Heterotrophic enzymatic biotransformations of organic micropollutants in activated sludge

Unveiling transformation processes of cardiovascular pharmaceuticals in wastewater based on nontarget screening

Cardiovascular pharmaceuticals were extensively detected and generally coexist with their transformation products (TPs) in wastewater. However, knowledges on TPs and transformation processes for cardiovascular pharmaceuticals remained largely unclear. To fill this knowledge gap, nontarget screening combined with batch experiments were employed to reveal the transformation of five cardiovascular pharmaceuticals (atenolol, metoprolol, propranolol, bezafibrate and candesartan) in aerobic activated sludge. The removal rate constants per unit of biomass ranged from 0.0105 to 0.0571 L g SS-1 h-1 for five cardiovascular pharmaceuticals. Atenolol and bezafibrate exhibited more excellent removal efficiency (over 99 %) than other three cardiovascular pharmaceuticals. Subsequently, 33 TPs were tentatively identified and 16 of them were not reported in previous studies. Based on identified TPs, transformation pathways of five cardiovascular pharmaceuticals were proposed, which suggested acetylation, ammoniation, carboxylation, dealkylation, decarboxylation, dihydroxylation, demethylation, epoxidation, formylation, hydrogenation, hydrolysis, hydroxylation, methylation and oxidation were involved in the transformation of cardiovascular pharmaceuticals in wastewater. Notably, N- dealkylation at the site of secondary and tertiary amine, acetylation at the site of primary amine and dehydrogenation at the site of linear alkyl were summarized as the specific transformation patterns across different cardiovascular pharmaceuticals. Furthermore, the predicted results suggested that about 30 % TPs have higher persistence and bioaccumulation than parent compounds while about 40 % TPs harbored higher toxicity than parent compounds of cardiovascular pharmaceuticals. Collectively, this study unveiled the fate and transformation pathways of five cardiovascular pharmaceuticals and summarized the specific transformation patterns for them in aerobic activated sludge, which is theoretically useful to effectively remove pharmaceuticals from wastewater.

Aerobic biodegradation of micropollutants by nitrifiers and heterotrophs: Changes in biodegradation rate constant depending on levels of growth substrates and microbial activities

This study investigated how the biodegradation rate constant (kbio) of 11 micropollutants (MPs) responded to changes in the concentrations of growth substrates and microbial activities while considering the predominant microbial degraders of MPs. Metformin, losartan, valsartan, and cimetidine (group A) were biodegraded predominantly by nitrifiers. MPs of group A showed a positive correlation with kbio and nitrifying activity, while a negative correlation was observed with the initial concentration of ammonium, possibly due to competitive inhibition. Atenolol, caffeine, and naproxen (group B) were biodegraded predominantly by heterotrophs, with kbio remaining stable despite changes in organic matter concentration or heterotrophic activity. Olmesartan, candesartan, diclofenac, and sulfamethoxazole (group C) showed low kbio regardless of growth substrate concentration and microbial activity, which could be attributed to their chemical structures. These findings suggest that the kbio of MPs in WWTPs could respond differently to growth substrate concentration and microbial activity depending on their predominant degraders.

Revealing the underestimated risks of pharmaceutical transformation products in wastewater by suspect and targeted screening

Transformation products (TPs) of pharmaceuticals have raised great concerns due to the extensive detection and potentially higher concentration and toxicity than parents. However, the related knowledge on TPs of pharmaceuticals in wastewater were limited. To fill this gap, suspect screening workflow was developed to identify TPs from 28 pharmaceuticals in 12 wastewater treatment plants (WWTPs) located in Yangtze River Delta region of China. Based on the developed suspect lists included structural information and predicted retention time for 1643 TPs, 67 TPs were successfully identified at confidence levels of ≥3 and 61.12 % of them originated from non-steroidal anti-inflammatory drugs. Subsequently, target screening revealed that 4‑hydroxy-diclofenac, diclofenac-benzoic acid, N-demethylation tramadol, 10,11-dihydro-10-dihydroxycarbamazepine and 10,11-dihydro-10,11-epoxycarbamazepine exhibited high concentration up to μg/L in WWTPs. Comparatively, the cumulative concentration of TPs was higher than parents of pharmaceuticals in effluent of WWTPs. In addition, the predicted results revealed that 29.85 %, 82.09 % and 19.91 % TPs have higher toxicity, persistence and bioaccumulation than parents. Furthermore, diclofenac-benzoic acid and 10,11-dihydro-10,11-epoxycarbamazepine exhibited higher eco-risks than their corresponding parents and N-demethylation tramadol was found to be with moderated eco-risks in effluent of WWTRPs. Collectively, the present study provides holistic information on TPs for 28 pharmaceuticals in wastewater and highlights the importance for TPs of pharmaceuticals in WWTPs from the aspect of concentration, toxicity and eco-risks. In the future, not only parents, but also TPs of pharmaceuticals should be effectively managed and attenuated in wastewater.

