Evaluation of degradation behavior over tetracycline hydrochloride by microbial electrochemical technology: Performance, kinetics, and microbial communities

Optimization of degradation conditions for sulfachlorpyridazine by Bacillus sp. DLY-11 and analysis of biodegradation mechanisms

Sulfachloropyridazine (SCP) is a common sulfonamide antibiotic pollutant found in animal excreta. Finding highly efficient degrading bacterial strains is an important measure to reduce SCP antibiotic pollution. Although some strains with degradation capabilities have been screened, the degradation pathways and biotransformation mechanisms of SCP during bacterial growth are still unclear. In this study, a strain capable of efficiently degrading SCP, named Bacillus sp. DLY-11, was isolated from pig manure aerobic compost. Under optimized conditions (5 % Vaccination dose, 51.5 ℃ reaction temperature, pH=7.92 and 0.5 g/L MgSO4), this strain was able to degrade 97.7 % of 20 mg/L SCP within 48 h. Through the analysis of nine possible degradation products (including a new product of 1,4-benzoquinone with increased toxicity), three potential biodegradation pathways were proposed. The biodegradation reactions include S-N bond cleavage, dechlorination, hydroxylation, deamination, methylation, sulfur dioxide release, and oxidation reactions. This discovery not only provides a new efficient SCP-degrading bacterial strain but also expands our understanding of the mechanisms of bacterial degradation of SCP, filling a knowledge gap. It offers important reference for the bioremediation of antibiotic pollutants in livestock and poultry farming.

Mechanisms of inhibition and recovery under multi-antibiotic stress in anammox: A critical review

With the escalating global concern for emerging pollutants, particularly antibiotics, microplastics, and nanomaterials, the potential disruption they pose to critical environmental processes like anaerobic ammonia oxidation (anammox) has become a pressing issue. The anammox process, which plays a crucial role in nitrogen removal from wastewater, is particularly sensitive to external pollutants. This paper endeavors to address this knowledge gap by providing a comprehensive overview of the inhibition mechanisms of multi-antibiotic on anaerobic ammonia-oxidizing bacteria, along with insights into their recovery processes. The paper dives deeply into the various ways antibiotics interact with anammox bacteria, focusing specifically on their interference with the bacteria's extracellular polymers (EPS) - crucial components that maintain the structural integrity and functionality of the cells. Additionally, it explores how anammox bacteria utilize quorum sensing (QS) mechanisms to regulate their community structure and respond to antibiotic stress. Moreover, the paper summarizes effective removal methods for these antibiotics from wastewater systems, which is crucial for mitigating their inhibitory effects on anammox bacteria. Finally, the paper offers valuable insights into how anammox communities can recuperate from multi-antibiotic stress. This includes strategies for reintroducing healthy bacteria, optimizing operational conditions, and using bioaugmentation techniques to enhance the resilience of anammox communities. In summary, this paper not only enriches our understanding of the complex interactions between antibiotics and anammox bacteria but also provides theoretical and practical guidance for the treatment of antibiotic pollution in sewage, ensuring the sustainability and effectiveness of wastewater treatment processes.

The underlying mechanisms of oxytetracycline degradation mediated by gut microbial proteins and metabolites in Hermetia illucens

Hermetia illucens larvae can enhance the degradation of oxytetracycline (OTC) through its biotransformation. However, the underlying mechanisms mediated by gut metabolites and proteins are unclear. To gain further insights, the kinetics of OTC degradation, the functional structures of gut bacterial communities, proteins, and metabolites were investigated. An availability-adjusted first-order model effectively evaluated OTC degradation kinetics, with degradation half-lives of 4.18 and 21.71 days for OTC degradation with and without larval biotransformation, respectively. Dominant bacteria in the larval guts were Enterococcus, Psychrobacter, Providencia, Myroides, Enterobacteriaceae, and Lactobacillales. OTC exposure led to significant differential expression of proteins, with functional classification revealing involvement in digestion, transformation, and adaptability to environmental stress. Upregulated proteins, such as aromatic ring hydroxylase, acted as oxidoreductases modifying the chemical structure of OTC. Unique metabolites, aclarubicin and sancycline identified were possible OTC metabolic intermediates. Correlation analysis revealed significant interdependence between gut bacteria, metabolites, and proteins. These findings reveal a synergistic mechanism involving gut microbial metabolism and enzyme structure that drives the rapid degradation of OTC and facilitates the engineering applications of bioremediation.

Integrated bio-electrochemical approach to Norfloxacin (NFX) degradation: Efficacy, degradation mechanisms, and toxicological insights

Norfloxacin (NFX), a widely used fluoroquinolone antibiotic, poses significant environmental concerns due to its persistence in ecosystems and its potential to foster antibiotic resistance. This study explores the degradation of NFX using a bio-electrochemical system (BES) facilitated by Bacillus subtilis isolated from animal waste sludge. Experimental parameters were optimized to maximize removal efficiency, with the optimal conditions determined as an NFX concentration of 200 mg/L, pH 7, and an applied potential of 1.2 V. The degradation pathway was elucidated through the identification of intermediate products, ultimately leading to the complete mineralization of NFX. To assess the environmental impact of BES-treated water, a series of eco-toxicity assays were conducted. Microbial diversity analysis revealed that soil exposed to BES-treated water maintained a balanced microbial community, contrasting with the disruptions observed in soils exposed to untreated NFX-contaminated water. Phytotoxicity tests, earthworm toxicity assay, and Artemia hatchability & lethality assays further confirmed the reduced toxicity of the BES-treated water. These findings highlight the efficacy of BES in the degradation of NFX, demonstrating its potential as a sustainable strategy for the remediation of antibiotic-contaminated environments and the mitigation of associated ecological risks.

