Types Of Extracellular Polymeric Substances Research Articles

Analysis of the Effects of Surfactants on Extracellular Polymeric Substances

Reservoirs after chemical flooding usually have residual chemicals, which can affect the driving effect of subsequent microbial drives. Among them, the effect of surfactants on the metabolites of oil-recovering bacteria is the most obvious. Therefore, this paper investigates the influence mechanism of sodium dodecyl sulfate (SDS) on the nature and structure of Extracellular Polymeric Substances (EPS) produced by metabolism of Enterobacter cloacae, through a variety of characterization to analysis the components and structure of EPS under SDS stress. The results showed that Enterobacter cloacae was identified as a glycolipid-producing strain, the main components of EPS were polysaccharides and proteins. The polysaccharide composition (%: w/w) was glucosamine, 37.2; glucose, 31.5; rhamnose, 26.3; xylose, 1.7; and unidentified sugar, 3.3; and the main component of proteins was polyglutamic acid. EPS under the stress of SDS showed an increase in the content of functional groups such as -C=O and -COOH and an increase in the cellular particle size, and production of EPS increased by 10.69 × 103 mg/L when the SDS concentration was 2.5 × 102 mg/L; 3D-EEM results showed that the components of all three types of EPS The 3D-EEM results showed that all three types of EPS fractions contained tryptophan and protein-like substances, humic acid-like substances were only distributed in the solubilized extracellular polymers (SL-EPS), and aromatic proteins were only present in the loosely bound type (LB-EPS) and tightly bound type (TB-EPS). In addition, the peaks representing humic-like substances showed a blue shift, indicating that SDS had the greatest effect on SL-EPS. This study provides a guidance for refining the mechanism of strain EPS response to reservoir residual surfactant SDS, and provides a more comprehensive and in-depth understanding of surfactant-protein interactions.

Influence of soluble, loosely bound and tightly bound extracellular polymeric substances (EPS) produced by Desulfovibrio vulgaris on EH40 steel corrosion

Soluble, loosely bound and tightly bound extracellular polymeric substances (S-EPS, LB-EPS, TB-EPS) of Desulfovibrio vulgaris were extracted to investigate their effects on EH40 steel corrosion in 3.5 wt% NaCl solution. Results showed that three types of EPS with different components have opposite effects on corrosion. S-EPS mainly composed of humic acids adhere to EH40 steel surface to form a passive film and inhibit corrosion. However, proteins are the main components in LB-EPS and TB-EPS, the presence of which accelerates corrosion. Especially for TB-EPS, the anodic and cathodic reactions are both promoted due to binding and catalyzing ability of active protein.

Screening and characterization of bioflocculant isolated from thermotolerant Bacillus sp. ISTVK1 and its application in wastewater treatment

Bioflocculants are extracellular polymeric substances (EPS) that are produced by several microorganisms including bacteria. They find application in wastewater treatment wherein they are employed as flocculating agents for removal of suspended particles during the secondary clarification process. In this study, EPS produced by a previously studied thermotolerant strain Bacillus sp. ISTVK1 was analyzed for its flocculation property. The bacteria was cultured in basal and mineral media and the EPS extracted from the two types of cultures were analyzed for their structure, composition, and flocculation efficiency (%), which was tested on kaolin in terms of parameters like duration, pH, temperature and salts. Both types of EPS showed highest flocculating activity on 6th day, at pH 6, and temperature 32.7 °C and with salt AlCl3. When tested on real wastewater, physico-chemical analysis showed reduction in organics in samples treated with EPS and EPS+AlCl3. Aromatic contaminants like Diisobutyl benzene-1,2-dicarboxylate (Retention Time (R.T.) 22.55) and 2-Phenyl-n,n-bis(1-phenylethyl)-1,1-cyclobutanedicarboxamid (R.T. 44.21) were not detected in the bioflocculant treated samples. The study highlighted the applicability of bacterial EPS as a cost-effective bioflocculant for real wastewater.

