Batch and semi-continuous treatment of cassava wastewater using microbial fuel cells and metataxonomic analysis.

The treatment of agroindustrial wastewater using microbial fuel cells (MFCs) is a technological strategy to harness its chemical energy while simultaneously purifying the water. This manuscript investigates the organic load effect as chemical oxygen demand (COD) on the production of electricity during the treatment of cassava wastewater by means of a dual-chamber microbial fuel cell in batch mode. Additionally, specific conditions were selected to evaluate the semi-continuous operational mode. The dynamics of microbial communities on the graphite anode were also investigated. The maximum power density delivered by the batch MFC (656.4 µW m - 2 ) was achieved at the highest evaluated organic load (6.8 g COD L - 1 ). Similarly, the largest COD removal efficiency (61.9%) was reached at the lowest organic load (1.17 g COD L - 1 ). Cyanide degradation percentages (50-70%) were achieved across treatments. The semi-continuous operation of the MFC for 2 months revealed that the voltage across the cell is dependent on the supply or suspension of the organic load feed. The electrode polarization resistance was observed to decreases over time, possibly due to the enrichment of the anode with electrogenic microbial communities. A metataxonomic analysis revealed a significant increase in bacteria from the phylum Firmicutes, primarily of the genus Enterococcus.

Reduction of Toxic Metal Ions and Production of Bioelectricity through Microbial Fuel Cells Using Bacillus marisflavi as a Biocatalyst.

Industrialization has brought many environmental problems since its expansion, including heavy metal contamination in water used for agricultural irrigation. This research uses microbial fuel cell technology to generate bioelectricity and remove arsenic, copper, and iron, using contaminated agricultural water as a substrate and Bacillus marisflavi as a biocatalyst. The results obtained for electrical potential and current were 0.798 V and 3.519 mA, respectively, on the sixth day of operation and the pH value was 6.54 with an EC equal to 198.72 mS/cm, with a removal of 99.08, 56.08, and 91.39% of the concentrations of As, Cu, and Fe, respectively, obtained in 72 h. Likewise, total nitrogen concentrations, organic carbon, loss on ignition, dissolved organic carbon, and chemical oxygen demand were reduced by 69.047, 86.922, 85.378, 88.458, and 90.771%, respectively. At the same time, the PDMAX shown was 376.20 ± 15.478 mW/cm2, with a calculated internal resistance of 42.550 ± 12.353 Ω. This technique presents an essential advance in overcoming existing technical barriers because the engineered microbial fuel cells are accessible and scalable. It will generate important value by naturally reducing toxic metals and electrical energy, producing electric currents in a sustainable and affordable way.

Potential Use of Andean Tuber Waste for the Generation of Environmentally Sustainable Bioelectricity.

The growing demand for agricultural products has increased exponentially, causing their waste to increase and become a problem for society. Searching for sustainable solutions for organic waste management is increasingly urgent. This research focuses on considering the waste of an Andean tuber, such as Olluco, as a fuel source for generating electricity and becoming a potential sustainable energy source for companies dedicated to this area. This research used Olluco waste as fuel in single-chamber microbial fuel cells using carbon and zinc electrodes. An electric current and electric potential of 6.4 ± 0.4 mA and 0.99 ± 0.09 V were generated, operating with an electrical conductivity of 142.3 ± 6.1 mS/cm and a pH of 7.1 ± 0.2. It was possible to obtain a 94% decrease in COD and an internal resistance of 24.9 ± 2.8 Ω. The power density found was 373.8 ± 28.8 mW/cm2 and the current density was 4.96 A/cm2. On day 14, the cells were connected in earnest, achieving a power of 2.92 V and generating enough current to light an LED light bulb, thus demonstrating the potential that Olluco waste has to be used as fuel in microbial fuel cells.

Use of Pineapple Waste as Fuel in Microbial Fuel Cell for the Generation of Bioelectricity.

The excessive use of fossil sources for the generation of electrical energy and the increase in different organic wastes have caused great damage to the environment; these problems have promoted new ways of generating electricity in an eco-friendly manner using organic waste. In this sense, this research uses single-chamber microbial fuel cells with zinc and copper as electrodes and pineapple waste as fuel (substrate). Current and voltage peaks of 4.95667 ± 0.54775 mA and 0.99 ± 0.03 V were generated on days 16 and 20, respectively, with the substrate operating at an acid pH of 5.21 ± 0.18 and an electrical conductivity of 145.16 ± 9.86 mS/cm at two degrees Brix. Thus, it was also found that the internal resistance of the cells was 865.845 ± 4.726 Ω, and a maximum power density of 513.99 ± 6.54 mW/m2 was generated at a current density of 6.123 A/m2, and the final FTIR spectrum showed a clear decrease in the initial transmittance peaks. Finally, from the biofilm formed on the anodic electrode, it was possible to molecularly identify the yeast Wickerhamomyces anomalus with 99.82% accuracy. In this way, this research provides a method that companies exporting and importing this fruit may use to generate electrical energy from its waste.

