Waste water treatment by exoelectrogenic bacteria isolated from technogenically transformed lands

The capacity of sulfur-reducing bacteria Desulfuromonas acetoxidans IMV B-7384, Geobacter sp. CB35 and Desulfuromusa sp. CB30 and green photosynthesizing bacteria Chlorobium limicola IMV K-8 for exoelectrogenesis was investigated during their growth in wastewater of industrial and municipal origin. The strains of exoelectrogens, which are characterized by resistance to heavy metal ions, were isolated from the man-made Yavorivske lake located in the Lviv Oblast in Ukraine (D. acetoxidans IMV-7384, Ch. limicola IMV K-8) and mine waste heaps of the Chervonohrad mining industry region (Geobacter sp. CB 30 and Desulfuromusa sp. CB 35). Bacteria D. acetoxidans IMВ B-7384 proved to be the most effective exoelectrogens. The power density of a microbial fuel cell (MFC) with the application of D. acetoxidans IMV B-7384 and the infiltrate of the Lviv solid waste landfill was 2.0 ± 0.05 W/m2 and the reduction of chemical oxygen demand of wastewater was 99%. The new approach to improving the MFC performance was investigated. It includes a combination of phototrophic microorganisms Ch. limicola and heterotrophic microorganisms, which reduce the content of nitrates, nitrites, ammonia, sulfates, sulfites, hydrogen sulfide, while simultaneously generating electric current

Photosynthetic membrane-less microbial fuel cells to enhance microalgal biomass concentration

The aim of this study was to quantitatively assess the net increase in microalgal biomass concentration induced by photosynthetic microbial fuel cells (PMFC). The experiment was conducted on six lab-scale PMFC constituted by an anodic chamber simulating an anaerobic digester connected to a cathodic chamber consisting of a mixed algae consortia culture. Three PMFC were operated at closed circuit (PMFC+) whereas three PMFC were left unconnected as control (PMFC-). PMFC+ produced a higher amount of carbon dioxide as a product of the organic matter oxidation that resulted in 1.5–3 times higher biomass concentration at the cathode compartment when compared to PMFC-Peer ReviewedPostprint (author's final draft

Future Microbial Applications for Bioenergy Production: A Perspective

The fast receding concentration of fossil fuels and the mounting global demand of energy has necessitated the production of alternate fuels to replace the conventional fossil fuels so as to counter the increased deposition of greenhouse gasses in the atmosphere, which has led to considerable climatic changes. These changes could result in catastrophic repercussions in the near future, including rising temperature and sea levels. Evidently, the utilization of fossil fuels for electricity and heat production and for transportation accounts for 25% and 14% of the total greenhouse gas emissions, respectively (IPCC, 2014). Therefore, nowadays, the production of economically feasible and eco-friendly renewable energy fuels is the world's highest demand that indicates the potential to simultaneously replace the conventional fuels and reduce the environmental concern. The use of versatile microorganisms to generate renewable energy fuels from the biomass and biological wastes can diminish this menacing concern to a large extent. The interest in the production of various biofuels using microorganisms has been steadily increasing in the recent years (Table 1) (Liao et al., 2016), particularly because of the metabolic diversity of different microorganisms that enables the production of biofuels from various substrates. For example, most of the bacteria can easily convert sugars into ethanol, and cellulolytic microbes can utilize plant-driven substrates. Cyanobacteria and microalgae possess the potential to photosynthetically reduce the atmospheric CO2 into biofuels, and methanotrophs can use methane to produce methanol (Liao et al., 2016). In addition, some of the bacteria such as Geobacter sulfurreducens and Shewanella oneidensis exhibit specific “molecular machinery” that helps transfer electrons from microbial outer-membrane to conductive surfaces (Kracke et al., 2015), subsequently, this feature can be deployed in bioelectrochemical devices for biohydrogen and bioelectricity generation. The impending need to address the challenges involved in enabling these microorganisms to become a more feasible option for replacing the conventional fossil fuels has been discussed in this paper with possible future directions

Does pre-enrichment of anodes with acetate to select for <em>Geobacter</em> spp. enhance performance of microbial fuel cells when switched to more complex substrates?

