Sustainable bioelectricity generation using Cladophora sp. as a biocathode in membrane-less microbial fuel cell.

In this study, the Cladophora sp. is used to provide oxygen to the cathode of the photosynthetic biocathode membrane-less microbial fuel cell (PB-MLMFC). Non-aerated (NA-MLMFC) and mechanically-aerated (MA-MLMFC) MLMFCs are operated under similar operating conditions to evaluate the performance of PB-MLMFC with the presence of Cladophora sp. The PB-MLMFC exhibits the highest dissolved oxygen (DO) concentration, which results in a more efficient oxygen reduction reaction and a significant improvement in the electricity generation performance. The maximum power density of PB-MLMFC is 619.1 mW m-2, which is the highest power density known to be reported for algal cathode MFCs in the literature. The electrochemical analysis shows that theCladophora sp.reduces the charge (Rct) and mass transfer (Rmt) resistances of the PB-MLMFC, and improves the bioelectrochemical activity of the anode microorganisms. The study reveals that Cladophora sp. provides a cost-effective and renewable approach for practical applications of MLMFCs.

Quorum quenching strategy for biofouling control in membrane photobioreactor.

This study aims to reduce membrane fouling in membrane photobioreactor (MPBR) through the quorum quenching (QQ) strategy. For this purpose, the QQ beads (immobilized Rhodococcus sp. BH4) were added to the MPBR, and antifouling ability was evaluated in consideration of the changes in transmembrane pressure (TMP), extracellular polymeric substance (EPS), microbial community, and cake layer morphology on the membrane surface. The results showed that the TMP of control MPBR (MPBR-C) reached 818 mbar and 912 mbar on the operation hours of 35 and 170, while the TMP of experimental MPBR (MPBR-QQ) was only 448 mbar and 676 mbar, respectively. The QQ strategy effectively reduced the EPS content in MPBR. The microscopic observations indicated that the QQ diminished the cake layer formation and pore-blocking on the membrane surface. Comparisons of 16S and 18S gene communities revealed minor differences between bacterial and eukaryotic species in MPBRs at phylum and class levels.

Inhibition of AHL-mediated quorum sensing to control biofilm thickness in microbial fuel cell by using Rhodococcus sp. BH4.

Anode biofilm thickness is a key point for high and sustainable power generation in microbial fuel cells (MFCs). Over time, the formation of a thicker biofilm on anode electrode hinders the power generation performance of MFC by causing a longer electron transfer path and the accumulation of undesirable components in anode biofilm. To overcome these limitations, we used a novel strategy named quorum quenching (QQ) for the first time in order to control the biofilm thickness on the anode surface by inactivation of signal molecules among microorganisms. For this purpose, the isolated QQ bacteria (Rhodococcus sp. BH4) were immobilized into alginate beads (20, 40, and 80 mg/10 ml sodium alginate) and added to the anode chamber of MFCs. The MFC exhibited the best electrochemical activity (1924 mW m-2) with a biofilm thickness of 26 µm at 40 mg Rhodococcus sp. BH4/10 ml sodium alginate. The inhibition of signal molecules in anode chamber reduced the production of extracellular polymeric substance (EPS) by preventing microbial communication amonganode microorganisms. Microscopic observations revealed that anode biofilm thickness and the abundance of dead bacteria significantly decreased with an increase in Rhodococcus sp. BH4 concentration in MFCs. Microbiome diversity showed an apparent difference among the microbial community structures of anode biofilms in MFCs containing vacant and Rhodococcus sp. BH4 beads. The data revealed that the QQ strategy is an efficient application for improving MFC performance and may shed light on future studies.

Effect of the tetracycline antibiotics on performance and microbial community of microbial fuel cell.

The adverse effect of tetracycline antibiotics on microbial activity is one of the serious risks for the biologic wastewater treatment process. The microbial fuel cells (MFCs) are a promising technology for wastewater treatment and renewable power generation process. For this reason, the investigation of the inhibition effect of the tetracyclines on the MFCs is essential for reducing damage on the environment. This paper focused on the performance of MFCs under different antibiotic concentrations at the range of 0.25-50 mg/L. The power generation performance, microbial community and biofilm characteristics (morphology, resistance and viability) of MFCs were investigated in detail. The results indicated that the increase in the antibiotic concentration significantly affected the MFC performance and microbial community. A modified non-competitive inhibition model was used to predict the inhibition effect of tetracycline antibiotics on the MFCs.

Nitinol as a suitable anode material for electricity generation in microbial fuel cells.