Unlocking the potential of Chinese herbal medicine residue-derived biochar as an efficient adsorbent for high-performance tetracycline removal

This study employed hydrothermal carbonization (HTC) in conjunction with ZnCl2 activation and pyrolysis to produce biochar from one traditional Chinese medicine astragali radix (AR) residue. The resultant biochar was evaluated as a sustainable adsorbent for tetracycline (TC) elimination from water. The adsorption performance of TC on two micropore-rich AR biochars, AR@ZnCl2 (1370 m2 g-1) and HAR@ZnCl2 (1896 m2 g-1), was comprehensively evaluated using adsorption isotherms, kinetics, and thermodynamics. By virtue of pore diffusion, π-π interaction, electrostatic attraction, and hydrogen bonding, the prepared AR biochar showed exceptional adsorption properties for TC. Notably, the maximum adsorption capacity (930.3 mg g-1) of TC on HAR@ZnCl2 can be achieved when the adsorbent dosage is 0.5 g L-1 and C0 is 500 mg L-1 at 323 K. The TC adsorption on HAR@ZnCl2 took place spontaneously. Furthermore, the impact of competitive ions behavior is insignificant when coexisting ion concentrations fall within the 10-100 mg L-1 range. Additionally, the produced biochar illustrated good economic benefits, with a payback of 701 $ t-1. More importantly, even after ten cycles, HAR@ZnCl2 still presented great TC removal efficiency (above 77%), suggesting a good application prosperity. In summary, the effectiveness and sustainability of AR biochar, a biowaste-derived product, were demonstrated in its ability to remove antibiotics from water, showing great potential in wastewater treatment application.

Biotransformation characteristics of tetracycline by strain Serratia marcescens MSM2304 and its mechanism evaluation based on products analysis and genomics

Microbial biotransformation is a recommended and reliable method in face of formidable tetracycline (TC) with broad-spectrum antibacterial activity. Herein, comprehensive characteristics of a newfound strain and its molecular mechanism in process of TC bioremediation were involved in this study. Specifically, Serratia marcescens MSM2304 isolated from pig manure sludge grew well in presence of TC and achieved optimal removal efficiency of 61% under conditions of initial TC concentration of 10 mg/L, pH of 7.0, cell inoculation amount of 5%, and tryptone of 10 g/L as additional carbon. The pathways of biotransformation include EPS biosorption, cell surface biosorption and biodegradation, which enzymatic processes of biodegradation were occurred through TC adsorbed by biofilms was firstly broken down by extracellular enzymes and part of TC migrated towards biofilm interior and degraded by intracellular enzymes. Wherein extracellular polysaccharides in extracellular polymeric substances (EPS) from biofilm of strain MSM2304 mainly performed extracellular adsorption, and changes in position and intensity of CO, =CH and C-O-C/C-O of EPS possible further implied TC adsorption by it. Biodegradation accounting for 79.07% played a key role in TC biotransformation and could be fitted well by first-order model that manifesting rapid and thorough removal. Potential biodegradation pathway including demethylation, dihydroxylation, oxygenation, and ring opening possibly involved in TC disposal process of MSM2304, TC-degrading metabolites exhibited lower toxicity to indicator bacteria relative to parent TC. Whole genome sequencing as underlying molecular evidence revealed that TC resistance genes, dehydrogenases-encoding genes, monooxygenase-encoding genes, and methyltransferase-encoding genes of strain MSM2304 were positively related to TC biodegradation. Collectively, these results favored a theoretical evaluation for Serratia marcescens MSM2304 as a promising TC-control agent in environmental bioremediation processes.

Fabrication of 2D/1D Bi2WO6/halloysite nanotubes photocatalyst towards water purification: a support effect onin situconstruction and electron-hole separation

In this research work, a reusable and efficient 2D/1D heterogeneous structured photocatalyst based on amine-functionalized halloysite nanotubes (MHNTs) and Bi2WO6nanosheet (BWO) was prepared using a facile hydrothermal method for decomposing PPCPs under simulated sunlight. On the degradation of tetracycline hydrochloride (TCH), the effects of composite catalysts prepared under various conditions were discussed. The results showed that over BWO/MHNTs with a mass ratio was 3:1, the synthesizing temperature was 120 °C and the precursor pH value was 1, the TCH (10 mg l-1) degradation efficiency reached 100% after 1 h irradiation of simulated sunlight. Moreover, BWO/MHNTs composites kept good recovery and stable photocatalytic activity after 5 cycles. The excellent dispersion of Bi2WO6on the surface of clay minerals and the oxygen vacancy enhanced electron-hole separation may be responsible for the its high activity and stability. Futhermore, the radical capture test demonstrated that ·O-2was primarily responsible for the photodegradation of TCH. Thus, BWO/MHNTs composites exhibit a good application prospect in the field of sunlight-driven photocatalytic degradation towards PPCPs pollutants in water.

