Effect Of Extracellular Polymeric Substances Research Articles

Effects of Extracellular Polymeric Substances and Specific Compositions on Enhancement of Copper Bioleaching Efficiency from Waste Printed Circuit Boards

Bioleaching has been proven to be an efficient and environment-friendly method for processing metalliferous ore and waste printed circuit boards (PCBs), a type of urban mine waste. Extracellular polymeric substances (EPS) play a major role in the attachment of bacteria to the surface of sulfide minerals. However, there are few reports on the effects of EPS components on the bioleaching of metals from PCBs. In this study, synthetic EPS were used to investigate the effects of the composition of exo-polymers on the bioleaching of copper from waste PCBs, including the process efficiency. The copper extraction rate in bioleaching assays with synthetic EPS was 11.7% greater than in those without synthetic EPS. Moreover, the composition of EPS was proven to be a crucial factor affecting the efficiency of copper bioleaching, with EPS containing arginine yielding the highest recovery (95.2% copper). Under the condition of 0.5 g/L synthetic EPS added at the early stage of log phase, the copper leaching efficiency from waste PCBs was highly improved. This study provides important insights into how to analyze the working mechanisms of EPS for a better recovery efficiency.

Effects of extracellular polymeric substances on silver nanoparticle bioaccumulation and toxicity to Triticum aestivum L.

The potential effects of extracellular polymeric substances (EPS) on the behavior and toxicity of silver nanoparticle (Ag-NPs) and silver sulfide nanoparticle (Ag2S-NPs) remains ambiguous. The interaction of EPS from Bacillus subtilis with Ag2S-NPs, metallic Ag-NPs, or ionic Ag, and the associated plant safety had been examined in this study. The biological impacts of Ag-NPs and Ag2S-NPs were Ag form-dependent and highly influenced by microbial EPS. Compared with metallic Ag-NPs, Ag2S-NPs exert inert biological impacts, as revealed by 3.44 times lower Ag bioaccumulation in wheat (Triticum aestivum L.) seedlings and nearly reduce plant biomass when wheat was subjected to 1.0 mg-Ag L−1 of Ag-NPs and Ag2S-NPs with the transfer factors of 151.56–930.87 vs. 12.52–131.81, respectively. These observations were coincident with the low dissolved Ag ([Ag]diss) in the Ag2S-NPs treatment than the Ag-NPs treatment (114.0 vs. 0.0791, μg L−1). Compared with the enhanced toxicity of Ag2S-NPs to wheat, Bacillus subtilis EPS significantly alleviate the phytotoxicity of Ag-NPs, as revealed by the relative root elongation (7.15–45.40% decrease vs. 2.39–11.75% increase), and malondialdehyde (1.47–83.22% increase vs. 8.57–25.25% decrease) and H2O2 (11.27–71.78% increase vs. 5.16–36.67% decrease) contents. These constrasting plant responses of B. subtilis EPS are mainly caused by their complexation property with toxic Ag+ and nutrient elements for wheat stressed by Ag-NPs and Ag2S-NPs, respectively. Our findings highlight the importance of rhizospheric EPS in affecting the biogeochemistry and ecotoxicity of metal nanoparticles including Ag-NPs and Ag2S-NPs in agricultural systems.

Effect of extracellular polymeric substances on the phosphorus adsorption characteristics of sediment particles

Extracellular polymeric substances (EPS) have a great impact on the characteristics of sediment particles and their environmental effects in hydro-environmental systems, yet little effort has been made to study the considerable variability in the element adsorption process of sediment particles caused by EPS. Understanding the variability of the adsorption characteristics of sediment particles associated with EPS and quantifying the scale of the adsorption isotherm parameters are important for understanding how EPS mediate sediment properties and environmental factors. In this paper, isothermal equilibrium adsorption experiments are done on phosphorus to study the influence of EPS on the adsorption characteristics of sediment particles, and the Langmuir adsorption isotherm is applied to analyze the adsorption rule of sediment particles under the impact of EPS. The current research demonstrates that significant differences will take place in the adsorption characteristics of sediments coated with EPS at different development phases and the phosphorus adsorption capacity of sediment particles increases with the growth of EPS. The difference in the adsorption percentage between sediment particles coated with EPS of 0 and 6 weeks growth time is about 42%–60% for different initial aqueous phosphorus concentration. A formula describing the adsorption isotherm parameter of the maximum material (element) adsorption capacity of sediment particles change over time is further proposed based on the experimental data. The current study provides some evidence for the interaction of sediment particles, EPS, and adsorbed elements in the water environment.

