미생물연료전지에서 Geobacter sulfurreducens를 이용한 전기생산과 수소생산효소를 이용한 전기 촉매적 수소생산

다국어 초록 (Multilingual Abstract)

The promise of generating electricity from the oxidation of organic substances using metal-reducing bacteria is drawing attention as an alternate form of bio-technology with positive environmental implications. Metal-reducing bacterium, Geobacter sulfurreducens is available for mediator-less microbial fuel cell (MFC) because it has biological nanowires(pili) which transfer electrons to outside the cell. In this study, in the anode chamber of the MFC system using G. sulfurreducens, the concentrations of NaCl, sodium phosphate and sodium bicarbonate as electrolytes were mainly optimized for the generation of electricity from acetate. 0.4%(w/v) NaClO and 0.5 M H2SO4 could be utilized for the sterilization of acrylic plates and proton exchange membrane (major construction materials of the MFC reactor), respectively. When NaCl concentration in anode phosphate buffer increased from 5 to 50 mM, power density increased from 6 to 20 mW/m2. However, with increasing sodium phosphate buffer concentration from 5 to 50 mM, power density significantly decreased from 18 to 1 mW/m2. Twenty-four mM sodium bicarbonate did not affect electricity generation as well as pH under 50 mM phosphate buffer condition. Optimized anode chamber of MFC using G. sulfurreducens generated relatively high power density (20 mW/m2) with the maximum coulombic efficiency (41.3%). And we examined various experimental factors to obtain the maximum power output. sparged to the cathode chamber, the cells produced electricity stably over 60 days with the regular addition of 20 mM acetate, generating the maximum power density of 7 mW/m2 with a 5,000 Ω load.
Bioelectrocatalytic hydrogen (H2) production was studied using Thiocapsa roseopersicina hydrogenase in microbial fuel cell system equipped with carbon-paper electrodes. Sodium dithionite (SD), as an electron donor, and hydrogenase, as a catalyst, were used in the anodic oxidation reaction and in the cathodic reduction reaction, respectively. Methyl viologen (MV) was added for the electron relays in both reactions. The concentrations of phosphate buffer, MV and hydrogenase in the reaction chambers were optimized, in which the concentration of SD was fixed at 20 mM. Parameters including the cathode surface area, the distance between electrodes, and the external load were optimized to complete the system. Catalytic current generation in the cathode was increased from 0.12 to 0.19 mA and from 0.07 to 0.12 mA, in proportion to the hydrogenase concentration (34.8 – 347.5 µg/mL) and the cathode surface area (2.0 – 11.5 cm2), respectively however, it decreased from 0.37 to 0.08 mA and from 0.12 to 0.09 mA with the increase of the electrical load (5 – 1000 Ω and the distance between electrodes (1.5 – 3.5 cm), respectively. The optimal MV concentrations were 2.5 – 5 mM in the cathode chamber. The bioelectrocatalytic H2 production rate was calculated from the cathodic current in argon atmosphere, and the maximal value under the partially optimized conditions was estimated to be 0.16 μmol H2/min/mg-protein, which was less than 8% of the actual specific H2 production activity of the hydrogenase enzyme. This study indicates that T. roseopersicina hydrogenase has a high potential for bioelectrocatalytic H2 production still, much effort could be required to develop a proper biofuel-cell system that provides for efficient transfer of electrons and protons.

목차 (Table of Contents)

• 1. 서론 1
• 1.1. 미생물연료전지 개요 1
• 1.2. 국내외 연구 동향 3
• 1.3. 연구 목적 4
• 2. 재료 및 실험 방법 6
• 2.1. 미생물연료전지 시스템 구축 6
• 2.2. 전자공여체 및 최종전자수용체 및 실험조건 7
• 2.3. 전기적활성미생물 및 배양 11
• 2.4. G. sulfurreducens 성장 12
• 2.5. 수소생산효소 12
• 2.6. 데이터 수집과 전력산출량 및 효율 계산 13
• 2.7. SEM 촬영 13
• 3. 미생물연료전지를 이용한 전기생산 15
• 3.1. 반응기 멸균의 영향 15
• 3.2. G. sulfurreducens의 전기생산 19
• 3.3. 연속 회분 운전 23
• 3.4. 저항에 따른 분극 곡선 26
• 3.5. NaCl의 영향 28
• 3.6. Sodium phosphate buffer의 영향 30
• 3.7. Sodium bicarbonate의 영향 33
• 3.8. N2/CO2의 영향 35
• 3.9. Acetate 농도의 영향 37
• 3.10. G. sulfurreducens의 전극에의 고정화 39
• 3.11. 백금에 의한 미생물연료전지 효율 향상 41
• 4. 생물전기 촉매적 수소생산 43
• 4.1. 효소 농도에 의한 영향 43
• 4.2. 전자매개체 농도에 의한 영향 46
• 4.3. 양극 표면적에 의한 영향 48
• 4.4. 전극간 거리에 따른 영향 50
• 4.5. 외부 저항에 따른 영향 52
• 5. 결론 54