Treatment of laundry wastewater using extracellular polymeric substances (EPS)

The problem of management and treatment of wastewater from commercial laundries is a matter of concern. The present study provides an effective and eco-friendly solution to the treatment of wastewater from commercial laundries in Quebec (Canada) by using the extracellular polymeric substance (EPS) as a bio-flocculant. EPS was produced from the valorization of crude glycerol and paper mill sludge by a bacterial strain (BS-04). Two different types of EPS: Slime EPS (S-EPS) and Broth EPS (B-EPS) were used for the treatment of commercial laundry wastewater (CLWW). This is the first study for the treatment of CLWW using bio-flocculant EPS. A comparison between the conventional treatment of laundry wastewater (LWW) by chemical coagulants (FeSO4, CaCl2, Alum) and enhanced treatment by bio-flocculant EPS has been drawn in the study. Moreover, LWW treatment by a combination of EPS and chemical coagulants was also investigated. It was observed that S-EPS (0.6 g/L) gave better flocculation activity (FA) than B-EPS. S-EPS alone can remove 83.20% of turbidity, 77.69% of suspended solids (SS), and 76.37% of chemical oxygen demand (COD). The best results were obtained by combining S-EPS (0.6 g/L) with alum (300 mg/L) at pH 7 for a treatment time of 30 min. This combination was able to remove 98% of turbidity, 95.42% of SS, and 83.08% of COD from LWW. When treatment time has been increased to 4 h at pH 7, it resulted in more than 88% COD removal from CLWW.Graphical

Transformations of Ferrihydrite-Extracellular Polymeric Substance Coprecipitates Driven by Dissolved Sulfide: Interrelated Effects of Carbon and Sulfur Loadings.

The association of poorly crystalline iron (hydr)oxides with organic matter (OM), such as extracellular polymeric substances (EPS), exerts a profound effect on Fe and C cycles in soils and sediments, and their behaviors under sulfate-reducing conditions involve complicated mineralogical transformations. However, how different loadings and types of EPS and water chemistry conditions affect the sulfidation still lacks quantitative and systematic investigation. We here synthesized a set of ferrihydrite-organic matter (Fh-OM) coprecipitates with various model compounds for plant and microbial exopolysaccharides (polygalacturonic acids, alginic acid, and xanthan gum) and bacteriogenic EPS (extracted from Bacillus subtilis). Combining wet chemical analysis, X-ray diffraction, and X-ray absorption spectroscopic techniques, we systematically studied the impacts of C and S loadings by tracing the temporal evolution of Fe mineralogy and speciation in aqueous and solid phases. Our results showed that the effect of added OM on sulfidation of Fh-OM coprecipitates is interrelated with the amount of loaded sulfide. Under low sulfide loadings (S(-II)/Fe < 0.5), transformation to goethite and lepidocrocite was the main pathway of ferrihydrite sulfidation, which occurs more strongly at pH 6 compared to that at pH 7.5, and it was promoted and inhibited at low and high C/Fe ratios, respectively. While under high sulfide loadings (S(-II)/Fe > 0.5), the formation of secondary Fe-S minerals such as mackinawite and pyrite dominated ferrihydrite sulfidation, and it was inhibited with increasing C/Fe ratios. Furthermore, all three synthetic EPS proxies unanimously inhibited mineral transformation, while the microbiogenic EPS has a more potent inhibitory effect than synthetic EPS proxies compared at equivalent C/Fe loadings. Collectively, our results suggest that the quantity and chemical characteristics of the associated OM have a strong and nonlinear influence on the extent and pathways of mineralogical transformations of Fh-OM sulfidation.

Residual extracellular polymeric substances (EPS) detected by fluorescence microscopy on dental implants after different decontamination

Since the existing used detecting techniques were unable to distinguish the types of extracellular polymeric substances (EPS) components (polysaccharides, proteins, and nucleic acids et al.), it is needy to apply more targeted methods to detect the residual EPS components on decontaminated dental implants. Herein we aimed to assess whether fluorescence microscopy method was feasible for detecting residual EPS components on decontaminated dental implants. Six clinical-retrieved dental implants suffered severe peri-implantitis were collected, and also Staphylococcus aureus (S. aureus) cultured titanium discs were prepared. Before and after decontamination (Er:YAG laser, air-abrasive, and citric acid), corresponding fluorochrome stains were used to label polysaccharides, proteins, and nucleic acids on the samples for identification and then observed under confocal laser scanning microscopy (CLSM). Besides, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) detection techniques were also used. The results showed that fluorescent signals of EPS components are strong before decontamination and decreased after treatments, indicating that the intensity can roughly reflect the amounts. This preliminary study proved that EPS-stained fluorescence microscopy was feasible as a detection tool of choice for implant decontamination outcome evaluation. However, further study incorporating large sample size and quantified data should be carried out.