Copyright \ua9 2023 Christgen, Spurr, Milner, Izadi, McCann, Yu, Curtis, Scott and Head. Many factors affect the performance of microbial fuel cells (MFCs). Considerable attention has been given to the impact of cell configuration and materials on MFC performance. Much less work has been done on the impact of the anode microbiota, particularly in the context of using complex substrates as fuel. One strategy to improve MFC performance on complex substrates such as wastewater, is to pre-enrich the anode with known, efficient electrogens, such as Geobacter spp. The implication of this strategy is that the electrogens are the limiting factor in MFCs fed complex substrates and the organisms feeding the electrogens through hydrolysis and fermentation are not limiting. We conducted a systematic test of this strategy and the assumptions associated with it. Microbial fuel cells were enriched using three different substrates (acetate, synthetic wastewater and real domestic wastewater) and three different inocula (Activated Sludge, Tyne River sediment, effluent from an MFC). Reactors were either enriched on complex substrates from the start or were initially fed acetate to enrich for Geobacter spp. before switching to synthetic or real wastewater. Pre-enrichment on acetate increased the relative abundance of Geobacter spp. in MFCs that were switched to complex substrates compared to MFCs that had been fed the complex substrates from the beginning of the experiment (wastewater-fed MFCs - 21.9 \ub1 1.7% Geobacter spp.; acetate-enriched MFCs, fed wastewater - 34.9 \ub1 6.7% Geobacter spp.; Synthetic wastewater fed MFCs – 42.5 \ub1 3.7% Geobacter spp.; acetate-enriched synthetic wastewater-fed MFCs - 47.3 \ub1 3.9% Geobacter spp.). However, acetate pre-enrichment did not translate into significant improvements in cell voltage, maximum current density, maximum power density or substrate removal efficiency. Nevertheless, coulombic efficiency (CE) was higher in MFCs pre-enriched on acetate when complex substrates were fed following acetate enrichment (wastewater-fed MFCs – CE = 22.0 \ub1 6.2%; acetate-enriched MFCs, fed wastewater – CE =58.5 \ub1 3.5%; Synthetic wastewater fed MFCs – CE = 22.0 \ub1 3.2%; acetate-enriched synthetic wastewater-fed MFCs – 28.7 \ub1 4.2%.) The relative abundance of Geobacter ssp. and CE represents the average of the nine replicate reactors inoculated with three different inocula for each substrate. Efforts to improve the performance of anodic microbial communities in MFCs utilizing complex organic substrates should therefore focus on enhancing the activity of organisms driving hydrolysis and fermentation rather the terminal-oxidizing electrogens

Biocatalytic electrode improvement strategies in microbial fuel cell systems

Microbial fuel cells (MFCs) produce electricity as a result of the microbial metabolism of organic substrates, hence they represent a sustainable approach for energy production and waste treatment. If the technology is to be implemented in industry, low cost and sustainable bioelectrodes must be developed to increase power output, increase waste treatment capacity, and improve service intervals. Although the current application of abiotic electrode catalysts, such as platinum and electrode binders such as Nafion leads to greater MFC performance, their use cost prohibitive. Novel bioelectrodes which use cost effective and sustainable materials are being developed. These electrodes are developed with the intention to reduce start‐up time, reduce costs, extend life‐span and improve core MFC performance metrics (ie. power density, current density, chemical oxygen demand (COD) reduction and Coulombic efficiency (CE)). Comparison of different MFC systems is not an easy task. This is due to variations in MFC design, construction, operation, and different inocula (in the case of mixed‐culture MFCs). This high intra system variability should be considered when assessing MFC data, operation and performance. In this review article, we examine the major issues surrounding bioanode and biocathode improvement in different MFC systems, with the ultimate goal of streamlining and standardising improvement processes

Performance Investigation of the Reverse Anoxic/Anaerobic/Oxic Microbial Fuel Cell

A reverse anaerobic/anoxic/aerobic (A2O) process is recognized as a developed biological nutrient removal process for wastewater treatment. A few researchers recently integrated a microbial fuel cell (MFC) into an A2O process to generate electricity during wastewater treatment. However, no published studies show the outcome of combining the MFC with the reverse A2O process. The performance of a reverse A2O-MFC during the treatment of raw duck pond water was investigated in this study. For suitable electrode placement, nine patterns of anode and cathode location (CH01-CH09) were also investigated. As a result, 60-79%, 14-52%, 57-82%, and 50-82% of phosphates, nitrates, total ammonia nitrogen, and COD were removed, respectively. Lineweaver-Burk plots could be used to estimate the system's phosphate removal rates. The highest electrical energy was observed at CH05 (162.5 Wh) in the first period of the treatment operation and at CH02 (710.3 Wh) in the second period. The electrode placement patterns of CH05, where the anode and cathode were installed in an anaerobic tank and an oxic tank, and CH02, where the anode and cathode were installed in an anoxic tank and an anaerobic tank, were recommended for the reverse A2O-MFC with a 35-cm electrode distance