Biotic and abiotic removal of acetaminophen during sidestream partial nitritation processes: Underlying mechanisms and transformation pathways

Pharmaceutical residues in sidestream wastewater pose the hazardous threats to ecosystem and human health. In this work, the biotic and abiotic degradation of acetaminophen were investigated during the sidestream partial nitritation process. Results demonstrated that the abiotic removal efficiency of acetaminophen was positively correlated with nitrite concentration, whereas the biotransformation of acetaminophen was mainly dependent on metabolic types and free nitrous acid (FNA) concentrations. 91.6 % of acetaminophen, acting as the sole carbon and/or energy source to support the growth of ammonia-oxidizing bacteria (AOB) and heterotrophs, was removed by adsorption (6.2 %) and biotransformation (consisting of 49.4 % AOB-induced metabolism and 36.0 % heterotrophs-induced metabolism) when lacking nitrite and FNA. Increasing FNA from 0.03 mg N L-1 to 0.15 mg L-1 led to decrease in acetaminophen removal (from 78.8 % to 60.1 %) and ammonia oxidation, ascribed to the inhibitory effect of FNA on AOB activity. Nitro substitution occurred under AOB-induced cometabolism, while hydroxylation was conducted by heterotrophs. N-deacetylation, ring cleavage, hydroxylation, nitro-reduction, and deamination at lower FNA levels (0.03 mg N L-1) contributed to the formation of small molecular products, supporting the feasibility of sidestream partial nitritation in the effective elimination of acetaminophen. This work provides strategies for optimizing anti-inflammatory drugs removal via the regulation of FNA in the sidestream wastewater treatment process.

Broad Microbial Community Functions in a Conventional Activated Sludge System Exhibit Temporal Stability

Wastewater microbial communities within conventional activated sludge (CAS) systems can perform hundreds of biotransformations whose relative importance, frequency, and temporal stability remain largely unexplored. To improve our understanding of biotransformations in CAS systems, we collected 24 h composite samples from the influent and effluent of a CAS system over 14 days, analyzed samples using high-resolution mass spectrometry (HRMS), and conducted a nontarget analysis of our HRMS acquisitions. We found that over 50% of the chemical features in the influent were completely removed, and the daily number of detected features exhibited low variability with a coefficient of variation of 0.07. Additionally, we found 352 Core chemical features present in every sample at both locations. We used chemical features to search for evidence of 19 potential biotransformations and detected 9 of these biotransformations at a frequency of over 80 times per day, where evidence for dehydrogenations, hydroxylations, and acetylations was most frequently detected. The daily number of detections for the 9 biotransformations exhibited coefficients of variation ranging from 0.13-0.20, revealing the broad temporal stability for these wastewater microbial community functions. This stability contrasts with the previously observed temporal variability for micropollutant biotransformations, suggesting that micropollutant biotransformations are linked to specialized microbial community functions.

Biotransformation pathways of pharmaceuticals and personal care products (PPCPs) during acidogenesis and methanogenesis of anaerobic digestion

