Search

The in situ modification of the NF electrode was developed by integrated microbial corrosion and microbial mineralization using S. oneidensis for OER.

A novel microfiber-like biohydrogel was fabricated by a facile approach relying on electroactive bacteria-induced graphene oxide reduction and confined self-assembly in a capillary tube. The microfiber-like biohydrogel (d = ∼1 mm) embedded high-density living cells and activated efficient electron exchange between cells and the conductive graphene network. Further, a miniature whole-cell electrochemical biosensing system was developed and applied for fumarate detection under −0.6 V (vs Ag/AgCl) applied potential. Taking advantage of its small size, high local cell density, and excellent electron exchange, this microfiber-like biohydrogel-based sensing system reached a linear calibration curve (R2 = 0.999) ranging from 1 nM to 10 mM. The limit of detection obtained was 0.60 nM, which was over 1300 times lower than a traditional biosensor for fumarate detection in 0.2 μL microdroplets. This work opened a new dimension for miniature whole-cell electrochemical sensing system design, which provided the possibility for bioelectrochemical detection in small volumes or three-dimensional local detection at high spatial resolutions.

Biomethanation is of great interest as it can transform CO2 to methane under ambient conditions. In particular, genetically engineered bacterium of Rhodopseudomonas palustris showed great promise for one-step biomethanation powered by solar energy, which is attractive for CO2 fixation as well as solar energy storage. However, biomethanation with R. palustris under visible light is inefficient due to its poor visible light response. In this study, CdS quantum dots with excellent visible light response were prepared and R. palustris/CdS hybrid cells were constructed. Interestingly, this bio-nano-hybrid cells showed high cell viability without significant cell damage, and the biomethanation performance of was enhanced about ~ 79% compared to that of the bare R. palustris cells. Moreover, the effects of different parameters on the methane production of this bio-nano-hybrid cells were determined, and the methane production rate was further improved by parameter optimization. This work demonstrated an efficient approach to reinforce the biomethanation of bacteria under unfavorable light wavelength, which would be helpful to extend the light spectra for photo-driven biomethanation.

A signal amplification system for electrochemical sensing was established by bio-nanohybrid cells (BNC) based on bacterial self-assembly and biomineralization. The BNC was constructed by partially encapsulating a

Silver (Ag) and palladium (Pd) nanoparticles were synthesized via a green synthesis route, which was mediated with the extract of Daucus carota leaves. The morphological, crystalline and structural nature of the synthesized nanoparticles was characterized by UV-Vis spectrophotometer, and TEM, XRD and FT-IR analyses. High antibacterial activities of the prepared Ag and Pd nanoparticles were observed towards different water-borne pathogens of Klebsiella pneumonia, Vibrio cholera and Escherichia coli. The catalytic efficiency of the prepared nanoparticles for the removal of rhodamine 6G (Rh-6G) dye was also evaluated. Nearly 98% of the Rh-6G dye was decolorized by the synthesized Pd nanoparticles within 2 min, and the synthesized Ag nanoparticles took 30 min for 89.4% decolorization. This work provided greener nanocatalysts for pollutant treatment and demonstrated the power of green biosynthesis for metallic nanoparticles.

Semiconductor quantum dots (QDs) have shown excellent advantages in photocatalysis owing to the unique optical properties, adjustable bandgap and high specific surface area. However, the small size...

The soil microbial fuel cell (SMFC) is a new device that was originally designed to generate electricity from organic matter in soil using microorganisms. Currently, SMFC based biosensors are emerging as a new and promising research direction for real-time and rapid monitoring of soil quality or soil pollution. Compared to conventional biosensors, SMFC based biosensors exhibit advantages such as low-cost, simple design, in-situ, and long-term self-powering monitoring, which makes it become attractive devices for in-situ long-term soil quality or soil pollution monitoring. Thus, this review aims to provide a comprehensive overview of SMFC based biosensors. In this review, different prototypes of SMFC based biosensors developed in recent years are introduced, the biosensing mechanisms and the roles of SMFC are highlighted, and the emerging applications of these SMFC based biosensors are discussed. Since the SMFC based biosensors are applied in open-air conditions, the effects of different environmental factors on the biosensing response are also summarized. Finally, to further expand the understanding and boost the practical application of the SMFC based biosensors, future perspectives including fundamental mechanism exploration and investigation of the full-scale application are proposed.