Role of extracellular polymeric substances in the adhesion interaction of Streptococcus mutans on TiO2 and SiO2 surfaces with different wettability

The purpose of the work is to evaluate the effect of extracellular polymeric substance (EPS) on the surface properties of Streptococcus mutans, and on the interaction between the bacteria and anti-adhesion nanostructured surfaces. Interactions between Streptococcus mutans with or without EPS and nanostructured surfaces were measured with atomic force microscope. Acid-base, Van der Waals, and electrostatic interactions were evaluated according to XDLVO theory. The absorption of glucan was evaluated by quartz crystal microbalance method. Results indicate Streptococcus mutans adhere stronger on surfaces with lower surface energy in both EPS and non-EPS conditions, because acid-base interaction is dominant. It indicates the superhydrophobic surface is lack of durability and reliability in the underwater anti-adhesion. Larger adhesion forces of Streptococcus mutans are shown in EPS than non-EPS conditions. That is due to more hydrogen bonds formed between glucan and substrate surfaces, and the EPS reducing surface energy and affecting acid-base interaction.

New insights into the effect of extracellular polymeric substance on the sludge dewaterability based on interaction energy and viscoelastic acoustic response analysis

To elucidate the effects of extracellular polymeric substance (EPS) on the sludge dewaterability, this study comparatively investigated the changes in EPS composition and spatial distribution, together with the sludge dewaterability after lysozyme (LZM) conditioning. The protein concentration in the tightly bound EPS (TB-EPS) increased from 3.47 mg g−1 DS to 4.99 mg g−1 DS within the first 2 min, then gradually decreased, which could be described by a piecewise linear function. Unlike TB-EPS, the protein content variation trend in both soluble EPS (S-EPS) and loosely bound EPS (LB-EPS) followed the typical first-order kinetics. Additionally, the extended DLVO theory was employed in combination with viscoelastic acoustic response analysis to further explore the impact of EPS composition on water adhesion and microbial cell. After the extraction of S-EPS from the conditioned sludge, the adsorption free energy (ΔGadh) of EPS ascended to −61.05 mJ m−2, indicating the weakened microbial hydrophobicity. By contrast, the ΔGadh value declined after the subsequent extraction of LB-EPS and TB-EPS. Meanwhile, the adsorption potential energy between S-EPS and microbial cells showed an increasing trend, whereas the repulsion potential energy between TB-EPS and microbial cells fell to 1.40 × 104 kT, signifying a weakened adsorption capacity to water. Accordingly, the viscosity and shear modulus of each EPS layer were reduced after conditioning, which contributed to the transformation of bound water into free water. These changes reasonably explained the results that the water content in the dewatered sludge after conditioning was reduced to 58.54%, and the bound water content decreased by 15.06%.

Effects of Extracellular Polymeric Substances on the Formation and Methylation of Mercury Sulfide Nanoparticles.

Growing evidence has suggested that microbial biofilms are potential environmental "hotspots" for the production and accumulation of a bioaccumulative neurotoxin, methylmercury. Here, we demonstrate that extracellular polymeric substances (EPS), the main components of biofilm matrices, significantly interfere with mercury sulfide precipitation and lead to the formation of nanoparticulate metacinnabar available for microbial methylation, a natural process predominantly responsible for the environmental occurrence of methylmercury. EPS derived from mercury methylating bacteria, particularly Desulfovibrio desulfuricans ND132, substantially increase the methylation potential of nanoparticulate mercury. This is likely due to the abundant aromatic biomolecules in EPS that strongly interact with mercury sulfide via inner-sphere complexation and consequently enhance the short-range structural disorder while mitigating the aggregation of nanoparticulate mercury. The EPS-elevated bioavailability of nanoparticulate mercury to D. desulfuricans ND132 is not induced by dissolution of these nanoparticles in aqueous phase, and may be dictated by cell-nanoparticle interfacial reactions. Our discovery is the first step of mechanistically understanding methylmercury production in biofilms. These new mechanistic insights will help incorporate microbial EPS and particulate-phase mercury into mercury methylation models, and may facilitate the assessment of biogeochemical cycling of other nutrient or toxic elements driven by EPS-producing microorganisms that are prevalent in nature.