Pharmaceuticals and personal care products (PPCPs) exhibit varying biodegradability during the acidogenic and methanogenic phases of anaerobic digestion. However, there is limited information regarding the end products generated during these processes. This work investigates the biotransformation products (BTPs) generated in a two-phase (TP) acidogenic-methanogenic (Ac-Mt) bioreactor using advanced suspect and nontarget strategies. Fourteen BTPs were confidently identified from ten parent PPCPs including carbamazepine (CBZ), naproxen (NPX), diclofenac (DCF), ibuprofen (IBU), acetaminophen (ACT), metoprolol (MTP), sulfamethoxazole (SMX), ciprofloxacin (CIP), methylparaben (MPB) and propylparaben (PPB). These BTPs were linked with oxidation reactions such as hydroxylation, demethylation and epoxidation. Their generation was related to organic acid production, since all metabolites were detected during acidogenesis, with some being subsequently consumed during methanogenesis, e.g., aminothiophenol and kynurenic acid. Another group of BTPs showed increased concentrations under methanogenic conditions, e.g., hydroxy-diclofenac and epoxy-carbamazepine. The most PPCPs showed high removal efficiencies (> 90 %) - SMX, CIP, NPX, MTP, ACT, MPB, PPB, while DCF, CBZ and IBU demonstrated higher persistence - DCF (42 %); CBZ (40 %), IBU (47 %). The phase separation of anaerobic digestion provided a deeper understanding of the biotransformation pathways of PPCPs, in addition to enhancing the biodegradability of the most persistent compounds, i.e., DCF, CBZ and IBU.

Exploring long-term retention and reactivation of micropollutant biodegradation capacity

The factors limiting micropollutant biodegradation in the environment and how to stimulate this process have often been investigated. However, little information is available on the capacity of microbial communities to retain micropollutant biodegradation capacity in the absence of micropollutants or to reactivate micropollutant biodegradation in systems with fluctuating micropollutant concentrations. This study investigated how a period of 2 months without the addition of micropollutants and other organic carbon affected micropollutant biodegradation by a micropollutant-degrading microbial community. Stimulation of micropollutant biodegradation was performed by adding different types of dissolved organic carbon (DOC)-extracted from natural sources and acetate-increasing 10 × the micropollutant concentration, and inoculating with activated sludge. The results show that the capacity to biodegrade 3 micropollutants was permanently lost. However, the biodegradation activity of 2,4-D, antipyrine, chloridazon, and its metabolites restarted when these micropollutants were re-added to the community. Threshold concentrations similar to those obtained before the period of no substrate addition were achieved, but biodegradation rates were lower for some compounds. Through the addition of high acetate concentrations (108 mg-C/L), gabapentin biodegradation activity was regained, but 2,4-D biodegradation capacity was lost. An increase of bentazon concentration from 50 to 500 µg/L was necessary for biodegradation to be reactivated. These results provide initial insights into the longevity of micropollutant biodegradation capacity in the absence of the substance and strategies for reactivating micropollutant biodegrading communities.

Enzymatic and non-enzymatic removal of organic micropollutants with spent mushroom substrate of Agaricus bisporus

Water bodies are increasingly contaminated with a diversity of organic micropollutants (OMPs). This impacts the quality of ecosystems due to their recalcitrant nature. In this study, we assessed the removal of OMPs by spent mushroom substrate (SMS) of the white button mushroom (Agaricus bisporus) and by its aqueous tea extract. Removal of acesulfame K, antipyrine, bentazon, caffeine, carbamazepine, chloridazon, clofibric acid, and N, N-diethyl-meta-toluamide (DEET) by SMS and its tea was between 10 and 90% and 0-26%, respectively, in a 7-day period. Sorption to SMS particles was between 0 and 29%, which can thus not explain the removal difference between SMS and its tea, the latter lacking these particles. Carbamazepine was removed most efficiently by both SMS and its tea. Removal of OMPs (except caffeine) by SMS tea was not affected by heat treatment. By contrast, heat-treatment of SMS reduced OMP removal to < 10% except for carbamazepine with a removal of 90%. These results indicate that OMP removal by SMS and its tea is mediated by both enzymatic and non-enzymatic activities. The presence of copper, manganese, and iron (0.03, 0.88, and 0.33 µg L-1, respectively) as well as H2O2 (1.5 µM) in SMS tea indicated that the Fenton reaction represents (part of) the non-enzymatic activity. Indeed, the in vitro reconstituted Fenton reaction removed OMPs > 50% better than the teas. From these data it is concluded that spent mushroom substrate of the white button mushroom, which is widely available as a waste-stream, can be used to purify water from OMPs.

