Application of electro-active biofilms

The concept of an electro-active biofilm (EAB) has recently emerged from a few studies that discovered that certain bacteria which form biofilms on conductive materials can achieve a direct electrochemical connection with the electrode surface using it as electron exchanger, without the aid of mediators. This electro-catalytic property of biofilms has been clearly related to the presence of some specific strains that are able to exchange electrons with solid substrata (eg Geobacter sulfurreducens and Rhodoferax ferrireducens). EABs can be obtained principally from natural sites such as soils or seawater and freshwater sediments or from samples collected from a wide range of different microbially rich environments (sewage sludge, activated sludge, or industrial and domestic effluents). The capability of some microorganisms to connect their metabolisms directly in an external electrical power supply is very exciting and extensive research is in progress on exploring the possibilities of EABs applications. Indeed, the best known application is probably the microbial fuel cell technology that is capable of turning biomass into electrical energy. Nevertheless, EABs coated onto electrodes have recently become popular in other fields like bioremediation, biosynthesis processes, biosensor design, and biohydrogen production

Biological and microbial fuel cells

Biological fuel cells have attracted increasing interest in recent years because of their applications in environmental treatment, energy recovery, and small-scale power sources. Biological fuel cells are capable of producing electricity in the same way as a chemical fuel cell: there is a constant supply of fuel into the anode and a constant supply of oxidant into the cathode; however, typically the fuel is a hydrocarbon compound present in the wastewater, for example. Microbial fuel cells (MFCs) are also a promising technology for efficient wastewater treatment and generating energy as direct electricity for onsite remote application. MFCs are obtained when catalyst layer used into classical fuel cells (polymer electrolyte fuel cell) is replaced with electrogenic bacteria. A particular case of biological fuel cell is represented by enzyme-based fuel cells, when the catalyst layer is obtained by immobilization of enzyme on the electrode surface. These cells are of particular interest in biomedical research and health care and in environmental monitoring and are used as the power source for portable electronic devices. The technology developed for fabrication of enzyme electrodes is described. Different enzyme immobilization methods using layered structures with self-assembled monolayers and entrapment of enzymes in polymer matrixes are reviewed. The performances of enzymatic biofuel cells are summarized and approaches on further development to overcome current challenges are discussed. This innovative technology will have a major impact and benefit to medical science and clinical research, health care management, and energy production from renewable sources. Applications and advantages of using MFCs for wastewater treatment are described, including organic matter removal efficiency and electricity generation. Factors affecting the performance of MFC are summarized and further development needs are accentuated

BIOELECTRICITY PRODUCTION FROM CASSAVA MILL EFFLUENTS USING MICROBIAL FUEL CELL TECHNOLOGY

A Microbial Fuel Cell (MFC) is a biochemical-catalyzed system that generates electricity by oxidation of biodegradable organic substance in the presence of microorganisms or enzymes. Microbial fuel cell technology is a new form of renewable and sustainable technology for electricity generation as it recovers energy from renewable materials such as organic wastes and wastewaters that can constitute environmental pollution if not disposed without proper treatment. This work therefore investigated the possibility of electricity generation from cassava mill effluent using MFC. The cassava mill effluent was found to generate voltage and current to the maximum of 275 mV and 2.75 mA, respectively, corresponding to a maximum power density of 189 mW/m2. The voltage and current generation was respectively and significantly influenced with change in temperature, pH, concentration (strength) of effluent and addition of nutrient. Thus, it can be concluded that bioelectricity can directly be generated from cassava mill effluent using the MFC technology. http://dx.doi.org/10.4314/njt.v35i2.1

POWER ENHANCEMENT AND APPLICATIONS OF MICROBIAL FUEL CELLS

Ph.DDOCTOR OF PHILOSOPH

Adaptation of biofuel cell technology for electricity generation from wastewater and lactose measurement : a thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy

