Biocathode regulates enrofloxacin degradation by coupling with different co-metabolism conditions

Efficient removal of enrofloxacin in swine wastewater using eukaryotic-bacterial symbiotic membraneless bioelectrochemical system

A eukaryotic-bacterial symbiotic membraneless bioelectrochemical system (EBES) reactor with eukaryotic-bacteria symbiotic cathode was developed to treat swine wastewater containing enrofloxacin (ENR), which had high performance at ENR tolerance and operational stability. With ENR concentrations shifting from 2 to 50 mg/L, the removal efficiencies of ENR, chemical oxygen demand (COD) and NH4+-N always were higher than 95 %, and the maximum power output (≥343 mW/m3) could be achieved. At 20 mg/L ENR, the removal efficiencies of ENR, COD and NH4+-N respectively reached to 99.4 ± 0.1 %, 98.5 % ± 0.1 %, and 96.3 % ± 0.5 %, corresponding to the open circuit voltage and maximum power density (Pmax) of EBES were 851 mV and 455 mW/m3. The community analyses showed that bacteria (Comamonas, Rhodobacter, Rhodococcus, and Vermiphilaceae et al.), algae (Chlorella) and fungi (Rozellomycota, Trebouxiophyceae, Exophiala, and Aspergillus et al.) at genus level were the dominate populations in the EBES, and their abundance increased with ENR concentration, suggesting they played key roles to remove ENR and another nutrient element. The low relative abundances (1.9 ×10-7 to 1.1 ×10-5 copies/g) of aac (6')-ib-cr, qnrA, qnrD, qnrS, and gyrA in effluent revealed that the present EBES reactor had superior capabilities in controlling antibiotic-resistance genes and antibiotic-resistant bacteria. Our trial experiments provided a novel way for antibiotic livestock wastewater treatment.

Co-metabolism of microorganisms: A study revealing the mechanism of antibiotic removal, progress of biodegradation transformation pathways

The widespread use of antibiotics has resulted in large quantities of antibiotic residues entering aquatic environments, which can lead to the development of antibiotic-resistant bacteria and antibiotic-resistant genes, posing a potential environmental risk and jeopardizing human health. Constructing a microbial co-metabolism system has become an effective measure to improve the removal efficiency of antibiotics by microorganisms. This paper reviews the four main mechanisms involved in microbial removal of antibiotics: bioaccumulation, biosorption, biodegradation and co-metabolism. The promotion of extracellular polymeric substances for biosorption and extracellular degradation and the regulation mechanism of enzymes in biodegradation by microorganisms processes are detailed therein. Transformation pathways for microbial removal of antibiotics are discussed. Bacteria, microalgae, and microbial consortia's roles in antibiotic removal are outlined. The factors influencing the removal of antibiotics by microbial co-metabolism are also discussed. Overall, this review summarizes the current understanding of microbial co-metabolism for antibiotic removal and outlines future research directions.

Enhanced removal of PPCPs and antibiotic resistance genes in saline wastewater using a bioelectrochemical-constructed wetland system

Pharmaceuticals and personal care products (PPCPs) are insufficiently degraded in saline wastewater treatment processes and are found at high concentrations and detection frequencies in aquatic environments. In this study, the wetland plant Thalia dealbata was selected using a screening plant experiment to ensure good salt tolerance and high efficiency in removing PPCPs. An electric integrated vertical-flow constructed wetland (E-VFCW) was developed to improve the removal of PPCPs and reduce the abundance of antibiotic resistance genes (ARGs). The removal efficiency of ofloxacin, enrofloxacin, and diclofenac in the system with anaerobic cathodic and aerobic anodic chambers is higher than that of the control system (41.84 ± 2.88%, 47.29 ± 3.01%, 53.29 ± 2.54%) by approximately 20.31%, 16.04%, and 35.25%. The removal efficiency of ibuprofen in the system with the aerobic anodic and anaerobic cathodic chamber was 28.51% higher than that of the control system (72.41 ± 3.06%) and promotes the reduction of ARGs. Electrical stimulation can increase the activity of plant enzymes, increasing their adaptability to stress caused by PPCPs, and PPCPs are transferred to plants. Species related to PPCPs biodegradation (Geobacter, Lactococcus, Hydrogenophaga, and Nitrospira) were enriched in the anodic and cathodic chambers of the system. This study provides an essential reference for the removal of PPCPs in saline-constructed wetlands.

