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Electroactive Biofilm Formation of Shewanella oneidensis MR-1 in Microbial Electrochemical System
Serah CHOI,In Seop CHANG 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
A microbial electrochemical system (MES) is a system that converts chemical energy into electrical energy by utilizing electrochemically active bacteria (EAB) as catalysts. Like many other bacteria, most EABs build biofilms on electrodes that are electron acceptors. EAB oxidizes the substrate and transfers the generated electrons to the electrode through an extracellular electron transfer (EET) system. Therefore, both the macro-scale biofilm formation state and the nano-scale microbial EET system are key factors in the development of MES. So far, direct electron transport systems, which require close physical contact between electrodes and cells, and indirect electron transport systems, which rely on electron mediators diffused between cells and electrodes, have been identified. In this study, it is suggested that the electron transfer method between the electrode and the cell will show different trends depending on the distance from the electrode of the microorganism in the biofilm.
Choi, Serah,Kim, Bongkyu,Chang, In Seop Elsevier 2018 Bioresource technology Vol.254 No.-
<P><B>Abstract</B></P> <P>In this study, the electrochemical properties of a <I>Shewanella oneidensis</I> MR-1 biofilm were investigated using a mini-microbial electrochemical system. The performance of the biofilm was shown, using discharge test and cyclic voltammetry investigations, to improve over time. Differential pulse voltammograms were also acquired to determine the type of extracellular electron transfer that took place and to characterize the structure of the microbial biofilm formed on the electrode of the electrochemical system. These results indicated that extracellular electron transfer <I>via</I> a flavin-like mediator chemical predominated as the biofilm grew. The results, combined with a comparison of the measured current density with the calculated value of a seamless single-layered biofilm, also suggested that <I>S. oneidensis</I> MR-1 formed a multi-layered biofilm on the electrode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>S. oneidensis</I> MR-1 was found to form a multi-layered biofilm. </LI> <LI> Over time, long-distance EET of the biofilm became activated. </LI> <LI> As the biofilm grew, EET <I>via</I> a flavin-like mediator became dominant. </LI> <LI> The measured current density was greater than that of dense single-layered biofilm. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Study on the Role of Foreign Affiliates in GVCs Trade
최명식,Serah Choi,Bongsuk Sung 국제인문사회연구학회 2024 Studies on Humanities and Social Sciences (SHSC) Vol.6 No.1
Study on the Role of Foreign Affiliates in GVCs Trade Myoungshik Choi,* Serah Choi,** & Bongsuk Sung*** Abstract: This study investigates the multinational affiliates play an important role in explaining the international trade and investment. It analyzes both the self-selective effect which explains why some firms operate in more than one country while others do not and the learning-by effect which explains why firms use vertical supply chains rather than simply use own foreign facilities. Our empirical results are: First, the high productivity of firms increases FDI. Second, the integration increases foreign affiliates. Third, value-added trade within global value chains increases the profits of both exporters and foreign affiliates. Fourth, intra-firm trade decreases the profits of exporters and foreign affiliates. Key implications stand out: One is that the higher productivity of firms can increase the network of FDI-international trade. The other is that global value chained trade can increase the profits more than interiorization of one firm. This study suggests that it could be more benefits for high productive firms to increase GVCs free trade. Key Words: Foreign Affiliates, Global Value Chains, Learning-by Effect, Self-selection Effect, Value-added Exports □ Received: Jan. 1, 2024, Revised: Feb. 13, 2024, Accepted: Feb. 20, 2024* First Author, Professor, Kyonggi Univ., Email: msc50355@gmail.com** Co-author 1, Graduate Student, Sungkyunkwan, Univ. *** Co-author 2, Professor, Kyonggi Univ.
Self-recoverable voltage reversal in stacked microbial fuel cells due to biofilm capacitance
Kim, Bongkyu,Choi, Serah,Jang, Jae Kyung,Chang, In Seop Elsevier Applied Science 2017 Bioresource technology Vol.245 No.1
<P><B>Abstract</B></P> <P>In order to assess the effects of biofilm capacitance on self-recovering voltage reversals, the restored current is determined and compared with the measured biofilm capacitance by analyzing the results of electrochemical impedance spectroscopy. This comparison demonstrates that self-recovering voltage reversals are caused by temporary damage to, and the recovery of, biofilm capacitance which arises due to the ability of redox enzymes in the electron transfer system to temporarily store electrons. Thus, the development of procedures for voltage reversal control and for the maintenance of serially connected microbial fuel cells (MFCs) should take into account such temporary voltage reversal phenomenon. This discovery and characterization of self-recovering voltage reversals is expected to be practically useful to enhance the reliability of MFCs to be scaled up and implemented in practical systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Voltage reversals can occur temporarily in stacked MFCs. </LI> <LI> Stacked MFCs can recover from voltage reversals without any external manipulation. </LI> <LI> These self-recovering voltage reversals are due to biofilm capacitance. </LI> <LI> Biofilm capacitance is the ability of enzymes to temporarily store electrons. </LI> <LI> Self-recovering voltage reversals must be considered to enhance MFC reliability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>