At low exposure, MBGS enhances organic matter removal through microbial enrichment and efficient estrogen transformation. However, higher E3 levels destabilize granule structure, impairing carbon, nitrogen, and phosphorus removal.
E3, a potent natural estrogen, is now widely detected in municipal sewage, hospital effluents, and livestock wastewater. Even at trace levels, its high biological activity raises concerns about ecological and human health impacts. Conventional wastewater treatment, dominated by activated sludge, often fails to adequately remove estrogens due to their resistance to microbial breakdown, while advanced physicochemical techniques remain costly and may generate toxic byproducts. MBGS offers a promising, sustainable alternative by integrating phototrophic microalgae and heterotrophic bacteria into self-aggregated granules capable of degrading recalcitrant pollutants. Given these challenges, understanding how MBGS adapts to estrogenic stress is essential for designing effective EDC-removal systems.
A study (DOI:10.48130/biocontam-0025-0004) published in Biocontaminant on 03 November 2025 by Bin Ji’s team, Wuhan University of Science and Technology, reveals both the adaptive biodegradation potential and the vulnerability of MBGS under estrogenic stress, offering new insights for developing robust, biologically based wastewater treatment technologies.
In this study, the authors exposed MBGS to a gradient of E3 concentrations (0, 0.1, 1, and 10 mg/L) and systematically coupled multiscale analyses to track its response. Granule morphology and settling behavior were evaluated by monitoring size, sludge volume index (SVI₅), and settling velocity (ZSV), while cyanobacterial integrity, chlorophyll, and glycogen contents were quantified to assess structural damage. Extracellular polymeric substances (EPS) secretion and composition (proteins, PN; polysaccharides, PS) were measured, and FT-IR spectroscopy was used to probe molecular interactions between EPS and E3. Concurrently, pollutant removal (COD, NH₄⁺-N, PO₄³⁻-P) was monitored in day–night cycles, and E3 degradation kinetics were modeled to separate biodegradation from EPS adsorption. UHPLC-HRMS identified transformation products, whereas metagenomic analysis resolved shifts in microbial community structure and functional genes, including catabolic (hshA, hsaA, hsaB, hsaC, xylE) and energy-related (mqo, GLU, ppk1, atpA) markers. Results showed that 1–10 mg/L E3 severely disrupted filamentous Cyanobacteria, reducing chlorophyll and glycogen, enlarging granules, increasing SVI₅, and decreasing ZSV, while 0.1 mg/L slightly improved granule settling and COD removal. E3 stress induced EPS overproduction, especially PS, which formed a physicochemical barrier and provided functional groups (N–H, C=O, COO⁻, O–H, C–O) that adsorbed E3, with adsorption contributing 21.9% of E3 removal in the early phase. Nevertheless, high E3 triggered PN depletion and upregulation of oxidative stress genes (SOD, CAT), indicating metabolic reallocation toward detoxification. Pollutant and E3 removal were strongly concentration- and light-dependent: at 0.1 mg/L, E3 removal reached 97.9% (day) and 85.7% (night), whereas 10 mg/L yielded only 12.6% and 10.6%, with slower degradation rates at night due to oxygen limitation. Metagenomics revealed E3-induced collapse of Cyanobacteria and key phosphorus-accumulating taxa, reduced energy- and nutrient-related gene abundance, and enrichment of Sphingomonadaceae and Rhodanobacteraceae, which carried core catabolic genes for stepwise conversion of E3 to less toxic metabolites E1, A1, and B1.
The findings highlight MBGS as a promising platform for sustainable treatment of estrogen-contaminated wastewater, especially at low and moderate E3 levels where microbial consortia effectively transform E3 into low-toxicity metabolites. The system’s reliance on microbial synergy and internal oxygen cycling offers a low-energy alternative to conventional physicochemical methods. However, the structural vulnerability of Cyanobacteria under high estrogenic stress underscores the need for system reinforcement when treating industrial or hospital effluents with elevated E3 concentrations. These insights provide a scientific basis for engineering more resilient MBGS systems to manage endocrine disruptors in real-world wastewater streams.
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References
DOI
10.48130/biocontam-0025-0004
Original Source URL
https://doi.org/10.48130/biocontam-0025-0004
Funding information
The research leading to these results was funded by the National Natural Science Foundation of China under Grant Agreement Nos 52261135627 and 52270048.
About Biocontaminant
Biocontaminant is a multidisciplinary platform dedicated to advancing fundamental and applied research on biological contaminants across diverse environments and systems. The journal serves as an innovative, efficient, and professional forum for global researchers to disseminate findings in this rapidly evolving field.