Sulfamethoxazole degradation by Pseudomonas silesiensis F6a isolated from bioelectrochemical technology-integrated constructed wetlands

Interfacial Engineering of a Z-Scheme Bi2O2S/NiTiO3 Heterojunction Photoanode for the Degradation of Sulfamethoxazole in Water

To develop a semiconductor interface with enhanced spatial separation of carriers under visible light irradiation for the photoelectrochemical (PEC) oxidation process, we explored the fabrication of a Bi2O2S/NiTiO3 heterojunction photoanode for the removal of sulfamethoxazole in water. The Bi2O2S/NiTiO3 photoanode was synthesized via an in situ hydrothermal process, and it exhibited better light absorption and charge separation, as well as a reduced rate of recombination of photoexcited charge species compared to pristine Bi2O2S and NiTiO3. The improved photoelectrocatalytic performance was attributed to the synergistic interaction between Bi2O2S and NiTiO3 and the presence of an S-O bond at the heterojunction interface, thus resulting in Z-scheme heterojunction formation. Various characterization methods such as XPS, UV-DRS, electrochemical impedance spectroscopy, photoluminescence, FESEM, TEM, and photocurrent response measurements were explored to explain the optical and electrochemical properties of the semiconductor heterojunction. The PEC degradation process was optimized, demonstrating a degradation efficiency removal of 80% for 5 mg/L sulfamethoxazole in water, with a TOC removal of 45.5%. A Z-scheme heterojunction formation mechanism was proposed to explain the enhanced photoelectrocatalytic activity of the photoanode. This work generally contributes to the development of efficient and sustainable photoanodes for environmental remediation.

Enhanced bioelectrochemical degradation of Thiabendazole using biostimulated Tunisian hypersaline sediments: kinetics, efficiency, and microbial community shifts

Thiabendazole (TBZ), a recalcitrant fungicide, is frequently applied in postharvest fruit treatment and generates significant volumes of industrial wastewater (WW) that conventional treatment plants cannot handle. This explores a bioelectrochemical system (BES) for TBZ degradation using Tunisian hypersaline sediments (THSs) as inoculum. Four sets of BES, along with biological controls, were tested using THS subjected to different levels of TBZ biostimulation. Sediments underwent one, two, or three biostimulation phases with increasing TBZ concentrations (0, 10, 100, and 300 mg kg-1). Potentiostatic control was applied to BES, polarized at 0.1 V vs. saturated calomel reference electrode (SCE), with a carbon felt working electrode (72 cm2 L-1) and maintained at 25°C. While current production was very low, sediments biostimulated with 100 mg kg-1 kg TBZ produced the highest current density (3.2 mA m-2), a 5-fold increase over untreated sediments (0.6 mA m-2). GC-FID analysis showed >99% TBZ degradation in all reactors. The TBZ half-elimination time from 27 days with biological treatments to 19 days in BES and further to 6 days following biostimulation. Bacterial analysis revealed a substantial microbial community shift after biostimulation, with a reduction in Bacillota (-64%) and an increase in Proteobacteria (+62%), dominated by Pseudomonas (45%) and Marinobacter (16%). These findings provide insight into the selective potential of biostimulation cycles to enhance microbial community composition and improve BES performance for TBZ wastewater treatment.

Mechanism of microplastics promoting sulfamethoxazole biodegradation in activated sludge as revealed by DNA-stable isotope probing

