Yang-Yang Yu

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.

Label-free detection with micro optical fluidic systems (MOFS): a review

AbstractThe paper reviews the state-of-art for micro optical fluidic systems (MOFS), or optofluidics, which employs optics and fluidics in a microsystem environment to perform novel functionalities and in-depth analysis in the biophysical area. Various topics, which include the introduction of MOFS in biomedical engineering, the implementation of near-field optics and also the applications of MOFS to biophysical studies, are discussed. Different optical detection techniques, such as evanescent wave, surface plasmon resonance, surface enhanced Raman scattering, resonators and transistors, have been studied extensively and integrated into MOFS. In addition, MOFS also provides a platform for various studies of cell biophysics, such as cell mass determination and cell Young’s modulus measurement. FigureCell encapsulation and trapping for refractive index measurement in MOFS

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.

Amplification of electrochemical signal by a whole-cell redox reactivation module for ultrasensitive detection of pyocyanin

A bioelectrochemical sensing system based on a novel whole-cell redox reactivation/cycling module for ultrasensitive detection of pyocyanin (the biomarker of Pseudomonas aeruginosa infections) was developed. The electroactive bacteria mediated redox reactivation module was constructed using Shewanella oneidensis MR-1 cells as the bioelectro-catalyst and lactate as the electron donor. It could regenerate reductive pyocyanin from its oxidative state, which enabled pyocyanin molecule repeatedly registered by the electrode. Uniquely, with this redox reactivation module, the electrochemical response of pyocyanin was amplified about 405 times (1.3 μA/nM vs. 3.2nA/nM). Thus, an ultrasensitive bioelectrochemical sensing system for pyocyanin quantification was developed by integrating the pyocyanin reactivation module with conventional electrochemical detection system. Remarkably, with this developed biosensing system, an extremely low LOD of 47±1pM was reached. Additionally, this biosensing system showed excellent resistance to interferences from human fluids or bacterial contamination. This work provided a simple, ultrasensitive and robust tool for pyocyanin detection, and more importantly, demonstrated a new dimension for electrochemical signal amplification in biosensing.

The effect of external resistance on biofilm formation and internal resistance in Shewanella inoculated microbial fuel cells

External resistance is one of the important factors that affect the performance of microbial fuel cells (MFCs). In this study, bioelectrochemical and biofilm characterization was conducted for Shewanella oneidensis MR-1 inoculated MFCs with 250 Ω, 500 Ω, 2 kΩ, 6 kΩ and 22 kΩ resistors. Overall, a smaller external resistance resulted in a higher maximum power density and more riboflavin secretion. A maximum power density of 136.8 ± 3.1 mW m−2 was achieved when MFCs were operated with a 500 Ω resistor, which was 3.7 times that with a 22 kΩ resistor. Electrochemical impedance spectra (EIS) analysis verified an increased internal resistance with a higher external resistance. Meanwhile, more biofilm mass and extracellular polymer substances (EPS) were confirmed on the MFC anode with a higher external resistance.

Bioengineering of Bacterial Extracellular Electron Transfer Towards Sustainable Wastewater Treatment

Extracellular electron transfer (EET) referring to electron exchange between cells and solid matters is a unique electron transport process in bacteria that enables cells with very special character of electrode respiration. Based on bacterial electrode respiration, various bioelectrochemical systems (BES) for efficient wastewater treatment have been developed during the past decades. Besides augmentation of wastewater treatment, the BES are capable of harvesting the energy and recovery of resources from wastewater and can also produce value-added products by upgrading CO2 that was emitted during wastewater treatment. Therefore, BES hold a great promise to develop an energy-saving, emission-reducing, and economic feasible wastewater treatment approach for sustainable development, while EET efficiency engineering became the key step for the performance optimization of BES. In this chapter, typical EET pathways in several model exoelectrogens were introduced, and the potential of EET engineering for performance improvement of BES was highlighted. Moreover, future research directions for EET and BES engineering were also discussed.