Mitigating mechanism of nZVI-C on the inhibition of anammox consortia under long-term tetracycline hydrochloride stress: Extracellular polymeric substance properties and microbial community evolution

In this study, activated carbon-loaded nano-zero-valent iron (nZVI-C) composites were added to anaerobic ammonium oxidation bacteria (AnAOB) to overcome the inhibition of tetracycline hydrochloride (TCH). Results showed that 500 mg L^-1 nZVI-C effectively mitigated the long-term inhibition of 1.5 mg L^-1 TCH on AnAOB and significantly improved the total nitrogen removal efficiency (TNRE) (from 65.27% to 86.99%). Spectroscopic analysis revealed that nZVI-C increased the content of N-H and CO groups in EPS, which contributed to the adsorption of TCH. The accumulation of humic acid-like substances in EPS was also conducive to strengthening the extracellular defense level. In addition, TCH-degrading bacteria (Clostridium and Mycobacterium) were enriched in situ, and the abundance of Ca. Brocadia was significantly increased (from 10.69% to 18.59%). Furthermore, nZVI-C increased the abundance of genes encoding tetracycline inactivation (tetX), promoted mineralization of TCH by 90%, weakening the inhibition of TCH on microbial nitrogen metabolism. nZVI-C accelerated the electron consumption of anammox bacteria by upregulating the abundance of electron generation genes (nxrA, hdh) and providing electrons directly.

Role of bio-electrochemical technology for enzyme activity stimulation in high-consumption pharmaceuticals biodegradation

Active pharmaceutical ingredients (APIs) and their intermediate residues have recently been considered a serious concern. Among technologies, bio-electrochemical technologies (BETs) have stimulated the production of bio-electrical energy. This review aims to examine the benefit and mechanism of BETs on the degradation of high-consumption pharmaceutical compounds, including antibiotic, anti-inflammatory, and analgesic drugs, and the stimulation of enzymes induced in a bioreactor. Moreover, intermediates and the proposed pathways of pharmaceutical compound biodegradation in BETs are to be explained in this review. According to studies performed exclusively, the benefit of BETs is using bio-electroactive microbes to mineralize recalcitrant pharmaceutical contaminants by promoting enzyme activity and energy. Since BETs use the electron transfer chain between bio-anode/-cathode and pharmaceuticals, the enzyme activity is essential in the oxidation and reduction of phenolic rings of drugs and the ineffective detoxification of effluent from the treatment plant. This study is suggested a vital and influential role of BETs in mineralizing and enzyme induction in bioreactors. Eventually, a content of future developments or outlooks of BETs are propounded to improve the pharmaceutical industries' wastewater problems.

The mechanism of phosphate solubilizing of Pseudomonas sp. TC952 and its solubilizing process on TC removal

Antibiotics undergo a series of complex transport and transformation route after entering the environment; however, there is scarce information about the effects of the bacterial phosphate-solubilizing process on tetracycline (TC) transformation. In this study, Pseudomonas sp. TC952 was identified as phosphate-solubilizing bacterium with high phosphate-solubilizing ability even under TC stress; it could solubilize maximum phosphate with a production of 400 mg/L soluble phosphate in 2 days. TC did not affect phosphate solubilizing in a short time incubation, but slightly promoted in a long incubation time. TC was adsorbed by inorganic phosphate with high efficiency of 53.09% within 1 day. Four tetracycline antibiotic resistance and sixteen inorganic phosphate-solubilizing-related genes were identified in the genome, which revealed the phosphate-solubilizing mechanism was that strain TC952 secrete organic acid to resolve inorganic phosphate and also secrete siderophore to chelate inorganic phosphate. So, during the inorganic phosphate-solubilizing process of strain TC952, TC was de-adsorbed from inorganic phosphate, and the solution was acidified into pH 4.3 through secreting organic acid to dissolve inorganic phosphorus, which resulted in Ca²⁺ and PO₄^3- releasing into the solution. Finally, the acidic condition and PO₄^3- enhanced TC hydrolysis. The mechanism of phosphate-solubilizing process on TC removal and genome analysis provides us new insight of the TC migration and transformation route in the environment.

The capability of chloramphenicol biotransformation of Klebsiella sp. YB1 under cadmium stress and its genome analysis

Co-contamination by antibiotics and heavy metal is common in the environment, however, there is scarce information about antibiotics biodegradation under heavy metals stress. In this study, Klebsiella sp. Strain YB1 was isolated which is capable of biodegrading chloramphenicol (CAP) with a biodegradation efficiency of 22.41% at an initial CAP of 10 mg L^-1 within 2 days. CAP biodegradation which fitted well with the first-order kinetics. YB1 still degrades CAP under Cd stress, however 10 mg L^-1 Cd inhibited CAP biodegradation by 15.1%. Biotransformation pathways remained the same under Cd stress, but two new products (Cmpd 19 and Cmpd 20) were identified. Five parallel metabolism pathways of CAP were proposed with/without Cd stress, including one novel pathway (pathway 5) that has not been reported before. In pathway 5, the initial reaction was oxidation of CAP by disruption of C-C bond at the side chain of C1 and C2 with the formation of 4-nitrobenzyl alcohol and CY7, then these intermediates were oxidized into p-nitrobenzoic acid and CY1, respectively. CAP acetyltransferase and nitroreductase and 2,3/4,5-dioxygenase may play an important role in CAP biodegradation through genome analysis and prediction. This study deepens our understanding of mechanism of antibiotic degradation under heavy metal stress in the environment.