Nitinols (Nickel-titanium alloys) have a good electrical conductivity and biocompatibility with human tissue and bacteria and, therefore, can be effectively used as an anode material in bioelectrochemical systems. This paper aimed to use nitinols (at different Ni/Ti ratios) as an anode material for microbial fuel cells (MFCs) in order to achieve higher power density. The maximum power densities of the MFCs using NiTi-1, NiTi-2, and NiTi-3 electrodes were 555 mW/m2, 811 mW/m2, and 652 mW/m2, respectively. More bacterial adhesion was observed on the NiTi-2 electrode. Electrochemical impedance spectroscopy (EIS) results showed low charge transfer resistance at MFCs fabricated with NiTi. The biofilm observations indicate that bacterial attachment is better with NiTi-2 as compared with that on NiTi-1 and NiTi-3. The resulting mesopore and macropore rich structure significantly promote microbial colonization, enabling formation of compact electroactive biofilms with additional benefit from the excellent biocompatibility and chemical stability of NiTi-2. Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) results indicated that five groups of bacteria were the dominant phyla in the MFCs: environmental samples, b-proteobacteria, g-proteobacteria, d-proteobacteria, and CFB group bacteria. The high biocompatibility, electrical conductivity and stability of nitinols make them a more attractive anode material for MFCs.

Comprehensive evaluation of autohydrogenotrophic membrane biofilm reactor treating OTC-enriched water medium.

In the recent years, there has been considerable debate about the potential impacts of antibiotics present in various environments on the public health and ecology. Oxytetracycline (OTC) is one of tetracycline antibiotic group used for growth and treatment of animals and humans. In this study, OTC and nitrate (NO3-N) were simultaneously reduced using a hydrogen-based membrane biofilm reactor (H2-MBfR). The system successfully accomplished OTC and nitrate removals. The fluxes of OTC and NO3-N were 8.96 mg OTC/m2 day and 1100 mg N/m2 day, respectively. On the other hand, the fluxes of H2 utilized for OTC and NO3-N reductions were calculated as maximum values of 1.71 and 395 mg H2/m2 day, respectively. The concentrations of transformation products of OTC formed at ppb levels. The dominant species in all the experimental periods with OTC biodegradation referred to Naxibacter sp., Uncultured Beta proteobacterium, Janthinobacterium sp. and Alicycliphilus denitrificans in autotrophic biofilm community degrading OTC.

Hydrogen-based membrane biofilm reactor for tetracycline removal: biodegradation, transformation products, and microbial community.

Tetracycline (TC) in aqueous environment could be reductively degraded by using a hydrogen-based membrane biofilm reactor (H2-MBfR) under denitrifying conditions as it provides an appropriate environment for the antibiotic-degrading bacteria in biofilm communities. This study evaluates the performance of H2-MBfR for simultaneous removal of nitrate and TC, formation of degradation products of TC, and community analysis of the biofilm grown on the gas-permeable hollow fiber membranes. Hence, a H2-MBfR receiving approximately 20 mg N/l nitrate and 0.5 mg/l TC was operated under different H2 pressures, hydraulic retention times (HRTs), and influent TC concentrations in order to provide various nitrate and TC loadings. The results showed that H2-MBfR accomplished successfully the degradation of TC, and it reached TC removal of 80-95 % at 10 h of HRT and 6 psi (0.41 atm) of H2 gas pressure. TC degradation took placed at increased HRT and H2 pressures while nitrate was the preferred electron acceptor for most of the electrons generated from H2 oxidation used for denitrification. The transformation products of TC were found at part per billion levels through all the experiments, and the concentrations decreased with the increasing HRT regardless of H2 pressure. Analyses from clone library showed that the microbial diversity at the optimal conditions was higher than that at the other periods. The dominant species were revealed to be Betaproteobacteria, Acidovorax caeni, and Alicycliphilus denitrificans.

Chlortetracycline removal by using hydrogen based membrane biofilm reactor.

In the last years, increasing attention has been paid on the presence of antibiotics in aqueous environments due to their ecological damage and potential adverse effects on organisms. Membrane biofilm reactors (MBfR) have been gained a significant popularity as an advanced wastewater treatment technology in removing of organic micro-pollutants. In this study, the performance of H2-MBfR for simultaneous removal of nitrate and chlortetracycline, formation of transformation products and community analysis of the biofilm grown on the gas permeable hollow fiber membranes was evaluated by considering effect of the hydraulic retention time, surface loadings of target pollutants and H2 pressure. The results showed that the simultaneous chlortetracycline (96%) and nitrate removal (99%) took placed successfully under the conditions of 5h HRT and 2psi H2 pressure. It has been determined that the main elimination process was biodegradation and Betaproteobacteria species was responsible for chlortetracycline degradation.

Performance of mixed algae for treatment of slaughterhouse wastewater and microbial community analysis.

This study investigated organic matter (OM) and nutrient removal efficiency of mixed algal species from slaughterhouse wastewater (SWW) by using photo-bioreactor. For this purpose, different dilution multiples of 10, 4, and 2 were applied to the SWW, and pure wastewater was finally used for algal cultivation. OM and nutrient removal performance in an algal photo-bioreactor were severely affected by the dilution ratio. After 7 days of cultivation, the highest removal percentages of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) were 89.6, 70.2, and 96.2 %, respectively. Furthermore, the changes in eukaryotic algae and cyanobacterial species in the algal photo-bioreactors were investigated using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The results indicated that cyanobacterial species were more efficient than eukaryotic species in removing nutrients from the SWW. This study suggests that mixed algal photo-bioreactors could be used efficiently in the treatment of SWW.

Effect of Tetracycline Antibiotics on Performance and Microbial Community of Algal Photo-Bioreactor.