Performance and membrane fouling behaviors analysis with SVR-LibSVM model in a submerged anaerobic membrane bioreactor treating low-strength domestic sewage

Abstract A submerged anaerobic membrane bioreactor (SAnMBR) was operated for low-strength domestic sewage treatment over a period of 190 days. Average chemical oxygen demand (COD) removal efficiency ranged from 64.41 to 83.49%, and the removal of ammonia nitrogen (NH 4 + -N) and total phosphorus (TP) were relatively poor. No acidification occurred in the reactor during operation. The performance and membrane fouling behaviors of SAnMBR were investigated and support vector regression model with LibSVM package (SVR-LibSVM) was established to predict performance and analyze the effect of extracellular polymeric substances (EPSs) on membrane fouling. The effect of organic loading rate (OLR) on COD removal efficiency at each stage was also studied according to the model. Both transmembrane pressure (TMP) and total membrane resistance ( R t ) have a significant decline when membrane flushing was carried out. However, physical flushing could alleviate rather than eliminate membrane fouling.

Effects of extracellular polymeric substance fractions on polyacrylamide demand and dewatering performance of digested sludges

High polymer demand in sludge conditioning is an intractable aspect of the water industry. This study investigated the effects of extracellular polymeric substances (EPS) fractions on polyacrylamide demand for conditioning and dewatering performance. Specifically, it examined aerobically and anaerobically digested sludges from seven full-scale wastewater treatment plants (WWTPs). Our study successfully quantified the contributions of soluble EPS to polyacrylamide demand during conditioning and explained the role of tightly bound EPS (TB-EPS) in determining the digested sludges’ dewatering performance. Results show that the concentrations of soluble EPS in the sludges varied between 92 and 1148 mg/L. Experimental results also demonstrated that between 25% and 80% of polyacrylamides used for conditioning were wasted in “parasitic” reactions with soluble EPS. The residual cationic polyacrylamide left in solution, after the parasitic reactions, was substantial and varied between 35 and 254 mg/L. Despite this outcome, the zeta potential values of dewatered sludge cakes remained negative, i.e. between −24 and −35 mV. These indicated that the residual soluble cationic polyacrylamides would not have been absorbed on the negatively charged sludge particles. This explained the relatively poor performance of the dewatering stage in the treatment plants studied. Furthermore the results suggested the TB-EPS attached to the sludge particles would be responsible for the poor dewatering. We postulated that the TB-EPS would gelify and immobilize the water surrounding the sludge particles. Our study suggested that new and more effective polymers for conditioning are needed to both: (i) reduce polymer demand; and (ii) improve the dewatering performance.

Optimization of extraction method for extracellular polymeric substances of Phanerochaete chrysosporium

There are many methods for extracting extracellular polymeric substances of white rot fungi. In this experiment, we studied the efficiency of NaOH method, EDTA-2Na method and high-speed centrifugation method. Without destroying the cell structure and the activity of extracellular polymeric substances, we maximized the effect of extracellular polymeric substances. The results showed that in the ultrasonic centrifugation method, the polysaccharide concentration in the extracted EPS solution gradually increased with the increase of the ultrasonic action time. The concentration of polysaccharide in the EPS solution extracted under the ultrasonic action for 10 min and 12000 rpm was the highest (613.638 mg/L); on the whole, the ultrasonic treatment time has a greater impact on the extraction efficiency of polysaccharides in the extracellular polymer of Phanerochaete chrysosporium, and the polysaccharide concentration changes greatly. This study can provide useful information for the follow-up experiments related to extracellular polymeric substances of white rot fungi.