Transformation process and phytotoxicity of sulfamethoxazole and N4-acetyl-sulfamethoxazole in rice

Sulfonamide antibiotics, extensively used in human and veterinary therapy, accumulate in agroecosystem soils through livestock manure and sewage irrigation. However, the interaction between sulfonamides and rice plants remains unclear. This study investigated the transformation behavior and toxicity of sulfamethoxazole (SMX) and its main metabolite, N4-acetyl-sulfamethoxazole (NASMX) in rice. SMX and NASMX were rapidly taken up by roots and translocated acropetally. NASMX showed higher accumulating capacity, with NASMX concentrations up to 20.36 ± 1.98 μg/g (roots) and 5.62 ± 1.17 μg/g (shoots), and with SMX concentrations up to 15.97 ± 2.53 μg/g (roots) and 3.22 ± 0.789 μg/g (shoots). A total of 18 intermediate transformation products of SMX were identified by nontarget screening using Orbitrap-HRMS, revealing pathways such as deamination, hydroxylation, acetylation, formylation, and glycosylation. Notably, NASMX transformed back into SMX in rice, a novel finding. Transcriptomic analysis highlights the involvements of cytochrome P450 (CYP450), acetyltransferase (ACEs) and glycosyltransferases (GTs) in these biotransformation pathways. Moreover, exposure to SMX and NASMX disrupts TCA cycle, amino acid, linoleic acid, nucleotide metabolism, and phenylpropanoid biosynthesis pathways of rice, with NASMX exerting a stronger impact on metabolic networks. These findings elucidate the sulfonamides' metabolism, phytotoxicity mechanisms, and contribute to assessing food safety and human exposure risk amid antibiotic pollution.

A comprehensive insight into the transformation pathways and products of fluoxetine and venlafaxine in wastewater based on molecular networking nontarget screening

Fluoxetine (FLX) and venlafaxine (VEN) are widely used antidepressant pharmaceuticals and were frequently detected in wastewater. Despite incomplete mineralization during biological wastewater treatment processes has been revealed, little is known about their transformation products (TPs) formed in the biological systems. To fill this gap, batch reactors and molecular networking nontarget screening were employed to identify the TPs and explore the transformation pathways of FLX and VEN in wastewater. On the basis, the concentrations of the TPs in wastewater treatment plants (WWTPs) were determined and their toxicity was predicted. The removal rate constants per unit of biomass of FLX and VEN were up to 0.3192 and 0.1644 L/(gMLSS*d) in batch experiments, respectively. Subsequently, 11 TPs of VEN and 11 TPs of FLX were tentatively identified, among which 9 TPs of FLX and 5 TPs of VEN were newly reported in this study. The proposed transformation pathways provided new insights into the transformation reactions including dehydrogenation, N-formylation and hydroxylation for FLX, and formylation, epoxidation and methylation for VEN. Particularly, N-succinylation and demethylation were the dominant transformation pathways for FLX and VEN during transformation processes. The results of sampling campaigns revealed that the accumulated concentration of TPs were higher than the concentrations of VEN in effluent of WWTPs. In silico prediction results suggested that certain TPs have higher toxicity, persistence and biodegradability than their corresponding parent compounds of FLX and VEN. In addition, VEN-TP264(a) showed higher ecological risks than VEN. This study revealed the transformation processes and fate of FLX and VEN in wastewater, indicating that greater concerns should be exerted on the toxicity detection and control of the TPs of FLX and VEN in the treated wastewater.

Optimizing ciprofloxacin removal through regulations of trophic modes and FNA levels in a moving bed biofilm reactor performing sidestream partial nitritation

The performance of partial nitritation (PN)-moving bed biofilm reactor (MBBR) in removal of antibiotics in the sidestream wastewater has not been investigated so far. In this work, the removal of ciprofloxacin was assessed under varying free nitrous acid (FNA) levels and different trophic modes. For the first time, a positive correlation was observed between ciprofloxacin removal and FNA levels, either in the autotrophic PN-MBBR or in the mixotrophic PN-MBBR, mainly ascribed to the FNA-stimulating effect on heterotrophic bacteria (HB)-induced biodegradation. The maximum ciprofloxacin removal efficiency (∼98 %) and removal rate constant (0.021 L g-1 SS h-1) were obtained in the mixotrophic PN-MBBR at an average FNA level of 0.056 mg-N L-1, which were 5.8 and 51.2 times higher than the corresponding values in the autotrophic PN-MBBR at 0 mg FNA-N L-1. Increasing FNA from 0.006 to 0.056 mg-N L-1 would inhibit ammonia oxidizing bacteria (AOB)-induced cometabolism and metabolism from 10.2 % and 6.9 % to 6.2 % and 6.4 %, respectively, while HB-induced cometabolism and metabolism increased from 31.2 % and 22.7 % to 41.9 % and 34.5 %, respectively. HB-induced cometabolism became the predominant biodegradation pathway (75.9 %-85.8 %) in the mixotrophic mode. Less antimicrobial biotransformation products without the piperazine or fluorine were newly identified to propose potential degradation pathways, corresponding to microbial-induced metabolic types and FNA levels. This work shed light on enhancing antibiotic removal via regulating both FNA accumulation and organic carbon addition in the PN-MBBR process treating sidestream wastewater.