Effect of extracellular macromolecules from lactic acid bacteria on the immune response of black tiger shrimp (Penaeus monodon)

Extracellular polymeric substances (EPS) are known as prebiotic-like compounds that promote the growth of beneficial bacteria in the intestinal tract of humans and animals. To demonstrate the prebiotic potential of EPSs produced from lactic acid bacteria, Lactobacillus plantarumand Bifidobacterium bifidum, this study demonstrated the influence of these bacteria on the immune response in shrimp to infection with pathogenic bacteria. Vibrio parahaemolyticusdisease. The results showed that the diet supplemented with different types of EPS stimulated immunity of black tiger shrimp against acute hepatopancreatic necrosis disease, also known as early mortality syndrome in shrimp caused by Vibrio parahaemolyticus. The addition of EPS to shrimp feed significantly increased total white blood cell count, respiratory burst activity, phenoloxidase and superoxide dismutase activity. The study results show that EPS produced by lactic acid bacteria shows potential as a prebiotic, which can become an alternative to the use of antibiotics in shrimp farming to inhibit the growth of pathogens.

A combination therapy strategy for treating antibiotic resistant biofilm infection using a guanidinium derivative and nanoparticulate Ag(0) derived hybrid gel conjugate.

Bacteria organized in biofilms show significant tolerance to conventional antibiotics compared to their planktonic counterparts and form the basis for chronic infections. Biofilms are composites of different types of extracellular polymeric substances that help in resisting several host-defense measures, including phagocytosis. These are increasingly being recognized as a passive virulence factor that enables many infectious diseases to proliferate and an essential contributing facet to anti-microbial resistance. Thus, inhibition and dispersion of biofilms are linked to addressing the issues associated with therapeutic challenges imposed by biofilms. This report is to address this complex issue using a self-assembled guanidinium–Ag(0) nanoparticle (AD-L@Ag(0)) hybrid gel composite for executing a combination therapy strategy for six difficult to treat biofilm-forming and multidrug-resistant bacteria. Improved efficacy was achieved primarily through effective biofilm inhibition and dispersion by the cationic guanidinium ion derivative, while Ag(0) contributes to the subsequent bactericidal activity on planktonic bacteria. Minimum Inhibitory Concentration (MIC) of the AD-L@Ag(0) formulation was tested against Acinetobacter baumannii (25 μg mL−1), Pseudomonas aeruginosa (0.78 μg mL−1), Staphylococcus aureus (0.19 μg mL−1), Klebsiella pneumoniae (0.78 μg mL−1), Escherichia coli (clinical isolate (6.25 μg mL−1)), Klebsiella pneumoniae (clinical isolate (50 μg mL−1)), Shigella flexneri (clinical isolate (0.39 μg mL−1)) and Streptococcus pneumoniae (6.25 μg mL−1). Minimum bactericidal concentration, and MBIC50 and MBIC90 (Minimum Biofilm Inhibitory Concentration at 50% and 90% reduction, respectively) were evaluated for these pathogens. All these results confirmed the efficacy of the formulation AD-L@Ag(0). Minimum Biofilm Eradication Concentration (MBEC) for the respective pathogens was examined by following the exopolysaccharide quantification method to establish its potency in inhibition of biofilm formation, as well as eradication of mature biofilms. These effects were attributed to the bactericidal effect of AD-L@Ag(0) on biofilm mass-associated bacteria. The observed efficacy of this non-cytotoxic therapeutic combination (AD-L@Ag(0)) was found to be better than that reported in the existing literature for treating extremely drug-resistant bacterial strains, as well as for reducing the bacterial infection load at a surgical site in a small animal BALB/c model. Thus, AD-L@Ag(0) could be a promising candidate for anti-microbial coatings on surgical instruments, wound dressing, tissue engineering, and medical implants.

