Key Takeaways & Executive Findings
- •• • Synergistic addition of 6 mmol·L−1 lactate and microbial immobilization increased maximum power density to 22.06 mW·m−2, a 194% improvement over the blank, and raised maximum output voltage to 88.75 mV (2.09× non-immobilized), demonstrating effective enhancement of SMFC electrochemical performance. • • At the optimal lactate concentration (6 mmol·L−1), TOC and TN removal rates reached 29.02% and 28.4%, respectively, outperforming the control (22.41% and 21.42%), while high lactate concentrations caused TOC accumulation due to metabolic inhibition, indicating a critical threshold for carbon source dosing. • • 16S rRNA analysis identified Bacillota and Pseudomonadota as the dominant phyla on the anode, both possessing electroactive and pollutant-degrading functions, confirming that lactate enriches functional bacteria and immobilization prevents their loss, thereby stabilizing the microbial community. • • The combined strategy of lactate regulation and immobilization addresses the bottlenecks of low electron transfer efficiency and unstable microbial communities in traditional SMFCs, offering a scalable approach for in-situ remediation of eutrophic and industrially polluted sediments with simultaneous energy recovery.
Abstract
Sediment microbial fuel cells (SMFCs) are a green technology for simultaneous polluted sediment remediation and energy recovery, yet their performance is constrained by insufficient anodic microbial activity and low electron transfer efficiency. This study employed lactate addition combined with composite engineered microbial immobilization to synergistically optimize SMFC performance by enhancing microbial stability and carbon source supply. Results showed that lactate, as an easily utilized electron donor, promoted electrochemical activity, achieving a maximum power density of 22.06 mW·m−2 at 6 mmol·L−1, a 194% improvement over the blank group. Immobilization further enhanced electron transfer efficiency, with the highest output voltage (88.75 mV) being 2.09 times that of the non-immobilized group. For pollutant degradation, the 6 mmol·L−1 lactate group achieved TOC and TN removal rates of 29.02% and 28.4%, respectively, outperforming the control (22.41% and 21.42%). However, high lactate concentrations inhibited microbial metabolism, leading to TOC accumulation. 16S rRNA analysis revealed that the anodic microbial community was dominated by Bacillota and Pseudomonadota, both possessing electroactive and pollutant-degrading capabilities, indicating that lactate and immobilization exert a synergistic effect in SMFCs, simultaneously enhancing electricity generation and pollutant removal efficiency.
1. Introduction
Conventional sediment microbial fuel cells (SMFCs) face critical bottlenecks that hinder their practical deployment: low power output, unstable performance, and insufficient anodic microbial activity. These limitations stem from poor electron transfer kinetics and the inability to maintain a robust electroactive biofilm in complex sediment environments. While substrate addition (e.g., acetate, glucose) has been explored to provide carbon sources and electron donors, it alone cannot ensure long-term operational stability. Similarly, microbial immobilization techniques have shown promise in enhancing biofilm formation and electron transfer, but their full potential is realized only when combined with appropriate substrate management.
This study addresses these challenges by integrating lactate regulation with composite engineered microbial immobilization. Lactate serves as an easily metabolized electron donor that enriches electroactive bacteria (e.g., Bacillota and Pseudomonadota), while immobilization on the anode surface prevents microbial washout and maintains high local cell density. The synergistic approach not only boosts power density by 194% but also improves pollutant removal (TOC and TN) by up to 30%, demonstrating a viable pathway for simultaneous energy recovery and sediment remediation. By systematically optimizing lactate concentration and immobilization protocols, this work provides a mechanistic understanding and a practical strategy to overcome the long-standing performance barriers of SMFCs.
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YU Jianjun, QI Jiarui, WU Yutiancheng, LI Xiaofeng, XIE Wen, WU Chenyang (2026). Application and Mechanistic Study of Lactate Regulation and Microbial Immobilization Technology in Sediment Microbial Fuel Cell Systems. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202511062
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Frequently Asked Questions
What is the optimal lactate concentration for maximizing SMFC performance, and what happens at higher concentrations?
The optimal lactate concentration is 6 mmol·L−1, yielding a maximum power density of 22.06 mW·m−2 and TOC/TN removal rates of 29.02%/28.4%. At higher concentrations, lactate inhibits microbial metabolism, leading to TOC accumulation and reduced performance, indicating a critical threshold for carbon source dosing.
How does microbial immobilization contribute to the enhanced electron transfer and system stability?
Immobilization fixes electroactive bacteria (e.g., Bacillota, Pseudomonadota) onto the anode surface, preventing their loss in the sediment environment and maintaining high local cell density. This enhances biofilm formation, extracellular electron transfer, and overall system stability, as evidenced by a 2.09-fold increase in maximum output voltage compared to non-immobilized systems.
What are the dominant microbial phyla enriched on the anode, and what functional roles do they play?
16S rRNA analysis identified Bacillota and Pseudomonadota as the dominant phyla. These bacteria possess both electroactive capabilities (facilitating electron transfer) and pollutant-degrading functions (e.g., organic matter and nitrogen removal), making them key contributors to the simultaneous enhancement of power generation and pollutant removal.
Can this synergistic strategy be scaled up for real-world sediment remediation applications?
The strategy is designed for in-situ remediation of polluted sediments, particularly in eutrophic and industrial-contaminated sites. The use of low-cost carbon materials and commercially available microbial agents, combined with simple lactate addition, suggests potential for scalability. However, field-scale validation is required to assess long-term performance under variable environmental conditions.
What are the limitations of this study, and what future research is needed?
The study was conducted in laboratory-scale reactors over a limited duration. Future work should investigate long-term stability, the effects of sediment heterogeneity, and the fate of immobilized microbes in natural systems. Additionally, economic assessments comparing this approach to conventional remediation technologies are necessary to evaluate commercial viability.
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