Bacterial community composition and function succession under aerobic and anaerobic conditions impacts the biodegradation of 17β-estradiol and its environmental risk

Deciphering the core bacterial community structure and function and their response to environmental factors in activated sludge from pharmaceutical wastewater treatment plants

Pharmaceutical wastewater is recognized for its heightened concentrations of organic pollutants, and biological treatment stands out as an effective technology to remove these organic pollution. Therefore, a comprehensive exploration of core bacterial community compositions, functions, and their responses to environmental factors in pharmaceutical wastewater treatment plants (PWWTPs) is important for understanding the removal mechanism of these organic pollutants. This study comprehensively investigated 36 activated sludge (AS) samples from 15 PWWTPs in China. The results revealed that Proteobacteria (45.41%) was the dominant phylum in AS samples, followed by Bacteroidetes (19.54%) and Chloroflexi (4.13%). While the dominant genera were similar in both aerobic and anaerobic treatment processes, their relative abundances exhibited significant variations. Genera like HA73, Kosmotoga, and Desulfovibrio were more abundant during anaerobic treatment, while Rhodoplanes, Bdellovibrio, and Hyphomicrobium dominated during aerobic treatment. 13 and 10 core operational taxonomic units (OTUs) were identified in aerobic and anaerobic sludge, respectively. Further analysis revealed that core OTUs belonging to genera Kosmotoga, Desulfovibrio, Thauera, Hyphomicrobium, and Chelativorans, were associated with key functions, including sulfur metabolism, methane metabolism, amino acid metabolism, carbohydrate metabolism, toluene degradation, and nitrogen metabolism. Furthermore, this study highlighted the crucial roles of environmental factors, such as COD, NH4+-N, SO42-, and TP, in shaping both the structure and core functions of bacterial communities within AS of PWWTPs. Notably, these factors indirectly affect functional attributes by modulating the bacterial community composition and structure in pharmaceutical wastewater. These findings provide valuable insights for optimizing the efficiency of biochemical treatment processes in PWWTPs.

Advances in identifying and managing emerging contaminants in aquatic ecosystems: Analytical approaches, toxicity assessment, transformation pathways, environmental fate, and remediation strategies

Emerging contaminants (ECs) are increasingly recognized as threats to human health and ecosystems. This review evaluates advanced analytical methods, particularly mass spectrometry, for detecting ECs and understanding their toxicity, transformation pathways, and environmental distribution. Our findings underscore the reliability of current techniques and the potential of upcoming methods. The adverse effects of ECs on aquatic life necessitate both in vitro and in vivo toxicity assessments. Evaluating the distribution and degradation of ECs reveals that they undergo physical, chemical, and biological transformations. Remediation strategies such as advanced oxidation, adsorption, and membrane bioreactors effectively treat EC-contaminated waters, with combinations of these techniques showing the highest efficacy. To minimize the impact of ECs, a proactive approach involving monitoring, regulations, and public education is vital. Future research should prioritize the refining of detection methods and formulation of robust policies for EC management.

Free and conjugated forms of metabolites are indispensable components of steroids: The first evidence from an estuarine food web

Steroids have attracted particular attention as environmental contaminants because of their severe endocrine-disrupting effects. Previous studies have predominantly focused on parent steroids; however, the levels and proportions of the free and conjugated forms of their metabolites remain largely unclear, especially in food webs. Here, we first characterized the free and conjugated forms of parent steroids and their metabolites in 26 species in an estuarine food web. The steroids were dominated by their metabolites in water samples, whereas parent compounds were predominant in sediment samples. The total mean steroid concentrations in the biota samples that underwent non-enzymatic hydrolysis decreased in the following order: crabs (27 ng/g) > fish (5.9 ng/g) > snails (3.4 ng/g) > shrimps and sea cucumbers (1.2 ng/g); and those in the biota samples that underwent enzymatic hydrolysis decreased in the following order: crabs (57 ng/g) > snails (9.2 ng/g) > fish (7.9 ng/g) > shrimps and sea cucumbers (3.5 ng/g). The proportion of metabolites in the enzymatic hydrolysis biota samples was higher (38-79%) than that (2.9-65%) in non-enzymatic ones, indicating that the free and conjugated forms of metabolites in aquatic organisms were not negligible. Most synthetic steroids were either bioaccumulative or highly bioaccumulative. Importantly, in the invertebrate food web, 17α-methyltestosterone was biomagnified, while 17β-boldenone underwent trophic dilution. Although the estuarine water had a median ecological risk level, the health risks via aquatic product consumption were very low. This study provides novel insights into the composition and trophic transfer of steroids in an estuarine food web for the first time and highlights that free and conjugated metabolites should receive more attention, particularly in biota samples.

