Protonated carbon nitride elicits microalgae for water decontamination

Impact of climate change on the toxicity of bisphenol A in Mytilus galloprovincialis and assessment of phycoremediation using Nannochloropsis salina via a multi-biomarker strategy and modeling

In the current study, the mussels Mytilus galloprovincialis, exposed to four varying temperatures (17, 20, 23, and 26 °C), were contaminated with 50 μg/L of bisphenol A both with and without Nannochloropsis salina. The toxicity evaluation is determined by quantifying various biomarkers related to oxidative stress, neurotoxicity, and cellular damage. The key findings indicate that the toxicity of bisphenol A is heightened by rising temperature. The impact of bisphenol A is most evident at 26 °C, leading to excessive production of reactive oxygen species, depletion of non-enzymatic antioxidants, and activation of antioxidant enzymes (catalase and glutathione-S-transferase). The rise in malondialdehyde levels confirms lipid peroxidation caused by bisphenol A and intensified by thermal stress. These findings have been supported by strong molecular interactions between bisphenol A and lectin mytilec apo-form and proximal thread matrix protein 1 from M. galloprovincialis following the computational modeling assay. The incorporation of N. salina as a food additive helped, firstly, to mitigate the stress effects and, secondly, resulted in a noticeable enhancement of oxidative balance and filtration ability, along with decreased lipid peroxidation.

Construction and optimization of low carbon-to-nitrogen ratio-adapted Chlorococcum-Bacteria symbiosis for energy-efficient wastewater remediation

This study developed a microalgae-bacteria symbiosis (MBS) system using Chlorococcum robustum AY122332.1 isolated from rare earth tailings wastewater to treat synthetic municipal wastewater. Systematic optimization identified a 1:1 bacteria-microalgae ratio (MBS 1) as optimal, achieving nearly 100 % removal of ammonia and 92.2 ± 0.6 % of chemical oxygen demand. Microbial community analysis identified significant enrichment of nitrogen-transforming consortia in MBS 1, particularly Thauera (7.43 % relative abundance), whose nitrite reductase activity and polyhydroxyalkanoate biosynthesis capacity enhanced simultaneous nitrification-denitrification. The optimized system showed superior stability with an elevated zeta potential (+17.72 mV) driven by protein-rich extracellular polymeric substances production and humic acid accumulation. These biopolymers facilitated microaggregate formation through ligand bridging and hydrophobic interactions, creating redox-stratified microenvironments that supported functional microbial niches. The synergistic interactions in the MBS system enabled efficient nutrient recovery while maintaining ecological resilience under carbon-limited conditions, providing new insights into sustainable wastewater bioremediation processes.

Extracellular polymeric substances in indigenous microalgal-bacterial consortia: advances in characterization techniques and emerging applications

Extracellular polymeric substances (EPS) synthesized by indigenous microalgal-bacterial consortia (IMBC) play multifunctional roles in enhancing wastewater treatment efficiency, nutrient sequestration, and ecological system stability. This comprehensive review critically evaluates state-of-the-art analytical methods for characterizing EPS composition, physicochemical properties, and functional dynamics, including colorimetry, Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). While these methods provide critical insights into EPS structure-function relationships, challenges persist in resolving spatial heterogeneity, real-time secretion dynamics, and molecular-scale interactions within complex IMBC systems. Emerging technologies such as expansion microscopy (ExM), electrochemical impedance spectroscopy (EIS), and integrated multi-omics approaches are highlighted as transformative tools for in situ EPS profiling, offering nanoscale resolution and temporal precision. By synthesizing these innovations, this review proposes a multidisciplinary framework to decode EPS-mediated microbial symbiosis, optimize IMBC performance, and advance applications in sustainable bioremediation, bioenergy, and circular resource recovery.

Effect of polypropylene microplastics on the performance of membrane bioreactors in wastewater treatment

Membrane bioreactors (MBRs) can effectively remove microplastics (MPs) because of their good rejection performance. However, the influence of MP concentration and particle size on the short-term and long-term operation efficiency of MBRs remains unclear. To address this issue, this study investigated the effects of short-term stress and long-term accumulation of polypropylene microplastics (PP-MPs) with different particle sizes on the operational efficiency of MBRs by running three MBR systems at four concentration stages. Variations in pollutant removal, biological activity, composition of extracellular polymeric substances (EPS), membrane fouling, and microbial communities in the MBRs were systematically investigated. The results showed that low concentrations (0.02 g/L) of PP-MPs stimulated the biological activity in the MBRs in the short term, and small particle size PP-MPs exhibited higher biological toxicity while accelerating membrane fouling. With an increase in time and concentration (0.2-2.0 g/L), PP-MPs showed significant toxic inhibition effects, increasing EPS secretion and accelerating membrane fouling. This effect was more significant for small particle size PP-MPs. In addition, at 0.02 g/L of PP-MPs, the richness and diversity of microbial communities in activated sludge tend to increase, such as the relative abundance of Bacteroidota, while the growth of Proteobacteria is inhibited. The results of this study provide a reference for understanding the effects of short-term stress and long-term accumulation of MPs on MBR efficiency. It provides reference for exploring the influence of MPs with different particle sizes on MBR reactor and the future research direction.

