Biological self-protection inspired engineering of nanomaterials to construct a robust bio-nano system for environmental applications.

Nanomaterials can empower microbial-based chemical production or pollutant removal, e.g., nano zero-valent iron (nZVI) as an electron source to enhance microbial reducing pollutants. Constructing bio-nano interfaces is critical for bio-nano system operation, but low interfacial compatibility due to nanotoxicity challenges the system performance. Inspired by microorganisms' resistance to nanotoxicity by secreting extracellular polymeric substances (EPS), which can act as electron shuttling media, we design a highly compatible bio-nano interface by modifying nZVI with EPS, markedly improving the performance of a bio-nano system consisting of nZVI and bacteria. EPS modification reduced membrane damage and oxidative stress induced by nZVI. Moreover, EPS alleviated nZVI agglomeration and probably reduced bacterial rejection of nZVI by wrapping camouflage, contributing to the bio-nano interface formation, thereby facilitating nZVI to provide electrons for bacterial reducing pollutant via membrane-anchoring cytochrome c. This work provides a strategy for designing a highly biocompatible interface to construct robust and efficient bio-nano systems for environmental implication.

Treatment of domestic wastewater and extracellular polymeric substance accumulation in siphon-type composite vertical subsurface flow constructed wetland.

In this study, the siphon-type composite vertical flow constructed wetland (Sc-VSsFCW) was constructed with anthracite and shale ceramsite chosen as the substrate bed materials. During the 90-day experiment, typical pollutant removal effects of wastewater and extracellular polymeric substance (EPS) accumulation were investigated. Meanwhile, X-ray diffraction and scanning electron microscopy were used to examine the phase composition and surface morphology to analyze adsorptive property. Additionally, we evaluated the impact of siphon effluent on clogging and depolymerization by measuring the EPS components' evolution within the system. The findings reveal that both the anthracite and shale ceramsite systems exhibit impressive removal efficiencies for total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP), chemical oxygen demand (COD), ammonium nitrogen (NH4 +-N), and nitrate nitrogen (NO3 --N). However, as the experiment progressed, TP removal rates in both systems gradually declined because of the saturation of adsorption sites on the substrate surfaces. Although the dissolved oxygen (DO) levels remained relatively stable throughout the experiment, pH exhibited distinct patterns, suggesting that the anthracite system relies primarily on chemical adsorption, whereas the shale ceramsite system predominantly utilizes physical adsorption. After an initial period of fluctuation, the permeability coefficient and porosity of the system gradually stabilized, and the protein and polysaccharide contents in both systems exhibited a downward trend. The study underscores that anthracite and shale ceramsite have good effectiveness in pollutant removal as substrate materials. Overall, the hydraulic conditions of the double repeated oxygen coupling siphon in the Sc-VSsFCW system contribute to enhanced re-oxygenation capacity and permeability coefficient during operation. The changes in EPS content indicate that the siphon effluent exerts a certain depolymerization effect on the EPS within the system, thereby mitigating the risk of biological clogging to a certain extent. PRACTITIONER POINTS: The system can still maintain good pollutant treatment effect in long-term operation. The re-oxygenation method of the system can achieve efficient and long-term re-oxygenation effect. The siphon effluent has a certain improvement effect on the permeability coefficient and porosity, but it cannot effectively inhibit the occurrence of clogging. The EPS content did not change significantly during the operation of the system, and there was a risk of biological clogging.

Mechanisms underlying the detrimental impact of micro(nano)plastics on the stability of aerobic granular sludge: Interactions between micro(nano)plastics and extracellular polymeric substances.

Microplastics (MPs) and nanoplastics (NPs) present in wastewater can pose a negative impact to aerobic granular sludge (AGS). Herein, this study found that MPs and NPs (20 mg/L) deteriorated the sludge settleability and granule integrity, resulting in a 15.7 % and 21.9 % decrease in the total nitrogen removal efficiency of the AGS system, respectively. This was possibly due to the reduction of the extracellular polymeric substances (EPS) content. The subsequent analysis revealed that tyrosine, tryptophan, and humic acid-like substances in EPS exhibited a higher propensity for chemisorption and inhomogeneous multilayer adsorption onto NPs compared to MPs. The binding of EPS onto the surface of plastic particles increased the electronegativity of the MPs, but facilitated the aggregation of NPs through reducing the electrostatic repulsion, thereby mitigating the adverse effects of MPs/NPs on the AGS stability. Additionally, comprehensive analysis of the extended Derjaguin-Landau-Verwey-Overbeek theory indicated that the suppressed aggregation of microorganisms was the internal mechanisms contributing to the inadequate stability of AGS induced by MPs/NPs. This study provides novel insights into the detrimental mechanisms of MPs/NPs on the AGS stability, highlighting the key role of EPS in maintaining the structural stability of AGS when exposed to MPs/NPs.

