將固氮菌應用於具有空氣陰極或微藻生物陰極 之微生物燃料電池效能比較

Comparison of performance of microbial fuel cells using A. vinelandii with air cathode or algae bio-cathode

柯俊宇(Chun-Yu Ke)

指導教授 ： 王翔郁

國立清華大學/原子科學院/工程與系統科學系/碩士(2017年)

摘要

微生物燃料電池，是一個藉微生物將化學物轉換為電能的裝置，並可同時處理廢水，惟目前仍受限於功率密度低下，而尚未有大規模商業化的例子。本研究旨在測試固氮菌(Azotobactor vinelandii)是否能應用於微生物燃料電池發電，並利用微藻生物陰極電池提升電池之功率密度。首先測試固氮菌A. vinelandii分別配置在陰陽兩極，對於電池功率輸出之影響，在前述實驗中獲得的最佳電極設置，將被進一步使用於建立微藻生物陰極燃料電池，並觀察陰極培養微藻為電池帶來的影響，驗證是否有提升功率輸出或能生產生物質之潛力。
首先在雙槽式微生物燃料電池中(陽極為已知產電菌Proteus hauseri ZMd44)，測試將固氮菌投入陰極對電池造成的影響，發現在1kΩ外電阻運作下，電池電壓平台從60 mV降低至 20 mV，功率密度表現平均從0.5 mW/m2 降低至幾近0 mW/m2，顯示固氮菌以及其培養液不適於運用在陰極。接著改將A. vinelandii投入陽極，並與已知產電菌P. hauseri ZMd44比較，藉由架設空氣陰極微生物燃料電池比較極化曲線的差異，在不同的陰極設置(PTFE空氣陰極，PVDF空氣陰極，PTFE空氣陰極+PEM)下，功率密度與P. hauseri ZMd44比較，分別有3.6%，31.2%，19.6%之提升，指出A. vinelandii具有作產電菌的潛力。
最後，考慮前述實驗結果，挑選A. vinelandii作為陽極產電菌及PVDF空氣陰極架設雙槽式微生物燃料電池，比較在陰極培養柵藻Scenedesmus abundans GH-D11與否，對於陰極溶氧、電池功率以及生物量成長進行觀察，結果顯示，陰極培養S. abundans GH-D11之組別，陰極溶氧量降低5%，但功率密度卻提升了39.3%，從極化曲線可看出功率增加是因為內電阻自6423 Ω降低為1449 Ω；而在生物量方面，在電池極化曲線測量期間，含 S. abundans GH-D11之陰極液於682 nm之光學密度值為1.5，但仍遠低於母培養瓶之光學密度值範圍5~10。總結來說在本研究的實驗配置下，陰極培養S. abundans GH-D11雖對提升陰極飽和溶氧量沒有幫助，卻可藉由降低內電阻之方式提升電池之功率密度；而在生物量方面在電池內培養則沒有較原始培養瓶內佳，仍有可以最佳化實驗條件的空間。

關鍵字

微生物燃料電池 ； 固氮菌 ； 微藻生物陰極 ； 空氣陰極

並列摘要

Microbial fuel cell (MFC) is a device that can transform organic substrates to electricity and treat wastewater at the same time. But it is limited to its low power density and have not been applied with a commercial scale. The purpose of this study is to explore the possibilities of using Azotobacter vinelandii in MFCs. Different MFC designs and cathodes, including a microalgae bio-cathode, are applied to increase the power density. First, the influences of A. vinelandii, either in anode or in cathode, on the power density is investigated. The optimal setup obtained in the above tests is applied to construct the MFC with the microalgae bio-cathode to investigate if microalgae can help increase power density or can produce sufficient biomass.
Results show that when two-chamber MFCs, with known electrogenic Proteus hauseri ZMd44 in the anode and A. vinelandii in the cathode, operated under a 1kΩ external load, output voltage decreased from 60 mV to 20 mV and average power density decreased from 0.5 mW/m2 to almost 0 mW/m2. This shows that A. vinelandii was not suitable for applications on the cathode. When A. vinelandii was applied in the anode with different cathode designs (PTFE air cathode, PVDF air cathode, PTFE air cathode with PEM), the power density increased by 3.6 %, 31.2 %, 19.6 %, respectively, compared with those using P. hauseri ZMd44 in the anode. This suggests that A. vinelandii has the potential in serving as an electricity generating microorganisms in MFCs.
Finally, applying the optimal parameters obtained in the above tests (A. vinelandii as the anode microbes and PVDF air cathode as the cathode electrode), a two-chamber MFC with microalgae bio-cathode has been constructed to investigate the effects of Scenedesmus abundans GH-D11 on the MFC performance. Results show that the MFC with S. abundans GH-D11 in the cathode had 5 % lower dissolved oxygen compared with the control experiment (BG-11 medium in the cathode) but had 39.3 % higher power density, owing to the merit of the lower internal resistance of 1499 Ω (6423 Ω for the control experiment). However, the optical density (OD) of S. abundans GH-D11 only increased to 1.5 and it was much lower than the OD value in the original 1L culture (OD= 5~10). Optimization of culture of S. abundans GH-D11 is necessary in the future to improve the biomass productivity. In conclusion, A. vinelandii has great potential in producing electricity in MFCs and S. abundans GH-D11 in this study increased power density not by increasing the dissolved oxygen but by decreasing the internal resistance.

並列關鍵字

Microbial fuel cell ； bio-cathode ； air cathode ； Azotobacter vinelandii

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