Tetracycline (TC) is the second most commonly used antibiotic despite its high toxicity and persistence. In this study, a new approach for the anaerobic biodegradation of TC in a microbial fuel cell (MFC), with glucose–TC mixtures as the substrate, under gradient acclimation conditions was explored. Within 7 days, approximately 79.1% of TC was degraded by the MFC. This value was higher than that obtained through a traditional anaerobic method (14.9%). The TC degradation rates in MFCs with a closed circuit were 31.6% higher than those in MFCs with an open circuit. Furthermore, zebrafish assessment showed that no toxicity was observed after MFC treatment. Microbial community analysis was performed on the anode of the MFCs under gradient acclimation conditions, and the results showed that TC was effectively degraded by the synergy of fermentative bacteria, acid-producing bacteria and electrogenic bacteria. This work confirmed that the anaerobic biodegradation of TC by MFCs is a cost-effective and environmentally friendly method.

•Reduced graphene oxide/biofilm has been fabricated by microbially self-assembly.•Reduced graphene oxide/biofilm developed 3D electroactive biofilms for MES.•High acetate production rate was generated by reduced graphene oxide/biofilm.•Reduced graphene oxide/biofilm improved the electron transfer rates.Microbial electrosynthesis (MES) is a biocathode-driven process, producing high-value chemicals from CO2. Here, an in situ self-assembled graphene oxide (rGO)/biofilm was constructed, in MES, for high efficient acetate production. GO has been successfully reduced by electroautotrophic bacteria for the first time. An increase, of 1.5 times, in the volumetric acetate production rate, was obtained by self-assembling rGO/biofilm, as compared to the control group. In MES with rGO/biofilm, a volumetric acetate production rate of 0.17 g l−1 d−1 has been achieved, 77% of the electrons consumed, were recovered and the final acetate concentration reached 7.1 g l−1, within 40 days. A three-dimensional rGO/biofilm was constructed enabling highly efficient electron transfer rates within biofilms, and between biofilm and electrode, demonstrating that the development of 3D electroactive biofilms, with higher extracellular electron transfer rates, is an effective approach to improving MES efficiency.Download high-res image (75KB)Download full-size image

•A new metal complex-based chemosensor for PPi was synthesized.•This new metal complex-based chemosensor exhibited highly selective and sensitive response toward PPi in aqueous solution.•The new complex was applied to monitoring the hydrolysis reaction of PPi and the polymerase chain reaction in DNA synthesis, respectively.A new dinuclear-copper(II) complex (Cu-L2) with two ammonium arms based on bis-2-((pyridin-2-ylmethylamino)methyl)phenol as the coordinated unit was synthesized. The complex exhibited high affinity with pyrophosphate (PPi) in aqueous solution. Using pyrocatechol violet (PV) as a colorimetric indicator, the indicator displacement assay (IDA) was carried out to determine the binding constant between the complex and PPi. A ca. 784-fold enhancement was founded when compared Cu-L2 to ammonium-free counterpart (Cu-L1). The new dinuclear complex was successfully used to monitor the hydrolysis of PPi catalyzed by pyrophosphatase (PPase). Furthermore, by employing esculetine as a fluorescent indicator, the complex was also used to detect PPi released during polymerase chain reaction (PCR).Graphical abstract for “A dinuclear-copper(ii) complex-based sensor for pyrophosphate and its applications to detecting pyrophosphatase activity and monitoring polymerase chain reaction”

To demonstrate that an enhanced sediment microbial fuel cell (SMFC) system can accelerate the degradation of cellulose in fresh water sediments as the accumulation of cellulose in lake sediments may aggravate the lake marsh, increase organic matter content and result in rapid deterioration of water quality and damage the ecosystem.After 330 days the highest cellulose removal efficiency (72.7 ± 2.1 %) was achieved in the presence of a SMFC with a carbon nanotube decorated cathode, followed by a SMFC without the cathode decoration (64.4 ± 2.8 %). The lowest cellulose removal efficiency (47.9 ± 2.1 %) was in the absence of SMFC. The sediment characterization analysis confirmed that the carbon nanotube decorated cathode enhances the electron transfer rate in the SMFC and improves the dissolved organic matter oxidation rate.This study offers a relatively simple and promising new method for cellulose degradation in sediment.

•Difference on performance of SMFC with adding the sheet iron existed.•Sheet iron out of the circuit was to improve the iron reduction microbial activity.•Sheet iron in the circuit produced a large number of electrons from the electrochemical corrosion.•We report a an easy and effective method for improving the performance of SMFC.In this study, we demonstrate the effect of iron sheet on the output power of sediment microbial fuel cells (SMFCs). An SMFC with iron sheet present, but not in the circuit (SMFC-GF-iron) displayed a maximum power density of 63 mW m−2, whereas we find 37 mW m−2 for that SMFC with the iron sheet not present (SMFC-GF). Furthermore, the SMFC with an iron sheet in the circuit (SMFC-iron) had a maximum power density of 170 mW m−2. The effect of sheet iron, out of the circuit, was to improve the iron reduction microbial activity, while, within the circuit, it produced a large number of electrons from the electrochemical corrosion yielding higher power production. The study suggests that the addition of iron sheet to an SMFC is an easy and effective method for enhancing the output power of SMFCs.