Manganese redox cycling in immobilized bioreactors for simultaneous removal of nitrate and 17β-estradiol: Performance, mechanisms and community assembly potential

The application of bio-manganese (Mn) redox cycling for continuous removal of contaminants provides promise for addressing coexisting contaminants in groundwater, however, the feasibility of constructing Mn redox cycling system (MCS) through community assembly remains to be elucidated. In this study, Mn-reducing strain MFG10 and Mn-oxidizing strain MFQ7 synergistically removed 94.67 % of 17β-estradiol (E2) within 12 h. Analysis of potential variations in Mn oxides suggested that MCS accelerated the production of reactive oxygen species (ROS) and Mn(III), which interacted to promote E2 removal. After continuous operation of the Mn ore-based immobilized bioreactor for 270 days, the experimental group (EG) achieved average removal efficiencies of 89.63 % and 97.57 % for NO₃^--N and E2, respectively. High-throughput sequencing results revealed complex symbiotic relationships in EG. Community assembly significantly enhanced the metabolic and physiological activity of the bioreactor, which promoting the expression of core functions including nitrogen metabolism, Mn cycling and organic matter resistance.

The enhanced degradation behavior of oxytetracycline by black soldier fly larvae with tetracycline resistance genes in the larval gut: Kinetic process and mechanism

Black soldier fly larvae (larvae) can digest organic wastes and degrade contaminants such as oxytetracycline (OTC). However, compared to the kinetic processes and enhanced mechanisms used in the traditional microbial degradation of OTC, those employed by larvae are largely uncharacterized. To obtain further details, a combined analysis of larval development, larval nutritional values (crude protein, crude fat and the composition of fatty acids) and the expression of tetracycline resistance genes (TRGs) in the larval gut was performed for the degradation of OTC added to substrates and for oxytetracycline bacterial residue (OBR). When the larvae were exposed to the substrates, the degradation processes were enhanced significantly (P < 0.01), with a 4.74-7.86-fold decrease in the degradation half-life (day^-1) and a 3.34-5.74-fold increase in the final degradation efficiencies. This result was attributed to the abundant TRGs (with a detection rate of 35.90%∼52.14%) in the larval gut. The TRGs presented the resistance mechanisms of cellular protection and efflux pumps, which ensured that the larvae could tolerate elevated OTC concentrations. Investigation of the TRGs indicated that enzymatic inactivation enhanced OTC degradation by larvae. These findings demonstrate that the larval degradation of antibiotic contaminants is an efficient method based on abundant TRGs in the larval gut, even though OTC degradation results in OBR. In addition, a more optimized system for higher reductions in antibiotic levels and the expansion of larval bioremediation to other fields is necessary.

Electrochemical degradation of tetracycline hydrochloride in sulfate solutions on boron-doped diamond electrode: The accumulation and transformation of persulfate

In this study, a novel electrifying mode (divided power-on and power-off stage) was applied in the system of BDD activate sulfate to degrade tetracycline hydrochloride (TCH). The BDD electrode could activate sulfate and H₂O to generate sulfate radicals (SO₄^•-) and hydroxyl radicals (^•OH) to remove TCH, and SO₄^•- could dimerize to form S₂O₈^2-. Then, the S₂O₈^2- was activated by heat and quinones to generate SO₄^•- for the continuous degradation of TCH during the power-off stage. In addition, the intermittent time has a significant effect on the degradation of TCH. Factors, affecting the accumulation of S₂O₈^2-, were analyzed using a full factorial design, and the accumulation of S₂O₈^2- could reach 16.2 mM in 120 min. The results of electron spin resonance and radical quenching test showed that SO₄^•-, ^•OH, direct electron transfer (DET), and non-radical in the system could effectively degrade TCH, and SO₄^•- was dominated. The intermediate products of TCH were analyzed by HPLC-QTOF-MS/MS, and the TCH mainly underwent hydroxylation, demethylation and ring opening reactions to form small molecules, and finally mineralized. The results of the feasibility analysis revealed that some intermediates have high toxicity, but the system could improve the toxicity. The results of energy consumption indicated that the intermittent electrifying mode could make full use of the persulfate generated during the power-on stage and reduce about 30% energy consumption. In conclusion, this work demonstrated that it was economically feasible to degrade TCH in wastewater by activating sulfate with BDD electrodes with an intermittent electrifying mode.

Direct Z-scheme mediated SmVO4/UiO-66-NH2 heterojunction nanocomposite for the degradation of antibiotic tetracycline hydrochloride molecules under sunlight

The use of tetracycline hydrochloride (TCH) for veterinary, human therapy, and agriculture has risen in the past few decades, making it to become one of the most exploited antibiotics. However, TCH residue in the environment is causing issues related to the evolution of antibiotic-resistant bacteria. To address such a problem, photodegradation offers a potential solution to decompose these pollutants in wastewater and thereby mitigates negative environmental impacts. In this context, the research focuses on the use of the rare-earth metal oxide samarium orthovanadate (SmVO₄) with nanorod structure, coupled with UiO-66-NH₂ for the photocatalytic degradation. Their photocatalytic activity to degrade antibiotic TCH molecules is explored under simulated solar light irradiation. The integration of UiO-66-NH₂ with SmVO₄ enhanced the light absorption, recombination resistance, carrier lifetime (from 0.382 to 0.411 ns) and specific surface area (from 67.17 to 246 m²/g) of the composite system as confirmed from multiple analyses. The obtained results further indicated that SmVO₄/UiO-66-NH₂ nanocomposites could form a direct Z-scheme based heterojunction. Such mechanism of charge transfer leads to the effective degradation of TCH molecules up to 50% in 90 min under solar light, while it is degraded only 30% in the case of bare-SmVO₄ nanorods. In this work, the incorporation of UiO-66-NH₂ positively influences photoelectrochemical properties and improves the overall photoredox properties of SmVO₄ for the degradation of complex compounds like antibiotic TCH molecules. Therefore, UiO-66-NH₂ can be proposed as an effective material to sensitize the rare-earth based photocatalytic material.

