Bird Hannah, Velasquez-Orta Sharon, Heidrich Elizabeth
School of Engineering, Newcastle University, Newcastle upon Tyne, United Kingdom.
Front Microbiol. 2025 Jan 6;15:1511142. doi: 10.3389/fmicb.2024.1511142. eCollection 2024.
Microbial Fuel Cells (MFCs) are innovative environmental engineering systems that harness the metabolic activities of microbial communities to convert chemical energy in waste into electrical energy. However, MFC performance optimization remains challenging due to limited understanding of microbial metabolic mechanisms, particularly with complex substrates under realistic environmental conditions. This study investigated the effects of substrate complexity (acetate vs. starch) and varying mass transfer (stirred vs. non-stirred) on acclimatization rates, substrate degradation, and microbial community dynamics in air-cathode MFCs. Stirring was critical for acclimating to complex substrates, facilitating electrogenic biofilm formation in starch-fed MFCs, while non-stirred MFCs showed limited performance under these conditions. Non-stirred MFCs, however, outperformed stirred systems in current generation and coulombic efficiency (CE), especially with simple substrates (acetate), achieving 66% CE compared to 38% under stirred conditions, likely due to oxygen intrusion in the stirred systems. Starch-fed MFCs exhibited consistently low CE (19%) across all tested conditions due to electron diversion into volatile fatty acids (VFA). Microbial diversity was higher in acetate-fed MFCs but unaffected by stirring, while starch-fed MFCs developed smaller, more specialized communities. Kinetic analysis identified hydrolysis of complex substrates as the rate-limiting step, with rates an order of magnitude slower than acetate consumption. Combined hydrolysis-fermentation rates were unaffected by stirring, but stirring significantly impacted acetate consumption rates, likely due to oxygen-induced competition between facultative aerobes and electrogenic bacteria. These findings highlight the trade-offs between enhanced substrate availability and oxygen-driven competition in MFCs. For real-world applications, initiating reactors with dynamic stirring to accelerate acclimatization, followed by non-stirred operation, may optimize performance. Integrating MFCs with anaerobic digestion could overcome hydrolysis limitations, enhancing the degradation of complex substrates while improving energy recovery. This study introduces novel strategies to address key challenges in scaling up MFCs for wastewater treatment, bridging the gap between fundamental research and practical applications to advance environmental systems.
微生物燃料电池（MFCs）是一种创新的环境工程系统，它利用微生物群落的代谢活动将废物中的化学能转化为电能。然而，由于对微生物代谢机制的了解有限，特别是在现实环境条件下处理复杂底物时，MFC性能的优化仍然具有挑战性。本研究调查了底物复杂性（乙酸盐与淀粉）和不同传质条件（搅拌与不搅拌）对空气阴极MFCs中驯化速率、底物降解和微生物群落动态的影响。搅拌对于适应复杂底物至关重要，有助于在以淀粉为底物的MFCs中形成产电生物膜，而在这些条件下不搅拌的MFCs性能有限。然而，不搅拌的MFCs在电流产生和库仑效率（CE）方面优于搅拌系统，特别是对于简单底物（乙酸盐），不搅拌条件下的CE达到66%，而搅拌条件下为38%，这可能是由于搅拌系统中氧气的侵入。在所有测试条件下，以淀粉为底物的MFCs的CE始终较低（19%），这是因为电子转移到了挥发性脂肪酸（VFA）中。以乙酸盐为底物的MFCs中的微生物多样性较高，但不受搅拌影响，而以淀粉为底物的MFCs形成的群落较小且更具特异性。动力学分析确定复杂底物的水解是限速步骤，其速率比乙酸盐消耗速率慢一个数量级。水解 - 发酵的综合速率不受搅拌影响，但搅拌显著影响乙酸盐消耗速率，这可能是由于兼性需氧菌和产电细菌之间的氧气诱导竞争。这些发现突出了MFCs中底物可用性增强与氧气驱动竞争之间的权衡。对于实际应用，启动反应器时先进行动态搅拌以加速驯化，然后进行不搅拌操作，可能会优化性能。将MFCs与厌氧消化相结合可以克服水解限制，增强复杂底物的降解，同时提高能量回收。本研究引入了新策略来应对扩大MFCs用于废水处理的关键挑战，弥合基础研究与实际应用之间的差距，以推动环境系统发展。