Effect of extracellular polymeric substances on arsenic accumulation in Chlorella pyrenoidosa

Inorganic arsenic (iAs) in its dominant dissolved phase in the environment is known to pose major threats to ecological and human health. While the biological effects in many arsenic-bearing freshwaters have been extensively studied, the behavior and bioaccumulation of dissolved iAS in the presence of extracellular polymeric substances (EPS) still remains to be a critical knowledge gap. In this study, the uptakes and kinetic characteristics of iAs were studied using Chlorella pyrenoidosa (a typical freshwater green algae) by addressing the different effects of EPS on arsenite (AsШ) and arsenate (AsV). The arsenic uptake capacity increased as the exposure concentration increased from 0 to 300 µmol L−1, and the uptake rate constants (Ku) in the Bio-dynamic model were greater for AsV than AsШ (0.63–11.57 L g−1 h−1 vs. 0.44–5.43 L g−1 h−1). The toxic effects as mitigated by EPS were observed through the morphological changes of algal cells by TEM and SEM. When compared with the EPS-free algal cells (EPS-F), EPS-covered cells (EPS-C) had a higher arsenic adsorption capacity through EPS-enhanced surface adsorption and reduced intracellular uptake. The overall decrease (35% and 23.3% for AsШ and AsV, respectively) in the maximum uptake capacity in intact algae cells favors cell’s tolerance to the toxic effects of iAs. These observed discrepancies between AsШ and AsV and between EPS-C and EPS-F were further elucidated through morphological images (TEM and SEM) and molecular/atomic spectroscopic data that combine three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Altogether, the spectroscopic evidence revealed the interactions of iAs with C–O–C, C–O–H and –NH2 functional groups in EPS’ tyrosine- and tryptophan-like proteins as the binding sites. Overall, this study for the first time provides comprehensive evidence on the iAs-EPS interactions. Such insights will benefit our understanding of the biogeochemical processes of iAs and the strategic development of bioremediation techniques involving microalgae in the natural and engineered systems.

Effect of extracellular polymeric substances (EPS) conditioned by combined lysozyme and cationic polyacrylamide on the dewatering performance of activated sludge

Extracellular polymeric substance (EPS) and the water within it account for about 80% of the total sludge mass, significantly correlated with sludge charge properties, particle size, and dewaterability, while their relation is still ambiguous. To clarify the effect of EPS characteristics on the activated sludge dewaterability, the sludge conditioned by cationic polyacrylamide (CPAM) and lysozyme alone or in combination was comparatively investigated by the means of the SPSS17 software incorporation with chemical analysis. According to the results, the combined conditioning increased both dewatering extent and dewatering rate with the water content as low as 57.79%. It was mainly attributed to the destruction of microbial cell wall and EPS structure by enzymatic conditioning, beneficial for the release of protein (PN) and polysaccharide (PS), as well as the conversion of intracellular water and some bound water into free water. Additionally, Pearson's correlation and factor analysis confirmed the significant influence of EPS properties on sludge dewaterability and explored their detailed relationship. It was indicated the most crucial factors consisted of PNS (PN in S-EPS), PNL (PN in LB-EPS), PNT (PN in TB-EPS), and PST (PS in TB-EPS) accounted for 72.83% in all of the total variance for the contribution to the dewatered water content. Moreover, the high concentration of PNS and PNL led to the zeta potential rising to −9.74 mV, and the destruction of EPS structure was favorable for sludge to form smaller particle size and compact floc structure. All the results were confirmed by the microstructure changes of the sludge flocs.

Effects of extracellular polymeric substances and microbial community on the anti-scouribility of sewer sediment

Sewer sediment is the main source of overflow pollution, and the anti-scouribility of sewer sediment directly determines the amount of the discharged contaminants. In this study, sewer sediments of different depths were collected from combined and storm sewers in Shanghai, China. The anti-scouribility, represented by the shear stress of each layer of sewer sediment, was detected in situ. The microbial community and extracellular polymeric substances (EPS), including carbohydrates and proteins present in the sewer sediments were characterized. The results indicated that the distribution of the anti-scouribility of sewer sediment is regulated. There were positive correlations between the content of EPS, proteins, and carbohydrates, and the anti-scouribility of sediments (Pearson Corr. = 0.604, sig. = 0.219; Pearson Corr. = 0.623, sig. = 0.234; Pearson Corr. = 0.727, sig. = 0.359, respectively). Furthermore, the microbial community had a positive influence on anti-scouribility. In particular, the gram-positive bacterial phyla of Bacteroidetes and Firmicutes may be important and influential for the improvement of anti-scouribility of sediment owing to their production of cellulose.