Enhancement of landfill leachate treatment using extracellular polymeric substances as bio-flocculants

Fermentation of Klebsiella pneumoniae was conducted using crude glycerol fortified with secondary paper mill sludge as a carbon source in 5 L fermenter. After 96 hours of fermentation, the fermented broth contained mostly microbial cells surrounded by extracellular polymeric substances (EPS) and other particulate residues from paper mill sludge and glycerol. When this fermented broth is used as it is, it is called broth EPS (B-EPS). When the fermented broth is centrifuged, the supernatant solution is separated from the rest of the microbial cells and from sludge residues. This supernatant is called Slime-EPS (S-EPS). Both types of EPS were used for treatment of landfill leachate. S-EPS showed better flocculation activity (85%) than B-EPS (70%). EPS was also used in combination of Al2(SO4)3 or FeSO4. The removal efficiency of COD with use of S-EPS combined with FeSO4 (more than 80% of COD removal) was higher than with S-EPS alone (48% of COD removal). Better results were recorded when S-EPS (0.015 g/L) was combined with FeSO4 (2 g/L) at pH 8. A remarkable reduction of the following parameters was recorded: COD (82%), total nitrogen (44%), phosphorus (50%) and removal of metals such as Ca (64.3%) and Mg (62.4%).

Stickiness of extracellular polymeric substances on different surfaces via magnetic tweezers

Organic particle dynamics in the surface ocean plays a critical part in the marine carbon cycle. Aggregation of marine organic particles drives their downward transport to support various marine organisms on their transit to the sediments. Extracellular polymeric substances (EPS) from various microbes are a major contributor to the oceanic organic particle pool. The stickiness of EPS is expected to play a determining role in the aggregation process of particles; however, stickiness parameters are usually indirectly estimated through data fitting without direct assessment. Here a magnetic tweezer method was developed to quantitatively assess the stickiness of three model EPS produced by: Amphora sp., (diatom), Emiliania huxleyi (coccolithophore), and Sagittula stellata (bacteria), under different in vitro environmental conditions (salinity or EDTA complexed cations) and surface matrices (EPS-EPS and bare glass). Our results showed the stickiness of three microbial EPS decreasing for S. stellata > E. huxleyi > Amphora sp., in line with their decreasing protein-to-carbohydrate (P/C) ratios (related to their relative hydrophobicity). The data not only emphasize the importance of hydrophobicity on EPS stickiness, but also demonstrates that salinity and the nature of the substrate surface can influence the stickiness. Furthermore, we investigated stickiness between various types of EPS, and the observed selective stickiness of EPS between species may shed light on the interactions among heterogeneous marine microorganisms. Overall, this newly developed system provides a platform to assess the EPS stickiness to advance our understanding of the aggregation and sedimentation process of organic particles that are critical for the fate of organic carbon as well as for biofilm formation and microbial colonization of surfaces in the ocean.

Denitrification performance and mechanism of a novel isolated Acinetobacter sp. FYF8 in oligotrophic ecosystem

The main purpose of this study is to isolate and purify oligotrophic denitrifying bacteria, Acinetobacter sp. FYF8, so as to study the denitrification capacity and characteristics in response to oligotrophic ecosystem. The RSM showed that the best denitrification efficiency was 97.90% under 7.58 pH, 20.69 °C temperature, and 2.83 C/N ratio. Nitrogen balance experiments showed that the nitrogen gas conversion ratio was 39.88, 68.85, and 78.79% at 2.0, 2.5, and 3.0 C/N ratio, respectively. According to 3D-EEM, tyrosine, tryptophan and aromatic protein were the metabolites produced by strain FYF8. The concentration of polysaccharide (PS) and proteins (PN) in different types of extracellular polymeric substances (EPS) and the variation trend were quantitatively studied. Different functional groups such as CH2, C = O, and C-O-C was characterized by FTIR. These findings indicated that the denitrification strategy of strain FYF8 was related to EPS, which might be a reserve carbon storage in carbon scarcity.

