Title Page
Contents
ABSTRACT 18
Ⅰ. Background of the research 20
1.1. Background and motivation 20
1.2. Utilization of microorganisms as bio-catalysts in fuel cells 21
1.3. Utilization of photosynthetic organisms as bio-catalysts in fuel cells 22
Ⅱ. Cyanobacteria-based double-mediated photomicrobial electrochemical cells are promising future energy sources for electricity generation and hydrogen production 28
2.1. Introduction 28
2.2. Experimental 31
2.2.1. Cell cultures and activity measurement 31
2.2.2. Dual-functioning DM-PMEC for photocurrent and oxygen evolution rate measurements 32
2.2.3. Construction of a complete DM-PMEC 32
2.2.4. Hydrogen production from DM-PMEC and analysis 34
2.3. Results and discussion 35
2.3.1. Measurement of oxygen evolution rate for different quinones 35
2.3.2. Need for double mediators for the effective electron transfer from A. variabilis to ITO 39
2.3.3. Optimization of DMBQ, Fe(CN)₆³⁻ concentrations, and A. variabilis amount to enhance photocurrent 43
2.3.4. Incident photo-to current conversion efficiency (IPCE) and turnover frequency (TOF) 47
2.3.5. Construction of a complete photo-microbial electrochemical cell and its performance 49
2.3.6. Solar hydrogen production from DM-PMEC 54
2.3.7. Parameter calculation for solar hydrogen production from DM-PMEC 56
2.3.8. Optimization of reaction conditions 61
2.4. Conclusions 72
Ⅲ. Direct extracellular electron transfer from Escherichia coli through modified carbon nanoparticles 73
3.1. Introduction 73
3.2. Experimental 76
3.2.1. Bacterial strains and cultivation medium 76
3.2.2. Preparation of modified carbon nanoparticles 76
3.2.3. Preparation of 4-carboxyphenyl modified carbon cloth electrode 77
3.2.4. Preparation of a 4AP-CNPs/E. coli 77
3.2.5. Surface characterization of the modified carbon cloth surface 79
3.2.6. Electrochemical measurements of glucose oxidation 79
3.3. Results and discussion 81
3.3.1. Characterization of 4AP-CNPs and 4CP-CC 81
3.3.2. Optimization of 4AP-CNPs and E. coli ratio 84
3.3.3. Electron transfer pathway between 4AP-CNPs/E. coli and electrode 84
3.3.4. Correlation between E. coli growth curve and current density 88
3.3.5. Glucose oxidation currents of 4AP-CNPs/E. coli on 4CP-CC 93
3.3.6. Characterization by electron microscopy 96
3.4. Conclusions 101
Ⅳ. The crucial role of photosynthetic activity in determining photocurrent measurements in cyanobacteria 102
4.1. Introduction 102
4.2. Experimental 104
4.2.1. Cell cultures and engineering condition 104
4.2.2. Measurements of chlorophyll concentration and oxygen evolution activity 104
4.2.3. Preparation for electrochemical measurements 105
4.2.4. Incident photo-to current conversion efficiency (IPCE) and turnover frequency (TOF) 105
4.3. Results and discussion 107
4.3.1. The identification and cultivation of genetically engineered cyanobacteria 107
4.3.2. The correlation between oxygen evolution and photosynthetic activity 107
4.3.3. Standardization based on oxygen production activity 112
4.3.4. Factors that decrease photosynthetic activity 120
4.4. Conclusions 124
Ⅴ. Dark current generation utilizing cyanobacterial respiratory pathways 125
5.1. Introduction 125
5.2. Experimental 127
5.2.1. Cell cultures and chlorophyll a concentration 127
5.2.2. Activity measurements of cyanobacteria 127
5.2.3. Photocurrent measurements 129
5.3. Results and discussion 131
5.3.1. The generation of dark current from A. variabilis 131
5.3.2. The necessity of double mediators for dark current 136
