Wiring of Escherichia coli With Different Electron Transport Mediators

Natural Sciences & Environment Journal (NSEJ), Volume 2, Jan 2017

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Abstract
Gram-negative Escherichia coli strain JM109 looks promising for energy generation in biofuel cells. The cells we are using over express the di-heme membrane protein from Bacillus subtilis succinate:quinone reductase. This protein has two b-type hemes: heme bL with a midpoint potential of -132 mV vs NHE and heme bH with a midpoint potential of+16 mV vs NHE. The protein is present in the inner cell membrane and can potentially be used to enhance the wiring between the cell and different electron transfer mediators. The role of mediators in microbial biosensors and biofuel cells is to take electrons from the oxidizing enzymes and/or respiratory chain and transport them to the surface of the electrode and thus to replace the natural electron acceptor - oxygen, in the case of aerobic bacteria for example. In this way artificial electron shuttles can enhance electron transfer between microbial cells and electrodes. It is well known that different water-soluble mediators such as 2,6-dichlorophenol indophenol (DCPIP) or ferricyanide (FeCN) and hydrophobic ferrocene derivatives can be effectively used for coupling microbial metabolism and electrodes . One recent trend in wiring of living cells and electrodes is to use polymeric mediators, which exhibit efficient electron shuttling properties for multiple layers of microbial cells [2,3]. In the current study the application of different artificial electron transport mediators for efficient electrical wiring of gram-negative bacteria E. coli JM109 were investigated. Different characteristics of the system containing a graphite electrode modified with cells, a Ag|AgCl (0.1 M KCl) electrode and a platinum wire used as reference and auxiliary electrodes, respectively, were evaluated in flow analysis mode when glucose was used as a substrate. The influence of pH of buffer solution and presence of oxygen on the current response was evaluated. E. coli JM109 cells immobilized on the surface of graphite electrode did not show any direct electron transport. We have not been able to show any current response from the cells in the presence of DCPIP-solution or ferrocene immobilized on the surface of the electrode. However we obtained very good results with a flexible osmium redox polymeric mediator and the water-soluble mediator - ferricyanide.

Author(s): Sergey Alferov, Vasile Comana, Tobias Gustavssonc, Cecilia Hagerhallc, Lo Gortona

Urban floods in the Arouca village (Portugal): Influence of surface runoff network and land use dynamics

Natural Sciences & Environment Journal (NSEJ), Volume 2, Jan 2017

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Urban flooding is a phenomenon which reflects the increasing urbanization process of the territory. Although not intensively studied in Portugal, urban flood episodes are growing throughout the country in frequency and affected areas. This type of flooding, assuming in many cases the flash floods characteristics, is the result of water concentration in topographically depressed areas during episodes of intense rainfall over short time. This floods events are enhanced by soil sealing and by malfunction or undersized pluvial rainwater drainage systems. The most critical phase of these events occurs when the capacity of this underground drainage system is exceeded, causing the inversion in flow direction and consequently, its concentration in nodal points and emergence at the surface. To understand the dynamics of the surface runoff in the Arouca urban area (Portugal), it was analysed the role played by each element of the urban grid towards the surface runoff process. For this, it was considered: (1) the slopes that favor the rapid and intense spread of the flow, (2) the topography and the urban morphology that interfere directly in the surface drainage pattern. By the interpretation of aerial photos and recent orthophotos, it was also analysed the evolution of land use in the last five decades, aiming to understand the effect that gradual sealing promoted in the increase of the superficial flow component. The collected inventory has enabled the identification of the most susceptible areas in the village and the exposed elements to this risk. The most problematic areas corresponds to the lower areas of the village and some streets where occurs a dual concentration of the runoff, i.e., the surface and the pluvial drainage flows. On the other hand, there was an increase of 21% on artificial surfaces, as a consequence of forest and agricultural areas decline between 1958 and 2005. The chosen methodological approach and the obtained results are a contribution to improve the land planning on the Arouca municipality.

Author(s): In?s Marafuz,Alberto Gomes

The importance of selecting relevant impact categories and alignment of LCIA methods with the Millennium Ecosystem Assessment Reporting Categories

Natural Sciences & Environment Journal (NSEJ), Volume 2, Jan 2017

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International awareness and application of life cycle assessment (LCA) as an objective framework and method to assess true environmental and human health impacts has grown substantially in the advent of the new millennium. The framework of LCA, a holistic system based approach to identify and assess impacts associated with products, processes and services, is readily understood and widely supported. In practice, the methods that underlie the interpretation of impacts are deficient in scope of the relevant impacts that have been identified in the broader aspects of sustainability and ecosystem services. The purpose of this paper is twofold: first, to bring awareness to the importance of selecting relevant and appropriate impact categories when conducting life cycle assessment studies; second, to present an approach to align the life cycle impact assessment (LCIA) methods to a broader, worldwide perspective that includes the concerns of both developed and developing nations. As such, the proposed approach to alignment is based on the UNEP Millennium Ecosystem Assessment (MA) Framework. Key benefits include the promotion of a global consensus by researchers and policy makers; a means of integration with the broader international community of sustainability experts in government, industry and non-governmental organizations; and most important achieve a means of validating the efforts to raise human well-being and reduce abject poverty through life cycle assessment based on the work and comprehensive data and analysis that has been done through the MA efforts.