Microplastics (MPs) often coexist with sulfonamide antibiotics (SAs) in the activated sludge of wastewater treatment plants (WWTPs). Microbial degradation is a crucial pathway for SAs removal in the activated sludge, though its response to MPs still yet to be disclosed. Here, we combined DNA-stable isotope probing (DNA-SIP), PICRUSt and MENA techniques to explore the impact of MPs on the microbial biodegradation of sulfamethoxazole (SMX) in the activated sludge. DNA-SIP revealed 20 genera were responsible for the SMX degradation in the activated sludge, with 13 of these genera being firstly linked with sulfonamide biodegradation. The potential SMX-degrading bacteria showed complex synergistic interaction with the other microbes. Eight degradation pathways were constructed based on the nine identified SMX-related degradation genes. MPs addition enhanced the SMX biodegradation by altering the structure of degrading microbes, increasing their relative abundance and promoting the synergistic interactions between potential SMX-degrading bacteria and other microbes in activated sludge. Besides, genes related to abundant energy production and biofilm formation were involved in SMX degradation in the activated sludge with MPs. Our study reveals the MPs influence on SMX biodegradation in activated sludge, and disclose the potential underlying mechanisms, which will benefit the regulation on antibiotic removal in WWTPs.

Efficient sulfamethoxazole biotransformation and detoxification by newly isolated strain Hydrogenophaga sp. SNF1 via a ring ortho-hydroxylation pathway

Sulfonamides are frequently detected with high concentrations in various environments and was regarded as a serious environmental risk by fostering the dissemination of antibiotic resistance genes. This study for the first time reported a strain SNF1 affiliated with Hydrogenophaga can efficiently degrade sulfamethoxazole (SMX). Strain SNF1 prefers growing under extra carbon sources and neutral condition, and could degrade 500 mg/L SMX completely within 16 h. Under the conditions optimized by response surface method (3.11 g/L NaAc, 0.77 g/L (NH4)2SO4, pH = 7.53, and T = 34.38 ℃), a high removal rate constant 0.5104 /h for 50 mg/L SMX was achieved. Coupling the intermediate products identification with comparative genomic analysis, a novel SMX degradation pathway was proposed. Unlike Actinomycetota degraders, SMX was deaminized and ring ortho-hydroxylated in strain SNF1 using a Rieske dioxygenase in combination with glutamine synthetase system. Rieske dioxygenase gene expression was up-regulated by 1.09 to 6.02-fold in response to 100 mg/L SMX. When SMX is fully degraded, its antimicrobial activity drops by over 90 %, and its anticipated toxicity to aquatic organisms were overall reduced. These findings provided new insights into SMX-degrading microorganisms and mechanisms and highlighted the potential of Hydrogenophaga. sp. SNF1 for biological elimination of SMX from wastewater.

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 degradation of contaminants of emerging concern: metabolic, genetic and omics insights for enhanced bioremediation

The perpetual release of natural/synthetic pollutants into the environment poses major risks to ecological balance and human health. Amongst these, contaminants of emerging concern (CECs) are characterized by their recent introduction/detection in various niches, thereby causing significant hazards and necessitating their removal. Pharmaceuticals, plasticizers, cyanotoxins and emerging pesticides are major groups of CECs that are highly toxic and found to occur in various compartments of the biosphere. The sources of these compounds can be multipartite including industrial discharge, improper disposal, excretion of unmetabolized residues, eutrophication etc., while their fate and persistence are determined by factors such as physico-chemical properties, environmental conditions, biodegradability and hydrological factors. The resultant exposure of these compounds to microbiota has imposed a selection pressure and resulted in evolution of metabolic pathways for their biotransformation and/or utilization as sole source of carbon and energy. Such microbial degradation phenotype can be exploited to clean-up CECs from the environment, offering a cost-effective and eco-friendly alternative to abiotic methods of removal, thereby mitigating their toxicity. However, efficient bioprocess development for bioremediation strategies requires extensive understanding of individual components such as pathway gene clusters, proteins/enzymes, metabolites and associated regulatory mechanisms. "Omics" and "Meta-omics" techniques aid in providing crucial insights into the complex interactions and functions of these components as well as microbial community, enabling more effective and targeted bioremediation. Aside from natural isolates, metabolic engineering approaches employ the application of genetic engineering to enhance metabolic diversity and degradation rates. The integration of omics data will further aid in developing systemic-level bioremediation and metabolic engineering strategies, thereby optimising the clean-up process. This review describes bacterial catabolic pathways, genetics, and application of omics and metabolic engineering for bioremediation of four major groups of CECs: pharmaceuticals, plasticizers, cyanotoxins, and emerging pesticides.