Protonated carbon nitride for rapid photocatalytic sterilization via synergistic oxidative damage and physical destruction

Photocatalytic disinfection is an eco-friendly strategy for countering bacterial pollution in aquatic environments. Numerous strategies have been devised to facilitate the generation of reactive oxygen species (ROS) within photocatalysts, ultimately leading to the eradication of bacteria. However, the significance of the physical morphology of photocatalysts in the context of sterilization is frequently obscured, and the progress in the development of physical-chemical synergistic sterilization photocatalysts has been relatively limited. Herein, graphitic carbon nitride (g-C3N4) is chemically protonated to expose more sharp edges. PL fluorescence and EIS results indicate that the protonation can accelerate photogenerated carrier separation and enhance ROS production. Meanwhile, the sharp edges on the protonated g-C3N4 facilitate the physical disruption of cell walls for further promoting oxidative damage. Protonated C3N4 demonstrated superior bactericidal performance than that of pristine g-C3N4, effectively eliminating Escherichia coli within 40 minutes under irradiation. This work highlights the significance of incorporating physical and chemical synergies in photocatalyst design to enhance the disinfection efficiency of photocatalysis.

Macroscopically uniform interface layer with Li+ conductive channels for high-performance Li metal batteries

The numerous grainboundaries solid electrolyte interface, whether naturally occurring or artificially designed, leads to non-uniform Li metal deposition and consequently results in poor full-battery performance. Herein, a lithium-ion selective transport layer is reported to achieve a highly efficient and dendrite-free lithium metal anode. The layer-by-layer assembled protonated carbon nitride nanosheets present uniform macroscopical structure without grainboundaries. The carbon nitride with ordered pores in basal plane provides high-speed lithium-ion transport channels with low tortuosity. Consequently, the assembled 324 Wh kg-1 pouch cell exhibits 300 stable cycles with a capacity retention of 90.0% and an average Coulombic efficiency up to 99.7%. The ultra-dense Li metal anode makes current collector-free anode possible, achieving high energy density and long cycle life of a 7 Ah cell (506 Wh kg-1, 160 cycles). Thus, it is proved that a macroscopically uniform interface layer with lithium-ion conductive channels could achieve Li metal battery with promising application potential.

Biodegradation of organic micropollutants by anoxic denitrification: Roles of extracellular polymeric substance adsorption, enzyme catalysis, and reactive oxygen species oxidation

The control of organic micropollutants (OMPs) in water environments have received significant attention. Denitrification was reported to exhibit good efficiency to remove OMPs, and the mechanisms involved in are too intricate to be well illustrated. In this study, we selected nitrobenzene [NB] and bisphenol A [BPA] as model pollutants and aimed to unravel the mechanisms of Paracoccus Denitrificans in the removal of OMPs, with a specific emphasis on aerobic behavior during denitrification processes. We demonstrated the formation of extracellular superoxide radicals, i.e., extracellular •O2-, using a chemiluminescence probe and found that extracellular polymeric substance adsorption, extracellular •O2-, and microbial assimilation contributed approximately 40 %, 10 %, and 50 % to OMPs removal, respectively. Transcriptome analysis further revealed the high expression and enrichment of several pathways, such as drug metabolism-other enzymes, of which a typical aerobic enzyme of polyphenol oxidase [PPO] participates in the degradation of NB and BPA. Importantly, all the immediate products showed a significant decrease in toxicity during the aerobic activity-related OMPs degradation process based on the proposed degradation pathways. This study demonstrates the formation of extracellular •O2- and the mechanisms of extracellular •O2-- and PPO-mediated OMPs biodegradation, and offers new insights into OMPs control in widely-used denitrification treatment processes.

