Yang-Chun Yong

Macroporous and Monolithic Anode Based on Polyaniline Hybridized Three-Dimensional Graphene for High-Performance Microbial Fuel Cells

Microbial fuel cell (MFC) is of great interest as a promising green energy source to harvest electricity from various organic matters. However, low bacterial loading capacity and low extracellular electron transfer efficiency between the bacteria and the anode often limit the practical applications of MFC. In this work, a macroporous and monolithic MFC anode based on polyaniline hybridized three-dimensional (3D) graphene is demonstrated. It outperforms the planar carbon electrode because of its abilities to three-dimensionally interface with bacterial biofilm, facilitate electron transfer, and provide multiplexed and highly conductive pathways. This study adds a new dimension to the MFC anode design as well as to the emerging graphene applications.

Highly Active Bidirectional Electron Transfer by a Self-Assembled Electroactive Reduced-Graphene-Oxide-Hybridized Biofilm†

Low extracellular electron transfer performance is often a bottleneck in developing high-performance bioelectrochemical systems. Herein, we show that the self-assembly of graphene oxide and Shewanella oneidensis MR-1 formed an electroactive, reduced-graphene-oxide-hybridized, three-dimensional macroporous biofilm, which enabled highly efficient bidirectional electron transfers between Shewanella and electrodes owing to high biomass incorporation and enhanced direct contact-based extracellular electron transfer. This 3D electroactive biofilm delivered a 25-fold increase in the outward current (oxidation current, electron flux from bacteria to electrodes) and 74-fold increase in the inward current (reduction current, electron flux from electrodes to bacteria) over that of the naturally occurring biofilms.

Enhancement of extracellular electron transfer and bioelectricity output by synthetic porin.

The microbial fuel cell (MFC), is a promising environmental biotechnology for harvesting electricity energy from organic wastes. However, low bacterial membrane permeability of electron shuttles is a limiting factor that restricts the electron shuttle‐mediated extracellular electron transfer (EET) from bacteria to electrodes, thus the electricity power output of MFCs. To this end, we heterologously expressed a porin protein OprF from Pseudomonas aeruginosa PAO1 into Escherichia coli, which dramatically increased its membrane permeability, delivering a much higher current output in MFCs than its parental strain (BL21). We found that the oprF‐expression strain showed more efficient EET than its parental strain. More strikingly, the enhanced membrane permeability also rendered the oprF‐expression strain an efficient usage of riboflavin as the electron shuttle, whereas its parental strain was incapable of. Our results substantiated that membrane permeability is crucial for the efficient EET, and indicated that the expression of synthetic porins could be an efficient strategy to enhance bioelectricity generation by microorganisms (including electrogenic bacteria) in MFCs. Biotechnol. Bioeng. 2013; 110: 408–416.

Enhancement of bioelectricity generation by manipulation of the electron shuttles synthesis pathway in microbial fuel cells.

Microbial fuel cells (MFCs) are promising for generating bioenergy and treating organic waste simultaneously. However, low extracellular electron transfer (EET) efficiency between electrogens and anodes remains one of the major bottlenecks in practical applications of MFCs. In this paper, pyocyanin (PYO) synthesis pathway was manipulated to improve the EET efficiency in Pseudomonas aeruginosa-inoculated MFCs. By overexpression of phzM (methyltransferase encoding gene), the maximum power density of P. aeruginosa-phzM-inoculated MFC was enhanced to 166.68 μW/cm(2), which was four folds of the original strain. In addition, the phzM overexpression strain exhibited an increase of 1.6 folds in PYO production and about a onefold decrease in the total internal resistance than the original strain, which should underlie the enhancement of the EET efficiency and the electricity power output (EPT). On the basis of these results, the manipulation of electron shuttles synthesis pathways could be an efficient approach to improve the EPT of MFCs.

Engineering quorum sensing signaling of Pseudomonas for enhanced wastewater treatment and electricity harvest: A review

Cell-cell communication that enables synchronized population behaviors in microbial communities dictates various biological processes. It is of great interest to unveil the underlying mechanisms of fine-tuning cell-cell communication to achieve environmental and energy applications. Pseudomonas is a ubiquitous microbe in environments that had wide applications in bioremediation and bioenergy generation. The quorum sensing (QS, a generic cell-cell communication mechanism) systems of Pseudomonas underlie the aromatics biodegradation, denitrification and electricity harvest. Here, we reviewed the recent progresses of the genetic strategies in engineering QS circuits to improve efficiency of wastewater treatment and the performance of microbial fuel cells.

