3,818 research outputs found
Metabolic flux change in Klebsiella pneumoniae L17 by anaerobic respiration in microbial fuel cell
No full textThe metabolic flux in microbial fuel cells (MFCs) is significantly different from conventional fermentation because the electrode in MFCs acts as a terminal electron acceptor. In this study, the difference in the carbon metabolism of Klebsiella pnuemoniae L17 (Kp L17) during growth in MFCs and conventional bioreactors was studied using glucose as the sole carbon and energy source. For metabolic flux analysis (MFA), the in silico metabolic flux model of Kp L17 was also constructed. The MFC bioreactor operated in oxidative mode, where electrons are removed by the anode electrode, generated a smaller quantity of reductive metabolites (e.g., lactate, 2,3-butanediol and ethanol) compared to the conventional fermentative bioreactor (non-MFC). Stoichiometric analysis indicated that the cellular metabolism in MFC had partially (or significantly) shifted to anaerobic respiration from fermentation, the former of which was similar to that often observed under micro-aerobic conditions. Electron balance analysis suggested that 30% of the electrons generated from glucose oxidation were extracted from the microbe and transferred to the electrode. These results highlight the potential use of MFCs in regulating the carbon metabolic flux in a bioprocess.ope
전극 특성에 따른 CDI 담수 장치 성능 모델 개발
No full text학위논문(석사) - 한국과학기술원 : 원자력및양자공학과, 2010.08, [ xi, 83 p. ]Demand for clean water is increasing rapidly due to population growth, desertification, and pollution. Capacitive deionization, CDI, is a newly interested technology with its economic merits over existing ones like evaporation and reverse osmosis. The one of main issues on this technology lies on the electrode development. From the first success on a stable electrode development like carbon aerogel, various types of electrodes have been emerged. However, key mechanism and parameters of this technology are not yet provided.
This research focuses on revealing how the CDI works and what parameter affects the performance most. For the current experimental techniques have limits in producing well-defined pore arrangement, a simulation tool based on the most sophisticated governing equations has been developed. The governing equations involve Nernst-Planck equation with a convection term to follow ion movement and Poisson equation to follow potential development. The above tool is verified by comparing with analytical solutions and other researcher’s results.
The first simulation tool for CDI uses the decoupled implicit scheme; however, the scheme faces the numerical constraint of poor convergence. The maximum time step size is highly limited to 1.E-8s. Then an under-relaxation scheme is introduced with the limited success: we can increase its time step size by about 1,000 times higher than that of the decoupled scheme. Finally, the coupled implicit scheme, which solves the equations on concentration and potential simultaneously, is adopted. The newly developed scheme does not suffer from the convergence problem and is found to be optimal for CDI simulation.
As the simulation domain, we select a region containing one pore and one electrode gap, to efficiently appreciate key parameters. Key performance indicator, KPI, and system parameters are determined. KPI is defined by the salt removal rate: salt removal amount per electrode volume divided by salt removal ...한국과학기술원 : 원자력및양자공학과
Multi-dimensional simulation tool development for the performance evaluation of a CDI electrode and its geometry parameter optimization
No full textConceptual design of passive containment cooling system with air holdup tanks of improved APR+
No full textMetabolic shift of Klebsiella pneumoniae L17 by electrode-based electron transfer using glycerol in a microbial fuel cell
No full textKlebsiella pneumoniae is used widely for the production of value-added chemicals from glycerol, and is known as an exoelectrogen with an externally provided electron shuttle. In this study, the metabolic shift in K. pneumoniae L17 by the activation of electrode-based respiration was examined using microbial fuel cells (MFCs). The mRNA expression levels of the related enzymes for glycerol conversion were compared under electrode-driven anaerobic respirational conditions (i.e., MFC) and fermentative conditions (i.e., non-MFC). mRNA expression clearly responded to the electrode-based electron transfer with simultaneous current generation and changes in metabolite production. The NAD+-dependent pathways were activated and more acetate (21.7 vs. 14.6���mM), 3-HP (7.6 vs. 5.3���mM) and 1,3-PDO (45.5 vs. 38.1���mM) and less ethanol production were observed under MFC conditions than under non-MFC (39.6 vs 66.7���mM). Stoichiometric metabolic flux analysis was examined in MFC condition. These results suggest that electron excretion to the carbon electrode drives the metabolic pathway shift of K. pneumoniae L17, and can provide an active control strategy for the fermentative pathway of glycerol.This study was supported by the Mid-Career Researcher Programs (NRF-2018R1A2B6005460) and Cl Gas Refinery Program (NRF-2018M3D3A1A01055756) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning, Korea
Evaluation of Energetic Potential of Slaughterhouse Waste and Its Press Water Obtained by Pressure-Induced Separation via Anaerobic Digestion
No full textAnaerobic digestion has the potential to convert organic waste materials into valuable energy. At the same time, using press water from biomass materials for energy generation while taking advantage of the resulting cake for other purposes is an emerging approach. Therefore, this study aimed to investigate the residual potential expected from a typical biogas feedstock after it has been mechanically separated into liquid and solid phases. Hence, in this study, the rumen contents of ruminants (cow, goat, and sheep) and their proportionate ratios were obtained from an abattoir in Ghana. Resource characterization of the waste samples was carried out in the central laboratory of the HFR, Germany. Anaerobic batch tests for biogas (biomethane) yield determination were set up using the Hohenheim Biogas Yield Test (HBT). The inoculum used was obtained from an inoculum production unit at the Hohenheim University biogas laboratory. The trial involved two different forms of the sample: mixture of rumen contents, press water, and inoculum, each in four (4) replicates. The trial was carried out at a mesophilic temperature of 37 °C. Results obtained over a seventy (70) day period were transformed into biogas yields. Overall, the results show that the current contents are suitable for biogas generation as an option as opposed to the current form of disposal at a refuse dump. However, using these mixtures in their original forms is more technically viable than using press water without further treatment
Modeling salt removal performance of capacitive deionization (CDI) electrode for desalination
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