Deciphering the molecular interaction of extracellular polymeric substances of a marine bacterium Pseudomonas furukawaii PPS-19 with petroleum hydrocarbons and development of bioadsorbent.

Petroleum hydrocarbon contamination is a serious hazard to marine environments, affecting ecosystems and marine life. However, extracellular polymeric substances (EPS) of marine bacteria constituting various hydrophilic and hydrophobic functional groups sequester petroleum hydrocarbons (PHs). In this study, interaction of EPS of Pseudomonas furukawaii PPS-19 with PHs such as crude oil, n-dodecane, and pyrene and its impact on PHs adsorption was investigated. Protein component of EPS was increased after treatment with PHs. Red shift of UV-Vis spectra implied change in molecular structure of EPS. Functional groups of proteins (CO, NH2) and polysaccharides (C-C, C-OH, C-O-C) predominantly interacted with PHs. Interaction with PHs affected secondary structure of EPS. Change in binding energies of corresponding functionalities of C 1s, O 1s, and N 1s confirmed the interaction. Disruption of crystalline peaks led to increased pore size in EPS primarily due to the increase in surface electronegativity. Static quenching mechanism unveils formation of complex between fulvic acid of EPS and PHs. Relative expression of alg8 gene was significantly increased in the presence of n-dodecane (6.31 fold) (P < 0.05; One way ANOVA). n-dodecane and pyrene adsorption capacity of Immobilized EPS was significantly higher (356.5 and 338.2 mg g-1, respectively) (P < 0.001; One way ANOVA) than control. Adsorption rate fits into the pseudo-second-order kinetic model. This study establishes that interaction of PHs causes structural and physical changes in EPS and EPS could be used as an adsorbent material for the sequestration of PHs pollution.

Accelerated healing of intractable biofilm-infected diabetic wounds by trypsin-loaded quaternized chitosan hydrogels that disrupt extracellular polymeric substances and eradicate bacteria.

Complex and stubborn bacterial biofilm infections significantly hinder diabetic wound healing and threaten public health. Therefore, a dressing material that effectively clears biofilms and promotes wound healing is urgently required. Herein, we introduce a novel strategy for simultaneously dispersing extracellular polymeric substances and eradicating drug-resistant bacteria. We prepared an ultrabroad-spectrum and injectable quaternized chitosan (QCS) hydrogel loaded with trypsin, which degrades biofilm extracellular proteins. Increased temperature initiated QCS gelation to form the hydrogel, enabling the sustained release of trypsin and effective adherence of the hydrogel to irregularly shaped wounds. To reproduce clinical scenarios, biofilms formed by a mixture of Staphylococcus aureus (S. aureus), Methicillin-resistant S. aureus, and Pseudomonas aeruginosa were administered to the wounds of rats with streptozotocin-induced diabetes. Under these severe infection conditions, the hydrogel efficiently suppressed inflammation, promoted angiogenesis, and enhanced collagen deposition, resulting in accelerated healing of diabetic wounds. Notably, the hydrogel demonstrates excellent biocompatibility without cytotoxicity. In summary, we present a trypsin-loaded QCS hydrogel with tremendous clinical applications potential for the treatment of chronic infected wounds.

Multiple drivers and mechanisms of solid-water interfacial interactions in sludge dewatering: Roles of polarity and molecular structure of extracellular polymeric substances.

