Progress 09/05/06 to 06/30/10
Outputs
Progress Report Objectives (from AD-416) Develop a system for the biological production of hydrogen from agricultural resources. The research is expected to produce information and technologies for the application of microbial fuel cells in the bioconversion of agricultural biomass and biomass derived carbohydrates into hydrogen that can be used as a fuel source. Approach (from AD-416) Strains of anaerobic bacteria or yeast that are known to degrade specific biomass sugars efficiently will be grown in half cells where current generation can be monitored. The electrode in the half cell will consist of carbon paper, which is attached to a potentiostat (CH Instruments). Breakdown of biomass sugars will be monitored by HPLC (1100, Hewlett- Packard). Next, electrochemically-active strains will be employed in microbial fuel cells. Several biomass sugars will be tested in the bioanode with the matching isolates present, and a potentiostat will be used to provide a minimum amount of potential to assist electrolysis in the cathode. The conversion of biomass sugars will be monitored by HPLC. The production rate of hydrogen will be monitored with a precision gas meter (MilliGascounter, Ritter) and a gas chromatograph (5890, Hewlett- Packard) and the hydrogen yield in moles of hydrogen per mole of biomass sugar degraded will be calculated. For the isolates with the highest hydrogen yield, the energy production in the electrochemically-assisted microbial fuel cell will be compared to two conventional microbial fuel cells in series connected to an electrolysis vessel. Such a system may produce enough potential to power hydrolysis without the requirement of electrochemical assistance. Researchers on this project have been working to develop a microbial fuel cell (MFC) system that can convert biomass sugars to hydrogen through an electrochemically assisted hydrogen production step. During the currect year, we compared the bioelectrochemical performance of Shewanella oneidensis in a pure-culture and in a co-culture with the homolactic acid fermenter Lactococcus lactis. While S. oneidensis alone can only use lactate as electron donor for current production, the co-culture is able to convert glucose into current with a similar coulombic efficiency of ~17%. With (electro)-chemical analysis and transcription profiling, we found that the bioelectrochemical systems (BES) performance and S. oneidensis physiology were not significantly different whether grown as a pure- or co-culture. Thus, the microbes worked together in a purely substrate based (neutral) relationship. These co-culture experiments represent an important step in understanding microbial interactions in BES communities with the goal to design complex microbial communities, which specifically convert target substrates into electricity. The Authorized Departmental Officer's Designated Representative monitored the activities of this agreement via e-mail contacts (weekly/monthly), phone calls, and an annual written technical report. This represents the final report of cooperative agreement 3620-41000- 133-01S which terminated June 30, 2010. Over the course of the research project the results obtained advanced the application of bioelectrochemical systems, especially microbial fuel cells, for power generation from renewable sugar substrates and the advancement of a microbial electrolysis cell for bioelectrochemical hydrogen production. Major achievements were in reactor design (combination of up-flow and shell and tube designs) and operation (applying oxygen to the microbial anode to increase microbial reaction rates; applying pressure to overcome oxygen limitations in the cathode; using dissolved CO2 gas in the cathode as a sustainable buffer medium; and to provide electron neutrality). Scientific investigations were deepened into the microbial processes of substrate to electric current conversion with advanced studies on gene expression under different reactor operation conditions for two different microorganisms (Shewanella oneidensis and Bacteroides thetaiotaomicron).
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) Develop a system for the biological production of hydrogen from agricultural resources. The research is expected to produce information and technologies for the application of microbial fuel cells in the bioconversion of agricultural biomass and biomass derived carbohydrates into hydrogen that can be used as a fuel source. Approach (from AD-416) Strains of anaerobic bacteria or yeast that are known to degrade specific biomass sugars efficiently will be grown in half cells where current generation can be monitored. The electrode in the half cell will consist of carbon paper, which is attached to a potentiostat (CH Instruments). Breakdown of biomass sugars will be monitored by HPLC (1100, Hewlett- Packard). Next, electrochemically-active strains will be employed in microbial fuel cells. Several biomass sugars will be tested in the bioanode with the matching isolates present, and a potentiostat will be used to provide a minimum amount of potential to assist electrolysis in the cathode. The conversion of biomass sugars will be monitored by HPLC. The production rate of hydrogen will be monitored with a precision gas meter (MilliGascounter, Ritter) and a gas chromatograph (5890, Hewlett- Packard) and the hydrogen yield in moles of hydrogen per mole of biomass sugar degraded will be calculated. For the isolates with the highest hydrogen yield, the energy production in the electrochemically-assisted microbial fuel cell will be compared to two conventional microbial fuel cells in series connected to an electrolysis vessel. Such a system may produce enough potential to power hydrolysis without the requirement of electrochemical assistance. Significant Activities that Support Special Target Populations Researchers have been working to develop a microbial fuel cell (MFC) system that can convert biomass sugars to hydrogen through an electrochemically assisted hydrogen production step. In the current year, the effects of aeration of Shewanella oneidensis on potentiostatic current production, iron (III) reduction, hydrogen production in a microbial electrolysis cell, and electric power generation in a MFC were studied. The potentiostatic performance of aerated S. oneidensis was considerably enhanced compared to anaerobically grown cultures. Biocatalyzed hydrogen production rates with aerated S. oneidensis were also studied and were comparable with those reported for mixed cultures, but is ~10 times higher than reported for an anaerobic culture of S. oneidensis. The main reasons for enhanced electrochemical performance are higher levels of active biomass and more efficient substrate utilization under aerobic conditions. Coulombic efficiencies, however, were greatly reduced due to losses of reducing equivalents to aerobic respiration in the anode chamber. The next challenge will be to optimize the aeration rate of the bacterial culture to balance between maximization of bacterial activation and minimization of aerobic respiration in the culture. The Authorized Departmental Officer's Designated Representative monitored the activities of this agreement via e-mail contacts (weekly/monthly), phone calls, and an annual written technical report.