Author(s): Thomas Gloria

Inter-annual variability of the Cold ridge and atmospheric driving forces

Natural Sciences & Environment Journal (NSEJ), Volume 2, Jan 2017

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The cold ridge can be defined as an episodic extended sloping tongue of cold water off the Tsitsikamma coast in the Agulhas bank. This feature owes its existence to primary and secondary production as it enhances more nutrient rich water into the surface. The predictability and the mechanism leading to its development is yet to be understood, however Roberts (2005) indicated that its existence and periodicity is a function of wind forcing. Analysis of the sea surface temperature data collected from Tsitsikamma and Knysna indicates that there is seasonality in the variation of cold and warm episodes of the water column. The wind stress analysis over the area shows an inter-annual relation with the temperature analysis and these can also be said about the CAP index. The large scale global climatic perturbation, the SOI time series also relates to the local sea level pressure (SLP) analysis with high peak values of SLP found during the 97/98 summer season of the El Nino event. The variation observed in the SST data, wind analysis and the sea level pressure altogether are important tools to understand for predicting the occurrence of the cold ridge.

Author(s): Aluwani E. Ramulifho

Electrochemical and Photo-Assisted Electrochemical Degradation of Real Textile Effluent

Natural Sciences & Environment Journal (NSEJ), Volume 2, Jan 2017

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The textile industry is one of the most polluting sectors in terms of volume and complexity of effluent discharge. Textile wastewater is characterized by high chemical oxygen demand (COD) and total organic carbon (TOC), as well as, strong color. Conventional treatment of textile wastewater generally consists of coupling chemical coagulation with biological treatment. However, these methods cannot be employed where the wastewater is resistant to biological treatment. An alternative path could be the application of electrochemical technology, which benefits from advantages such as versatility, environmental compatibility and potential cost effectiveness. The present study evaluates the efficiency of electrochemical (EC) and photo-assisted electrochemical (PAEC) degradation of real textile effluent under galvanostatic conditions. The effluent was provided by the Brazilian textile company Tecelagem Sao Carlos SA. It was collected in two stages: (a) without any pretreatment and (b) after biological treatment. A single-compartment photo-electrochemical filter-press cell was used with a commercially available Ti/Ru0.3Ti0.7O2 - DSA? electrode (area = 14 cm2) with a Ti-mesh cathode (area = 14 cm2). The UV radiation was provided by a 250 W Hg lamp. A constant temperature of 28?C was used. All electrolyses were performed adding NaCl and Na2SO4 as the supporting electrolyte in different proportions, keeping constant ionic strength at 0.15 mol L-1. For the study of the effect of current density the following values were: 10, 20, 40, 60, 80 and 120 mA cm-2. When the untreated (no electrolyte addition) effluent is treated there is little or no color or TOC removal, even at the higher current densities. As the conductivity of the effluent is low (~2 mS cm-1), electrochemical treatment of the as-received effluent is extremely inefficient. When salts are added to the effluent, the efficiency of the process improves. As a result when the current density is increased there is a concurrent increase in the extent of colour removal and TOC. The effect of substituting stepwise the Na2SO4 with NaCl was studied and it was observed that the color, COD and TOC removal increases almost linearly with the chloride ion concentration. This is due to the in-situ formation of the Cl2 and free chlorine species in solution (e.g. OCl-). With the addition of the salts the conductivity of the effluent increases (17 mS cm-1) and as a result the operating cell potential is reduced and the energy consumption is lower. Overall the photo-assisted method is observed to be more efficient than the purely electrochemical system. When the biologically treated effluent is electrochemically treated, analogous results to those obtained for the untreated effluent are obtained - inefficient color removal in the absence of salts and increased efficiency with NaCl - however, the energy efficiency is much greater. These results indicate that the EC and PAEC methods are best employed as a final treatment process (polishing) after biological treatment. As Cl2 is formed in- situ the results will also be presented with a determination of the extent of formation of harmful chlorinated degradation by-products.