A biosensor monitoring approach for toxic algae: Construction of calibration curves to infer cell numbers in field material

A variety of shellfish toxin-producing Harmful Algal Blooms (HABs) occur every year in coastal temperate waters worldwide. These toxic HABs may cause lengthy (months) harvesting bans of mussels and other suspension feeding bivalves exposed to their blooms. To safeguard public health and the shellfish industry, European Union regulations request periodic monitoring of potentially toxic microalgae in seawater and phycotoxins in live bivalve molluscs from shellfish production areas. Monitoring of other toxic microalgae, e.g., fish killers, is based solely on cell counts. Morphological identification and quantification of microalgal cells with light microscopy is time-consuming, requires a good expertise, and accurate identification to species level (e.g., Pseudo-nitzschia species) may require electron microscopy. Toxicity varies among morphologically similar species; there are toxic and non-toxic strains of the same species. Molecular techniques using ribosomal DNA sequences offer a possibility to identify and detect precisely the potentially toxic genus/species. In an earlier project (MIDTAL), specific probes against rRNA sequences of all HAB taxa, known at the time of the project, affecting shellfish areas worldwide were designed, and those affecting Europe were tested and calibrated against rRNA extracts of clonal cultures and field samples. Microarray technology was adopted to relate to cell numbers the fluorescence signal from the reaction of all target species probes spotted in the microarray slides with those present in a single sample extract. The EMERTOX project aimed to develop a more automatic "Lab on a chip" (LOC) technology, including a non- (cell) disruptive water concentration system and biosensors for HAB cells detection. Here, calibration curves are presented against toxic microalgae (cultures and field samples) causing endemic and emerging toxicity events in Galicia (NW Spain) and Portugal. Results here relating cell numbers to electrochemical signals will be used in an early warning biosensor for toxic algae.

The effects of microplastics and nanoplastics on nitrogen removal, extracellular polymeric substances and microbial community in sequencing batch reactor

Wastewater treatment plants can be nanoplastics (NPs) and microplastics (MPs) sinks and sources. The effects of NPs and MPs on nitrogen removal and extracellular polymeric substances (EPS) during activated sludge process need further investigation. Results showed that polystyrene NPs (NPS) and 100 mg/L polystyrene MPs (MPS) decreased the specific nitrate reduction rate, resulting in nitrate accumulation. The negative effects on functional genes involved in denitrification (narG, napA, nirS and nosZ) were the main mechanism. NPS stimulated EPS secretion, but MPS inhibited it. NPS and MPS increased the ratio of protein to polysaccharide except for 10 mg/L MPS and changed the secondary structure of protein in EPS, affecting flocculation ability of activated sludge. The changes of microbial abundance in activated sludge could be the main factor to the alterations of EPS and nitrogen removal. These results may facilitate understanding the impacts of NPs and MPs on wastewater treatment processes.

Supplementation of exogenous phytohormones for enhancing the removal of sulfamethoxazole and the simultaneous accumulation of lipid by Chlorella vulgaris

In this study, the phytohormone gibberellins (GAs) were used to enhance sulfamethoxazole (SMX) removal and lipid accumulation in the microalgae Chlorella vulgaris. At the concentration of 50 mg/L GAs, the SMX removal achieved by C. vulgaris was 91.8 % while the lipid productivity of microalga was at 11.05 mg/L d^-1, which were much higher than that without GAs (3.5 % for SMX removal and 0.52 mg/L d^-1 for lipid productivity). Supplementation of GAs enhanced the expression of antioxidase-related genes in C. vulgaris as a direct response towards the toxicity of SMX. In addition, GAs increased lipid production of C. vulgaris by up-regulating the expression of genes related to carbon cycle of microalgal cells. In summary, exogenous GAs promoted the stress tolerance and lipid accumulation of microalgae at the same time, which is conducive to improving the economic benefits of microalgae-based antibiotics removal as well as biofuel production potential.

Towards advanced nutrient removal by microalgae-bacteria symbiosis system for wastewater treatment

In this study, the microalgae-bacteria symbiosis (ABS) system by co-culturing Chlorella sorokiniana with activated sludge was constructed for pollutants removal, and the according interaction mechanism was investigated. The results showed that the ABS system could almost completely remove ammonia nitrogen, and the removal efficiency of total nitrogen and total phosphorus could accordingly reach up to 65.3 % and 42.6 %. Brevundimonas greatly promoted microalgal biomass growth (maximum chlorophyll-a concentration of 9.4 mg/L), and microalgae contributed to the increase in the abundance of Dokdonella and Thermomonas in ABS system, thus facilitating nitrogen removal. The extended Derjaguin-Landau-Verwey-Overbeek theory indicated a repulsive potential barrier of 561.7 KT, while tryptophan-like proteins and tyrosine-like proteins were key extracellular polymeric substances for the formation of flocs by microalgae and activated sludge. These findings provide an in-depth understanding of interaction mechanism between microalgae and activated sludge for the removal of contaminants from wastewater.