The Growth of Extended Melem Units on g-C3N4 by Hydrothermal Treatment and Its Effect on Photocatalytic Activity of g-C3N4 for Photodegradation of Tetracycline Hydrochloride under Visible Light Irradiation

In this work, the growth of extended tri-s-triazine units (melem units) on g-C₃N₄ (CN) by hydrothermal treatment and its effect on the photodegradation efficiency of tetracycline hydrochloride (TC) is investigated. The CN-180-x and CN-200-6 samples were prepared using different hydrolysis times and temperatures, and they were characterized by multiple physicochemical techniques. In addition, their photodegradation performance was evaluated under visible light irradiation. Compared to the CN, CN-180-6 possesses remarkable photocatalytic degradation efficiency at 97.17% towards TC removal in an aqueous solution. The high visible-light-induced photo-reactivity of CN-180-6 directly correlates to charge transfer efficiency, numerous structural defects with a high specific surface area (75.0 m² g^-1), and sufficient O-functional groups over g-C₃N₄. However, hydrothermal treatment at a higher temperature or during a longer time additionally induces the growth of extended melem units on the surface of g-C₃N₄, resulting in the inhibition of the charge transfer. In addition, the superoxide radical is proven to be generated from photoexcited reaction and plays a key role in the TC degradation.

Simultaneous denitrification and antibiotic degradation of low-C/N-ratio wastewater by a three-dimensional biofilm-electrode reactor: Performance and microbial response

Three-dimensional biofilm-electrode reactors (3D-BERs) were fabricated and used to simultaneously remove nitrate and metronidazole (MNZ) from low-C/N-ratio wastewater. The results showed that 1 mg/L MNZ significantly promoted nitrate removal. After MNZ was added to the reactor, the removal efficiencies of total nitrogen (TN) and NO₃^--N increased significantly from 18.97% and 52.09% to 71.63% and 99.98% within 6 h, respectively. The MNZ-removal kinetics conformed to a pseudo-first-order model, and the removal rate constant reached a maximum value of 0.853 h^-1, which was 4.1 and 2.8 times higher than that of pure microorganisms and pure electrochemical reactors, respectively. This indicated that the 3D-BERs constructed in this study were capable of simultaneous MNZ degradation and denitrification. In the presence of nitrate, six MNZ-degradation intermediates were identified, and four MNZ transformation pathways were proposed, including cleavage of hydroxyethyl groups, reduction of nitro groups, N-denitration, and deprotonation of side-chain hydroxyl groups. High-throughput sequencing revealed that the reactor was rich in various MNZ-degraders and denitrifiers, such as Hydrogenophaga, Methylomonas, Crenohrix, Dechloromonas, and Methylophilus. A function prediction analysis of nitrogen metabolism showed that the 3D-BER reactor with MNZ had higher denitrification activity than the other reactors tested. It was speculated that the intermediates produced by MNZ could act as carbon sources allowing denitrifying bacteria to perform denitrification, which made a nonnegligible contribution to the removal of nitrogen.

Enhanced performance of microbial fuel cell with electron mediators from tetracycline hydrochloride degradation

Tetracycline hydrochloride (TCH) is a typical antibiotic pollutant with high toxicity and persistence. The degradation of TCH and the generation of the associated electron mediator in a dual chamber microbial fuel cells (MFCs) were studied. The results of liquid chromatography revealed that TCH could be effectively removed (>93%) in MFCs mode. The maximum COD removal was 88.14 ± 1.47% in MFCs while it was 69.57 ± 1.36% in open circuit MFCs. According to cyclic voltammetry, the presence of the relevant redox peaks clearly suggested that the intermediates from TCH degradation could act as endogenous electron mediator. The highest power density of 120.02 ± 2.76 mW/m² and the lowest internal resistance of 18.68 Ω were achieved in MFC with 2 mg/L of TCH. Microbial community analysis illustrated that Bacteroides, Comamonas, Clostridium_sensu_stricto, Desulfovibrio and Geobacter were enriched and played a dominant role in TCH degradation and power generation. Electrochemical active bacteria had certain tolerance to TCH and the inhibiting threshold value of TCH was below 5 mg/L. This study provided a new thinking that low concentration of TCH could produce electron mediators to improve the performance of MFC system.

A comprehensive review on biodegradation of tetracyclines: Current research progress and prospect

The release of tetracyclines (TCs) in the environment is of significant concern because the residual antibiotics may promote resistance in pathogenic microorganisms, and the transfer of antibiotic resistance genes poses a potential threat to ecosystems. Microbial biodegradation plays an important role in removing TCs in both natural and artificial systems. After long-term acclimation, microorganisms that can tolerate and degrade TCs are retained to achieve efficient removal of TCs under the optimum conditions (e.g. optimal operational parameters and moderate concentrations of TCs). To date, cultivation-based techniques have been used to isolate bacteria or fungi with potential degradation ability. Moreover, the biodegradation mechanism of TCs can be unveiled with the development of chemical analysis (e.g. UPLC-Q-TOF mass spectrometer) and molecular biology techniques (e.g. 16S rRNA gene sequencing, multi-omics sequencing, and whole genome sequencing). In this review, we made an overview of the biodegradation of TCs in different systems, refined functional microbial communities and pure isolates relevant to TCs biodegradation, and summarized the biodegradation products, pathways, and degradation genes of TCs. In addition, ecological risks of TCs biodegradation were considered from the perspectives of metabolic products toxicity and resistance genes. Overall, this article aimed to outline the research progress of TCs biodegradation and propose future research prospects.