Microbial CO

Microbial fuel cell (MFC) was a promising technology for energy harvesting from wastewater. However, inefficient bacterial extracellular electron transfer (EET) limited the performance as well as the applications of MFC. Here, a new strategy to reinforce the EET by engineering synthetic extracellular matrix (ECM) with cytochrome fused curli was developed. By genetically fusing a minimal cytochrome domain (MCD) with the curli protein CsgA and heterogeneously expressing in model exoelectrogen of Shewanella oneidensis MR-1, the cytochrome fused electroactive curli network was successfully constructed and assembled. Interestingly, the strain with the MCD fused synthetic ECM delivered about 2.4 times and 2.0 times higher voltage and power density output than these of wild type MR-1 in MFC. More impressively, electrochemical analysis suggested that this synthetic ECM not only introduced cytochrome of MCD, but also attracted more self-secreted electrochemically active substances, which might facilitate the EET and improve the MFC performance. This work demonstrated the possibility to manipulation the EET with ECM engineering, which opened up new path for exoelectrogen design and engineering.

Macrolide antibiotics are one of the major groups of emerging pharmaceutical contaminants that have been detected in aquatic systems. Photocatalytic degradation under UV light is useful for mineralization of various pharmaceutical pollutants but very limited studies are available for degradation of azithromycin (AZY) using visible light. In the present study, a novel ZrO2/Ag@TiO2 nanorod ternary nanocomposite was prepared by a simple hydrothermal and photodeposition method for efficient degradation of AZY under visible light. The composite was detailed characterized by XRD, XPS and TEM analyses, which revealed the formation of cubic ZrO2 and Ag nanoparticles on TiO2 nanorods (TNR). More than 90% of azithromycin (20 mg/L) was degraded after 8 h of visible light irradiation. The plausible transformation pathway for azithromycin was proposed based on the LC/MS-IT-TOF analysis. The phytotoxicity evaluation of the azithromycin and its degraded products was assessed on Vigna radiata. The germination index (GI) of azithromycin was found to be 12.3% before degradation while it increased to 81.05% after 8 h of degradation, indicating this photodegradation process achieved nearly complete detoxification. Furthermore, the toxicity of the degradation products was determined on the basis of Escherichia coli colony forming unit assay which confirmed high detoxification efficiency. Thus, this work demonstrated an efficient strategy for visible light degradation and detoxification of azithromycin, which provided new insight on macrolide antibiotic photodegradation and would be promising for antibiotic wastewater treatment.

The toxicity and persistence of the halogenated aromatics, particularly brominated phenolic compounds have drawn serious concerns to the environment, emphasizing the potential effects on human health and ecosystems balance. Advanced oxidation process (AOP) has received much attention as an alternative for the conventional wastewater treatment methods to treat water contaminated with toxic pollutants. This study investigated the degradation and detoxification of p-bromophenol (p-BP) by a novel Zr/Ag-TiO2@rGO photocatalyst under visible light. Upon 3 h of visible light irradiation over Zr/Ag-TiO2@rGO, more than 95% of p-BP (15 mg/L) degradation was achieved at a rate of 0.23 min−1. The degradation products were identified by GC-MS and possible degradation pathway was proposed. The phytotoxicity evolution of the degraded products was assessed on Vigna radiata (V. radiata), in which seeds treated with pure p-BP showed less germination (40%) compared to degradation products (100%). Furthermore, the germination index (GI) of p-BP was found to be 11.1% before degradation while it increased to 80.5% after 3 h of degradation indicated that this photodegradation process achieved detoxification of p-BP. Thus, this study demonstrated that p-BP elimination and detoxification could be simply achieved with Zr/Ag-TiO2@rGO nanocomposite under visible light irradiation, which provides new solution for wastewater treatment and water reuse in crop irrigation.