Influence of redox condition and inoculum on micropollutant biodegradation by soil and activated sludge communities

Micropollutant biodegradation is selected by the interplay among environmental conditions and microbial community composition. This study investigated how different electron acceptors, and different inocula with varying microbial diversity, pre-exposed to distinct redox conditions and micropollutants, affect micropollutant biodegradation. Four tested inocula comprised of agricultural soil (Soil), sediment from a ditch in an agricultural field (Ditch), activated sludge from a municipal WWTP (Mun AS), and activated sludge from an industrial WWTP (Ind AS). Removal of 16 micropollutants was investigated for each inoculum under aerobic, nitrate reducing, iron reducing, sulfate reducing, and methanogenic conditions. Micropollutant biodegradation was highest under aerobic conditions with removal of 12 micropollutants. Most micropollutants were biodegraded by Soil (n = 11) and Mun AS inocula (n = 10). A positive correlation was observed between inoculum community richness and the number of different micropollutants a microbial community initially degraded. The redox conditions to which a microbial community had been exposed appeared to positively affect micropollutant biodegradation performance more than pre-exposure to micropollutants. Additionally, depletion of the organic carbon present in the inocula resulted in lower micropollutant biodegradation and overall microbial activities, suggesting that i) an additional carbon source is needed to promote micropollutant biodegradation; and ii) overall microbial activity can be a good indirect indicator for micropollutant biodegradation activity. These results could help to develop novel micropollutant removal strategies.

Methanotrophic oxidation of organic micropollutants and nitrogen upcycling in a hybrid membrane biofilm reactor (hMBfR) for simultaneous O2 and CH4 supply

Pharmaceuticals and other organic micropollutants (OMPs) present in wastewater effluents are of growing concern, as they threaten environmental and human health. Conventional biological treatments lead to limited removal of OMPs. Methanotrophic bacteria can degrade a variety of OMPs. By employing a novel bubble-free hybrid membrane biofilm bioreactor (hMBfR), we grew methanotrophic bacteria at three CH4 loading rates. Biomass productivity and CH4 loading showed a linear correlation, with a maximum productivity of 372 mg-VSS·L-1·d-1, with corresponding biomass concentration of 1117.6 ± 56.4 mg-VSS·L-1. Furthermore, the biodegradation of sulfamethoxazole and 1H-benzotriazole positively correlated with CH4 oxidation rates, with highest biodegradation kinetic constants of 3.58 L·g-1·d-1 and 5.42 L·g-1·d-1, respectively. Additionally, the hMBfR recovered nutrients as microbial proteins, with an average content 39% DW. The biofilm community was dominated by Methylomonas, while the bulk was dominated by aerobic heterotrophic bacteria. The hMBfR removed OMPs, allowing for safer water reuse while valorising CH4 and nutrients.

Revealing specific transformation pattern of sulfonamides during wastewater biological treatment processes by molecular networking nontarget screening

Biotransformation of emerging contaminants (ECs) is of importance in various natural and engineered systems to eliminate the adverse effects of ECs toward organisms. In wastewater, structurally similar ECs may transform through similar reactions triggered by common enzymes. However, the transformation pattern for them was scarcely studied. To fill the research gaps, five sulfonamides were chosen as the targeted ECs with similar structure to explore the transformation pattern in wastewater biological treatment experiments at lab scale. Through molecular networking based nontarget screening, 45 transformation products (TPs) of sulfonamides were identified and 14 of them were newly found. On the basis, five specific transformation patterns were summarized for sulfonamides by transformation pathways comparing, reaction frequency analyzing and dominant TPs comparing. Results suggested that pterin-chelation and formylation (dominant transformation pathway) and acetylation, methylation and deamination reactions were commonly occurred for sulfonamides in wastewater. Among them, the role of formylation as the dominant transformation pathway for sulfonamides transformed in wastewater was firstly reported in present study. Subsequent frontier molecular orbital calculation suggested the active site of amino (N₁H₂-) may contribute the specific transformation pattern of sulfonamides. Present study reveals the specific transformation pattern of sulfonamides from the aspect of TPs and transformation pathways. In the future, knowledge on the specific transformation pattern can be used to regulate and enhance the removal of a class of ECs with similar structure rather than just one of ECs.