Biofuel cell (BFC) is an emerging renewable technology that can perform high direct energy conversion efficiency to electricity. BFC system uses low energy density sources, such as organics in wastewater and converts them into electricity. The system is based on biological catalysts such as microorganisms and enzymes, which are capable of consuming the organics in the sewage for metabolism. In the process, the BFC system will convert the organics in the wastewater and reduce the biological oxygen demand of the sewage to a safe level before it is released to the environment. Nevertheless, commercialisation of BFC applications are still a long way to go due to many weaknesses that have to be overcome. Culturing exoelectrogenic bacteria and applying new materials to enhance catalytic process in microbial fuel cell (MFC) are some of the options to improve MFC operation. The aims of this study are two-fold: To develop (i) a MFC for electricity generation from wastewater by bacteria isolated from a trickling filter, and (ii) an enzymatic fuel cell (EFC) for continuous measurement of lactose concentration in dairy wastewater as well as electricity generation. This thesis shows that the multi-cultured bacteria could generate electricity after 30 days exposure to oxygen at a concentration of 7.5 ppm and that the fabricated graphite-epoxy composite anodes possess the desired characteristics of a good electrode. Such fabricated electrodes can be prepared within a very short time-span compared to commercial electrodes. These electrodes are cheap and flexible for surface modification. However, due to inherent high resistance of the graphite-epoxy composite, it was unable to generate as much current intensity as commercial material electrodes. This study has highlighted several areas that can be further explored such as reducing inherent resistance in graphite composite electrode and the potential use of combined multi-walled carbon nanotube (MWCNT)-diazonium salt within graphite matrix as a reusable high performance electrode

Treated clinoptilolite-modified graphite felt bioanode microbial fuel cells for power generation and dye decolourisation

One important factor in microbial fuel cells (MFCs) study is the anode. In MFCs, the anode acts as the key component in the generation of bioelectricity and power. Despite the fact that there have been some improvements in the electrochemical performance of MFCs in recent years, their low power generation is still deemed a major drawback. The effects of surface modifications of the anode as biofilm carrier on the performance of MFCs were investigated. This research focused on the role of the novel fabricated anode as support material for the adhesion of bacterial consortium (NAR-2) consisted of Citrobacter sp. A1, Enterobacter sp. L17 and Enterococcus sp. C1 were used in MFCs reactor for the decolourisation of Acid Red 27 (AR27) and the simultaneous generation of electricity. The performance of a modified anode fabricated using surfactant-treated clinoptilolite (S-TC) with common type of carbonbased material, namely treated clinoptilolite-modified graphite felt (TC-MGF) anode was evaluated with different MFCs constructions. Prior to the MFCs experiments, the modification of anode was successfully verified using different spectroscopic and microscopic techniques such as EDX, FESEM, ATR-FTIR and BET analysis. In addition, screening of parameters for the adhesion of bacterial consortium NAR-2 onto TC-MGF anode (NAR-2-bioanode) was accomplished. The newly-developed TCMGF bioanode was implemented in the dual-chamber (H-type) of the MFC. The performance of TC-MGF bioanode was compared to the results obtained using nonmodified graphite felt (BGF) bioanode. Maximum power densities for BGF and TCMGF bioanodes were 458.8 ± 5.0 and 940.3 ± 4.2 mWm-2, respectively. In the following experimental, a small MFC reactor was fabricated with TC-MGF bioanode to compare the performance of the MFC with commonly used fuel cell membranes, Nafion (N-117 and N-115), which were examined along with the N-212 membrane in a single-chamber cubic di-air cathode (S-CCD-AC) design. The power density and columbic efficiency of N-115 membrane (1022.5 mWm-2 - 35.4%) were significantly higher than the values obtained for the N-117 (592 mWm-2 - 15.6%) and N-212 (493 mWm-2 - 12.3%) membranes. A novel MFC reactor with TC-MGF bioanode novel design (Conch shell) using the N-115 membrane having an air-cathode upflow (A-CU) MFC, as a combination of upflow and MFC technologies was used to compare the presence and absence of a membrane design. The A-CUMFC with membrane-less at flow rate 0.6 mL min-1, anode distance of 0.5 cm and a concentration of AR27 at 900 mg L-1, high decolourisation rate (98%) achieved in a 60-day operation, was 40% higher than that of the membrane-MFC. The average maximum power density obtained (1250 mWm-2) using the membrane-less MFC was higher than that of the membrane-MFC (1108 mWm-2) during the 80-day operation with TC-MGF bioanode