Sustained-release nitrate combined with microbial fuel cell: A novel strategy for PAHs and odor removal from sediment

Nitrate addition is a biostimulation technique that can improve both the oxidation of acid volatile sulfide (AVS) through autotrophic denitrification and the biodegradation of polycyclic aromatic hydrocarbons (PAHs) via heterotrophic denitrification. However, during the remediation, parts of the dissolved nitrate in the sediment migrates from the sediment to the overlying water, leading to the loss of effective electron acceptor. To overcome this limitation, a combined approached was proposed, which involved nitrocellulose addition and a microbial fuel cell (MFC). Results indicated the nitrate could be slowly released and maintained at a higher concentration over long term. In the combined system, the removal efficiencies of PAHs and AVS were 71.56% and 89.76%, respectively. Furthermore, the voltage attained for the MFC-nitrocellulose treatment was maintained at 146.1 mV on Day 70, which was 5.37 times higher than that of the MFC-calcium nitrate treatment. Sediments with nitrocellulose resulted in lower levels of nitrate and ammonium in the overlying water. Metagenomic results revealed that the combined technology improved the expression of nitrogen-cycling genes. The introduction of MFC inhibited sulfide regeneration during incubation by suppressing the enzyme activity like EC4.4.1.2. The enhanced biostimulation provided potential for in-situ bioremediation utilizing MFC coupled with slow-released nitrate (i.e., nitrocellulose) treatment.

Mechanism of 17β-estradiol degradation by Rhodococcus equi via the 4,5-seco pathway and its key genes

Steroid estrogens have been detected in oceans, rivers, lakes, groundwaters, soils, and even urban water supply systems, thereby inevitably imposing serious impacts on human health and ecological safety. Indeed, many estrogen-degrading bacterial strains and degradation pathways have been reported, with the 4,5-seco pathway being particularly important. However, few studies have evaluated the use of the 4,5-seco pathway by actinomycetes to degrade 17β-estradiol (E2). In this study, 5 genes involved in E2 degradation were identified in the Rhodococcus equi DSSKP-R-001 (R-001) genome and then heterologously expressed to confirm their functions. The transformation of E2 with hsd17b14 reached 63.7% within 30 h, resulting in transformation into estrone (E1). Furthermore, we found that At1g12200-encoded flavin-binding monooxygenase (FMO_At1g12200) can transform E1 at a rate of 51.6% within 30 h and can transform E1 into 4-hydroxyestrone (4-OH E1). In addition, catA and hsaC genes were identified to further transform 4-OH E1 at a rate of 97-99%, and this reaction was accomplished by C-C cleavage at the C4 position of the A ring of 4-OH E1. This study represents the first report on the roles of these genes in estrogen degradation and provides new insights into the mechanisms of microbial estrogen metabolism and a better understanding of E2 degradation via the 4,5-seco pathway by actinomycetes.

Fate and removal of emerging contaminants in anaerobic fluidized membrane bioreactor filled with thermoplastic gel as biofilm support

The Anaerobic Fluidized Membrane Bioreactor (AnFMBR) is a membrane-based hybrid technology that can overcome the limitations of conventional anaerobic sewage treatment. Although previous studies have demonstrated excellent performance in the removal of conventional organic pollutants, further research into the removal paths of emerging contaminants (ECs) under various operating conditions is required for proper design and development of the AnFMBR technology. Regarding this, the fate of four ECs in a lab-scale AnFMBR filled with thermoplastic gel for biofilm growth was investigated under various Hydraulic Retention Time (HRT) conditions. When the HRT was 13 h, diclofenac and 17β-estradiol were efficiently removed at 93% and 72% respectively. Even after an HRT reduction to 6.5 h, the system was still able to maintain high ECs removals (74% for diclofenac and 69% for 17β-estradiol). However, irrespective of HRT operational condition, smaller removals of 17a-ethinylestradiol (37-52%) were observed, while only marginal removals of amoxicillin were achieved (5-29%). Biotransformation was attributed as the main route for ECs removal. The results obtained in this study indicate that the membrane-based hybrid AnFMBR can be used to treat the target ECs without influence on anaerobic process. The technology had better removal efficiency for diclofenac and 17β-estradiol. However, the AnFMBR system exhibits high variability in EC removal and low capacity for amoxicillin removal, implying that a combination of other processes is still required to properly avoid the release of these contaminants into the environment.

