 3-nitrotyrosine, and 4-hydroxynonenal), inflammation (cortical CD68+ cells and NOS-II), and afferent arteriole damage were assessed by immunohistochemistry and morphometry. Activity of antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase was evaluated in renal cortex and medulla. Albumin overload induced massive proteinuria, oxidative stress with reduced activity of antioxidant enzymes, NF-kappaB activation, inflammatory cell infiltration, a significant presence of proteinaceous casts, systemic and glomerular hypertension, as well as arteriolar remodeling. Treatment with PDTC prevented or improved all of these findings. In this model of nephrotic syndrome, we demonstrate a key role for oxidative stress and inflammation in causing systemic and glomerular hypertension and proteinuria. Oxidative stress and inflammation may have a key role in accelerating renal injury associated with intense proteinuria.

Estórias infantis: um recurso para a promoçäo do desenvolvimento de crianças pré-escolares / Children teles: a resource for the promotion of the preschooler children`s development

Este trabalho aborda a contribuiçäo da atividade contar estórias no desenvolvimento infantil, focalizando a faixa etária de quatro a seis anos. Apresenta-se através do relato de prática realizada na cidade de Säo Carlos (SP) junto a pré-escolas que recebem crianças de diferentes classes sócio-econômicas. Os resultados mostram como a atividade foi avaliada pelas professoras/pajens, bem como as variaçöes de desempenho apresentadas pelas crianças das duferentes instituiçöes durante a apresentaçao das estórias. Ressalta-se que os recursos utilizados (personagens, palco etc.), além de estimular o interesse das crianças, podem ser confeccionados com materiais de baixo custo, estimulando e ampliando as possibilidades de criaçäo e aplicaçäo dos mesmos

Estorias infantis? um recurso para a promocao do desenvolvimento de criancas pre-escolares

Aborda a contribuicao da atividade 'contar estorias' no desenvolvimento infantil, focalizando a faixa etaria de quatro a seis anos. Apresenta-se atraves do relato de pratica realizada na cidade de Sao Carlos (SP) junto a pre-escolas que recebem criancas de diferentes classes socio-economicas. os resultdados mostram como a atividade foi avaliada pelas professoras/pajens, bem como as variacoes de desempenho apresentadas pelas criancas das diferentes instituicoes durante a apresentacao das estorias. Ressalta-se que os recursos utilizados (personagens, palco etc). alem de estimular o interesse das criancas, podem ser confeccionados com materiais de baixo custo, estimulando e ampliando as posibilidades de criacao e aplicacao dos mesmos.