Electric Current Generation by Increasing Sucrose in Papaya Waste in Microbial Fuel Cells.

The accelerated increase in energy consumption by human activity has generated an increase in the search for new energies that do not pollute the environment, due to this, microbial fuel cells are shown as a promising technology. The objective of this research was to observe the influence on the generation of bioelectricity of sucrose, with different percentages (0%, 5%, 10% and 20%), in papaya waste using microbial fuel cells (MFCs). It was possible to generate voltage and current peaks of 0.955 V and 5.079 mA for the cell with 20% sucrose, which operated at an optimal pH of 4.98 on day fifteen. In the same way, the internal resistance values of all the cells were influenced by the increase in sucrose, showing that the cell without sucrose was 0.1952 ± 0.00214 KΩ and with 20% it was 0.044306 ± 0.0014 KΩ. The maximum power density was 583.09 mW/cm2 at a current density of 407.13 A/cm2 and with a peak voltage of 910.94 mV, while phenolic compounds are the ones with the greatest presence in the FTIR (Fourier transform infrared spectroscopy) absorbance spectrum. We were able to molecularly identify the species Achromobacter xylosoxidans (99.32%), Acinetobacter bereziniae (99.93%) and Stenotrophomonas maltophilia (100%) present in the anode electrode of the MFCs. This research gives a novel use for sucrose to increase the energy values in a microbial fuel cell, improving the existing ones and generating a novel way of generating electricity that is friendly to the environment.

Long-term performance and acute toxicity assessment of scaled-up air-cathode microbial fuel cell fed by dairy wastewater.

Long-term performance of a scaled-up air-cathode microbial fuel cell (MFC) and toxicity removal were studied with dairy wastewater (DW) used as the substrate. The MFC in a semi-continuous flow was strategically inoculated with consortium of Shewanella oneidensis and Clostridium butyricum. The scaled-up approach delivered a maximum power density of 0.48 W/m3 (internal resistance of 73 Ω) removing 93% of total chemical oxygen demand and 95% of total biochemical oxygen demand at organic loading rate (OLR) of 0.9 kg COD/m3/d and hydraulic retention time (HRT) of 21 days. It also achieved high removal efficiency of nitrate (100%), organic nitrogen (57%), sulfate (90%) and organic phosphorus (90%). The power generation and DW degradation performance decreased with OLR of 1.8 kg COD/m3/d and HRT of 10.5 days. Furthermore, testing of acute toxicity with the microcrustacean, Daphnia similis, revealed high toxic effect of the raw DW, but no toxic effects of the MFC effluent during 95 days of operation. These outcomes demonstrated that scaled-up MFC fed with high-strength DW should be an effective system for pollutants removal and simultaneously energy recovery.

Competition between Second-Generation Ethanol and Bioelectricity using the Residual Biomass of Sugarcane: Effects of Uncertainty on the Production Mix.

Several economies around the world are using second-generation (2G) ethanol produced from agricultural residues, like sugarcane straw and bagasse, as a sustainable solution to replace petroleum products. Since first-generation (1G) ethanol uses the sugars of sugarcane, an integrated 1G⁻2G production would enable the production of more ethanol from the same amount of sugarcane without leading to increased use of arable land. The ethanol production process is complex, involving different high-energy consumption operations such as evaporation and distillation. The economic competitiveness of this process depends heavily on the amount of thermal and electrical energy produced using sugarcane straw and bagasse as input. Thus, the objective of this study was to use the mean-variance methodology to determine the optimal allocation of residual sugarcane biomass between 2G ethanol and bioelectricity productions, with simultaneous objectives of maximizing the return and minimizing the risk for investors of this sector. In this paper, four scenarios are analyzed. The first one is the base scenario that represents the current state of production costs and investments. scenarios 2, 3, and 4 considered four cuts of 10%, 20%, and 40% in the production cost of ethanol 2G, respectively. The results show the optimum biomass allocations and the growth rates of returns as a function of risk growth. It can be concluded that from scenario 4, the production of 2G ethanol becomes financially advantageous for the investor, presenting greater returns with smaller risks.

Application of microbial fuel cell technology for vinasse treatment and bioelectricity generation.

OBJECTIVE: Our study evaluated the performance of different two-chambered microbial fuel cell (MFC) prototypes, operated with variable distance between electrodes and Nafion membrane and specific inoculum concentration, applied for vinasse treatment. RESULTS: The performance of the developed MFC resulted in a maximum current density of 1200 mA m-2 and power density of 800 mW m-2 in a period of 61 days. MFC performed a chemical oxygen demand removal at a rate ranging from 51 to 60%. CONCLUSIONS: Taking our preliminary results into consideration, we concluded that the MFC technology presents itself as highly promising for the treatment of vinasse.