Effects Of Antibiotics And Hormones On Electricity Generation Using Microbial Fuel Cells

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2011Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2011Mikrobiyal yakıt hücreleri (MYH) oksijensiz ortamda mikroorganizmaları katalizör olarak kullanarak organik maddelerin oksidasyonu sonucu oluşan kimyasal enerjiyi doğrudan elektrik enerjisine çeviren sistemlerdir. Son yıllarda fermentasyon ürünlerini ve çeşitli atıksuları kullanarak elektrik üretimi araştırmacıların ilgisini çektiğinden bu konuda pek çok çalışma yapılmıştır. Elektrik üretiminin yanında bu sistemler atıksuyu arıttığından gelecekte pratik kullanımlar için potansiyel taşımaktadır. Mikrobiyal yakıt hücrelerinin diğer bir kullanım alanı ise biosensör olarak çalıştırılmalarıdır. Bu sistemlerin bugüne kadar yapılan araştırmalar sonucu elde edilen elektrik verimleri ticari olarak kullanımdan oldukça uzaktır. Kullanılabilir ve düşük maliyetli teknolojilerin geliştirilmesi için önümüzdeki yıllarda birçok temel araştırmalar yapılmalıdır. Bu çalışma temel olarak iki kısımdan oluşmaktadır. Birincisi iki hazneli microbiyal yakıt hücresinde saf kültür Shewanella putrefaciens kullanılarak farklı organik maddelerden elektrik üretimi olup, optimizasyon çalışmalarından sonra kültür edilmiş hücreler iki hazneli MYH’ne transfer edilmiştir. Shewanella putrefaciens elektrokimyasal olarak aktif, anot yüzeyine biyofilm yapabilme özelliğine sahip olup organik maddelerden elde edilen elektronları anot yüzeyine aracı bir medyatör kullanmadan verme özelliğine sahiptir. Böylece sentetik medyatörlerin toksik etkisi ve yenilenme gereği ortadan kaldırılmıştır. Deneyler sonunda elde edilen düşük güç yoğunluğu sebebiyle (0.8 mW/m2) çalışmaya karışık kültür bakteriler ile devam edilmiştir. Çalışmanın ikinci kısmında, tek hazneli mikrobiyal yakıt hücresinde aklime edilmiş karışık kültür mikroorganizmalar kullanılarak sodyum asetat ile beslenen sistem için elektrik üretimi, KOİ giderimi, Colombus verimliliği bulunmuştur. Sodyum asetat ile beslenen tek hazneli microbiyal yakıt hücresi ile elektrik üretimi üzerine farklı konsantrasyonlarda dört farklı hormon (estrone, 17β-estradiol, estriol ve 17α-ethinylestradiol) ile üç farklı antibiyotik (erythromycin, sulfamethoxazole, tetracycline) maddesi eklenerek bu maddelerin olası inhibisyon etkileri araştırılmıştır. Antibiyotikler 50, 100 ve 200 mg/L konsantrasyonlarında hazırlanıp asetat ile beraber sisteme verilmiştir. Öte yandan hormonlar ise 0,1, 0,5 ve 1 mg/L konsantrasyonlarda uygulanmıştır. Bu setlerin her biri sadece asetat kullanılan setlerle karşılaştırılmış ve akım, colombus verimliliği ve KOİ gideriminde farklılıklar değerlendirilmiştir. Böylece MYH sistemi bir nevi biyosensör olarak kullanılmıştır. Literatürde bu inhibitor maddelerin elektrojen (elektrik üreten) bakteriler üzerine etkisini gösteren benzer çalışmalara rastlamak pek mümkün olmadığından kıyaslama yapılamamakla beraber çalışmamızın orjinalliği açısından önem taşımaktadır. İncelenen antibiyotikler dünyada ve ülkemizde en fazla tüketilen ana gruplardan olması nedeniyle seçilmiştir. Sentetik hormonlar da son yıllarda yoğun kullanımı ile canlılar üzerinde olumsuz etkileri araştırmacılar tarafından gözlemlendiğinden bu çalışmada bakteriler üzerinde elektrik üretimi açısından değerlendirilmesi yapılmıştır.A microbial fuel cell (MFC) is a bioreactor that directly converts chemical energy occurring as a result of oxidation of organic compounds to electrical energy through catalytic reactions of microorganisms under anaerobic conditions. In recent years, since electricity generation from a microbial fuel cell by using fermentation products and different wastewaters as fuel draws researchers’ attention, lots of investigations have been made and well documented. Apart from electricity generation, these systems have a great potential for practical applications in the future due to wastewater treatment. The other purpose of MFC usage is a biosensor. The electricity efficiencies obtained recently in MFCs are far away from those required for commercial application and lots of fundamental works have to be done in order to develop usable technologies with low cost. This thesis consists of two stages in general. Firstly, it is purposed to generate electricity from different organic compounds by using two chambered MFC and pure culture Shewanella putrefaciens. After optimization experiments, cultivated cells are transferred to the two chambered MFC. Shewanella putrefaciens is bioelectrochemically active and can form a biofilm on the anode surface and transfer electrons directly (without mediator) by conductance through the membrane. When they are used, the anode acts as the final electron acceptor in the dissimilatory respiratory chain of the microbes in the biofilm. Thus, it is avoided from toxicity and instability of synthetic mediators. Because of poor power density of the system (0.8 mW/m2), it is continued with mixed culture. In the second phase of this study, by using acclimated mixed culture microorganisms in single chambered MFC, electricity generation, current, chemical oxygen demand (COD) removal, coulombic efficiency (CE) values were measured for the system fed with sodium acetate as carbon source. In single chambered MFC, 4 different estrogens (hormones) which are estrone, 17β-estradiol, estriol ve 17α-ethinylestradiol and 3 different antibiotics (erythromycin, sulfamethoxazole, tetracycline) are used. It is investigated inhibition responses of these matters in MFC system. During antibiotic experiments, one cycle is only acetate, following cycle is antibiotic plus acetate and it continues in this way. When the values of current and CE change after antibiotic plus acetate, the system is fed with only acetate repeatedly to recover to its original value. The concentrations of antibiotics are 50, 100 ve 200 mg/L and they are given to the system together with acetate. On the other hand, the concentrations of hormones are 0,1, 0,5 ve 1 mg/L and the same procedure is carried out. Each set is compared with only the sets in which acetate is used and differences in the current, CE and COD removal values are observed. Therefore, the MFC system is used in a way as a biosensor in this study. In literature, studies that show the effects of inhibitory matters on electrogen microorganisms are too limited. Thus, making a comparison is not quite possible and also the originality of our study gains an importance. Erythromycin (ERY), sulfamethoxazole (SMX) and tetracycline (TC) are chosen because they are widely used in Turkey and around the world. On the other hand, since it is observed by the researchers that widely usage of synthetic hormones in recent times has negative effects on fish, it is proved in this study that they show diversity in terms of electricity current of electrogen bacteria.DoktoraPh