Efficient removal of tetracycline using U-type continuous-flow bioelectrochemical system without ion exchange membrane or cathodic catalyst

A U-type membraneless continuous-flow bioelectrochemical system was developed to efficiently remove tetracycline and antibiotic resistance genes from synthetic wastewaters at hydraulic retention time of only eight hours. At the TC concentration of 20-80 mgL^-1 in feed, the removals of tetracycline all exceeded 95%, over 60-1200 mgL^-1 chemical oxygen demand, 30-150 mgL^-1 NH₄⁺-N, and at 5-25 °C, superior to the performances reported in literature. The maximum power of the BES system peaked at 0.416 Wm^-3 at 20 mgL^-1 TC feeding, corresponding to open circle voltage of 0.90 V and internal resistance of 799.8 Ω. The community analysis showed that the elevated TC loadings forced the predominate population to be evolved to TC-degrading consortium. The relative abundances of tetA, tetC, tetO, tetQ, and tetW in treated effluent ranged 1.20 × 10^-6 to 2.60 × 10^-4, revealing that the present BES reactor has superior removal efficiency of antibiotic resistance genes.

Indicators of water biotoxicity obtained from turn-off microbial electrochemical sensors

The development of biosensors is critical to reducing potential risks associated with contamination accidents. However, the application of microbial electrochemical sensors for water biotoxicity monitoring is hampered by the lack of an indicator with high response magnitudes. In this study, microbial electrochemical sensors were fabricated with interdigitated electrode arrays (IDAs), and indicators from various electrochemical analyses were comprehensively investigated. Only the peak of cyclic voltammetry (CV) was highly linearly correlated with the commonly used current indicator during the enrichment of the electroactive biofilm. The resistance fitted from the electrochemical impedance spectroscopy (EIS) data provided a comparable and even higher inhibition ratio (IR) than the current during toxicity assessments. The differential pulse voltammetry (DPV) did not exhibit a higher sensitivity than the CV peak. However, no clear response was observed in the real-time impedance analysis for use in water biotoxicity monitoring. Most of the microbes were in the propidium iodide (PI)-permeable state after the toxicity assessments, although the current was fully recovered. This study demonstrates the potential to use EIS data as indicators of water biotoxicity using microbial electrochemical sensors.

Profiling of co-metabolic degradation of tetracycline by the bio-cathode in microbial fuel cells

In this paper, a system of tetracycline (TEC) degradation by the bio-cathode in a microbial fuel cell (MFC) was constructed. Overall, the co-metabolic degradation performance of TEC was studied through single factor experiments and the ecological risk was evaluated using the E. coli growth inhibition rate and resistance genes. High throughput sequencing (HTS) was utilized to profile the biofilm community structure of the bio-cathode. Results showed that the degradation rate of TEC reached greater than 90% under optimal conditions, which was 10 mg L⁻¹ initial TEC concentration, 0.2–0.7 g L⁻¹ sodium acetate concentration and 12–18 L h⁻¹ aeration. Furthermore, compared with the aerobic biodegradation of TEC, the degradation efficiency of the MFC bio-cathode for TEC was significantly increased by 50% and the eco-toxicity of TEC after 36 hour degradation was reduced by 60.9%, and TEC ARGs in effluent were cut down. HTS results showed that electrochemically active bacteria Acetobacter and TEC-resistant degradation bacteria Hyphomicrobium, Clostridium and Rhodopseudomonas were the main dominant bacteria in the cathode biofilm. Besides, based on 5 intermediates, degradation pathways involving deamidation, denitro dimethylation, dedimethylation and dehydroxylation of TEC were proposed. The degradation of TEC on the bio-cathode was mainly caused by microbial co-metabolism action. This study would enrich the study of MFC bio-cathodic degradation of antibiotics in water.

In this paper, a system of tetracycline (TEC) degradation by the bio-cathode in a microbial fuel cell (MFC) was constructed.

Efficient removal of nitrate, manganese, and tetracycline in a novel loofah immobilized bioreactor: Performance, microbial diversity, and functional genes

The remediation of multiple pollutants in water, for instance, nitrate, heavy metals, and antibiotics is urgent and necessary for the global water resources protection. Herein, a modified loofah bioreactor was designed for simultaneous denitrification, manganese (Mn) oxidation, and tetracycline (TC) removal. The maximum removal efficiencies of NO₃^--N (91.97%), Mn(II) (71.25%), and TC (57.39%) were achieved at a hydraulic retention time (HRT) of 9 h, Mn(II) concentration of 20 mg L^-1, and TC concentration of 1 mg L^-1. SEM and XRD were carried out to characterize the bioprecipitation in the operation of bioreactor. TC addition affected the gaseous denitrification products, dissolved organic matter, as well as reduced the OTU in the bioreactor. The Zoogloea were regarded as the dominant species in the microbial community and played an essential role in the operation of bioreactor. Metagenomic analysis proved the great potential for denitrification, manganese oxidation, and antibiotic removal of loofah bioreactor.

Synergetic effect of photocatalysis and peroxymonosulfate activated by MIL-53Fe@TiO2 for efficient degradation of tetracycline hydrochloride under visible light irradiation

The MIL-53Fe was prepared by simple solvothermal method, and the MIL-53Fe photocatalysts showed lower photocatalytic activity for the degradation of tetracycline hydrochloride under visible light irradiation. After combined with TiO2,...