Author(s): P. A. Alves, G. R. P. Malpass, D. W. Miwa, A. J. Motheo

Solar Photoelectro-Fenton: a Very Efficient and Low Cost Environmentally Friendly Electrochemical Method for Water Remediation

Natural Sciences & Environment Journal (NSEJ), Volume 2, Feb 2017

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This lecture presents the fundamentals and some interesting applications of the solar photoelectro-Fenton (SPEF) method for the destruction of organics in wastewaters. This electrochemical advanced oxidation method is an environmentally friendly technique where hydrogen peroxide is continuously supplied to an acidic contaminated solution from the two-electron reduction of oxygen injected to a gas-diffusion cathode: O2(g) + 2 H+ + 2 e ?? H2O2 (1) The oxidizing power of electrogenerated H2O2 is then strongly enhanced by adding a small quantity of Fe2+ catalyst to the solution to give Fe3+ and hydroxyl radical (OH) by the well-known Fentons reaction: Fe2+ + H2O2 ? Fe3+ + OH + OH- (2) . An undivided cell is used to oxidize the pollutants by both, OH formed from reaction (2) and M(OH) produced from water oxidation at a high O2-overvoltage anode by reaction (3): M(H2O) ? M(OH) + H+ + e- (3) The SPEF process also involves the additional irradiation of the treated solution with sunlight to favor: (i) the photoreduction of Fe(OH)2+, which is the predominant Fe3+ species in acid medium, to Fe2+ and more OH by photo-Fenton reaction (4), and (ii) the photolysis of complexes formed between Fe(III) and final carboxylic acids such as shown for oxalic acid via reaction (5): Fe(OH)2+ + hv ? Fe2+ + OH (4) Fe(C2O4)n(3-2n) + hv ? 2 Fe2+ + (2n-1) C2O42- + 2 CO2 (5) Oxalic acid is formed during the oxidation of most aromatics and the fast photodecarboxylation of Fe(III)-oxalate complexes (Fe(C2O4)+, Fe(C2O4)2- and Fe(C2O4)33-) favors their decontamination. Exemples on the good oxidation ability of SPEF are presented for solutions of: (i) salicylic acid and the aminoacid a-methylphenylglycine using small electrolytic cells with a Pt or boron-doped diamond (BDD) anode and and O2-diffusion cathode, all them of 3 cm2 area, and (ii) the herbicide mecoprop and o-, m- and p- cresols using a flow plant of 2.5 l with a filter-press cell containing BDD and O2-diffusion electrodes of 20 cm2 area, coupled to a solar photoreactor with 600 ml of irradiation volume. Treated solutions were prepared with 0.05 M Na2SO4 and 0.25-1.0 mM Fe2+ at pH 3.0 and electrolyses were carried out by applying a constant current density between 25 and 150 mA cm-2. Comparative trials with electro-Fenton (EF) in the dark were also made to confirm the synergistic effect of sunlight during the SPEF process. While in the EF method a slow, but complete mineralization of all contaminants is found using a BDD anode due to the efficient oxidizing action of homogeneous OH and BDD(OH), the SPEF treatment yields a much faster decontamination with a Pt or BDD anode because of the efficient photodecomposition of Fe(III) complexes with UVA irradiation supplied by solar light. The efficiency of all degradation processes increases strongly with rising pollutant concentration and decreasing current density. The decay kinetics for all initial pollutants and the evolution of their aromatic by?products were followed by reversed-phase HPLC chromatography, whereas generated carboxylic acids were identified and quantified by ion-exclusion HPLC chromatography. Detection of reaction intermediates allows the proposal of a plausible sequence for the mineralization of each initial pollutant. In all cases the ultimate product is oxalic acid, which forms Fe(III)-oxalate complexes that can be destroyed with BDD(OH) in EF, but much more rapidly photolyzed to CO2 in SPEF. Other final acids like acetic or oxamic are also formed, undergoing slower destruction. The treatment of 128 mg l-1 of all cresols with 0.5 mM Fe2+ by SPEF in the flow plant leads to an energy cost for total mineralization as low as 6.6 kWh m-3 at 25 mA cm-2, showing the viability of this procedure for its possible application to wastewater remediation at industrial scale.

Author(s): Enric Brillas

The diel feeding biology of the pelagic goby Sufflogobius bibarbatus off Namibia

Natural Sciences & Environment Journal (NSEJ), Volume 2, Feb 2017

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The pelagic goby Sufflogobius bibarbatus is commonly found off the southwest coast of Africa between the Kunene River and St Sebastian Bay. The stomach contents of 1485 pelagic gobies were examined from two diel stations inshore and offshore off the Namibian coast during January 2006. The pelagic goby is a predator and the most frequently occurring prey items included polychaetes, euphausiids, copepods and amphipods. Larger fish mainly fed on polychaetes, whereas the diet of smaller and intermediate size classes appeared to be more diverse. Food containing ratios were lower during the night than by day, but more diverse. The results shed new light on the ecology of the species which is becoming increasingly important in the region.

Author(s): Cedras R.B.