A bioelectrochemical sensing system (BES) based on electroactive bacteria (EAB) has been used as a new and promising tool for water toxicity assessment. However, most EAB can reduce heavy metals, which usually results in low toxicity response. Herein, a starvation pre-incubation strategy was developed which successfully avoided the metal reduction during the toxicity sensing period. By integrating this starvation pre-incubation procedure with the amperometric BES, a sensitive, robust and mediator-free biosensing method for heavy metal toxicity assessment was developed. Under the optimized conditions, the IC50 (half maximal inhibitory concentration) values for Cu2+, Ni2+, Cd2+, and Cr6+ obtained were 0.35, 3.49, 6.52, 2.48 mg L−1, respectively. The measurement with real water samples also suggested this method was reliable for practical application. This work demonstrates that it is feasible to use EAB for heavy metal toxicity assessment and provides a new tool for water toxicity warning.

Microbial fuel cells (MFCs) are of great interest due to their capability to directly convert organic compounds to electric energy. In particular, MFCs technology showed great potential to directly harness the energy from xylose in the form of bioelectricity and biohydrogen simultaneously. Herein, we report a yeast strain of Cystobasidium slooffiae JSUX1 enabled the reduction and assembly of graphene oxide (GO) nanosheets into three-dimensional reduced GO (3D rGO) hydrogels on the surface of carbon felt (CF) anode. The autonomously self-modified 3D rGO hydrogel anode entitled the yeast-based MFCs with two times enhancement on bioelectricity and biohydrogen production from xylose. Further analysis demonstrated that the 3D rGO hydrogel attracted more yeast cells and reduced the interfacial charge transfer resistance, which was the underlying mechanism for the improvement of MFCs performance. This work offers a new strategy to reinforce the performance of yeast-based MFCs and provides a new opportunity to efficiently harvest energy from xylose.

In addition to disposal issues, the abundance of sludge and chicken manure has been a rising issue in Malaysia. Membrane-less microbial fuel cell (ML-MFC) technology can be considered as one of the potential solutions to the issues of disposal and electricity generation. However, there is still a lack of information on the performance of an ML-MFC powered by sludge and chicken manure. Hence, with this project, we studied the performance of an ML-MFC supplemented with sludge and chicken manure, and its operating parameters were optimized using response surface methodology (RSM) through central composite design (CCD). The optimum operating parameters were determined to be 35 °C, 75% moisture content, and an electrode distance of 3 cm. Correspondingly, the highest power density, COD removal efficiency, and biomass acquired through this study were 47.2064 mW/m2, 98.0636%, and 19.6730 mg/L, respectively. The obtained COD values for dewatered sludge and chicken manure were 708 mg/L and 571 mg/L, respectively. COD values were utilized as a standard value for the substrate degradation by Bacillus subtilis in the ML-MFC. Through proximate analyses conducted by elemental analysis and atomic absorption spectrometry (AAS), the composition of carbon and magnesium for sludge and chicken manure was23.75% and 34.20% and 78.1575 mg/L and 71.6098 mg/L, respectively. The proposed optimal RSM parameters were assessed and validated to determine the ML-MFC operating parameters to be optimized by RSM (CCD).

Four strains of bioflocculant-producing bacteria were isolated from a palm oil mill effluent (POME). The four bacterial strains were identified as Pseudomonas alcaliphila (B1), Pseudomonas oleovorans (B2), Pseudomonas chengduensis (B3), and Bacillus nitratireducens (B4) by molecular identification. Among the four bacterial strains, Bacillus nitratireducens (B4) achieved the highest flocculating activity (49.15%) towards kaolin clay suspension after eight hours of cultivation time and was selected for further studies. The optimum conditions for Eriochrome Black T (EBT) flocculation regarding initial pH, type of cation, and B4 dosage were determined to be pH 2, Ca2⁺ cations, and a dosage of 250 mL/L of nutrient broth containing B4. Under these conditions, above 90% of EBT dye removal was attained. Fourier transform infrared spectroscopic (FT-IR) analysis of the bioflocculant revealed the presence of hydroxyl, alkyl, carboxyl, and amino groups. This bioflocculant was demonstrated to possess a good flocculating activity, being a promissory, low-cost, harmless, and environmentally friendly alternative for the treatment of effluents contaminated with dyes.

