How UV photolysis accelerates the biodegradation and mineralization of sulfadiazine (SD)

Enhanced photocatalytic activity of Fe-, S- and N-codoped TiO2 for sulfadiazine degradation

The composite material based on N-, S-, and Fe-doped TiO2 (NSFe-TiO2) synthesized by wet impregnation was used as a photocatalyst to rapidly degrade sulfadiazine. The photocatalytic degradation behavior and mechanism of sulfadiazine on NSFe-TiO2 were investigated for revealing the role of degradation under ultraviolet light. The results showed that compared with TiO2, NSFe-TiO2 markedly improved the efficiency in photocatalytic degradation of sulfadiazine: more than 90% of sulfadiazine could be removed within 120 min by NSFe-TiO2 dosage of 20 mg L-1. The process conformed to first-order reaction kinetics model. The parameters such as loaded amount of NSFe-TiO2, solution pH value, humic acid concentration and recycle numbers on removal efficiency were also studied. Compared to neutral and alkaline conditions, acidic condition was not conducive to the photocatalysis. HA, Ca2+, Cu2+ and Zn2+ in the actual water body had mild inhibition on sulfadiazine degradation in UV/NSFe-TiO2 system. Fragments screened by high-resolution mass spectrometry were conducted to explore the oxidation mechanism and pathways of sulfadiazine degradation. On the whole, UV/NSFe-TiO2 photocatalysis has a good effect on sulfadiazine removal.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13762-023-04771-6.

Detection of Neonicotinoids in agriculture soil and degradation of thiacloprid through photo degradation, biodegradation and photo-biodegradation

The social and ecological influence of Neonicotinoids (NEOs) usage in agriculture sector is progressively higher. There are seven NEOs insecticides widely used for the insects control. Among the NEOs, thiacloprid (THD) was extensively used for insect control during crop cultivation. This study targets to analyse the contamination levels of NEOs in agricultural soil and identify photo-biodegradation of THD degradation using pure isolates and mixed consortium. The photo degradation (PD), biodegradation (BD) and photo-biodegradation (PBD) of THD were compared. The corn field agricultural soils were polluted by four NEOs, among them THD had greater contamination level (surface soil: 3901.2 ± 0.04 μg/g) and (sub-surface soil: 3988.6 ± 0.05 μg/g). Three soil free enriched bacterial strains following Bacillus atrophaeus (PB-2), Priestia megaterium (PB-3) (formerly known as Bacillus megaterium), and Peribacillus simplex (PB-4) (formerly known as Bacillus simplex) were identified by microbiological and molecular 16s rRNA gene sequencing. The PD, BD and PBD of THD were conducted and degradation rate was detected by instrument UPLC-MS-MS. The PBD process with blue-LEDs showed better THD degradation efficiency than PD and BD, where the specific THD degradation rate was 85 ± 0.2%, 87 ± 0.5%, and 89 ± 0.3%, respectively for PB-2, PB-3 and PB-4. Then, the photo-biodegradation performance is greater at 150, 175, 200 rpm, pH 7.0-9.0, and temperature 30-35 °C. After the PBD system deliver four intermediate metabolites, the THD degradation process maybe through nitro reduction, hydroxylation and oxidative cleavage pathway.

Light-dependent enhancement of sulfadiazine detoxification and mineralization by non-photosynthetic methanotrophs

Co-metabolism and photodegradation are two approaches for remediating trace organic compounds (TOrCs), however, interactions between the two with regards to TOrCs degradation have not been elucidated. In this study, sulfadiazine (SDZ) was chosen as a representative TOrC and Methylocystis bryophila as a typical strain. Under light conditions, about 80.6% of SDZ was removed by M. bryophila, but only 7.6% or 28.9% of SDZ was eliminated by either individual photodegradation or by co-metabolism. The SDZ stimulated more extracellular organic matter (EOM) production by M. bryophila. The enhanced SDZ degradation was attributed to indirect photolysis caused by the excited triplet state of EOM (³EOM*) and co-metabolism. The UPLC-QTOF-MS analysis showed that due to co-metabolism, the pyrimidine ring was broken and could further be oxidized into smaller molecules under light conditions, such as formic and acetic acids. The SDZ mineralization ratio increased from 9.9% under the co-metabolic condition alone to 36.5% under co-metabolism coupled with photodegradation. The Ames tests confirmed that the SDZ degradation products by co-metabolism were mutagenic, however, their toxicity was ameliorated by light during co-metabolism. In conclusion, light plays a crucial role in co-metabolic processes of TOrCs.