Functional role of mixed-culture microbe in photocatalysis coupled with biodegradation: Total organic carbon removal of ciprofloxacin

Ciprofloxacin is an extensively used fluoroquinolone antibiotic, which exists in aquatic environment, causing detrimental effects to the aquatic ecosystem and thus, indirectly to humans. Thus, an efficient and rapid removal method for ciprofloxacin is urgently needed. Intimately coupled photocatalysis and biodegradation has proven to be highly efficient, low-cost, and eco-friendly. In this study, cube polyurethane sponges modified with visible light-responsive g-C₃N₄ and mixed culture microbes were used to increase the ciprofloxacin removal efficiency. Subsequently, 94% of ciprofloxacin was removed by photocatalytic-biodegradation and 12 degradation products and possible degradation pathways were analyzed. Photocatalytic-biodegradation had a 1.57 times higher total organic carbon (TOC) removal rate than photocatalytic degradation. The microbial community structure after 72 h of photocatalytic biodegradation was examined. High microbial richness, evenness, and functional dominant species belong to Proteobacteria, which were closely associated with the utilization of antibiotics, may be majorly responsible for the highly efficient removal degradation process. Additionally, microbes retarded the interaction of photogenerated electrons and holes, which may contribute to the increasing mineralization. The findings demonstrated the potential ability of photocatalytic biodegradation in degrading bio-recalcitrant compounds and provide new insights into photocatalytic coupled with biodegradation for removal of ciprofloxacin.

Effects of two ecological earthworm species on tetracycline degradation performance, pathway and bacterial community structure in laterite soil

This study explored the change of tetracycline degradation efficiency, metabolic pathway, soil physiochemical properties and degraders in vermiremediation by two earthworm species of epigeic Eisenia fetida and endogeic Amynthas robustus. We found a significant acceleration of tetracycline degradation in both earthworm treatments, and 4-epitetracycline dehydration pathway was remarkably enhanced only by vermiremediation. Tetracycline degraders from soils, earthworm intestines and casts were different. Ralstonia and Sphingomonas were potential tetracycline degraders in soils and metabolized tetracycline through direct dehydration pathway. Degraders in earthworm casts (Comamonas, Acinetobacter and Stenotrophomonas) and intestines (Pseudomonas and Arthrobacter) dehydrated 4-epitetracycline into 4-epianhydrotetracycline. More bacterial lineages resisting tetracycline were found in earthworm treatments, indicating the adaptation of soil and intestinal flora under tetracycline pressure. Earthworm amendment primarily enhanced tetracycline degradation by neutralizing soil pH and consuming organic matters, stimulating both direct dehydration and epimerization-dehydration pathways. Our findings proved that vermicomposting with earthworms is effective to alter soil microenvironment and accelerate tetracycline degradation, behaving as a potential approach in soil remediation at tetracycline contaminated sites.

UV-enhanced nano-nickel ferrite-activated peroxymonosulfate for the degradation of chlortetracycline hydrochloride in aqueous solution

In this study, nano-nickel ferrite (NiFe2O4) was successfully prepared by hydrothermal synthesis and applied to the oxidative removal of chlortetracycline hydrochloride (CTH) in the presence of ultraviolet radiation (UV) and peroxymonosulfate (PMS). Several characterization methods were used to reveal the morphology and surface properties of nano-NiFe2O4, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared absorption (FTIR) spectroscopy. The removal efficiency of CTH, the factors affecting the reaction process and the reaction mechanism of PMS activated by UV combined with nano-NiFe2O4 (UV + nano-NiFe2O4/PMS) in aqueous solution were systematically studied. The results showed that the UV + nano-NiFe2O4/PMS system led to a higher removal efficiency of CTH than other parallel systems. The results also showed that the CTH removal efficiency was enhanced under optimal conditions ([nano-NiFe2O4] = 1 g L-1, [PMS] = 1 g L-1, [UV wavelength] = 254 nm and [pH] = 11) and that a removal efficiency of 96.98% could be achieved after 60 min. In addition, the influence of the PMS concentration, CTH concentration, dosage of added nano-NiFe2O4 and pH on the PMS activation efficiency and CTH oxidative degradation effect was studied. Inorganic anions such as Cl-, HCO3 -, CO3 2- and NO3 - increased the removal efficiency of CTH by 21.29%, 27.17%, 25.32% and 5.96% respectively, while H2PO4 - inhibited CTH removal, and the removal efficiency of CTH decreased 6.08% after 60 min. Free radical identification tests detected SO4 -˙, OH˙ and 1O2 and showed that these species participated in the degradation reaction of CTH. The results of LC-MS and TOC analysis showed that CTH was degraded in the UV + nano-NiFe2O4/PMS system through hydroxylation, demethylation, deamination, and dehydration reaction and finally mineralized into CO2. These findings confirmed that nano-NiFe2O4 is a green and efficient heterogeneous catalyst for activation of PMS and demonstrates potential applicability in the treatment of antibiotic wastewater.