Bioaugmented removal of 17β-estradiol, nitrate and Mn(II) by polypyrrole@corn cob immobilized bioreactor: Performance optimization, mechanism, and microbial community response

The coexistence of nitrate and endocrine substances (EDCs) in groundwater is of global concern. Herein, an efficient and stable polypyrrole@corn cob (PPy@Corn cob) bioreactor immobilized with Zoogloea sp. was designed for the simultaneous removal of 17β-estradiol (E2), nitrate and Mn(II). After 225 days of continuous operation, the optimal operating parameters and enhanced removal mechanism were explored, also the long-term toxicity and microbial communities response mechanisms under E2 stress were comprehensively evaluated. The results showed that the removal efficiencies of E2, nitrate, and Mn(II) were 84.21, 82.96, and 47.91%, respectively, at the optimal operating conditions with hydraulic retention time (HRT) of 8 h, pH of 6.5 and Mn(II) concentration of 20 mg L^-1. Further increased of initial E2 (2 and 3 mg L^-1) resulted in the inhibiting effect of denitrification and manganese oxidation, but excellent E2 removal efficiencies maintained, which were associated with the formation and continuous accumulation of biomanganese oxides (BMO). Characterization analysis of biological precipitation demonstrated that adsorption and redox conversion on the BMO surface played key roles in the removal of E2. In addition, different levels of E2 exposure are decisive factors in community evolution, and bioaugmented bacterial communities with Zoogloea as the core group can dynamically adapt to E2 stress. This study offers the possibility to better utilize microbial metabolism and to advance opportunities that depend on microbial physiology and material characterization applications.

Microbial processing of autochthonous organic matter controls the biodegradation of 17α-ethinylestradiol in lake sediments under anoxic conditions

The decay of algal biomass and aquatic plants in freshwater lakes leads to the overproduction of autochthonous organic matter (OM) and the exhaustion of dissolved oxygen, impacting the microbial community and subsequent biodegradation of emerging contaminants in sediment. This study explored how the microbial processing of aquatic plant- and algal-derived OM (POM and AOM) mediates 17α-ethinylestradiol (EE2) biodegradation in the anoxic sediments of Lake Taihu in China. In four months of microcosm incubations, the increased concentrations of protein-like substances in AOM and POM exhibited temporary activation on microbial metabolic enzyme activity (fluorescein diacetate hydrolase and dehydrogenase) and significantly promoted the carbon mineralization with iron reduction (P < 0.001). These in turn increased the EE2 biodegradation efficiency to 77-90 ng g^-1 in the anoxic sediment. However, a higher EE2 biodegradation of 109 ng g^-1 was achieved with the humic acid augmentation containing more quinone-like compounds, showing a weaker substrate-priming effect but accelerated redox cycling of iron and organic substrates in the later period of incubation. The microbial analysis further revealed that the quinone-like compounds in OM were more closely associated with microbial electron transfer and strengthened their interspecies syntrophic cooperation favorable to contaminant biodegradation, even though the connective members exposed to protein-like components upregulated more functional genes related to organic carbon and xenobiotics metabolism and biodegradation. Our findings will help predict the fate of estrogens in various sedimentary environments under increasing eutrophication and further climate change scenarios.