Sulfamethoxazole is Metabolized and Mineralized at Extremely Low Concentrations

The presence of organic micropollutants in water and sediments motivates investigation of their biotransformation at environmentally low concentrations, usually in the range of μg L-1. Many are biotransformed by cometabolic mechanisms; however, there is scarce information concerning their direct metabolization in this concentration range. Threshold concentrations for microbial assimilation have been reported in both pure and mixed cultures from different origins. The literature suggests a range value for bacterial growth of 1-100 μg L-1 for isolated aerobic heterotrophs in the presence of a single substrate. We aimed to investigate, as a model case, the threshold level for sulfamethoxazole (SMX) metabolization in pure cultures of Microbacterium strain BR1. Previous research with this strain has covered the milligram L-1 range. In this study, acclimated cultures were exposed to concentrations from 0.1 to 25 μg L-1 of 14C-labeled SMX, and the 14C-CO2 produced was trapped and quantified over 24 h. Interestingly, SMX removal was rapid, with 98% removed within 2 h. In contrast, mineralization was slower, with a consistent percentage of 60.0 ± 0.7% found at all concentrations. Mineralization rates increased with rising concentrations. Therefore, this study shows that bacteria are capable of the direct metabolization of organic micropollutants at extremely low concentrations (sub μg L-1).

Performance and mechanism of SMX removal by an electrolysis-integrated ecological floating bed at low temperatures: A new perspective of plant activity, iron plaque, and microbial functions

Improvements in plant activity and functional microbial communities are important to ensure the stability and efficiency of pollutant removal measures in cold regions. Although electrochemistry is known to accelerate pollutant degradation, cold stress acclimation of plants and the stability and activity of plant-microbial synergism remain poorly understood. The sulfamethoxazole (SMX) removal, iron plaque morphology, plant activity, microbial community, and function responses were investigated in an electrolysis-integrated ecological floating bed (EFB) at 6 ± 2 ℃. Electrochemistry significantly improved SMX removal and plant activity. Dense and uniform iron plaque was found on root surfaces in L-E-Fe which improved the plant adaptability at low temperatures and provided more adsorption sites for bacteria. The microbial community structure was optimized and the key functional bacteria for SMX degradation (e.g., Actinobacteriota, Pseudomonas) were enriched. Electrochemistry improves the relative abundance of enzymes related to energy metabolism, thereby increasing energy responses to SMX and low temperatures. Notably, electrochemistry improved the expression of target genes (sadB and sadC, especially sadC) involved in SMX degradation. Electrochemistry enhances hydrogen bonding and electrostatic interactions between SMX and sadC, thereby enhancing SMX degradation and transformation. This study provides a deeper understanding of the electrochemical stability of antibiotic degradation at low temperatures.

Microbial degradation and transformation of PPCPs in aquatic environment: A review

The Pharmaceuticals and Personal Care Products (PPCPs) presence at harmful levels has been identified in aquatic ecosystems all over the world. Currently, PPCPs are more common in aquatic regions and have been discovered to be extremely harmful to aquatic creatures. Waste-water treatment facilities are the primary cause of PPCPs pollution in aquatic systems due to their limited treatment as well as the following the release of PPCPs. The degree of PPCPs elimination is primarily determined by the method applied for the remediation. It must be addressed in an eco-friendly manner in order to significantly improve the environmental quality or, at the very least, to prevent the spread as well as effects of toxic pollutants. However, when compared to other methods, environmentally friendly strategies (biological methods) are less expensive and require less energy. Most biological methods under aerobic conditions have been shown to degrade PPCPs effectively. Furthermore, the scientific literature indicates that with the exception of a few extremely hydrophobic substances, biological degradation by microbes is the primary process for the majority of PPCPs compounds. Hence, this review discusses about the optimistic role of microbe concerned in the degradation or transformation of PPCPs into non/less toxic form in the polluted environment. Accordingly, more number of microbial strains has been implicated in the biodegradation/transformation of harmful PPCPs through a process termed as bioremediation and their limitations.