Augmentation of chloramphenicol degradation by Geobacter-based biocatalysis and electric field

Electroactive microorganisms and electrochemical technologies have been separately used for environmental remediation such as antibiotics removal, yet the efficiency of coupling these two methods for chlorinated antibiotics removal is poorly known. Here we tested the synergy of Geobacter sulfurreducens PCA, an electroactive bacteria, and an electrical field, on chloramphenicol removal. Removal is increased two-fold by increasing the temperature from 30°C to 37°C. The cyclic voltammograms and chronoamperometry tests demonstrated that G. sulfurreducens PCA catalyzed chloramphenicol chemical reduction with electrode as excusive electron donor. A critical voltage, -0.6 to -0.5 V vs. Ag/AgCl, was discovered for chloramphenicol degradation with an increase of removal rate about 2.62-folds, from 31.06% to 81.41%. Combined removal with both G. sulfurreducens PCA and an electrical field increased the apparent rate constant and reached 82.77% removal at -0.5 V. Specially, the combined removal at -0.5 V even presented more robust removal efficiency compared to -0.6 V (78.64%) without G. sulfurreducens PCA. Mass spectrometry of degradation products indicates the reduction of nitro into amine groups, and dechlorination into less toxic compounds. Overall, combined biocatalysis and an electrical field is a promising method to remove antibiotics from polluted environments.

Metagenomic analysis reveals functional genes in soil microbial electrochemical removal of tetracycline

Microbial fuel cells (MFCs) are capable of removing tetracycline in soils, in which the degradation efficiency of tetracycline is hindered by its strong adsorption capacity. Phosphate was chosen as a competitor for tetracycline adsorption to improve its removal rate in soil MFCs. The results showed that 42-50% of tetracycline was degraded within 7 days, which was 42-67% higher than open-circuit treatments. Compared with closed-circuit treatments without phosphate addition, the removal efficiencies of tetracycline after phosphate addition increased by 19-25% on day 51, and accumulated charge outputs were enhanced by 31-52%, while the abundance of antibiotic resistance genes decreased by 19-27%. Like Geobacter, the abundance of Desulfurispora and Anaeroomyxobacter in the anode showed similar tendencies with current densities, suggesting their dominant roles in bioelectricity generation. Gemmatimonadetes bacterium SCN 70-22, Azohydromonas australica, Steroidobacter denitrificans and Gemmatirosa kalamazoonesis were found to be potential electrotrophic microbes in the cathode. The expressed flavoprotein 2,3-oxidoreductase, quinol oxidase and fumarate reductase might have promoted the transfer efficiency of electrons from cathodes to cells, which finally accelerated the biodegradation rate of tetracycline in addition to the polyphenol oxidase. This study provides an insight into functional enzyme genes in the soil microbial electrochemical remediation.

A Study on the Reaction Kinetics of Anaerobic Microbes Using Batch Anaerobic Sludge Technique for Beverage Industrial Wastewater

In this study, a low-cost, efficient, and environmentally friendly anaerobic sludge process for the treatment of industrial beverage wastewater was investigated to analyze the effect of bacteria growth on the degradation of organic matter (chemical oxygen demand). Additionally, the mechanism, interactions between the microbe’s growth, and operating conditions of an anaerobic batch reactor along with the wastewater treatment efficiency were evaluated via microbial kinetics. The kinetic coefficients based on chemical oxygen demand (COD) by conventional techniques such as kinetic coefficients growth yield (0.46 mg VSS/mg COD), saturation coefficient (3500 mg/L COD), the maximum rate of substrate utilization per unit mass of biomass (0.0066 mg/L COD), growth rate by Monod equation, M (0.03833 L/h), and maximum growth rate, μm (0.03672 L/h) were calculated. The results show a higher rate of substrate degradation (0.54 day−1) due to the high COD removal efficiency (CRE) of 99.31% during 13 days that was achieved, which can be attributed to the active involvement of anaerobic microbes in the process of degradation. Based on these results, it can be concluded that the current study can be used as an effective way to analyze the industrial beverage wastewater at commercial levels.

Tetracycline inhibition and transformation in microbial fuel cell systems: Performance, transformation intermediates, and microbial community structure

Tetracycline (TC) transformation in the anode of an air cathode microbial fuel cell (MFC) and in the cathode of an MFC-Fenton system was investigated. TC at 10 mg/L in the anolyte was removed by 43-74% in 14-d cycles, mainly attributed to adsorption. The electrochemical activity, COD and acetate consumption of the anodic biofilm were inhibited by TC; inhibition was reversed when TC addition was stopped. Over 84 d of MFC operation with TC, Geobacter and Mycobacterium in the anode biofilm decreased, while Janthinobacterium and Comamonas increased. Over 99% of TC at 10-40 mg/L was removed within 8 h in the MFC-Fenton cathode. O₂^-•/HO₂• and •OH were responsible for the cathodic TC degradation. The maximum current was 0.93 mA (at 250 Ω) and increased by 36.3% by the MFC-Fenton reaction. Cathodic MFC-Fenton is an efficient and energy-saving process for TC removal, compared to slow and problematic anodic TC bio-oxidation.

Synthesis of an Ag@AgCl catalyst with amorphous copper as the support and its catalytic performance in the reduction of 4-nitrophenol

The support used in a composite catalyst has an important influence on the catalytic performance of the catalyst. Amorphous metals have good electron-transfer properties and the presence of defect structures on the surface will introduce additional active sites and should be excellent catalyst supports. In this study, an Ag@AgCl composite catalyst with amorphous Cu (a-Cu) as the support is prepared by a two-step precipitation method at room temperature and a light irradiation reduction method. Compared to the Ag@AgCl and a-Cu, the catalytic rate of the Ag@AgCl/a-Cu composite catalytic rate was 2.04 times and 6.69 times faster during the reduction of 4-NP in NaBH4 aqueous solution. The high-performance catalytic efficiency and reusability of Ag@AgCl/a-Cu may be attributed to the synergistic effect between Ag@AgC and amorphous metal elements. This work may provide an effective reference for the synthesis of high activity catalysts using amorphous metals as supports.