Impact of microbial inoculants combined with humic acid on the fate of estrogens during pig manure composting under low-temperature conditions

To investigate the efficiency of psychrotrophic cellulose-degrading fungal strains (PCDFSs) and estrogen-degrading bacteria (EDBs) combined with humic acid (HA) on estrone (E1) and 17-β-estradiol (E2) degradation, five compost groups (T, HA, EDB, PCDFS, and CK) were prepared and composted for 32 days at 11-14°C. The results indicated that inoculation increased the temperature to 62.2°C and promoted E1 degradation to the lowest level of 100.1 ng/kg, while E2 was undetected from day 16. Metagenomic analysis revealed that inoculation altered the microbial community structure by increasing the abundance of cellulose-degrading fungi, especially Meyerozyma (16.7%) (among PCDFSs), and of estrogen-degrading bacteria, particularly Microbacterium (13.4%) (involved in EDBs). Moreover, inoculation increased the levels (>0.500%) of Gene Ontology (GO) associated with estrogen degradation, like 3-β-hydroxy-delta 5-steroid dehydrogenase and monooxygenase. Redundancy analysis demonstrated that temperature and Microbacterium were positively correlated with estrogen degradation. Structural equation model indicated that temperature and estrogen-degrading bacterial genera exhibited positive, significant (p < 0.001) and direct impacts on estrogen degradation. This is the first study to suggest that applying microbial inoculants and HA could accelerate estrogen degradation during composting in cold regions. The research outcomes offer a practical reference for managing compost safety, thereby decreasing its potential environmental and human health impacts.

Bacterial contribution to 17β-estradiol mineralization in lake sediment as revealed by 13C-DNA stable isotope probing

The accumulation of estrogens in aquatic environments has drawn increasing public concern due to their adverse effects on aquatic ecosystems and human health. Bacteria play important roles in eliminating estrogens from the environment, but knowledge of the identity and functions of the microorganisms involved in metabolizing these steroid hormones in the natural microbial communities is lacking. Here, we added ¹³C-17β-estradiol (¹³C-E2) to sediments collected from Zhushan (ZS) Bay, Meiliang (ML) Bay, Gonghu (GH) Bay, and the central area (CA) of the Taihu Lake. The indigenous assimilators of E2 in the sediments were recognized using ¹³C-DNA stable isotope probing (DNA-SIP), and their effects on ¹³C-E2 mineralization were studied under aerobic condition. During the 30-day incubation period, ZS Bay had the highest cumulative percentage of ¹³C-E2 mineralization to ¹³CO₂ (65.5%), while CA presented the lowest (51.4%). Based on DNA-SIP, we saw that Novosphingobium, Ralstonia, Pseudomonas, Sphingomonas, Nitrosomonas, and Alcaligenes were involved in E2-derived ¹³C assimilation for the entire incubation period. Acinetobacter, Flavobacterium, and Mycobacterium only assimilated ¹³C for the first half of the incubation. H16 was identified as an E2 assimilator for the first time in this study. In addition, the temporal changes in assimilator abundances during the incubation period indicated that these genera played dominant roles at different stages in the process of E2 biodegradation. The bacteria engaged in the assimilation of E2 in situ were identified, and the rate of increase in the relative abundance of assimilators was significantly (P < 0.05) and positively correlated with the E2 mineralization in sediments. This information enhances our knowledge of in situ E2 biodegradation and provides a potential resource that could be used to eliminate estrogens in sediments.

A Review of Current and Emerging Approaches for Water Pollution Monitoring

The aquatic ecosystem is continuously threatened by the infiltration and discharge of anthropogenic wastewaters. This issue requires the unending improvement of monitoring systems to become more comprehensive and specific to targeted pollutants. This review intended to elucidate the overall aspects explored by researchers in developing better water pollution monitoring tools in recent years. The discussion is encircled around three main elements that have been extensively used as the basis for the development of monitoring methods, namely the dissolved compounds, bacterial indicator, and nucleic acids. The latest technologies applied in wastewater and surface water mapped from these key players were reviewed and categorized into physicochemical and compound characterizations, biomonitoring, and molecular approaches in taxonomical and functional analyses. Overall, researchers are continuously rallying to enhance the detection of causal source for water pollution through either conventional or mostly advanced approaches focusing on spectrometry, high-throughput sequencing, and flow cytometry technology among others. From this review’s perspective, each pollution evaluation technology has its own advantages and it would be beneficial for several aspects of pollutants assessments to be combined and established as a complementary package for better aquatic environmental management in the long run.