Impact of exposure of crude oil and dispersant (Corexit) on aggregation of extracellular polymeric substances

Spilled oil treated with Corexit dispersant can cause unintended impacts on marine environment systems including altering marine organic matter dynamics; however, impacts on microgels and marine oil snow (MOS) formation are still debated and remain to be fully understood. Extracellular polymeric substances (EPS) are a major source of marine organic carbon for MOS and microgel formation. EPS initial aggregation plays key roles in the oil degrading process and various biogeochemical reactions. Here we used four types of EPS with water accommodated fraction (WAF), chemically-enhanced WAF (CEWAF) and Corexit, to represent potential situations during oil spills and post-application of Corexit. We found that Corexit alone can inhibit EPS aggregation and disperse pre-existing microgels. CEWAF can enhance EPS aggregation with efficiency by up to 80%–100% and more aggregates accumulated within the air-water interface. Additionally, more hydrophobic EPS aggregates showed high resistance to Corexit dispersion while hydrophilic EPS were more sensitive. Effects of oil spills on marine gel particle formation are primarily determined by chemical characteristics (hydrophobicity and protein content) of the constituent EPS. This study offers unique insights for organic particle dynamics and identifies controlling factors for MOS or gel particles associated with oil spills and Corexit dispersant used.

Effects of biomass pyrolysis derived wood vinegar (WVG) on extracellular polymeric substances and performances of activated sludge

The effects of wood vinegar (WVG) on extracellular polymeric substances (EPS), and flocculation, sedimentation and dewatering performances of activated sludge were investigated in sequencing batch reactor (SBR) process. Results showed that polysaccharide (PS) and DNA were accounted for the largest and smallest proportion of EPS, respectively. With WVG injection, productions of soluble EPS (S-EPS), loosely bound EPS (LB-EPS), tightly bound EPS (TB-EPS), protein (PN), PS, and DNA were significantly increased. The optimal WVG concentration was found as 4 μl/l. The effects of WVG on different types of EPS followed an order of LB-EPS > TB-EPS > S-EPS. According to batch and long-term SBR operations, WVG could increase the biomass amount of activated sludge, which was beneficial to improve sewage treatment efficiencies. However, WVG showed negative impact on flocculation, sedimentation, and dewatering performance of activated sludge.

Membrane fouling by extracellular polymeric substances after ozone pre-treatment: Variation of nano-particles size

The application of ozone pre-treatment for ultrafiltration (UF) in drinking water treatment has been studied for more than 10 years, but its performance in mitigating or exacerbating membrane fouling has been inconclusive, and sometimes contradictory. To help explain this, our study considers the significance of the influent organic matter and its interaction with ozone on membrane fouling, using solutions of two representative types of extracellular polymeric substances (EPS), alginate and bovine serum albumin (BSA), and samples of surface water. The results show that at typical ozone doses there is no measurable mineralization of alginate and BSA, but substantial changes in their structure and an increase in the size of nano-particle aggregates (micro-flocculation). The impact of ozonation on membrane fouling, as indicated by the membrane flux, was markedly different for the two types of EPS and found to be related to the size of the nano-particle aggregates formed in comparison with the UF pore size. Thus, for BSA, ozonation created aggregate sizes similar to the UF pore size (100 k Dalton) which led to an increase in fouling. In contrast, ozonation of alginate created the nano-particle aggregates greater than the UF pore size, giving reduced membrane fouling/greater flux. For solutions containing a mixture of the two species of EPS the overall impact of ozonation on UF performance depends on the relative proportion of each, and the ozone dose, and the variable behaviour has been demonstrated by the surface water. These results provide new information about the role of nano-particle aggregate size in explaining the reported ambiguity over the benefits of applying ozone as pre-treatment for ultrafiltration.

Different Types of Diatom-Derived Extracellular Polymeric Substances Drive Changes in Heterotrophic Bacterial Communities from Intertidal Sediments.