Water occurrence states in sewage sludge, influenced by sludge physicochemical properties, are crucial for sludge dewaterability and have recently been regarded as a research hotspot. Here, the multifold characteristics of sludge flocs during hydrothermal treatment, including rheological properties, solid-water interfacial interactions, and the polarity distribution and molecular structure of extracellular polymeric substances (EPS), were systematically investigated, and the impact of these characteristics on sludge dewaterability was explored in depth. Hydrothermal treatment at 80 °C and 100 °C induced the conversion of free water into bound water, while an increase in temperature to 180 °C resulted in a significant decrease in bound water content, approximately 4-fold lower than at 100 °C. In addition to the conventional view of decreased sludge surface hydrophilicity at high temperatures, the decline in bound water was associated with the reduction in sludge apparent viscosity. XAD resin fractionation identified the hydrophobic/hydrophilic EPS (HPO-/HPI) ratio as an important factor determining water occurrence states. Especially, hydrolysis of HPI-related hydrophilic proteins and subsequent increase in HPO-related tryptophan-like substances played a dominant role in reducing sludge viscosity and facilitating the release of bound water. Protein conformational analysis revealed that the disruption of α-helix structures and disulfide bonds significantly reduced EPS water-holding capacity, providing strong evidence for the potential of targeting these dense structure units to enhance sludge dewaterability. These findings provide a holistic understanding of multidimensional drivers of water occurrence states in sludge, and guide directions for optimizing sludge treatment efficiency through EPS modification.

Chromium (VI) removal by magnetite nanoparticles immobilized with extracellular polymeric substances extracted from Lysinibacillus sp. WH.

Magnetite nanoparticles (nano-Fe3O4) and nano-Fe3O4 immobilized with bacterial extracellular polymeric substances (EPSs) extracted from Lysinibacillus sp. WH (Fe3O4/bact) were comparatively studied for the removal of Cr (VI) ions from aqueous solution in batch study. The objectives were to explore the removal of Cr (VI) efficiency by nano-Fe3O4 and Fe3O4/bact under varying bacterial concentrations at a range of acidic pH. Results indicated that 150 ppm Cr (VI) could be effectively removed by 5 g/L of nano-Fe3O4 at pH 4, with the efficiency of 89.2 ± 12%. The equilibrium time, determined by a pseudo-second-order model (R2 = 0.9983), was after 5 h, indicating chemical adsorption. The Cr (VI) removal by the nano-Fe3O4 immobilized with bacterial EPS was effective and steady under a wide range of acidic conditions although bacterial EPS has an alkaline nature. Here, we are the first to demonstrate that Cr (VI) removal efficiency by different concentrations of EPS was not significantly different, suggesting EPS concentration is possibly not the most crucial factor to be optimized for Cr (VI) removal in the future. This study shows the potential application of nano-Fe3O4 immobilized with bacterial EPS for wastewater treatment. PRACTITIONER POINTS: The equilibrium time for magnetite nanoparticles to remove Cr (VI) is 5 h, suggesting chemical adsorption. The Cr (VI) removal efficiency of either magnetite nanoparticles or bacterial EPS is stable under a wide range of acidic conditions. Magnetite nanoparticles immobilized with bacterial EPS extracted from Lysinibacillus sp. WH has a potential application for Cr (VI) removal in wastewater.

The effect of salinity on trimethoprim adsorption by activated sludge extracellular polymeric substances at trace concentration.

The saline wastewater produced in industrial activities and seawater use would flow into wastewater treatment plants and affect the characteristic of extracellular polymeric substance (EPS) of activated sludge, which could potentially impact the removal of antibiotics via adsorption. Nonetheless, the effect of salinity on trimethoprim adsorption by activated sludge extracellular polymeric substances at trace concentration and the underlying mechanism remain largely unknown. In this study, the effect of salinity on the adsorption removal of a typical antibiotic, i.e., trimethoprim (TMP) at trace concentration (25.0 µg/L) was evaluated. The results showed the content of EPS was decreased significantly from 56.36 to 21.70 mg/g VSS when the salinity was increased from 0 to 10 g/L. Protein fractions occupied the predominant component of EPS, whose concentration was decreased from 38.17 to 12.83 mg/g VSS. The equilibrium adsorption capacity of activated sludge for TMP was decreased by 49.70% (from 4.97 to 2.50 µg/g VSS). The fluorescence quenching results indicated the fluorescence intensity of tryptophan-like substances was decreased by 30% and the adsorption sites of EPS were decreased from 0.51 to 0.21 when the salinity was increased. The infrared spectrum and XPS results showed that the nitrogen-containing groups from protein were decreased significantly. The circular dichroic analysis showed α helix structure of protein in EPS was decreased with the increase of salinity, which was responsible for the decrease of adsorption capacity for TMP.

Distribution characteristics of sulfonamide antibiotics between water and extracellular polymeric substances in municipal sludge.