A novel portable oxidation-reduction potential and microbial fuel cell-based sensor to monitor microbial growth

Bioremediation, the most environment-friendly soil remediation method, should receive adequate attention. However, its efficiency has often been criticized, reflecting the dearth of information about microbial activity in the soil. Biosensors can use the signals sent by microorganisms to quantify and analyze microbial activity. Therefore, combining biosensors with bioremediation can enhance the application of bioremediation technology. This thesis focused on designing and fabricating of portable microbial fuel cell (MFC) and oxidation-reduction potential (ORP) based sensor to achieve in situ soil bioremediation application in the future. This is because conventional biosensors cannot reflect the detailed microbial growth characteristics during soil bioremediation. During the experiment, two portable sensors were designed. First, two cylindrical polypropylene bottles were compressed tightly to form a preliminary sensor containing a proton exchange membrane (PEM), an O-ring, and a cathode electrode. After successfully testing the preliminary sensor’s workability, a smaller, easier-to-assemble 3D-printed sensor was designed based on the same concept. The extracellular electrogenic bacterial Bacillus subtilis was used to test both sensors’ workability. MFC and ORP sensors provide voltage and redox potential outputs. By integrating real-time redox potential and voltage outputs, a typical microbial growth (potential parameter) curve can be created. The derivative optical density (OD) value (OD per hour) was found to correspond to the potential parameter. The preliminary sensor could acquire detailed microbial growth characteristics at 6.5 and 18 hours, and the 3D-printed sensor at 10 and 21 hours. The accompanying derivative OD values supported these conclusions. This novel sensor can monitor real-time microbial growth, report detailed growth characteristics in soil, and help select better bioremediation solutions. Future work is required to improve the responsive of the 3D-printed sensor to achieve higher-resolution result