Intertidal areas support extensive diatom-rich biofilms. Such microphytobenthic (MPB) diatoms exude large quantities of extracellular polymeric substances (EPS) comprising polysaccharides, glycoproteins and other biopolymers, which represent a substantial carbon pool. However, degradation rates of different EPS components, and how they shape heterotrophic communities in sediments, are not well understood. An aerobic mudflat-sediment slurry experiment was performed in the dark with two different EPS carbon sources from a diatom-dominated biofilm: colloidal EPS (cEPS) and the more complex hot-bicarbonate-extracted EPS. Degradation rate constants determined over 9 days for three sediment fractions [dissolved organic carbon (DOC), total carbohydrates (TCHO), and (cEPS)] were generally higher in the colloidal-EPS slurries (0.105–0.123 d−1) compared with the hot-bicarbonate-extracted-EPS slurries (0.060–0.096 d−1). Addition of hot-bicarbonate-EPS resulted in large increases in dissolved nitrogen and phosphorous by the end of the experiment, indicating that the more complex EPS is an important source of regenerated inorganic nutrients. Microbial biomass increased ~4–6-fold over 9 days, and pyrosequencing of bacterial 16S rRNA genes revealed that the addition of both types of EPS greatly altered the bacterial community composition (from 0 to 9 days) compared to a control with no added EPS. Bacteroidetes (especially Tenacibaculum) and Verrucomicrobia increased significantly in relative abundance in both the hot-bicarbonate-EPS and colloidal-EPS treatments. These differential effects of EPS fractions on carbon-loss rates, nutrient regeneration and microbial community assembly improve our understanding of coastal-sediment carbon cycling and demonstrate the importance of diverse microbiota in processing this abundant pool of organic carbon.

Evolutionary adaptations of biofilms infecting cystic fibrosis lungs promote mechanical toughness by adjusting polysaccharide production

Biofilms are communities of microbes embedded in a matrix of extracellular polymeric substances, largely polysaccharides. Multiple types of extracellular polymeric substances can be produced by a single bacterial strain. The distinct polymer components of biofilms are known to provide chemical protection, but little is known about how distinct extracellular polysaccharides may also protect biofilms against mechanical stresses such as shear or phagocytic engulfment. Decades-long infections of Pseudomonas. aeruginosa biofilms in the lungs of cystic fibrosis patients are natural models for studies of biofilm fitness under pressure from antibiotics and the immune system. In cystic fibrosis infections, production of the extracellular polysaccharide alginate has long been known to increase with time and to chemically protect biofilms. More recently, it is being recognized that chronic cystic fibrosis infections also evolve to increase production of another extracellular polysaccharide, Psl; much less is known about Psl’s protective benefits to biofilms. We use oscillatory bulk rheology, on biofilms grown from longitudinal clinical isolates and from genetically-manipulated lab strains, to show that increased Psl stiffens biofilms and increases biofilm toughness, which is the energy cost to cause the biofilm to yield mechanically. Further, atomic force microscopy measurements reveal greater intercellular cohesion for higher Psl expression. Of the three types of extracellular polysaccharides produced by P. aeruginosa, only Psl increases the stiffness. Stiffening by Psl requires CdrA, a protein that binds to mannose groups on Psl and is a likely cross-linker for the Psl components of the biofilm matrix. We compare the elastic moduli of biofilms to the estimated stresses exerted by neutrophils during phagocytosis, and infer that increased Psl could confer a mechanical protection against phagocytic clearance.

Composition and aggregation of extracellular polymeric substances (EPS) in hyperhaline and municipal wastewater treatment plants.

As important constituents of activated sludge flocs, extracellular polymeric substances (EPS) play significant roles in pollutants adsorption, the formation and maintenance of microbial aggregates, and the protection of microbes from external environmental stresses. In this work, EPS in activated sludge from a municipal wastewater treatment plant (M-WWTP) with anaerobic/anoxic/oxic (A2/O) process and a hyperhaline wastewater treatment plant (H-WWTP) with anaerobic/oxic (A/O) process were extracted by ultrasound method. The proteins and polysaccharides contents in EPS were determined by using a modified Lowry method and anthrone colorimetry respectively to analyze the detail differences in two types of WWTPs. Fourier transform-infrared spectroscopy and three-dimensional excitation-emission matrix fluorescence spectroscopy demonstrated proteins and polysaccharides were the dominant components of the two types of EPS, and the aromatic protein-like substances accounted for a larger proportion in EPS proteins. The results of the aggregation test indicated that EPS were good for the sludge aggregation, and the EPS in oxic sludge were more beneficial to sludge aggregation than that in anoxic sludge. Anoxic sludge EPS in H-WWTP showed a negligible effect on sludge aggregation. Comparative study on EPS of different tanks in the M-WWTP and H-WWTP was valuable for understanding the characteristics of EPS isolated from two typical wastewater treatment processes.