The interaction between extracellular polymeric substances (EPS) in municipal sludge and antibiotics in wastewater is critical in wastewater treatment, resource recovery, and sludge management. Therefore, it is increasingly urgent to investigate the distribution coefficient (Log K) of sulfonamide antibiotics (SAs) in EPS, particularly in sludge-derived dissolved organic carbon (DOC) and aqueous phase systems. Herein, through balance experiments, the concentrations of SAs were determined using alkaline extraction EPS (AEPS) and alginate-like extracellular polymer (ALE) systems, and the Log KDOC values were determined. The results showed that the Log KDOC of AEPS was higher than that of ALE, which exhibited a negative KDOC value, indicating an inhibitory effect on dissolution. For the three SAs studied, the Log KDOC values were in the following order: sulfamethoxazole > sulfapyridine > sulfadiazine. This order can be attributed to the differing physicochemical properties, such as polarity, of the SAs. Three-dimensional excitation-emission matrix fluorescence spectra and fitting results indicated a lack of aromatic proteins dominated by tryptophan and humus-like substances in ALE. Meanwhile, the hydrophobic interaction of aromatic proteins dominated by tryptophan was the main driving force in the binding process between AEPS and SAs.

Deciphering retention effect of extracellular polymeric substances to typical heavy metals and their interaction with key inner enzymes of Candidatus Kuenenia.

This study employed spectroscopy, metagenomics, and molecular simulation to investigate the inhibitory effects of Cd(II) and Cu(II) on the anammox system, examining both intracellular and extracellular effects. At concentrations of 5 mg/L, Cd(II) and Cu(II) significantly reduced nitrogen removal efficiency by 41.46 % and 62.03 %, respectively. Additionally, elevated metal concentrations were correlated with decreased extracellular polymeric substances (EPS), thereby reducing their capacity to absorb heavy metals, particularly Cu(II), which decreased from 76.47 % to 14.67 %. Spectral analysis revealed alterations in the secondary structures of EPS induced by Cd(II) and Cu(II), decreasing the ratio of extracellular protein α-helix to (ß-sheet + random coil), which resulted in looser extracellular protein configurations. The results of the metagenomics study showed that the abundance of Candidatus Kuenenia and its genes encoding nitrogen removal-related enzymes was reduced. The abundance of hzs-γ was reduced by 35.09 % at a concentration of 5 mg/L Cu(II). Conversely, genes associated with metal efflux enzymes, like czcR, increased by 54.86 % at 2 mg/L Cd(II). Molecular docking revealed robust bindings of Cd(II) to HZS-α (-342.299 ± 218.165 kJ/mol) and Cu(II) to HZS-γ (-880.934 ± 55.526 kJ/mol). This study elucidated the inhibitory mechanisms of Cd(II) and Cu(II) on the anammox system, providing insights into the resistance of anammox bacteria to heavy metals.

Preferential adsorption of medium molecular weight proteins in extracellular polymeric substance alleviates toxicity of small-sized microplastics to Skeletonema costatum.

Extracellular polymeric substances (EPS) secreted by organisms tend to encapsulate microplastics (MPs), forming an EPS-corona that affects the fate of MPs in marine ecosystems. However, the impact of the EPS-corona on the biotoxicity of MPs to marine organisms remains poorly understood. Herein, the effect of the EPS-corona on the toxicity of polystyrene (PS) MPs of different sizes (0.1 and 1 µm) to Skeletonema costatum (S. costatum) was investigated. The preferential adsorption of medium molecule weight (∼55 kDa) proteins onto PS MPs mainly contributed to the EPS-corona formation, decreasing the surface charge negativity of small-sized PS MPs (0.1 µm) by 72.4 %. Nitrogen (N) and oxygen (O) moieties in polysaccharides and proteins were identified as the preferential adsorption sites in the EPS-PS MPs interaction. Density functional theory (DFT) calculations confirmed the nuclear magnetic resonance spectroscopy (NMR) results, revealing that the binding mode between EPS and PS MPs was mainly hydrogen bonding. In addition, EPS-corona increased the cell density of S. costatum by 35.5-36.0 % when exposed to small-sized PS MPs (0.1 µm, 25-50 mg/L). These findings provide new insights into how EPS-corona affects the environmental fate and ecological risks associated with micro- and nano-sized plastics in marine ecosystems.

Effects of carrier surface hydrophilic modification on sludge granulation: From sludge characteristics, extracellular polymeric substances, and microbial community.