A model-based approach for the development of a bioelectrochemical sensor for biochemical oxygen demand in wastewater

Bioelectrochemical systems such as microbial fuel cells and microbial electrolysis cells are currently being researched for many different environmental engineering applications. Some of these applications include wastewater treatment coupled with electricity generation, wastewater treatment coupled with hydrogen production, powering of remote sensors, and as sensors for biochemical oxygen demand or volatile fatty acids. After introducing bioelectrochemical systems and the basic principles and mechanisms of their operation, this thesis will focus on a model-based approach to developing a sensor based on a microbial electrolysis cell to characterize wastewater biochemical oxygen demand. In a microbial electrolysis cell, a microbial biofilm growing on the anode of an electrochemical cell catalyzes the oxidation of organic matter and uses the anode as a terminal electron acceptor for respiration, thereby generating a measurable current. A polarization curve measures the response of the current generated to changes in the anode potential. In this study, four continuously operated microbial electrolysis cells with two different anode materials with differing surface properties have been used to model the relationship between acetate concentration in the bulk liquid and the shape of a polarization curve generated using low scan cyclic voltammetry. In terms of Monod kinetics, the anode potential determines the limitation placed on microbial respiration rate by the affinity of the electron acceptor for electrons, and is analogous to the effect of oxygen concentration on growth rate in an aerobic system. The Butler-Volmer Monod model is used to relate substrate concentration, anode potential, and generated current. Polarization curves generated at a range of different acetate concentrations were used to estimate the kinetic parameters of the model and to test its capability to predict substrate concentration. The results of this characterization of anode respiring biofilm respiration kinetics, presented in Chapter 3, show that this approach can differentiate between different substrate concentrations and that the fit and predictive capability of the model can be improved by optimizing the choice of anode materials and electrochemical techniques. This approach differs from other studies which attempt predict substrate concentration using only whole-cell current or total charge generated. Emphasis has also been placed on developing a sensor that is inexpensive and easy to operate, with the idea that such a sensor could allow better process monitoring and optimization at small or resource-limited wastewater treatment plants. To address this, a control and data acquisition system based on the Arduino Uno, an inexpensive microcontroller, was also developed. This study shows that an approach based on characterizing the kinetic parameters of an anode respiring biofilm in a microbial electrolysis cell and using the Butler-Volmer Monod model to estimate substrate concentration holds promise. To the best of this author’s knowledge, this is the first study to test the predictive capability of a kinetic model for bio-anode polarization curves. Other studies, discussed in Chapter 2, which have developed bioelectrochemical sensors for biochemical oxygen demand, chemical oxygen demand, specific substrates, or other wastewater quality parameters or conditions have shown that sensors based on microbial electrolysis cells and microbial fuel cells can correlate these parameters or conditions with current or total charge generated, and that such sensors have good long term stability and reasonably low response times. However, these biosensors are often subject to thermodynamic limitations on current production, leading to a very low upper detection limit. Furthermore, these previously developed biosensors do not account for the limitations that anode potential can impose on microbial respiration. A sensor based on a three-electrode microbial electrolysis cell and a kinetic respiration model for anode respiring biofilms such as the Butler-Volmer Monod model addresses the issues of thermodynamic limitations and anode potential effects. Future work to include characterization of the effects of other environmental conditions such as temperature, pH, and solution electroconductivity and to further refine the electrochemical techniques and electrode materials could be expected to dramatically improve biosensing capabilities for applications in wastewater treatment process monitoring and optimization