Microbial fuel cell-based biosensors for environmental monitoring: a review

The microbial fuel cell (MFC) is an innovative technology that was initially designed to harness energy from organic waste using microorganisms. It is striking how many promising applications beyond energy production have been explored in recent decades. In particular, MFC-based biosensors are considered to be the next generation biosensing technology for environmental monitoring. This review describes recent advances in this emerging technology of MFC-based biosensors, with a special emphasis on monitoring of biochemical oxygen demand and toxicity in the environment. The progress confirms that MFC-based biosensors could be used as self-powered portable biosensing devices with great potential in long-term and remote environmental monitoring.

Enhanced bioelectricity generation by improving pyocyanin production and membrane permeability through sophorolipid addition in Pseudomonas aeruginosa-inoculated microbial fuel cells.

Improvement on electron shuttle-mediated extracellular electron transfer (EET) is of great potential to enhance the power output of MFCs. In this study, sophorolipid was added to enhance the performance of Pseudomonas aeruginosa-inoculated MFC by improving the electron shuttle-mediated EET. Upon sophorolipid addition, the current density and power density increased ∼ 1.7 times and ∼ 2.6 times, respectively. In accordance, significant enhancement on pyocyanin production (the electron shuttle) and membrane permeability were observed. Furthermore, the conditions for sophorolipid addition were optimized to achieve maximum pyocyanin production (14.47 ± 0.23 μg/mL), and 4 times higher power output was obtained compared to the control. The results substantiated that enhanced membrane permeability and pyocyanin production by sophorolipid, which promoted the electron shuttle-mediated EET, underlies the improvement of the energy output in the P. aeruginosa-inoculated MFC. It suggested that addition of biosurfactant could be a promising way to enhance the energy generation in MFCs.

Regulation of aromatics biodegradation by rhl quorum sensing system through induction of catechol meta-cleavage pathway.

The mechanism for quorum sensing (QS) regulation on aromatics degradation was investigated. Deletion of rhl QS system resulted in a significant decrease in aromatics biodegradation as well as the activity of catechol 2,3-dioxygenase (C23O, key enzyme for catechol meta-cleavage pathway) in Pseudomonas aeruginosa CGMCC1.860. Interestingly, this repression could be relieved by N-butyryl homoserine lactone (the signaling molecule of rhl QS system) addition. In accordance, the transcription level of nahH (the gene encoding C23O) and nahR (transcriptional activator) also responded to rhl perturbation in a similar way. The results indicated that rhl QS system positively controlled the catechol meta-cleavage pathway, and hence improved aromatics biodegradation. It suggested manipulation of QS system could be a promising strategy to tune the catechol cleavage pathway and to control aromatics biodegradation.

Enhancement of power production with tartaric acid doped polyaniline nanowire network modified anode in microbial fuel cells.

The feasibility to use tartaric acid doped PANI for MFC anode modification was determined. Uniform PANI nanowires doped with tartaric acid were synthesized and formed mesoporous networks on the carbon cloth surface. By using this tartaric acid doped PANI modified carbon cloth (PANI-TA) as the anode, the voltage output (435 ± 15 mV) and power output (490 ± 12 mW/m(2)) of MFC were enhanced by 1.6 times and 4.1 times compared to that of MFC with plain carbon cloth anode, respectively. Strikingly, the performance of PANI-TA MFC was superior to that of the MFCs with inorganic acids doped PNAI modified anode. These results substantiated that tartaric acid is a promising PANI dopant for MFC anode modification, and provided new opportunity for MFC performance improvement.

Endogenously enhanced biosurfactant production promotes electricity generation from microbial fuel cells.

Microbial fuel cell (MFC) is considered as a promising green energy source and energy-saving pollutants treatment technology as it integrates pollutant biodegradation with energy extraction. In this work, a facile approach to enhance endogenous biosurfactant production was developed to improve the electron transfer rate and power output of MFC. By overexpression of rhlA, the key gene responsible for rhamnolipids synthesis, over-production of self-synthesized rhamnolipids from Pseudomonas aeruginosa PAO1 was achieved. Strikingly, the increased rhamnolipids production by rhlA overexpression significantly promoted the extracellular electron transfer of P. aeruginosa by enhancing electron shuttle (pyocyanin) production and increasing bacteria attachment on the anode. As a result, the strain with endogenously enhanced rhamnolipids production delivered 2.5 times higher power density output than that of the parent strain. This work substantiated that the enhancement on endogenous biosurfactant production could be a promising approach for improvement on the electricity output of MFC.