Aerobic granular sludge (AGS) is a powerful biotechnological tool capable of treating multiple pollutants simultaneously. However, the granulation process and pollutant removal efficiency still need to be further improved. In this study, Fe2O3- and MnO2-surface-modified straw foam-based AGS (Fe2O3@SF-AGS and MnO2@SF-AGS), with an average particle size of 3 mm, were developed and evaluated. The results showed that surface modification reduced the hydrophobic groups of carriers, facilitating the attachment and proliferation of microorganisms. Notably, MnO2@SF-AGS showed excellent granulation performance, reaching a stable state about one week earlier than the unmodified SF-AGS. The polymeric substance content of MnO2@SF-AGS was found to be 1.28 times higher than that of the control group. Furthermore, the removal rates for NH4+-N, TN, and TP were enhanced by 27.28%, 12.8%, and 32.14%, respectively. The bacterial communities exhibited significant variations in response to different surface modifications of AGS, with genera such as Saprospiraceae, Terrimonas, and Ferruginibacter playing a crucial role in the formation of AGS and the removal of pollutants specifically in MnO2@SF-AGS. The charge transfer of metal ions of MnO2@SF promotes the granulation process and pollutant removal. These results highlight that MnO2@SF-AGS is an effective strategy for improving nitrogen and phosphorus removal efficiency from wastewater.

Response Mechanism of Extracellular Polymeric Substances Synthesized by Alternaria sp. on Drought Stress in Alfalfa (Medicago sativa L.).

This study investigates how extracellular polymeric substances (EPS) synthesized by dark septate endophytic (DSE) improve alfalfa's drought resistance. Drought stress was simulated in hydroponic culture, and roots were treated with different EPS concentrations to determine their effects on drought tolerance and applicable concentrations. Hydroponic solutions with 0.25 and 0.50% EPS concentrations alleviated leaf wilting and increased total plant fresh weight by 35.8 and 57.7%, respectively. SEM shows that EPS attached to the roots and may have served to protect the root system. EPS treatment significantly depressed the MDA contents of the roots, stems, and leaves. Roots responded to drought stress by increasing soluble sugar contents and antioxidant enzyme activities, while mitigating stem and leaf stress by synthesizing lipid compounds, amino acids, and organic acid metabolites. Five metabolites in the stem have been reported to be associated with plant stress tolerance and growth, namely 3-O-methyl 5-O-(2-methyl propyl) (4S)-2,6-dimethyl-4-(2-nitrophenyl)-3,4-dihydropyridine-3,5-dicarboxylate, malic acid, PA (20:1(11Z)/15:0), N-methyl-4,6,7-trihydroxy-1,2,3,4-tetrahydroisoquinoline, and 2-(S-glutathionyl) acetyl glutathione. In summary, EPS treatment induced oxidative stress and altered plant metabolism, and this in turn increased plant antioxidant capacity. The results provide a theoretical basis for the application of EPS in commercial products that increase plant resistance and ecological restoration.

Phosphorous speciation in EPS extracted from Aerobic Granular Sludge.

Wastewater treatment technologies opened the door for recovery of extracellular polymeric substances (EPS), presenting novel opportunities for use across diverse industrial sectors. Earlier studies showed that a significant amount of phosphorus (P) is recovered within extracted EPS. P recovered within the extracted EPS is an intrinsic part of the recovered material that potentially influences its properties. Understanding the P speciation in extracted EPS lays the foundation for leveraging the incorporated P in EPS to manipulate its properties and industrial applications. This study evaluated P speciation in EPS extracted from aerobic granular sludge (AGS). A fractionation lab protocol was established to consistently distinguish P species in extracted EPS liquid phase and polymer chains. 31P nuclear magnetic resonance (NMR) spectroscopy was used as a complementary technique to provide additional information on P speciation and track changes in P species during the EPS extraction process. Findings showed the dominance of organic phosphorus and orthophosphates within EPS, besides other minor fractions. On average, 25% orthophosphates in the polymer liquid phase, 52% organic phosphorus (equal ratio of mono and diesters) covalently bound to the polymer chains, 16% non-apatite inorganic phosphorus (NAIP) precipitates mainly FeP and AlP, and 7% pyrophosphates (6% in the liquid phase and 1% attached to the polymer chains) were identified. Polyphosphates were detected in initial AGS but hydrolyzed to orthophosphates, pyrophosphates, and possibly organic P (forming new esters) during the EPS extraction process. The knowledge created in this study is a step towards the goal of EPS engineering, manipulating P chemistry along the extraction process and enriching certain P species in EPS based on target properties and industrial applications.