Microbial fuel cells (MFCs) showed great potential to harness sustainable electric energy from wastewater. Exploration of natural and high-performance electrode materials was highly required to overcome the big challenge of sustainability for microbial energy harvesting with MFCs. In this study, Spirogyra, a wide-spread biopollutant, was explored as a superior material to fabricate high performance and sustainable electrodes for MFCs. By simple carbonization, tens of centimeters long and conductive carbon belts with a self-constructed carbon nanoparticle coating were synthesized from Spirogyra filaments. Impressively, the carbon belts formed 3D non-woven interconnected macroporous networks with intriguing features of light weight and high biocompatibility. More strikingly, they activated highly efficient extracellular electron transfer due to excellent cell/electrode interaction, which is usually not achievable by conventional carbon electrodes. Consequently, Spirogyra electrodes outperformed other natural material derived or commercial electrodes in MFCs, suggesting that Spirogyra was the most superior natural material for sustainable electrodes, which provides new opportunities for more sustainable energy harvesting with MFCs.

Controllable synthesis of uniform graphene–metal oxide nanocomposites is of great interest in energy storage applications, due to the combination of their merits and the synergistic effects on the enhancement of their electrochemical performance. Herein, we report a controllable synthesis of uniform mesoporous H-Nb2O5/rGO nanocomposites, which exhibit higher reversible specific capacity (∼190 mA h g−1), and better rate capability and cycling stability (the capacitance retention is 96.5% over 500 cycles) than pristine H-Nb2O5 microflowers, attributed to their large specific surface area (364.17 m2 g−1), porous structure, and intimate interface. More remarkably, the H-Nb2O5/rGO-based lithium ion hybrid supercapacitor (LIHS) delivered a high energy density of 100.2 W h kg−1 at 50 W kg−1 and still retained 18.3 W h kg−1 at an ultrahigh power density of 20 000 W kg−1, as well as an excellent cycling stability. It is worth noting that some other nanocomposites, including Zn2Ti3O8/rGO, Si/rGO, NaNbO3/rGO, Nb4N5/rGO, and H-Nb2O5/2D g-C3N4, have also been successfully synthesized by this method, demonstrating that it can be extended to prepare other functional nanocomposites for applications in energy conversion and storage, photocatalytic hydrogen production, sensors, and so on.

Development of efficient and noble metal-free catalysts for oxygen evolution reaction (OER) is of great importance for practical energy-related technologies. Herein, one-step hydrothermal method is developed for the synthesis of a series of nickel selenides (NiSe2, NiSe, and Ni3Se2) and their multiwalled carbon nanotubes (MWCNTs) nanocomposites as electrocatalysts for OER. Among the NiSe2, NiSe, and Ni3Se2 catalysts, NiSe shows the highest activity, exhibiting an overpotential of 389 mV to achieve 10 mA/cm2 and a Tafel slope of 93 mV/dec in 1 M KOH. We further report a facile preparation of nickel selenides nanocrystals (particle size of ∼10 nm) grown on MWCNTs. The NiSe/MWCNTs nanocomposite shows improved activity toward OER, with an overpotential of 336 mV to reach 10 mA/cm2 and a Tafel slope of 78 mV/dec, which is close to the state-of-the-art RuO2 catalyst. The addition of MWCNTs during the synthesis not only introduces an abundance of nucleation sites, resulting in small particle sizes of NiSe crysta...

Nitroaromatic compounds (NACs) are widely used in modern industry and are considered as harmful pollutants due to their high toxicity and mutagenesis. Moreover, as the NACs contain one or more electron-withdrawing nitro-groups, they are resistant to biodegradation and are classified as recalcitrant pollutants. Thus, reduction of the nitro groups in NACs to form more biodegradable derivatives was considered as the most important step for NACs removal. Interestingly, it was found that some bacteria are able to reduce the nitro groups in NACs, and bioreduction was proved as a cost-effective way for NACs reduction. Particularly, the electroactive bacteria (EAB) with high NACs reduction efficiency have been identified recently. In this review, the transformation pathways for NACs bioreduction and the identified EAB species are summarized. Furthermore, the electron transfer pathways and strategies for augmentation on NACs bioreduction with EAB are highlighted. The research directions and perspectives for NACs bioreduction by EABs are also discussed.