Microbial electrochemical Cr(VI) reduction in a soil continuous flow system

Microbial electrochemical technologies represent innovative approaches to contaminated soil and groundwater remediation and provide a flexible framework for removing organic and inorganic contaminants by integrating electrochemical and biological techniques. To simulate in situ microbial electrochemical treatment of groundwater plumes, this study investigates Cr(VI) reduction within a bioelectrochemical continuous flow (BECF) system equipped with soil-buried electrodes, comparing it to abiotic and open-circuit controls. Continuous-flow systems were tested with two chromium-contaminated solutions (20-50 mg Cr(VI)/L). Additional nutrients, buffers, or organic substrates were introduced during the tests in the systems. With an initial Cr(VI) concentration of 20 mg/L, 1.00 mg Cr(VI)/(L day) bioelectrochemical removal rate in the BECF system was observed, corresponding to 99.5% removal within nine days. At the end of the test with 50 mg Cr(VI)/L (156 days), the residual Cr(VI) dissolved concentration was two orders of magnitude lower than that in the open circuit control, achieving 99.9% bioelectrochemical removal in the BECF. Bacteria belonging to the orders Solirubrobacteriales, Gaiellales, Bacillales, Gemmatimonadales, and Propionibacteriales characterized the bacterial communities identified in soil samples; differently, Burkholderiales, Mycobacteriales, Cytophagales, Rhizobiales, and Caulobacterales characterized the planktonic bacterial communities. The complexity of the microbial community structure suggests the involvement of different microorganisms and strategies in the bioelectrochemical removal of chromium. In the absence of organic carbon, microbial electrochemical removal of hexavalent chromium was found to be the most efficient way to remove Cr(VI), and it may represent an innovative and sustainable approach for soil and groundwater remediation. Integr Environ Assess Manag 2024;20:2033-2049. © 2024 The Author(s). Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Bioelectrochemical remediation of soil antibiotic and antibiotic resistance gene pollution: Key factors and solution strategies

In recent years, owing to the overuse and improper handling of antibiotics, soil antibiotic pollution has become increasingly serious and an environmental issue of global concern. It affects the quality and ecological balance of the soil and allows the spread of antibiotic resistance genes (ARGs), which threatens the health of all people. As a promising soil remediation technology, bioelectrochemical systems (BES) are superior to traditional technologies because of their simple operation, self-sustaining operation, easy control characteristics, and use of the metabolic processes of microorganisms and electrochemical redox reactions. Moreover, they effectively remediate antibiotic contaminants in soil. This review explores the application of BES remediation mechanisms in the treatment of antibiotic contamination in soil in detail. The advantages of BES restoration are highlighted, including the effective removal of antibiotics from the soil and the prevention of the spread of ARGs. Additionally, the critical roles played by microbial communities in the remediation process and the primary parameters influencing the remediation effect of BES were clarified. This study explores several strategies to improve the BES repair efficiency, such as adjusting the reactor structure, improving the electrode materials, applying additives, and using coupling systems. Finally, this review discusses the current limitations and future development prospects, and how to improve its performance and promote its practical applications. In summary, this study aimed to provide a reference for better strategies for BES to effectively remediate soil antibiotic contamination.

Bioelectrochemical anaerobic digestion mitigates microplastic pollution and promotes methane recovery of wastewater treatment in biofilm system

Bioelectrochemical systems (BES) offer significant potential for treating refractory waste and recovering bioenergy. However, their ability to mitigate microplastic pollution in wastewater remains unexplored. This study showed that BES facilitated the treatment of polyethylene (PE), polyvinyl chloride (PVC), and Mix (PE+PVC) microplastic wastewater and the methane recovery (40.61%, 20.02%, 21.19%, respectively). The lactate dehydrogenase (LDH), adenosine triphosphate (ATP), cytochrome c, and nicotinamide adenine dinucleotide (NADH/NAD+) ratios were elevated with electrical stimulation. Moreover, the applied voltage improved the polysaccharides content of the extracellular polymeric substances (EPS) in the PE-BES but decreased in PVC-BES, while the proteins showed the opposite trend. Metatranscriptomic sequencing showed that the abundance of fermentation bacteria, acetogens, electrogens, and methanogens was greatly enhanced by applying voltage, especially at the anode. Methane metabolism was dominated by the acetoclastic methanogenic pathway, with the applied voltage promoting the enrichment of Methanothrix, resulting in the direct conversion of acetate to acetyl-CoA via acetate-CoA ligase (EC: 6.2.1.1), and increased metabolic activity in the anode. Moreover, applied voltage greatly boosted the function genes expression level related to energy metabolism, tricarboxylic acid (TCA) cycle, electron transport, and transporters on the anode biofilm. Overall, these results demonstrate that BES can mitigate microplastic pollution during wastewater treatment.