Enhanced removal of antibiotics and antibiotic resistance genes in a soil microbial fuel cell via in situ remediation of agricultural soils with multiple antibiotics

Soil microbial fuel cells (MFCs) have been applied for the in situ remediation of soils polluted by single antibiotics. However, the investigation of only single antibiotic pollution has hindered MFC application in real-world soil remediation, where the effects of multiple antibiotics with similar chemical structures on the fate of antibiotics and their corresponding antibiotic resistance genes (ARGs) remain unknown. In this study, antibiotic removal rates, microbial community compositions, metabolite compositions, and ARG abundances were investigated in soil MFCs by adding two commonly used antibiotics (sulfadiazine, SDZ, and sulfamethoxazole, SMX), and comparing them with the addition of only a single antibiotic (SDZ). The antibiotic removal rate was higher in the soil MFC with addition of mixed antibiotics compared to the single antibiotic due to enhanced biodegradation efficiency in both the upper (57.24% of the initial antibiotic concentration) and lower layers (57.07% of the initial concentration) of the antibiotic-polluted soils. Bacterial community diversity in the mixed antibiotic conditions increased, and this likely resulted from the decreased toxicity of intermediates produced during antibiotic biodegradation. Moreover, the addition of mixed antibiotics led to lower risks of ARG release into soil environments, as reflected by higher abundances of host bacteria in the single antibiotic treatment. These results encourage the further development of soil MFC technology for in situ remediation of antibiotic-polluted soils.

Dynamics of a Bacterial Community in the Anode and Cathode of Microbial Fuel Cells under Sulfadiazine Pressure

Microbial fuel cells (MFCs) could achieve the removal of antibiotics and generate power in the meantime, a process in which the bacterial community structure played a key role. Previous work has mainly focused on microbes in the anode, while their role in the cathode was seldomly mentioned. Thus, this study explored the bacterial community of both electrodes in MFCs under sulfadiazine (SDZ) pressure. The results showed that the addition of SDZ had a limited effect on the electrochemical performance, and the maximum output voltage was kept at 0.55 V. As the most abundant phylum, Proteobacteria played an important role in both the anode and cathode. Among them, Geobacter (40.30%) worked for power generation, while Xanthobacter (11.11%), Bradyrhizobium (9.04%), and Achromobacter (7.30%) functioned in SDZ removal. Actinobacteria mainly clustered in the cathode, in which Microbacterium (9.85%) was responsible for SDZ removal. Bacteroidetes, associated with the degradation of SDZ, showed no significant difference between the anode and cathode. Cathodic and part of anodic bacteria could remove SDZ efficiently in MFCs through synergistic interactions and produce metabolites for exoelectrogenic bacteria. The potential hosts of antibiotic resistance genes (ARGs) presented mainly at the anode, while cathodic bacteria might be responsible for ARGs reduction. This work elucidated the role of microorganisms and their synergistic interaction in MFCs and provided a reference to generate power and remove antibiotics using MFCs.

Acceleration of biotic decolorization and partial mineralization of methyl orange by a photo-assisted n-type semiconductor