5.4. Conclusions 144
References 145
Abstract (in Korean) 161
〈Table 2-1〉 Comparison of performance of photosynthetic organism-based anodes. 48
〈Table 2-2〉 Parameters for H₂ production in DM-PMEC 63
〈Table 2-3〉 Parameters for H₂ production in DM-PMEC 69
〈Table 4-1〉 The IPCE and TOF values under 1 sun intensity (100 mW cm⁻²) 119
〈Figure 1-1〉 Carbon nanoparticles modified with the amine groups (blue dotted square) are designed for insertion into the outer membrane of electrochemically... 23
〈Figure 1-2〉 Schematic representation of the electron transfer pathways in the photosynthetic and respiratory processes of cyanobacteria. The red line... 25
〈Figure 1-3〉 Photoelectrons generated from water oxidation in cyanobacteria are effectively transferred to anode by double mediators and used for... 27
〈Figure 2-1〉 The dual-functioning electrochemical cell that measures oxygen evolution and photocurrent simultaneously. Light illuminates the cell from the top. 33
〈Figure 2-2〉 (A) Oxygen-evolving rate of A. variabilis (10 µg Chl a mL⁻¹) in the presence of DMBQ (red) and ferricyanide (blue), and in the absence of a...[이미지참조] 37
〈Figure 2-3〉 A schematic that explains how electrons are taken from TMs by DMBQ not by ferricyanide. 38
〈Figure 2-4〉 (A) and (B) respectively show cyclic voltammograms of DMBQ and ferricyanide at an ITO electrode (0.5 cm⁻²) in the presence of A. variabilis and... 41
〈Figure 2-5〉 Comparison of oxygen evolution rates from A. variabilis depending on single and double mediator. The solution contained 1X BG11 medium and 50... 44
〈Figure 2-6〉 (A) and (B) show photocurrent responses of A. variabilis as a function of DMBQ concentration at the fixed ferricyanide concentrations and as... 46
〈Figure 2-7〉 (A) Schematic representation of solar energy conversion into electricity using double mediators in PMEC. (B) Polarization and power density... 50
〈Figure 2-8〉 Lighting an LED and operating an electronic calculator using five series-connected DM-PMECs. 52
〈Figure 2-9〉 Series connection of five DM-PMECs for lighting a light-emitting diode. 53
〈Figure 2-10〉 Photocurrent and anode potential change with time in a DM-PMEC operated in a two-electrode system when external voltage of 1 V was... 55
〈Figure 2-11〉 (A) Schematic representation of hydrogen production in DM-PMEC. 57
〈Figure 2-12〉 (A) Photocurrent from dispersed A. variabilis with time at anode potential of 0.4 V vs. Ag/AgCl. The anodic and cathodic chambers were... 58
〈Figure 2-13〉 A photo image of the complete double mediated PMEC and hydrogen collection tube with dispersed A. variabilis (30 µg Chl a mL⁻¹) in 100 mM...[이미지참조] 60
〈Figure 2-14〉 The curve is divided into n sections with an equal time interval △t. The area of each section represents charge Qi. Energy is given by Qi x Ei where...[이미지참조] 62
〈Figure 2-15〉 (A) Plot of maximum photocurrent density vs. anolyte pH. (B) Plots of photocurrent density (yellow) and hydrogen production rate (blue) vs.... 66
〈Figure 2-16〉 Photocurrent dependence on the light intensity in a DM-PMEC containing A. variabilis (30 µg Chl a mL⁻¹). Current was measured in a...[이미지참조] 67
〈Figure 2-17〉 Gas chromatography analysis of the gases produced by DM-PMEC and standard samples of H₂ and O₂. 70
〈Figure 2-18〉 Linear sweep voltammetry of the cathode solution before and after DM-PMEC operation. The black line represents before operation of... 71
〈Figure 3-1〉 Schematic representation of surface modification steps. 4AP-CNPs; Aminophenyl modified carbon nano-particles, 4CP-CC; Carboxyl... 78