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Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) Develop a system for the biological production of hydrogen from agricultural resources. The research is expected to produce information and technologies for the application of microbial fuel cells in the bioconversion of agricultural biomass and biomass derived carbohydrates into hydrogen that can be used as a fuel source. Approach (from AD-416) Strains of anaerobic bacteria or yeast that are known to degrade specific biomass sugars efficiently will be grown in half cells where current generation can be monitored. The electrode in the half cell will consist of carbon paper, which is attached to a potentiostat (CH Instruments). Breakdown of biomass sugars will be monitored by high pressure liquid chromatography (HPLC) (1100, Hewlett-Packard). Next, electrochemically- active strains will be employed in microbial fuel cells. Several biomass sugars will be tested in the bioanode with the matching isolates present, and a potentiostat will be used to provide a minimum amount of potential to assist electrolysis in the cathode. The conversion of biomass sugars will be monitored by HPLC. The production rate of hydrogen will be monitored with a precision gas meter (MilliGascounter, Ritter) and a gas chromatograph (5890, Hewlett-Packard) and the hydrogen yield in moles of hydrogen per mole of biomass sugar degraded will be calculated. For the isolates with the highest hydrogen yield, the energy production in the electrochemically-assisted microbial fuel cell will be compared to two conventional microbial fuel cells in series connected to an electrolysis vessel. Such a system may produce enough potential to power hydrolysis without the requirement of electrochemical assistance. Significant Activities that Support Special Target Populations Researchers are working to identify bacterial and/or yeast strains that can convert biomass sugars to hydrogen in microbial fuel cells (MFC) through an electrochemically assisted hydrogen production step. A binary culture of Lactococcus lactis and Shewanella oneidensis was studied for an efficient conversion of glucose into electricity in a continuously operated chemostatic electrochemical reactor. In the binary culture with glucose as primary fuel, the current density was sustained compared to the lactate fed mono-culture of Shewanella. The examination of the metabolic interactions between two defined species of microorganisms eventually will help to understand the complex foodweb among mixed bacterial communities in MFCs. In other work, the effect of pressurizing the cathode chamber to increase the solubility of air and consequently the availability of oxygen was studied since MFC power densities are often constrained by the oxygen reduction reaction rate on the cathode electrode. Results from this study demonstrate that higher MFC power densities can be realized by increasing the cathode air pressure and point forward to a MFC design that can exploit this capability. The Authorized Departmental Officer's Designated Representative monitored the activities of this agreement via e-mail contacts (weekly/monthly), phone calls, and an annual written technical report. This work addresses NP 307, Component III.
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Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) Develop a system for the biological production of hydrogen from agricultural resources. The research is expected to produce information and technologies for the application of microbial fuel cells in the bioconversion of agricultural biomass and biomass derived carbohydrates into hydrogen that can be used as a fuel source. Approach (from AD-416) Strains of anaerobic bacteria or yeast that are known to degrade specific biomass sugars efficiently will be grown in half cells where current generation can be monitored. The electrode in the half cell will consist of carbon paper, which is attached to a potentiostat (CH Instruments). Breakdown of biomass sugars will be monitored by HPLC (1100, Hewlett- Packard). Next, electrochemically-active strains will be employed in microbial fuel cells. Several biomass sugars will be tested in the bioanode with the matching isolates present, and a potentiostat will be used to provide a minimum amount of potential to assist electrolysis in the cathode. The conversion of biomass sugars will be monitored by HPLC. The production rate of hydrogen will be monitored with a precision gas meter (MilliGascounter, Ritter) and a gas chromatograph (5890, Hewlett- Packard) and the hydrogen yield in moles of hydrogen per mole of biomass sugar degraded will be calculated. For the isolates with the highest hydrogen yield, the energy production in the electrochemically-assisted microbial fuel cell will be compared to two conventional microbial fuel cells in series connected to an electrolysis vessel. Such a system may produce enough potential to power hydrolysis without the requirement of electrochemical assistance. Significant Activities that Support Special Target Populations This report documents accomplishments under a Specific Cooperative Agreement between Agricultural Research Services (ARS) and the Washington University, St. Louis. Additional details of research can be found in the report for the parent research project 3620-41000-118-00D, entitled "Industrially Robust Enzymes and Microorganisms for Production of Sugars and Ethanol from Agricultural Biomass." Researchers are working to identify bacterial and/or yeast strains that can convert biomass sugars to hydrogen in microbial fuel cells (MFC) through an electrochemically assisted hydrogen production step. In this year of the research, two heated, continuously-fed MFC systems were designed and built that can be autoclaved for pure and bi-culture studies. The reactors are made of glass and have all the necessary ports on the anode and cathode chambers for reference electrodes and also to sample hydrogen gas in the cathode chamber. To our knowledge, this is the first continuously-fed MFC that can be maintained sterile and anaerobic, because most MFCs are operated as a batch. The MFC is being tested using pure cultures and co-cultures of anaerobic and facultative anaerobic bacteria. The Authorized Departmental Officer's Designated Representative (ADODR) monitored the activities of this agreement via e-mail contacts (weekly/monthly), phone calls, and an annual written technical report.
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