In this study, a n-type semiconductor perylene diimide (PDI) was coupled with biodegradation to accelerate the biotic decolorization and mineralization of methyl orange (MO) under light condition. The decolorization rates (k₁) of MO in pure and mixed cultures with PDI were promoted by 1.35 and 1.79 folds, respectively, comparing to the cultures without PDI. The total mineralization efficiency of 4-aminobenzenesulfonic acid (4-ABA) was achieved to 22.10 ± 0.84% when in the presence of PDI. The quinone-like group and oxidation-reduction capacity of PDI were detected by Fourier transform infrared spectroscopy and cyclic voltammetry, respectively, but the enhancement on the biotic decolorization of MO was not promoted under dark condition indicating that microbial extracellular electron transfer was not promoted. The 4-ABA was confirmed to be partially mineralized when the PDI exposure to light. The generated free radicals i.e., h⁺, ⸱OH, was demonstrated as active species to accelerate the decolorization and mineralization of MO by ESR test and radical quenching experiments. The bond breaking of MO and 4-ABA molecules were successfully predicted by density functional theory calculations and were further proven by liquid-chromatography mass spectra. The synergistic mechanism of decolorization and mineralization of MO by microorganism and photocatalysis was proposed. Moreover, High-throughput sequencing and Live/dead cell results indicated that the presence of PDI has no obvious toxicity to the microorganisms and will not change the microbial communities during the short-term treatment period. The results of study provided a biological intimate photocatalytic material and suggested a feasible way for its combination with biodegradation of azo dyes.

Photodegradation of sulfadiazine in different aquatic environments - Evaluation of influencing factors

The presence of antibiotics, such as sulfadiazine (SDZ), in the aquatic environment contributes to the generation of antimicrobial resistance, which is a matter of great concern. Photolysis is known to be a major degradation pathway for SDZ in surface waters. Therefore, influencing factors affecting SDZ photodegradation in different aquatic environments were here evaluated in order to have a better knowledge about its persistence in the environment. Photodegradation of SDZ was found to be more efficient at higher pH (t_1/2 = 6.76 h, at pH = 7.3; t_1/2 = 12.2 h, at pH = 6.3), in the presence of humic substances (HS) (t_1/2 between 1.76 and 2.42 h), as well as in the presence of NaCl (t_1/2 = 1.00 h) or synthetic sea salts (t_1/2 = 0.78 h). Using ˙OH and ¹O₂ scavengers, it was possible to infer that direct photolysis was the main pathway for SDZ photodegradation in ultrapure water. Furthermore, results under N₂ purging confirmed that ¹O₂ was not relevant in the phototransformation of SDZ. Then, the referred observations were used for the interpretation of results obtained in environmental matrices, namely the final effluent of a sewage treatment plant (STPF), fresh and brackish water (t_1/2 between 2.3 and 3.48 h), in which SDZ photodegradation was found to be much faster than in ultrapure water (t_1/2 = 6.76 h).

Investigating the biodegradation of sulfadiazine in soil using Enterobacter cloacae T2 immobilized on bagasse

The application of the antibiotic sulfadiazine (SD) in veterinary medicine has created serious environmental issues due to its high mobility and non-degradability. A novel immobilized cell system has been developed and showed significant SD biodegradation potential in soil.

Shifting interactions among bacteria, fungi and archaea enhance removal of antibiotics and antibiotic resistance genes in the soil bioelectrochemical remediation

BACKGROUND

Antibiotics and antibiotic resistance genes (ARGs) are two pollutants in soil, especially ARGs as one of the top three threats to human health. The performance of soil microbial fuel cells (MFCs) fuelled with antibiotics was investigated.

RESULTS

In this study, soil MFCs spiked with tetracycline exhibited optimal bioelectricity generation, which was 25% and 733% higher than those of MFCs spiked with sulfadiazine and control, respectively. Compared with the non-electrode treatment, not only did functional micro-organisms change in open- and closed-circuit treatments, but also the microbial affinities, respectively, increased by 50% and 340% to adapt to higher removal of antibiotics. For the open-circuit treatment, the ineffective interspecific relation of micro-organisms was reduced to assist the removal efficiency of antibiotics by 7-27%. For the closed-circuit treatment, an intensive metabolic network capable of bioelectricity generation, degradation and nitrogen transformation was established, which led to 10-35% higher removal of antibiotics. Importantly, the abundances of ARGs and mobile genetic element (MGE) genes decreased after the introduction of electrodes; especially in the closed-circuit treatment, the highest reduction of 47% and 53% was observed, respectively.