Investigation of membrane fouling in an anaerobic membrane bioreactor (AnMBR) treating pharmaceutical wastewater

This study is focused on the fouling of flat-sheet and hollow-fiber membranes in a lab-scale anaerobic membrane bioreactor (AnMBR). A comprehensive investigation including scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), fourier transform infrared (FT-IR) spectroscopy, confocal laser scanning microscopy (CLSM), zeta potential, optical profilometer and contact angle, and flux modelling was presented in this study. The effect of extracellular polymeric substances (EPS) accumulated on cake-layer were also considered. The cake-layer on the flat-sheet membrane formed much more than that on the hollow-fiber membrane. The thickness of cake-layer on the flat-sheet membrane was effectively decreased by physical stripping. However, proteins indicating structures of Amide I and Amide II, and carbohydrates were observed on the stripped hollow-fiber membrane. According to the flux modelling results, the cake-layer formation and intermediate-adsorption were found as effective mechanisms on both membranes. Especially, these mechanisms were more effective for the hollow-fiber membrane due to irreversible fouling.

Individual and Combined Effects of Extracellular Polymeric Substances and Whole Cell Components of Chlamydomonas reinhardtii on Silver Nanoparticle Synthesis and Stability.

The fresh water microalga Chlamydomonas reinhardtii bioreduced Ag+ to silver nanoparticles (AgNPs) via three biosynthetic routes in a process that could be a more sustainable alternative to conventionally produced AgNPs. The AgNPs were synthesized in either the presence of whole cell cultures, an exopolysaccharide (EPS)-containing cell culture supernatant, or living cells that had been separated from the EPS-containing supernatant and then washed before being suspended again in fresh media. While AgNPs were produced by all three methods, the washed cultures had no supernatant-derived EPS and produced only unstable AgNPs, thus the supernatant-EPS was shown to be necessary to cap and stabilize the biogenic AgNPs. TEM images showed stable AgNPs were mostly spherical and showed a bimodal size distribution about the size ranges of 3.0 ± 1.3 nm and 19.2 ± 5.0 nm for whole cultures and 3.5 ± 0.6 nm and 17.4 ± 2.6 nm for EPS only. Moreover, selected area electron diffraction pattern of these AgNPs confirmed their polycrystalline nature. FTIR of the as-produced AgNPs identified polysaccharides, polyphenols and proteins were responsible for the observed differences in the AgNP stability, size and shape. Additionally, Raman spectroscopy indicated carboxylate and amine groups were bound to the AgNP surface.

Effects of extracellular polymeric substances of Pseudomonas fluorescens, citrate, and oxalate on Pb sorption by an acidic Ultisol

The continuous production of low molecular weight (LMW) organic acids by plants and microorganisms coupled with the continuous presence of extracellular polymeric substances (EPS) in soils is a guarantee that the mobility of heavy metals in soils will be controlled. The effects of citrate, oxalate, and EPS on the adsorption of Pb by an acidic Ultisol were studied both as a function of pH and ionic strength. Electrokinetic potential measurements were also employed to observe to what extent each ligand affected the surface charge property of the Ultisol. All the ligands shifted the zeta potential of the Ultisol to the negative direction, implying that the surface charge of the soil became more negative. The effect on the zeta potential of the soil was observed in the order of oxalate ˃ citrate ˃ EPS. The quantity of Pb adsorbed at each pH (3.0–7.0) reflected the corresponding change in the zeta potential as induced by each ligand. The presence of the ligands shifted the isoelectric point of the Ultisol from 4.8 to 3.2 for the EPS system and below 3.0 for the citrate and oxalate systems. More Pb was adsorbed in the presence of oxalate than in the presence of citrate and EPS. The two most outstanding mechanisms that governed the adsorption of Pb by the Ultisol were (1) electrostatic attraction which was supported by the increase in negative zeta potential of the Ultisol and, (2) complexation which was supported by the lesser proportion of Pb adsorbed in the citrate system at higher pH and also by the spectroscopic data for EPS. The combination EPS + citrate + oxalate was more effective in enhancing the adsorption of Pb than the combination EPS + oxalate and EPS + citrate.