Simultaneous Removal of Sulfamethoxazole during Fermentative Production of Short-Chain Fatty Acids

This study explores the simultaneous sulfamethoxazole (SMX) removal and short-chain fatty acids (SCFAs) production by a Clostridium sensu stricto-dominated microbial consortium. SMX is a commonly prescribed and persistent antimicrobial agent frequently detected in aquatic environments, while the prevalence of antibiotic-resistant genes limits the biological removal of SMX. Under strictly anaerobic conditions, sequencing batch cultivation coupled with co-metabolism resulted in the production of butyric acid, valeric acid, succinic acid, and caproic acid. Continuous cultivation in a CSTR achieved a maximum butyric acid production rate and yield of 0.167 g/L/h and 9.56 mg/g COD, respectively, while achieving a maximum SMX degradation rate and removal capacity of 116.06 mg/L/h and 55.8 g SMX/g biomass. Furthermore, continuous anaerobic fermentation reduced sul genes prevalence, thus limiting the transmission of antibiotic resistance genes during antibiotic degradation. These findings suggest a promising approach for efficient antibiotic elimination while simultaneously producing valuable products (e.g., SCFAs).

Occurrence of antibiotics in wastewater: Potential ecological risk and removal through anaerobic-aerobic systems

Antibiotics are intensively used to improve public health, prevent diseases and enhance productivity in animal farms. Contrarily, when released, the antibiotics laden wastewater produced from pharmaceutical industries and their application sources poses a potential ecological risk to the environment. This study provides a discussion on the occurrence of various antibiotics in wastewater and their potential ecological risk in the environment. Further, a critical review of anaerobic-aerobic processes based on three major systems (such as constructed wetland, high-rate bioreactor, and integrated treatment technologies) applied for antibiotics removal from wastewater is performed. The review also explores microbial dynamics responsible for antibiotic biodegradation in anaerobic-aerobic systems and its economic feasibility at wider-scale applications. The operational problems and prospective modifications are discussed to define key future research directions. The appropriate selection of treatment processes, sources control, understanding of antibiotic fate, and adopting precise monitoring strategies could eliminate the potential ecological risks of antibiotics. Integrated bio-electrochemical systems exhibit antibiotics removal ≥95% by dominant Geobacter sp. at short HRT ∼4-10 h. Major process factors like organic loading rate, hydraulic loading rate (HRT), and solid retention time significantly affect the system performance. This review will be beneficial to the researchers by providing in-depth understanding of antibiotic pollution and its abatement via anaerobic-aerobic processes to develop sustainable wastewater treatment technology in the future.

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.

Sulfamethoxazole degradation by Aeromonas caviae and co-metabolism by the mixed bacteria

Sulfamethoxazole (SMX) is a frequently detected antibiotic in the environment and has attracted much attention. Aeromonas caviae strain GLB-10 was isolated, which could degrade SMX to Aniline and 3-Amino-5-methylisoxazole. Compared to the single bacteria, the mixed bacteria including stain GLB-10, Vibrio diabolicus strain L2-2, Zobellella taiwanensis, Microbacterium testaceum, Methylobacterium, etc, had an ultrahigh degradation efficiency to SMX, with 250 mg/L SMX being degraded in 3 days. In addition to bioproducts of single bacteria, SMX bioproducts by the mixed bacteria also included acetanilide and hydroquinone which were not detected in the single bacteria. The SMX degradation mechanism of the mixed bacteria was more complicated including acetylation, sulfur reduction 4S pathway, and ipso-hydrolysis. The molecular mechanism of the mixed bacteria degrading SMX was also investigated, revealing that the resistance mechanism related to protein outer membrane protein and catalase peroxidase were overexpressed, meanwhile, 6-hydroxynicotinate 3-monooxygenase and ammonia monooxygenase might be the key proteins in SMX degradation. The mixed bacteria could efficiently degrade SMX in different real environments including tap water, river water, artificial lake water, estuary, and, marine water, and have very great research value in bacterial co-metabolism and biodegradation of sulfonamides antibiotics in the environment.