CONCLUSIONS

Soil MFCs possess advantages for the elimination of antibiotics and ARGs with sevenfold to eightfold higher electricity generation than that of the control treatment. Compared with sulphonamides, the enhancement removal of tetracycline is higher, while both potential ARG propagation risk is reduced in soil MFCs. This study firstly synchronously reveals the relationships among bacteria, fungi and archaea and with ARGs and MGE genes in soil bioelectrochemical systems.

Simultaneous anaerobic and aerobic transformations of nitrobenzene

Aerobic biodegradation of nitrobenzene (NB) produces nitrophenol (NP), which has stronger toxicity than NB. Anaerobic biodegradation of NB produces aniline (AN), which has weaker toxicity, but is a dead-end product in anaerobic conditions. Accumulation of AN should be overcome by coupling anaerobic and aerobic transformations: NB is transformed to AN in an anaerobic zone of the bioreactor, and AN is then transformed in an aerobic zone. A vertical baffled bioreactor (VBBR) was employed for NB biodegradation with a controlled dissolved oxygen (DO) concentration. NB biodegradation was accelerated by simultaneous anaerobic and aerobic transformations, since AN was biotransformed by a mono-oxygenase reaction. Adding exogenous electron donor (acetate) enhanced NB removals when the DO concentration was ∼0.5 mg/L, because the donor accelerated mono-oxygenations of NB and AN. Coupling anaerobic and aerobic transformations can be a valuable strategy for biodegrading organic compounds that undergo aerobic and anaerobic biotransformations.

Overview of sulfonamide biodegradation and the relevant pathways and microorganisms

Sulfonamide antibiotics have aroused increasing concerns due to their ability to enhance the resistance of pathogenic bacteria and promote the spread of antibiotic resistance. Biodegradation plays an important role in sulfonamide dissipation in both natural and engineered ecosystems. In this article, we provided an overview of sulfonamide biodegradation in different systems and summarized the relevant sulfonamide-degrading species and metabolic pathways. The removal of sulfonamides depends on a variety of factors, such as the type and initial concentration of sulfonamides, the properties of water or soil, and treatment process. The removal efficiency of sulfonamides by engineered ecosystems can be improved by optimizing their operating conditions. Much higher sulfonamide removal was also observed in upgraded or advanced treatment systems than in conventional activated sludge systems. Ammonia oxidation might promote sulfonamide biodegradation. In addition, sulfonamide-degraders from different bacterial genera have been isolated and classified, but no bioaugmentation practice has been reported. Different pathways have been detected in sulfonamide biodegradation. Further efforts will be necessary to elucidate in-situ degraders and the metabolic pathways and functional genes of sulfonamide biodegradation.

Photocatalytic-oxidation and photo-persulfate-oxidation of sulfadiazine in a laboratory-scale reactor: Analysis of catalyst support, oxidant dosage, removal-rate and degradation pathway

The extent of sulfadiazine (SDZ) removal via photo-degradation (UV-C), photocatalysis with TiO₂ (UV-C/TiO₂) and photo-persulfate-oxidation (UV-C/PS) was investigated in a batch reactor under different UV-C power levels (i.e. 14, 28, 42 and 56 W). Moreover, effects of suspended/immobilized catalyst, i.e. TiO₂ slurry/TiO₂ supported on granular activated carbon (GAC-TiO₂), on SDZ removal and corresponding SDZ degradation kinetics under different catalyst loading (1-6 g/L) were explored. Around 41.7% SDZ removal was observed after 120 min in UV-C system at the highest power level, i.e. 56 W. On the other hand, photocatalysis with TiO₂ and GAC-TiO₂ has shown better SDZ removal than photo-degradation. In UV-C/TiO₂ (4 g/L and 28 W) and UV-C/GAC-TiO₂ (5 g/L and 28 W) systems, SDZ removals were 91.8% after 120 min and 100% after 60 min, respectively; however, TOC analysis has revealed that 45.4% and 60.8% SDZ was mineralized in these systems, respectively. In UV-C/PS system, near complete degradation of SDZ (99.8%) was observed within 10 min under 50 mg/L of PS and 28 W UV illumination. On the other hand, complete SDZ removal was observed in PS alone system at a dosage of 1000 mg/L but the formation of SO₄^2- was found to be a drawback. In photolysis and photocatalysis systems, SDZ removal followed pseudo-first-order kinetics whereas the kinetics followed pseudo-second-order in UV-C/PS system. The comparison of electrical energy consumed (E_EO) in different systems revealed that UV-C/GAC-TiO₂ and UV-C/PS system were energy efficient compared with other systems. The LC-MS analysis has confirmed the cleavage of C-N bonds in the pyrimidine ring followed by S-N bonds in the sulfonyl group, which was found to be the major degradation pathway of SDZ.