Role of extracellular polymeric substances on the behavior and toxicity of silver nanoparticles and ions to green algae Chlorella vulgaris

The effect of extracellular polymeric substances (EPS), vital organic matters and nutrient elements in the natural environment, on the behavior and toxicology of silver nanoparticles (AgNPs) and ions remains ambiguous. In this study, the role of EPS on the toxicity of AgNPs and dissolved silver ions (from AgNO3) to a green algae Chlorella vulgaris was investigated. After the removal of EPS, algae accumulated more silver, about 7.41- and 1.25-fold of those in the algae with EPS for AgNPs and AgNO3 treatments, respectively. The large amount of accumulated silver was bound to the algal cell surface for AgNPs treatment and was internalized in the algae for AgNO3 treatment, irrespective of the presence of EPS in algae. After exposure to AgNPs, the ruffles in the surfaces of algal cells were filled by AgNPs, and almost invisible. FTIR showed that for both AgNPs and AgNO3, the aldehyde groups on the cell surface were oxidized to carboxyl groups by silver ions, irrespective of the presence of EPS in algal cells, indicating that silver ions were released from the oxidization of AgNPs and reacted with algal cells. The content of chlorophyll showed that AgNPs depressed algal growth more remarkably than did AgNO3, independent of the presence of EPS in algae, suggesting that AgNPs had greater toxic effects on algae than did silver ions. The findings suggest that the barrier effect of EPS gave nanoparticles an extraordinary edge over ions, but EPS had no discerning effect on the interaction of algal cells with the silver ions released from AgNPs and AgNO3, and also on the effect of AgNPs and AgNO3 on algal growth.

Differential surface contact killing of pristine and low EPS Pseudomonas aeruginosa with Aloe vera capped hematite (α-Fe2O3) nanoparticles

Biogenic hematite (α-Fe2O3) nanoparticles (NPs) of average size <10 nm were synthesized using green approach with Aloe vera extract (ALE). The aim of the study was to assess the protective effect of extracellular polymeric substances (EPS) against antibacterial and antibiofilm activities of ALE-α-Fe2O3NPs in normal EPS producers (pristine) and experimentally modified (low-EPS) Pseudomonas aeruginosa (P. aeruginosa) cells and the mechanism of cell killing. Formation of ALE-α-Fe2O3NPs has been validated by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier-transformed infrared spectroscopy (FTIR) analysis. The FTIR data suggested the possible role OH group bearing organic compounds of ALE in metal reduction and nucleation of NPs. Gas Chromatography-Mass spectroscopy (GC–MS) analysis revealed the presence of oxime-methoxy-phenyl, ethanone 1-phenyl, hexadecanoic acid, cyclohexanol 2,6-dimethyl, tetracontane, stigmast-5-en-3-ol, cyclohexanol 2,6-dimethyl, and cyclohexasiloxane dodecamethyl on the surface of ALE-α-Fe2O3NPs. Cell viability assay and SEM imaging revealed significantly greater bacteriostatic and/or bactericidal effect of ALE-α-Fe2O3NPs in low EPS cells compared to pristine cells or bare-α-Fe2O3NPs. This is attributed to thinner protective layer of EPS around the low EPS cells, and higher dispersibility and stability of ALE-α-Fe2O3NPs. Absorption of ALE-α-Fe2O3NPs and bare-α-Fe2O3NPs on EPS surface and within EPS matrix was ascertained by atomic absorption spectroscopy (AAS). The results suggest differential internalization of ALE-α-Fe2O3NPs and bare-α-Fe2O3NPs in P. aeruginosa cells. The flow cytometry (FCM) results exhibited increased intracellular granularity in low EPS (18.94%) as compared with pristine (10.94%) cells, which signifies the greater internalization of ALE-α-Fe2O3NPs. Moreover, the proportionate increase in intracellular ROS generation in low EPS (20.47%) via-a-vis pristine (7.56%) cells was observed. Overall, the results elucidate that ALE-α-Fe2O3NPs-bacterial interaction leads to attachment of NPs to EPS surface, migration within the EPS matrix and penetration into cell, which eventually results in growth inhibition due to intracellular ROS activity. Owing to significant antibacterial and antibiofilm activities, ALE-α-Fe2O3NPs may serve as a good candidate for clinical management of extended spectrum beta lactamases (ESBL) positive P. aeruginosa.