Self-flocculating Chlorella vulgaris: A high-efficiency purification mechanism of radioactive Th4+ in an aquatic environment.

This study aimed to investigate the purification of radioactive thorium (Th4+) by Chlorella vulgaris in aquatic environments. Single-factor experiments and response surface optimization tests identified optimal purification conditions. The purification and metabolic response mechanisms of Chlorella to Th4+ were elucidated using physiological and biochemical analyses, three-dimensional excitation-emission matrix (3D-EEM) analysis, and metabolomic profiling. Increases in the Th4+ concentration caused Chlorella to self-flocculate, significantly improving the Th4+ purification efficiency. Under optimal conditions, the Th4+ purification efficiency for Th4+ in wastewater by Chlorella stabilized between 94.3 % and 98.2 %. Morphological analysis revealed that the purified Th4+ existed mainly in a stable residual state. Chlorella efficiently purified wastewater during treatment by regulating environmental pH, performing redox reactions, and utilizing extracellular polymeric substances (EPS) to interact with Th4+. Metabolomic analysis indicated that Chlorella adapted to the Th4+-contaminated environment and enhanced its purification function by adjusting the synthesis of metabolites, such as carbohydrates, nucleotides, and amino acids. Chlorella demonstrated a remarkable self-flocculation phenomenon and a high-efficiency purification capability for Th4+, offering new possibilities for environmental remediation. Its purification mechanism involves environmental regulation, redox reactions, and complex metabolic adjustments. The results presented here provide theoretical support for environmental remediation using Chlorella.

Application of biofilm dispersion-based nanoparticles in cutting off reinfection.

Bacterial biofilms commonly cause chronic and persistent infections in humans. Bacterial biofilms consist of an inner layer of bacteria and an autocrine extracellular polymeric substance (EPS). Biofilm dispersants (abbreviated as dispersants) have proven effective in removing the bacterial physical protection barrier EPS. Dispersants are generally weak or have no bactericidal effect. Bacteria dispersed from within biofilms (abbreviated as dispersed bacteria) may be more invasive, adhesive, and motile than planktonic bacteria, characteristics that increase the probability that dispersed bacteria will recolonize and cause reinfection. The dispersants should be combined with antimicrobials to avoid the risk of severe reinfection. Dispersant-based nanoparticles have the advantage of specific release and intense penetration, providing the prerequisite for further antibacterial agent efficacy and achieving the eradication of biofilms. Dispersant-based nanoparticles delivered antimicrobial agents for the treatment of diseases associated with bacterial biofilm infections are expected to be an effective measure to prevent reinfection caused by dispersed bacteria. KEY POINTS: • Dispersed bacteria harm and the dispersant's dispersion mechanisms are discussed. • The advantages of dispersant-based nanoparticles in bacteria biofilms are discussed. • Dispersant-based nanoparticles for cutting off reinfection in vivo are highlighted.

The effect of extracellular polymeric substances on MICP solidifying rare earth slags and stabilizing Th and U.

Microbially induced carbonate precipitation (MICP) has been used to cure rare earth slags (RES) containing radionuclides (e.g. Th and U) and heavy metals with favorable results. However, the role of microbial extracellular polymeric substances (EPS) in MICP curing RES remains unclear. In this study, the EPS of Lysinibacillus sphaericus K-1 was extracted for the experiments of adsorption, inducing calcium carbonate (CaCO3) precipitation and curing of RES. The role of EPS in in MICP curing RES and stabilizing radionuclides and heavy metals was analyzed by evaluating the concentration and morphological distribution of radionuclides and heavy metals, and the compressive strength of the cured body. The results indicate that the adsorption efficiencies of EPS for Th (IV), U (VI), Cu2+, Pb2+, Zn2+, and Cd2+ were 44.83%, 45.83%, 53.7%, 61.3%, 42.1%, and 77.85%, respectively. The addition of EPS solution resulted in the formation of nanoscale spherical particles on the microorganism surface, which could act as an accumulating skeleton to facilitate the formation of CaCO3. After adding 20 mL of EPS solution during the curing process (Treat group), the maximum unconfined compressive strength (UCS) of the cured body reached 1.922 MPa, which was 12.13% higher than the CK group. The contents of exchangeable Th (IV) and U (VI) in the cured bodies of the Treat group decreased by 3.35% and 4.93%, respectively, compared with the CK group. Therefore, EPS enhances the effect of MICP curing RES and reduces the potential environmental problems that may be caused by radionuclides and heavy metals during the long-term sequestration of RES.