Improvement of sulfamethoxazole (SMX) elimination and inhibition of formations of hydroxylamine-SMX and N4-acetyl-SMX by membrane bioreactor systems

Sulfamethoxazole (SMX) has frequently been detected in aquatic environments. In natural environment, not only individual microorganism but also microbial consortia are involved in some biotransformation of pollutants. The competition for space under consortia causing cell-cell contact inhibition changes the cellular behaviors. Herein, the membrane bioreactor system (MBRS) was applied to improve SMX elimination thorough exchanging the cell-free broths (CFB). The removal efficiency of SMX was increased by more than 24% whether under the pure culture of A. faecalis or under the co-culture of A. faecalis and P. denitrificans with MBRS. Meanwhile, MBRS significantly inhibited the formation of HA-SMX, and Ac-SMX from parent compound. Additionally, the cellular growth under MBRS was obviously enhanced, indicating that the increases in the cellular growth under MBRS are possibly related to the decreases in the levels of HA-SMX and Ac-SMX compared to that without MBRS. The intracellular NADH/NAD⁺ ratios of A. faecalis under MBRS were increased whether thorough itself-recycle of CFB or exchanging CFB between the pure cultures of A. faecalis and P. denitrificans, suggesting that the enhancement in the bioremoval efficiencies of SMX under MBRS by A. faecalis is likely related to the increases in the NADH/NAD⁺ ratio. Taken together, the regulation of cell-to-cell communication is preferable strategy to improve the bioremoval efficiency of SMX.

Effects of the antioxidant moieties of dissolved organic matter on triplet-sensitized phototransformation processes: Implications for the photochemical modeling of sulfadiazine

Previous studies have shown that the photodegradation of some pollutants, induced by the excited triplet states of chromophoric dissolved organic matter (³CDOM*), can be inhibited by back-reduction processes carried out by phenolic antioxidants occurring in dissolved organic matter (DOM). Here, for the first time to our knowledge, we included such an inhibition effect into a photochemical model and applied the model predictions to sulfadiazine (SDZ), a sulfonamide antibiotic that occurs in surface waters in two forms, neutral HSDZ and anionic SDZ^- (pK_a = 6.5). The input parameters of the photochemical model were obtained by means of dedicated experiments, which showed that the inhibition effect was more marked for SDZ^- than for HSDZ. Compared to the behavior of 2,4,6-trimethylphenol, which does not undergo antioxidant inhibition when irradiated in natural water samples, the back-reduction effect on the degradation of SDZ was proportional to the electron-donating capacity of the DOM. According to the model results, direct photolysis and OH reaction would account for the majority of both HSDZ and SDZ^- photodegradation in waters having low dissolved organic carbon (DOC < 1 mgC L^-1). With higher DOC values (>3-4 mgC L^-1) and despite the back-reduction processes, the ³CDOM* reactions are expected to account for the majority of HSDZ phototransformation. In the case of SDZ^- at high DOC, most of the photodegradation would be accounted for by direct photolysis. The relative importance of the triplet-sensitized phototransformation of both SDZ^- and (most importantly) HSDZ is expected to increase with increasing DOC, even in the presence of back reduction. An increase in water pH, favoring the occurrence of SDZ^- with respect to HSDZ, would enhance direct photolysis at the expense of triplet sensitization. SDZ should be fairly photolabile under summertime sunlight, with predicted half-lives ranging from a few days to a couple of months depending on water conditions.