Predicting and improving the microbial removal of organic micropollutants during wastewater treatment: A review

Organic micropollutants (OMPs) consist of widely used chemicals such as pharmaceuticals and pesticides that can persist in surface and groundwaters at low concentrations (ng/L to μg/L) for a long time. The presence of OMPs in water can disrupt aquatic ecosystems and threaten the quality of drinking water sources. Wastewater treatment plants (WWTPs) rely on microorganisms to remove major nutrients from water, but their effectiveness at removing OMPs varies. Low removal efficiency might be the result of low concentrations, inherent stable chemical structures of OMPs, or suboptimal conditions in WWTPs. In this review, we discuss these factors, with special emphasis on the ongoing adaptation of microorganisms to degrade OMPs. Finally, recommendations are drawn to improve the prediction of OMP removal in WWTPs and to optimize the design of new microbial treatment strategies. OMP removal seems to be concentration-, compound-, and process-dependent, which poses a great complexity to develop accurate prediction models and effective microbial processes targeting all OMPs.

Methane-Oxidizing Activity Enhances Sulfamethoxazole Biotransformation in a Benthic Constructed Wetland Biomat

Ammonia monooxygenase and analogous oxygenase enzymes contribute to pharmaceutical biotransformation in activated sludge. In this study, we hypothesized that methane monooxygenase can enhance pharmaceutical biotransformation within the benthic, diffuse periphytic sediments (i.e., "biomat") of a shallow, open-water constructed wetland. To test this hypothesis, we combined field-scale metatranscriptomics, porewater geochemistry, and methane gas fluxes to inform microcosms targeting methane monooxygenase activity and its potential role in pharmaceutical biotransformation. In the field, sulfamethoxazole concentrations decreased within surficial biomat layers where genes encoding for the particulate methane monooxygenase (pMMO) were transcribed by a novel methanotroph classified as Methylotetracoccus. Inhibition microcosms provided independent confirmation that methane oxidation was mediated by the pMMO. In these same incubations, sulfamethoxazole biotransformation was stimulated proportional to aerobic methane-oxidizing activity and exhibited negligible removal in the absence of methane, in the presence of methane and pMMO inhibitors, and under anoxia. Nitrate reduction was similarly enhanced under aerobic methane-oxidizing conditions with rates several times faster than for canonical denitrification. Collectively, our results provide convergent in situ and laboratory evidence that methane-oxidizing activity can enhance sulfamethoxazole biotransformation, with possible implications for the combined removal of nitrogen and trace organic contaminants in wetland sediments.

Pharmaceutical Biotransformation is Influenced by Photosynthesis and Microbial Nitrogen Cycling in a Benthic Wetland Biomat

In shallow, open-water engineered wetlands, design parameters select for a photosynthetic microbial biomat capable of robust pharmaceutical biotransformation, yet the contributions of specific microbial processes remain unclear. Here, we combined genome-resolved metatranscriptomics and oxygen profiling of a field-scale biomat to inform laboratory inhibition microcosms amended with a suite of pharmaceuticals. Our analyses revealed a dynamic surficial layer harboring oxic-anoxic cycling and simultaneous photosynthetic, nitrifying, and denitrifying microbial transcription spanning nine bacterial phyla, with unbinned eukaryotic scaffolds suggesting a dominance of diatoms. In the laboratory, photosynthesis, nitrification, and denitrification were broadly decoupled by incubating oxic and anoxic microcosms in the presence and absence of light and nitrogen cycling enzyme inhibitors. Through combining microcosm inhibition data with field-scale metagenomics, we inferred microbial clades responsible for biotransformation associated with membrane-bound nitrate reductase activity (emtricitabine, trimethoprim, and atenolol), nitrous oxide reduction (trimethoprim), ammonium oxidation (trimethoprim and emtricitabine), and photosynthesis (metoprolol). Monitoring of transformation products of atenolol and emtricitabine confirmed that inhibition was specific to biotransformation and highlighted the value of oscillating redox environments for the further transformation of atenolol acid. Our findings shed light on microbial processes contributing to pharmaceutical biotransformation in open-water wetlands with implications for similar nature-based treatment systems.