Synergistic effect of electrotrophic perchlorate reducing microorganisms and chemically modified electrodes for enhancing bioelectrochemical perchlorate removal

Perchlorate has been described as an emerging pollutant that compromises water sources and human health. In this study, a new electrotrophic perchlorate reducing microorganism (EPRM) isolated from the Atacama Desert, Dechloromonas sp. CS-1, was evaluated for perchlorate removal in water in a bioelectrochemical reactor (BER) with a chemically modified electrode. BERs were operated for 17 days under batch mode conditions with an applied potential of -500 mV vs. Ag/AgCl. Surface analysis (i.e., SEM, XPS, FT-IR, RAMAN spectroscopy) on the modified electrode demonstrated heterogeneous transformation of the carbon fibers with the incorporation of nitrogen functional groups and the oxidation of the carbonaceous material. The BERs with the modified electrode and the presence of the EAM reached high cathodic efficiency (90.79 ± 9.157%) and removal rate (0.34 ± 0.007 mol m-3-day) compared with both control conditions. The observed catalytic enhancement of CS-1 was confirmed by a reduction in the charge transfer resistance obtained by electrochemical impedance spectroscopy (EIS). Finally, an electrochemical kinetic study revealed an eight-electron perchlorate bioreduction reaction at -638.33 ± 24.132 mV vs. Ag/AgCl. Therefore, our results show the synergistic effect of EPRM and chemically modified electrodes on perchlorate removal in a BER.

Removal of chloramphenicol and resistance gene changes in electric-integrated vertical flow constructed wetlands

The performance of an electric-integrated vertical flow constructed wetland (E-VFCW) for chloramphenicol (CAP) removal, changes in microbial community structure, and the fate of antibiotic resistance genes (ARGs) were evaluated. CAP removal in the E-VFCW system was 92.73% ± 0.78% (planted) and 90.80% ± 0.61% (unplanted), both were higher than the control system which was 68.17% ± 1.27%. The contribution of anaerobic cathodic chambers in CAP removal was higher than the aerobic anodic chambers. Plant physiochemical indicators in the reactor revealed electrical stimulation increased oxidase activity. Electrical stimulation enhanced the enrichment of ARGs in the electrode layer of the E-VFCW system (except floR). Plant ARGs and intI1 levels were higher in the E-VFCW than in the control system, suggesting electrical stimulation induces plants to absorb ARGs, reducing ARGs in the wetland. The distribution of intI1 and sul1 genes in plants suggests that horizontal transfer may be the main mechanism dispersing ARGs in plants. High throughput sequencing analysis revealed electrical stimulation selectively enriched CAP degrading functional bacteria (Geobacter and Trichlorobacter). Quantitative correlation analysis between bacterial communities and ARGs confirmed the abundance of ARGs relates to the distribution of potential hosts and mobile genetic elements (intI1). E-VFCW is effective in treating antibiotic wastewater, however ARGs potentially accumulate.

Enhanced biodegradation of fluoroquinolones and the changes of bacterial communities and antibiotic-resistant genes under intermittent electrical stimulation

In this study, an anaerobic-aerobic coupling system under intermittent electrical stimulation was used to improve the biodegradation of synthetic wastewater containing fluoroquinolones (FQs). The effect of electrical stimulation on FQ removal performance is more pronounced with appropriate voltage and hydraulic retention time. In addition, the combination of anaerobic-anodic and aerobic-cathodic chambers is more conducive to improving the removal efficiency of FQs. Under 0.9 V, the removal efficiencies of ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin were significantly improved in the anaerobic-anodic and aerobic-cathodic system. The contribution of the anaerobic/aerobic anodic chambers to FQ removal was greater than that of the anaerobic/aerobic cathodic chambers. Electrical stimulation selectively enriched electroactive bacteria related to biodegradation (Desulfovibrio and Terrimonas), antibiotic-resistant bacteria (Atopobium and Neochlamydia), and nitrifying bacteria (SM1A02 and Reyranella). This study indicated the potential effectiveness of intermittent electrical stimulation in treating fluoroquinolone-containing wastewater in a biofilm reactor. However, electrical stimulation led to an increase in mobile genetic elements , induced horizontal gene transfer and enriched resistant bacteria, which accelerated the spread of antibiotic-resistant genes (ARGs) in the system, indicating that the diffusion of ARGs remains a challenge.

Microbial mechanisms of refractory organics degradation in old landfill leachate by a combined process of UASB-A/O-USSB

A combined process of anaerobic digestion (UASB), shortcut nitrification-denitrification (A/O), and semi-anoxic co-metabolism (operated by an up-flow semi-anoxic sludge bed; USSB) was constructed for the treatment of old landfill leachate (>10 years). The performance and mechanism of refractory organics degradation by the combined process (UASB-A/O-USSB) were investigated. The results showed that the semi-anoxic co-metabolism contributes 57 % of the totally degraded refractory organics. Specific microorganisms and their corresponding metabolic functions drive the degradation of refractory organics in each unit of the UASB-A/O-USSB process. In detail, organics with simple molecular structures were preferentially degraded by anaerobic digestion and shortcut denitrification, whereas those with complex structures were subsequently degraded in the oxic tanks and USSB reactor by shortcut nitrification and semi-anoxic co-metabolism. The structural equation model showed that the combined process of shortcut nitrification and semi-anoxic co-metabolism had a better effect on the degradation of recalcitrant organics than the single process. These findings provide information on how refractory organics are metabolically degraded in a combined process.