Centurial channel and landcover change of the valley floodplain and its implication on flood hazard, Kaoping River, Southern Taiwan

Natural Sciences & Environment Journal (NSEJ), Volume 2, Feb 2017

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The Kaoping River (KPR) is a small mountainous river with a length around 170 km, the area of 3250 km2 and a very high sediment yield (11,000 t km-1 yr-1). Its main trunk and major tributaries are characterized by braided channel pattern wherever the valley is wider. As many river valley around the world, its floodplains have experienced significant human modification over the 20th century. In 2009, Typhoon Morakot, with extremely intensive rainfall (> 150-year return period), caused severe flood hazards and has aroused great concern of the floodplain management especially when it is suspect that the frequency of extreme weather events is rising in Taiwna. This study aims to investigate the landcover change of the valley floodplains of KPRs two major tributaries, the Nantszhsien Stream and the Laonon Stream, over a century and its implication on the flood hazard. Landcover and geomorphic interpretation are completed by using historical maps, aerial photographs and orthomaps from early 20th to 2009 (after the typhoon) on a GIS platform. It is found that along with the process of channelization, the former floodplain has been reclaimed, mainly for agricultural purpose. The flooded area induced by Typhoon Morakot was within the former active-channels zone identified from 1948 aerial photos and historical maps published in 1920s for the study area. These pictorial materials together provide a good baseline for delineating the so-called fluvial territory that is wide and continuous enough to guarantee the floodable areas to minimize the risk to the inhabitants. It also contrasts the space of the river reservation zone, in which the development is prohibited by law

Author(s): Su-Min Shen

Seasonality and abundance of jellyfish in the northern Benguela ecosystem with preliminary observations on their fish associates

Natural Sciences & Environment Journal (NSEJ), Volume 2, Mar 2017

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The biomass of jellyfish off Namibia is currently thought to exceed that of finfish there, and this has implications for our understanding of ecosystem functioning in the region. Our knowledge about even the basic biology of jellyfish is scant. Here we examine seasonality of jellyfish off Namibia using information provided by the Namibian Ministry of Fisheries and Marine Resources from the commercial fisheries sector. The data span the period from the mid 1990s until 2006 and include information from both the demersal and pelagic sectors. The data cannot be considered quantitative and we are restricted to presenting information on seasonal changes in the percentage of trawls containing jellyfish; subdivided by depth and latitude. Jellyfish represent just one (the pelagic) lifehistory phase of the organisms and their release by the benthic life-history phase is often cued by sudden changes in temperature. Given that upwelling ecosystems are characterized by often sudden changes in temperature throughout the year, we hypothesize that jellyfish will be present all year around off Namibia. We also present some preliminary information on the possible associations between finfish and jellyfish.

Author(s): B. A. Flynn, M. J. Gibbons

Heterosis for Photosynthetic Characters in F1 hybrid rice (Oryza Sativa L.) produced from a lowland thermo-sensitive genic male sterile line and upland drought tolerance cultivars

Natural Sciences & Environment Journal (NSEJ), Volume 2, Mar 2017

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The experiment was conducted in a glass-house in order to determine the heterosis for photosynthetic characters in F1 hybrids produced by crossing a thermosensitive male sterile (TGMS) line, 103 s (female parent) and two drought-tolerant upland rice male-parent cultivars (Beodien and IR 71525). Three levels of soil-water potential, well watered (WW), moderate water deficit (MD), and severe water deficit (SD) were imposed at tillering stages. Heterosis for photosynthesis in terms of a carbondioxide exchange rate (CER) in single leaf as well as other related characters such as stomatal conductance, transpiration rate, specific leaf area, chlorophyll content and water use efficiency were measured in rice plants under drought and recovering conditions using a portable type of CO2/H2O gas analyzer (LI-6400, LI-COR, USA). The results showed that while suffering drought, the heterosis value for CER over the best parent (Hb) in two F1 decreased from 1.02 to 0.68. However, after recovering from drought this value increased in both F1 hybrids from 0.79 to 1.13. Heterosis for WUE increased in F1 103S/Beodien in both drought treatments (Hb from 0.73 to 3.07). This value increased in the 103S/IR 71525 (Hb = 0.66-0.55) in moderate drought conditions (Hb from 0.77 to 1.14), whereas it decreased (Hb from 1.14 to 0.23) under severe drought conditions. An insignificant heterosis for SPAD (an indicator of leaf chlorophyll content) was observed in F1 hybrid rice under all conditions. The interesting CER characteristic in F1 hybrid rice under drought conditions may be due to both greater stomatal conductance and water-use efficiency. Thus, the results indicate that it is possible to produce an F1 hybrid with high yield potential and drought tolerance by crossing a TGMS line with upland male-parent cultivars. Key Words: Photosynthesis, heterosis, F1 hybrid rice, drought tolerance, water use efficiency. ??

Author(s): Duong Thi Thu Hang, Pham Van Cuong, Hoang Viet Cuong, Toshihiro Mochizuki