Removal performance, biotransformation pathways and products of sulfamethoxazole in vertical subsurface flow constructed wetlands with different substrates

For decades, sulfamethoxazole (SMX) has been frequently detected in the aquatic environments due to its high usage and refractory to degradation. Constructed wetland (CW) is regarded as an efficient advanced wastewater technology to eliminate organic pollutants including SMX. In CW system, substrate adsorption and further biodegradation are extremely important in SMX removal; however, the removal performance of SMX by CWs with different substrates varies greatly, and the biotransformation pathways, products, and mechanisms of SMX remain unclear. To address this, we constructed a CW with conventional substrate (CS, gravel) as control (C-CW) and three CWs with emerging substrates (ES, biochar, zeolite and pyrite for B-CW, Z-CW and P-CW, respectively), and explored the performance and mechanisms of SMX removal in CWs. Results illustrated that the removal performance of SMX in CWs with ES reached 94.89-99.35%, and significantly higher than that with CS of 89.50% (p < 0.05). Biodegradation contributed >90% SMX removal in all CWs. The microbial compositions and functions differed among CWs at the middle layer (mixed layer), which shaped diverse resistance pattern and metabolism pathways of microbiomes under SMX stress: P-CW and B-CW cope with SMX stress by enhancing material and energy metabolism, whereas Z-CW does that by enhancing metabolism and exocytosis of xenobiotics. Additionally, nine transformation pathways with 15 transformation products were detected in this study. A reversible process of desamino-SMX being reconverted to SMX might exist in P-CW, which caused a lower SMX removal efficiency in P-CW. This study provided a comprehensive insight into the processes and mechanisms of SMX removal in CWs with different substrates, which would be a useful guidance for substrate selection in CWs in terms of enhanced micropollutants removal.

Insight into sulfamethoxazole effects on aerobic denitrification by strain Pseudomonas aeruginosa PCN-2: From simultaneous degradation performance to transcriptome analysis

It is a well-established fact that aerobic denitrifying strains are profoundly affected by antibiotics, but bacterium performing simultaneous aerobic denitrification and antibiotic degradation is hardly reported. Here, a typical aerobic denitrifying bacterium Pseudomonas aeruginosa PCN-2 was discovered to be capable of sulfamethoxazole (SMX) degradation. The results showed that nitrate removal efficiency was decreased from 100% to 88.12%, but the resistance of strain PCN-2 to SMX stress was enhanced with the increment of SMX concentration from 0 to 100 mg/L. Transcriptome analysis revealed that the down-regulation of energy metabolism pathways rather than the denitrifying functional genes was responsible for the suppressed nitrogen removal, while the up-regulation of antibiotic resistance pathways (e.g., biofilm formation, multi-drug efflux system, and quorum sensing) ensured the survival of bacterium and the carrying out of aerobic denitrification. Intriguingly, strain PCN-2 could degrade SMX during aerobic denitrification. Seven metabolites were identified by the UHPLC-MS, and three degradation pathways (which includes a new pathway that has never been reported) was proposed combined with the expressions of drug metabolic genes (e.g., cytP450, FMN, ALDH and NAT). This work provides a mechanistic understanding of the metabolic adaption of strain PCN-2 under SMX stress, which provided a broader idea for the treatment of SMX-containing wastewater.