〈Figure 3-2〉 (A) Cyclic voltammogram of the bare CC in a diazotization mixture. (B) Cyclic voltammograms of 1 mM Fe(CN)₆³⁻/⁴⁻ at a bare CC (black) and 4CP-...[이미지참조] 82
〈Figure 3-3〉 Photographs of CNPs and 4AP-CNPs suspension in PBS (pH 7.0) (A), FT-IR spectra of bare CNPs (black), 4AP-CNPs (red) (B). 83
〈Figure 3-4〉 Electrochemical responses of E. coli (0.5 mg) to the glucose oxidation depending on the ratio of E. coli and 4AP-CNPs at the carboxyl group-... 85
〈Figure 3-5〉 Cyclic voltammograms of E. coli and E. coli/4AP-CNPs (A, C) in 0.1 M phosphate buffer (pH 7) with 10 mM glucose at 10 mV s⁻¹. Fig. C is an... 87
〈Figure 3-6〉 Cyclic voltammograms of the supernatant (E. coli, E. coli + glucose) at 10 mV s⁻¹. The concentration of E. coli was increased 5 times (125... 89
〈Figure 3-7〉 Electrochemical responses of 4AP-CNPs without E. coli. The cyclic voltammetry was performed at 10 mV s⁻¹ scan rate after chronoamperometry... 90
〈Figure 3-8〉 Electrochemical responses of E. coli at two different temperature (4 °C_blue line, 37 °C_red line). The cyclic voltammetry was performed at 10 mV... 92
〈Figure 3-9〉 (A) Growth curve of E. coli in LB medium (black line) and (B) current density (bar) at specified growth phases (1.2, 3.6, 5.4 and 6.8 at OD 600... 94
〈Figure 3-10〉 (A) Current dependence of E. coli/4AP-CNPs on the glucose concentration (0.1, 1, 5, 10, 50 mM) at 0.4 V vs. Ag/AgCl in 0.1 M phosphate... 95
〈Figure 3-11〉 Dependence of current density on the glucose concentration. The linear dependency is observed at low concentrations up to 5 mM. 97
〈Figure 3-12〉 Scanning electron microscopic images of 4CP-CC, E. coli and E. coli/4AP-CNPs (A, B and C). D is the magnified view of a part of C. 99
〈Figure 3-13〉 Thin-section transmission electron microscopic (TEM) images of E. coli (A) and E. coli/4AP-CNPs (B). 100
〈Figure 4-1〉 (A) Schematic representation illustrating the chromosomal integration process in S. elongatus through homologous recombination. The... 108
〈Figure 4-2〉 (A) UV-visible absorption spectra at a wavelength of 750 nm, comparing the wild-type and genetically engineered cyanobacteria cultures after... 110
〈Figure 4-3〉 (A) The oxygen evolving activity of SeWT (10, 20 µg Chla mL⁻¹). Electrolyte solution: 1X BG-11 medium containing 50 mM HEPES (pH 7.5)...[이미지참조] 113
〈Figure 4-4〉 (A) Photocurrent responses of wild-type and engineered S. elogantus (1 µgChla) on a graphite rod electrode monitored by...[이미지참조] 117
〈Figure 4-5〉 (A) OmcS proteins were detectable by western blot analysis. wild-type and transgenic strains. SeWT, proteins extracted from wild-type S.... 122
〈Figure 5-1〉 Incubator of Anabaena variabilis. 128
〈Figure 5-2〉 Scheme of the sample preparation process for dark current measurement. W; working electrode, R; reference electrode, C; counter electrode. 130
〈Figure 5-3〉 Chronoamperometry of wild-type A. variabilis (15 µg Chl a mL⁻¹) in BG-11(1X) solution containing 50 mM HEPES-NaOH (pH 7.5) with 1 mM DMBQ....[이미지참조] 132
〈Figure 5-4〉 (A) Maximum dark current density variation with light exposure duration under photosynthetic conditions. Wild-type A. variabilis (15 µg Chl a mL⁻...[이미지참조] 134
〈Figure 5-5〉 Cyclic voltammograms of (A) single mediator (1 mM DMBQ) system and (C) double (1 mM DMBQ+7.5 mM ferricyanide) mediator system cell... 138
〈Figure 5-6〉 (A) Chronoamperometry of wild-type A. variabilis (5 µg Chl a mL⁻¹) in BG-11(1X) solution containing 50 mM HEPES-NaOH (pH 7.5) with mediator....[이미지참조] 142