Characterization of Extracellular Polymeric Substances (Eps) Produced by Cloacibacterium normanense Isolated from Wastewater Sludge for Sludge Settling and Dewatering

In this study, extracellular polymeric substances (EPSs) producing strain was isolated from municipal wastewater sludge (MWWS). Growth profile and the EPS production by Cloacibacterium normanense using wastewater sludge as raw material in shake flask fermentation for 96 h were investigated. The highest concentration of S-EPS (13.0 ± 0.8 g/L) and C-EPS (0.3 ± 0.1 g/L) were attained at 48 h of fermentation. S-EPS revealed higher flocculation activity (94.2%) and dewaterability (59.9%) than other types of EPS in kaolin suspension. The dewaterability of MWWS with 2 g suspended solids (SS)/L was improved by 37.6% using 0.02 ± 0.01 g/L of S-EPS and 600 mg/L of Al2(SO4)3. The study showed a promising approach of new isolated strain to produce high concentration EPS in sludge with high flocculation activity as well as good settling.

Spatiotemporal distribution of different extracellular polymeric substances and filamentation mediate Xylella fastidiosa adhesion and biofilm formation.

Microorganism pathogenicity strongly relies on the generation of multicellular assemblies, called biofilms. Understanding their organization can unveil vulnerabilities leading to potential treatments; spatially and temporally-resolved comprehensive experimental characterization can provide new details of biofilm formation, and possibly new targets for disease control. Here, biofilm formation of economically important phytopathogen Xylella fastidiosa was analyzed at single-cell resolution using nanometer-resolution spectro-microscopy techniques, addressing the role of different types of extracellular polymeric substances (EPS) at each stage of the entire bacterial life cycle. Single cell adhesion is caused by unspecific electrostatic interactions through proteins at the cell polar region, where EPS accumulation is required for more firmly-attached, irreversibly adhered cells. Subsequently, bacteria form clusters, which are embedded in secreted loosely-bound EPS, and bridged by up to ten-fold elongated cells that form the biofilm framework. During biofilm maturation, soluble EPS forms a filamentous matrix that facilitates cell adhesion and provides mechanical support, while the biofilm keeps anchored by few cells. This floating architecture maximizes nutrient distribution while allowing detachment upon larger shear stresses; it thus complies with biological requirements of the bacteria life cycle. Using new approaches, our findings provide insights regarding different aspects of the adhesion process of X. fastidiosa and biofilm formation.

A new classification paradigm of extracellular polymeric substances (EPS) in activated sludge: Separation and characterization of exopolymers between floc level and microcolony level

Extracellular polymeric substances (EPS) play a crucial role in the formation of activated sludge flocs. However, until now, the EPS are rather classified by the method used for extraction than by a theoretical consideration of their function and composition. In this paper, a new classification paradigm of EPS was proposed, which offered a novel approach to identify the role of EPS in the formation of activated sludge flocs. The current study gave an exploration to distinguish the EPS in the floc level (extra-microcolony polymers, EMPS) and in the microcolony level (extra-cellular polymers, ECPS). It was found that cation exchange resin treatment is efficient to disintegrate the flocs for EMPS extraction, however, inefficient to disaggregate the microcolonies for ECPS harvesting. A two-steps extraction strategy (cation exchange resin treatment followed by ultrasonication-high speed centrifugation treatment) was suggested to separate these two types of EPS in activated sludge flocs and the physicochemical characteristics of EMPS and ECPS were compared. The protein/polysaccharide ratio of ECPS was higher than that of EMPS and the molecular weight of proteins in EMPS and ECPS were found to be different. The ECPS contained higher molecular weight proteins and more hydrophobic substances than the EMPS contained. The result of excitation-emission matrix fluorescence spectroscopy analysis also showed that the EMPS and the ECPS have different fluorescent expressions and the components of EMPS were more diverse than that of ECPS. All results reported herein demonstrated that two different types of exopolymers exist in the activated sludge flocs and the inter-particle forces for aggregation of activated sludge flocs are not identical between the floc level and the microcolony level. It suggested that cation bridging interactions are more crucial in floc level flocculation, while the entanglement and hydrophobic interactions are more important in microcolony level cohesion.