Comparison of the Biological and Chemical Synthesis of Schwertmannite at a Consistent Fe2+ Oxidation Efficiency and the Effect of Extracellular Polymeric Substances of Acidithiobacillus ferrooxidans on Biomineralization.

Schwertmannite is an environmental mineral material that can promote the natural passivation of heavy metal elements, thereby reducing environmental pollution from toxic elements. However, the fundamental reason for the difference between the chemically (H2O2-FeSO4) and biologically (Acidithiobacillus ferrooxidans-FeSO4) synthesized schwertmannite is still unclear. In this study, X-ray diffraction, scanning electron microscopy, the Brunauer–Emmett–Teller method, and X-ray fluorescence spectrometry were used to compare the structure, specific surface area, and elemental composition of schwertmannite synthesized by biological and chemical methods. The removal capacity of As(III) by the two kinds of schwertmannite and the effects of extracellular polymeric substances (EPS) on biogenetic schwertmannite were also investigated. At a consistent Fe2+ oxidation efficiency, the chemical method synthesized more schwertmannite than the biological method over a 60-h period. The biosynthesized schwertmannite had a “chestnut shell” shape, with a larger particle size and specific surface than the chemically synthesized schwertmannite, which was relatively smooth. The saturated adsorption capacities of the biologically and chemically synthesized schwertmannite were 117.0 and 87.0 mg·g−1, respectively. After exfoliation of the EPS from A. ferrooxidans, the biosynthesized schwertmannite displayed a “wool ball” shape, with rough particle surfaces, many microporous structures, and a larger specific surface area. The schwertmannite yield also increased by about 45% compared with that before exfoliation, suggesting that the secretion of EPS by A. ferrooxidans can inhibit the formation of schwertmannite.

Protective effects of extracellular polymeric substances from Aphanizomenon flos-aquae on neurotoxicity induced by local anesthetics.

The neurotoxicity of local anesthetics has received an increasing amount of attention and more effective therapeutic agents are required. Extracellular polymeric substances from Aphanizomenon flos-aquae (EPS-A) are high molecular weight polysaccharides. The present study aimed to elucidate the protective effects of EPS-A on neurotoxicity induced by local anesthetics in an intraperitoneal injection bupivacaine rat model. The results of immunohistochemical staining inicated that following intraperitoneal injection of EPS-A the levels of apoptosis and caspase-3 decreased, and the expression levels of microtubule-associated protein 1A light chain 3 (LC3) and beclin1 increased. In order to further clarify the mechanism of the EPS-A-mediated protection, the expression of key proteins associated with autophagy was investigated by western blotting. The results suggested that the ratio of LC3-II/LC3-I and the expression level of beclin1 increased. Taken together, the results indicated that EPS-A induced neuroprotective effects on bupivacaine-induced neurotoxicity. The underlying mechanism may be associated with the inhibition of apoptosis, upregulation of autophagy and improvement of cell survival. The results suggested that EPS-A may be a candidate neuroprotective agent against neurotoxicity caused by local anesthetics.

Effects of extra-cellular polymeric substances towards physical properties of biomass under magnetic field exposure

Extra-cellular polymeric substances are responsible towards bioflocculation and settleability of sludge. This substances act as glue that holds the bioflocs to form larger aggregates by intervening both cells cohesion and adhesion. Different composition of this substances lead to different circumstances of sludge problem including bulking. Numerous studies have been conducted in optimizing the content of extra-cellular polymeric substances using various approaches. However, none of the approaches investigated on the use of magnetic field. Therefore, this study is aimed to investigate the effect of magnetic field on extra-cellular polymeric substances specifically its soluble-bound composition and its chemical constituents. Magnetic field of 88 mT was used in Reactor A, while Reactor B acted as control system. Results showed that Reactor A obtained mostly higher tightly bound extra-cellular polymeric substances compared to Reactor B in order of predominance: protein > polysaccharides > carbohydrates. These observations implied that magnetic field influenced the production of polymeric substances mainly its tightly bound constituent as well as protein and polysaccharides content. These productions were significant in improving bioflocculation and sludge settleability, thus minimizing potential occurrence of bulking.