New insights in photosynthetic microbial fuel cell using anoxygenic phototrophic bacteria.

Anoxygenic phototrophic bacteria (APB) pay a key role in biogeochemical cycles, and it can convert light energy to chemical energy by photosynthesis process. Photosynthetic microbial fuel cell (photo-MFC) is regarded as a promising energy-harvesting technology, which is also applied to environment treatment in recent years. The previous studies show that photo-MFC with APB have higher power putout than other bioelectrochemical systems. However, photo-MFC with APB is not reviewed due to some limited factors in the development process. In this review, photo-MFC with APB is treated according to its electron transfer pathways, the current understanding, APB strains, application, influence of substrates, and economic assessment. Meanwhile, knowledge of photosynthesis components and electron transfer pathways of APB is crucial for developing new energy and easing the serious energy crisis. Moreover, some new insights (the optimization of light source and self-sustaining bioelectricity generation) are proposed for the future explorations.

Biogenêse mitocondrial e exercício físico: hipótese do acoplamento elétrico-transcripcional / Mitochondrial biogenesis and physical exercise: electric-transcriptional coupling hypothesis

Resumo Uma das principais modificações ocorridas no organismo em decorrência do treinamento físico-esportivo envolvendo exercícios físicos de longa duração é o aumento na quantidade e qualidade funcional de mitocôndrias do tecido muscular esquelético. Não existe até o momento um mecanismo causal explicativo para esse fenômeno. A proposta a ser discutida neste ensaio é denominada por "hipótese do acoplamento elétrico-transcripcional". Segundo a mesma, modificações na atividade elétrica celular, principalmente de despolarização membranar, constituem-se em método de controle e regulação dos processos de biossíntese no organismo multicelular. Por exemplo, estudos que provocaram hiperpolarização artificial em células somáticas induziram diferenciação celular e supressão da proliferação, sendo que o contrário ocorreu com a despolarização. Ou seja, a despolarização celular durante o exercício físico devido a contração muscular intensa e constante pode ativar processos responsáveis por biossínteses e, possivelmente, duplicação de mitocôndria.

Abstract One of the main changes happened in skeletal muscle tissue as a result of physical and sport training with prolonged exercise is the increase in the quantity and functional quality of mitochondria. There is not yet an explanatory causal mechanism for this phenomenon. The suggestion to be discussed in this assay is called "electric-transcriptional coupling hypothesis". In this hypothesis, changes in electrical activity, mainly membrane depolarization, are considered methods used for the control of biosynthesis in multicellular organisms. For example, studies that resulted in somatic cell hyperpolarization induced suppression of differentiation and proliferation, and the opposite happened with depolarization. That is, cell depolarization that occur during the exercise as a consequence of intense and prolonged muscle contraction could activate processes responsible for biosynthesis and, possibly, mitochondrial replication.

LOS CAMPOS BIOELÉCTRICOS Y ALGUNAS APLICACIONES MÉDICAS - REVISIÓN / BIOELECTRIC FIELDS AND SOME MEDICAL APPLICATIONS - REVIEW

Con las investigaciones de Emil Du Bois-Reymond, uno de los fundadores de la electrofisiología, se dio inicio a la era de la bioelectricidad. DuBois documentó en detalle actividades eléctricas asociadas con excitación nerviosa, contracción muscular y procesos de cicatrización. En la actualidad es reconocido que los campos eléctricos (CE) están presentes en los organismos vivos y que direccionan e influyen procesos biológicos como la embriogénesis, regeneración y cicatrización de heridas. Diversos estudios han demostrado como los CE interfieren en la biosíntesis y la migración celular, dando lugar a nuevas estrategias para la reparación de ligamentos y regeneración de tejidos. En la actualidad las corrientes y CE biológicos suministran información necesaria para diversos tipos de diagnósticos y tratamientos. En este trabajo se hace una revisión de algunos estudios realizados alrededor de la generación de campos bioeléctricos endógenos, sus sustratos biológicos y aplicaciones médicas.

The era of bioelectricity began with the investigations of Emil Du Bois-Reymond, one of the founders of electrophysiology. DuBois documented in detail electrical activities associated with nerve excitation, muscle contraction and healing processes. It is currently recognized that electric fields (EFs) are present in living organisms and that they direct and influence biological processes such as embryogenesis, regeneration and wound healing. Several studies have shown how EFs interfere with biosynthesis and cell migration, leading to new strategies for repairing ligaments and for tissue regeneration. At present, biological EFs and currents provide information needed for different types of diagnoses and treatments. This paper reviews some studies focused on the generation of endogenous bioelectric fields, their biological substrates and medical applications.