Tetracycline antibiotics have been increasingly used in medical applications and have been found in wastewater treatment plants as a result of human and industrial activities. This study investigates the combined effects of tetracycline antibiotics on the performance of an algal photo-bioreactor operated under different antibiotic concentrations in the ranges of 0.25 to 30 mg/L and considers the inhibition of algal growth, carbon and nutrient removal rates, and eukaryotic and cyanobacterial algal community changes. The results indicated that increases in the concentration of tetracycline mixtures have adverse effects on the algal community and the performance of a photo-bioreactor, and the eukaryotic algae species were more sensitive to tetracycline antibiotics than were the cyanobacterial species. Cultivation tests showed that approximately 94 % growth inhibition of mixed algae occurred at 30 mg/L.

Combination of a novel electrode material and artificial mediators to enhance power generation in an MFC.

This study focuses on two main aspects: developing a novel cost-effective electrode material and power production from domestic wastewater using three different mediators. Methylene blue (MB), neutral red (NR) and 2-hydroxy-1,4-naphthoquinone (HNQ) were selected as electrode mediators with different concentrations. A tin-coated copper mesh electrode was tested as anode electrode. Maximum power density of the microbial fuel cell (MFC) with 300 µM MB was 636 mW/m². Optimal mediator concentrations with respect to the achieved maximum power output for MB, NR and HNQ were 300 µM, 200 µM and 50 µM, respectively. The results demonstrate that tin-coated copper mesh showed a higher biocompatibility and electrical conductivity.

Comprehensive comparison of a new tin-coated copper mesh and a graphite plate electrode as an anode material in microbial fuel cell.

This paper summarizes the comparison of a new tin-coated copper (t-coating Cu) mesh electrode with a graphite plate electrode for potential power generation and biocompatibility in a microbial fuel cell (MFC). The study, which used domestic wastewater, demonstrated that t-coating Cu mesh electrode produced a power density (271 mW/m(2)) approximately three times higher than that produced by a graphite electrode (87 mW/m(2)). Scanning electron microscopy (SEM) results revealed that bacterial morphology on the two electrodes significantly varied. The t-coating Cu mesh electrode surface had higher bacterial diversity because the open three-dimensional macro-mesh structure allowed an excellent electro-biofilm attachment. Kinetic performances evaluated using the Nernst-Monod equation demonstrated that the t-coating Cu mesh electrode had both higher power density and good biocompatibility in a large surface area, high chemical stability, and favorable metallic conductivity.

Bio-reduction of tetrachloroethen using a H2-based membrane biofilm reactor and community fingerprinting.

Chlorinated ethenes in drinking water could be reductively dechlorinated to non-toxic ethene by using a hydrogen based membrane biofilm reactor (H2-MBfR) under denitrifying conditions as it provides an appropriate environment for dechlorinating bacteria in biofilm communities. This study evaluates the reductive dechlorination of perchloroethene (PCE) to non-toxic ethene (ETH) and comparative community analysis of the biofilm grown on the gas permeable membrane fibers. For these purposes, three H2-MBfRs receiving three different chlorinated ethenes (PCE, TCE and DCE) were operated under different hydraulic retention times (HRTs) and H2 pressures. Among these reactors, the H2-MBfR fed with PCE (H2-MBfR 1) accomplished a complete dechlorination, whereas cis-DCE accumulated in the TCE receiving H2-MBfR 2 and no dechlorination was detected in the DCE receiving H2-MBfR 3. The results showed that 95% of PCE dechlorinated to ETH together with over 99.8% dechlorination efficiency. Nitrate was the preferred electron acceptor as the most of electrons generated from H2 oxidation used for denitrification and dechlorination started under nitrate deficient conditions at increased H2 pressures. PCR-DGGE analysis showed that Dehalococcoides were present in autotrophic biofilm community dechlorinating PCE to ethene, and RDase genes analysis revealed that pceA, tceA, bvcA and vcrA, responsible for complete dechlorination step, were available in Dehalococcoides strains.

Bioelectricity production using a new electrode in a microbial fuel cell.

Electrode materials play a key role in enhancing the electricity generation in the microbial fuel cell (MFC). In this study, a new material (Ti-TiO(2)) was used as an anode electrode and compared with a graphite electrode for electricity generation. Current densities were 476.6 and 31 mA/m(2) for Ti-TiO(2) and graphite electrodes, respectively. The PCR-DGGE analysis of enriched microbial communities from estuary revealed that MFC reactors were dominated by Shewanella haliotis, Enterococcus sp., and Enterobacter sp. Bioelectrochemical kinetic works in the MFC with Ti-TiO(2) electrode revealed that the parameters by non-linear curve fitting with the confidence bounds of 95% gave good fit with the kinetic constants of η (difference between the anode potential and anode potential giving one-half of the maximum current density) = 0.35 V, K (s) (Half-saturation constant) = 2.93 mM and J (max) = 0.39 A/m(2) for T = 298 K and F = 96.485 C/mol-e(-). From the results observed, it is clear that Ti-TiO(2) electrode is a promising candidate for electricity generation in MFC.