Key enzymes involved in anammox-based processes for wastewater treatment: An applied overview

The anaerobic ammonium oxidation (anammox) process has attracted significant attention as an economic, robustness, and sustainable method for the treatment of nitrogen (N)-rich wastewater. Anammox bacteria (AnAOB) coexist with other microorganisms, and particularly with ammonia-oxidizing bacteria (AOB) and/or heterotrophic bacteria (HB), in symbiosis in favor of the substrate requirement (ammonium and nitrite) of the AnAOB being supplied by these other organisms. The dynamics of these microbial communities have a significant effect on the N-removal performance, but the corresponding metabolic pathways are still not fully understood. These processes involve many common metabolites that may act as key factors to control the symbiotic interactions between these organisms, to maximize N-removal efficiency from wastewater. Therefore, this work overviews the current state of knowledge about the metabolism of these microorganisms including key enzymes and intermediate metabolites and summarizes already reported experiences based on the employment of certain metabolites for the improvement of N-removal using anammox-based processes. PRACTITIONER POINTS: Approaches knowledge about the biochemistry and metabolic pathways involved in anammox-based processes. Some molecular tools can be used to determine enzymatic activity, serving as an optimization in nitrogen removal processes. Enzymatic evaluation allied to the physical-chemical and biomolecular analysis of the nitrogen removal processes expands the application in different effluents.

Identifying Functional Groups that Determine Rates of Micropollutant Biotransformations Performed by Wastewater Microbial Communities

The goal of this research was to identify functional groups that determine rates of micropollutant (MP) biotransformations performed by wastewater microbial communities. To meet this goal, we performed a series of incubation experiments seeded with four independent wastewater microbial communities and spiked them with a mixture of 40 structurally diverse MPs. We collected samples over time and used high-resolution mass spectrometry to estimate biotransformation rate constants for each MP in each experiment and to propose structures of 46 biotransformation products. We then developed random forest models to classify the biotransformation rate constants based on the presence of specific functional groups or observed biotransformations. We extracted classification importance metrics from each random forest model and compared them across wastewater microbial communities. Our analysis revealed 30 functional groups that we define as either biotransformation promoters, biotransformation inhibitors, structural features that can be biotransformed based on uncharacterized features of the wastewater microbial community, or structural features that are not rate-determining. Our experimental data and analysis provide novel insights into MP biotransformations that can be used to more accurately predict MP biotransformations or to inform the design of new chemical products that may be more readily biodegradable during wastewater treatment.

Enzymatic cometabolic biotransformation of organic micropollutants in wastewater treatment plants: A review

Biotransformation of trace-level organic micropollutants (OMPs) by complex microbial communities in wastewater treatment facilities is a key process for their detoxification and environmental impact reduction. Therefore, understanding the metabolic activities and mechanisms that contribute to their biotransformation is essential when developing approaches aiming to minimize their discharge. This review addresses the relevance of cometabolic processes and discusses the main enzymatic activities currently known to take part in OMPs removal under different redox environments in the compartments of wastewater treatment plants. Furthermore, the most common methodologies to decipher such enzymes are discussed, including the use of in vitro enzyme assays, enzymatic inhibitors, the analysis of transformation products and the application of several -omic techniques. Finally, perspectives on major challenges and future research requirements to improve OMPs biotransformation are proposed.

Why Is the Biodegradation of Polyfluorinated Compounds So Rare?

Thousands of heavily fluorinated chemicals are found in the environment, impact human and ecosystem health, and are relatively resistant to biological and chemical degradation. Their persistence in the environment is due to the inability of most microorganisms to biodegrade them. Only a very few examples of polyfluorinated compound biodegradation are known, and the reported rates are very low. This has been mostly attributed to the low chemical reactivity of the C-F bond. This Perspective goes beyond that explanation to highlight microbiological reasons why polyfluorinated compounds resist metabolism. The evolutionary and physiological impediments must be appreciated to better find, study, and harness microbes that degrade polyfluorinated compounds.