Low toxic and highly biocompatible graphene-based nanomaterials are in high demand within the biomedical fields. In this study, a highly biocompatible bacterially reduced graphene oxide (BRGO) was prepared by a “Generally Recognized As Safe” (GRAS) strain Bacillus subtilis 168 mediated with Vitamin K3 (VK3). The hypothesis of VK3 mediating electron transfer between succinate:quinine oxidoreductase, from B. subtilis 168, and graphene oxide (GO) was proposed. BRGO was characterized by Raman spectroscopy, XPS and XRD and showed excellent properties. Furthermore, BRGO illustrates greater biocompatibility, with less toxicity, than GO and chemically reduced graphene oxide (CRGO) by zebrafish toxicity assessment, which demonstrates its great potential in various biomedical applications.

•Cobalt oxide/nanocarbon hybrid materials are prepared.•Co3O4/NCNT catalyst exhibits high catalytic activity for ORR.•Microbial fuel cell with Co3O4/NCNT cathode demonstrates good stability.Cobalt oxide/nanocarbon hybrid materials (graphene and carbon nanotube) are used as alternative cathode catalysts for oxygen reduction reaction in air-cathode microbial fuel cell (MFC) for the first time. Electrochemical results reveal that these hybrid materials exhibit high catalytic performance. In MFCs, the maximum power density of 469 ± 17 mW m−2 is achieved from the Co3O4/NCNT cathode, which is 5.3 times larger than that of the NCNT cathode. This value is competitive with those obtained using Pt/C (603 ± 23 mW m−2). Therefore, Co3O4/NCNT nanocomposite is an efficient and cost-effective cathode catalyst for practical MFC applications.

A multi-walled, carbon nanotube (MWNT)-modified graphite felt (GF) cathode was fabricated to improve the performance of sediment microbial fuel cells (SMFC). Three types of MWNT-modified GF cathodes were prepared by different electrophoretic deposition (EPD) times. Maximum power density of SMFC with MWNT-GF*** cathode at 60 min EPD was 215 ± 9.9 mW m−2. This was 1.6 times that of SMFC with a bare GF cathode. Cyclic voltammetry and the amount of biomass showed that biomass density and electrochemical activity increased as the electrophoretic deposition time extended. Therefore the electrode possesses the highest catalytic behavior toward O2 reduction reaction. This simple process of carbon nanotube modification of a cathode by EPD can serve as an effective technique to improve the performance of SMFC.

•C. vulgaris is efficient in situ oxygenators for the oxygen reduction reaction.•Carbon nanotube strengthens the oxygen reduction rate from C. vulgaris release.•C. vulgaris can be cultivated in SMFC without any further addition of CO2.•We report a simple method for improving the performance of SMFC.One major limiting factor for sediment microbial fuel cells (SMFC) is the low oxygen reduction rate in the cathode. The use of the photosynthetic process of the algae is an effective strategy to increase the oxygen availability to the cathode. In this study, SMFCs were constructed by introducing the algae (Chlorella vulgaris) to the cathode, in order to generate oxygen in situ. Cyclic voltammetry and dissolved oxygen analysis confirmed that C. vulgaris in the cathode can increase the dissolved oxygen concentration and the oxygen reduction rate. We showed that power generation of SMFC with algae-assisted cathode was 21 mW m−2 and was further increased to 38 mW m−2 with additional carbon nanotube coating in the cathode, which was 2.4 fold higher than that of the SMFC with bare cathode. This relatively simple method increases the oxygen reduction rate at a low cost and can be applied to improve the performance of SMFCs.

•Clostridium scatologenes ATCC 25775T is an acetogenic anaerobic bacteria known to be capable of synthesizing biofuels from CO2 or CO on its autotrophic mode and producing 3-methylindole and 4-methylphenol on its heterotrophic mode.•The genome of C. scatologenes ATCC 25775T consists of one circular chromosome with a size of 5, 749, 410 bp, comprising 5333 predicted opening reading frames (ORFs), 63 tRNA genes, and 27 rRNA genes.•All genes referring to the Wood-Ljungdahl pathway and biofuel forming pathways were detected on the chromosome of C. scatologenes ATCC 25775T. Significantly, there are 2 sets of gene clusters encoding conversion of acetyl-CoA to butyryl-CoA.•Several enzymes referring to malodorant production, such as l-tyrosine:asparate aminotransferase, l-tyrosine:histidinol-phosphate aminotransferase and 4-hydroxyphenylacetate decarboxylases, have been located on the chromosome of C. scatologenes ATCC 25775T.Clostridium scatologenes ATCC 25775T is an acetogenic anaerobic bacteria known to be capable of synthesizing volatile fatty acids and solvents from CO2 or CO on its autotrophic mode and producing 3-methylindole and 4-methylphenol on its heterotrophic mode. Here, we report the complete genome sequence of this strain, which might provide a lot of valuable information for developing metabolic engineering strategies to produce biofuels or chemicals from greenhouse gases.