Structural characterization of the extracellular stalk material of the diatom Didymosphenia geminata.

The study represents new bioanalytical characterization of mainly organic components of the poorly investigated extracellular polymeric substances (EPS) of the enigmatic diatom Didymosphenia geminata, an invasive, worldwide expanding species endangering diverse ecosystems. This microalga attaches its siliceous cells to rocky substrates using fibrous stalks, which are made of an EPS-based matrix stabilized by crystalline calcite. The EPS were analyzed using selected methods, including microscopic, spectroscopic, and spectrometric techniques. We identified diverse types of biomolecules. The presence of lipids, condensed aromatics, and heteroaromatic compounds in the EPS has been confirmed using high-resolution mass spectrometry (HR-MS). Additionally, both sulfur-containing functionalities and carboxylic acids were determined too using infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. For the first time, lignin compounds have been detected as one of the components of the EPS of the D. geminata diatom, using HR-MS and fluorescence microscopy (FM) in combination with specific staining techniques. By increasing the understanding of the chemistry and structural features of the stalks, we aim to develop potential applications and methods for removing these stalks from affected regions in the future, or, alternatively, to use them as a large-scale source of sustainable biocomposite material.

Algal extracellular polymeric substance compositions drive the binding characteristics, affinity, and phytotoxicity of graphene oxide in water.

Graphene oxide (GO, a popular 2D nanomaterial) poses great potential in water treatment arousing considerable attention regarding its fate and risk in aquatic environments. Extracellular polymeric substances (EPS) exist widely in water and play critical roles in biogeochemical processes. However, the influences of complex EPS fractions on the fate and risk of GO remain unknown in water. This study integrates fluorescence excitation-emission matrix-parallel factor, two-dimensional correlation spectroscopy, and biolayer interferometry studies on the binding characteristics and affinity between EPS fractions and GO. The results revealed the preferential binding of fluorescent aromatic protein-like component, fulvic-like component, and non-fluorescent polysaccharide in soluble EPS (S-EPS) and bound EPS (B-EPS) on GO via π-π stacking and electrostatic interaction that contributed to a higher adsorption capacity of S-EPS on GO and weaker affinity than of B-EPS. Moreover, the EPS fractions drive the morphological and structural alterations, and the attenuated colloid stability of GO in water. Notably, GO-EPS induced stronger phytotoxicity (e.g., photosynthetic damage, and membrane lipid remodeling) compared to pristine GO. Metabolic and functional lipid analysis further elucidated the regulation of amino acid, carbohydrate, and lipid metabolism contributed to the persistent phytotoxicity. This work provides insights into the roles and mechanisms of EPS fractions composition in regulating the environmental fate and risk of GO in natural water.

Intensified bioleaching of a spent Co-Mo catalyst through the addition of extracellular polymeric substances (EPSs) and its mechanism exploration.

The extraction and recovery of valuable metals from various spent catalysts via bioleaching represents a green, low-carbon and eco-friendly process. However, the pulp density of spent catalysts is usually 1.0% or lower owing to their toxicity, denoting low process capacity and poor practical potential. In this study, an intensified bioleaching strategy was used for the first time to promote the release efficiencies of both Co and Mo from a spent Co-Mo catalyst at a high pulp density of 10% by supplementing extracellular polymeric substances (EPSs). The results showed that the addition of 0.6 g L-1 EPSs harvested a maximum release of 73.6% for Co and 72.5% for Mo after 9 days of contact, with an evident elevation of 22.6% for Co and 24.4% for Mo, in contrast to no addition, respectively. The added EPS not only promoted the growth of plankton cells to produce more active molecules but also boosted the adhesion of leaching cells to the spent catalyst to form stable aggregates. Moreover, the resulting aggregates allowed for the gathering and confinement of the active small molecules, including Fe3+ and Fe2+, inside the micro-areas between the spent catalysts and the cells for quick electronic transfer as an interface oxidation/reduction reaction to free both Co and Mo from the spent catalyst.