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•Anaerobic granular sludge adsorbed more Zn and Cu than other two sludges.•Hydrophilic EPS of anaerobic granular sludge adsorbed more Zn and Cu than HPO-A.•Freundlich model for ...hydrophilic EPS adsorption while Langmuir equation for HPO-A EPS.•Amides 2 group was essential for heavy metals adsorption of anaerobic granular sludge.
Extracellular polymeric substances (EPS) in sludge samples played a major role in heavy metals removal during wastewater treatment. In this study, the binding quality, adsorption mechanism, as well as the chemical fractional contribution of the sludge EPS from activated sludge, anaerobic granular sludge and anaerobic flocculent sludge to the adsorption of Zn2+ and Cu2+ was investigated. For all three sludge samples, Cu2+ could be more easily adsorbed than Zn2+, and EPS extracted from the anaerobic granular sludge exhibited a relatively higher adsorption capacity than that of anaerobic flocculent sludge and activated sludge. Specifically, hydrophobic EPS of the activated sludge and anaerobic flocculent sludge was more efficient in adsorbing Cu2+ and Zn2+ than that of the hydrophilic EPS. However, hydrophilic EPS in anaerobic granular sludge played a greater role in heavy metals removal. The adsorption of those two heavy metals onto the unfractionated and hydrophobic EPS could be better described by the Langmuir isotherm, while Freundlich models fitted hydrophilic EPS. In addition, the effect of the heavy metals adsorption on the spectrum characteristics of the sludge EPS was also explored by analysis of FT-IR and fluorescent spectra.
•Flocs, aerobic and anaerobic granular sludge were selected for specific EPS comparison.•Protein (PN) contents in LB-EPS and TB-EPS of granular sludge were higher than that of flocs.•PN significantly ...contributed to the formation of granular sludge via surface charge adjustment.•Proteins with high molecular weight favored the sludge granulation.•Aromatic protein-like and tryptophan protein-like substances were more abundant in the granular sludge.
Extracellular polymeric substances (EPS) plays an important role in the formation of bioaggregates such as flocs, biofilm and granular sludge. However, the role of their specific components in sludge flocculation and granulation is still unclear. Three sludge samples including the flocs, aerobic and anaerobic granular sludge were investigated in this study and the specific components in different EPS structures of loosely bound-EPS (LB-EPS) and tightly bound-EPS (TB-EPS) were analyzed. Results showed that the protein (PN) contents in LB-EPS and TB-EPS of the aerobic and anaerobic granular sludge were 33.6±9.7 and 96.8±11.9, 27.1±2.8 and 61.6±4.2mgg−1VSS, respectively, which were both higher than the flocs of 8.5±1.5 and 43.1±2.7mgg−1VSS. But the polysaccharide (PS) contents in the three sludges were all about 30mgg−1VSS. The analysis of sludge surface charge indicated that they had a linear correlation with the PN content, which implied that PN significantly contributed to the formation of granular sludge. The results of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that the molecular weight of PN in flocs was mainly distributed in 14.3–66.2kDa, while it was 20.1–97.4kDa in the granular sludge, which indicated that the proteins with high molecular weight favors the sludge granulation. According to the three-dimensional fluorescence (EEM) results, the aromatic protein-like and tryptophan protein-like substances were more abundant in the granular sludge than that in flocs, suggesting they are the key components in the structural stability of granular sludge.
•State-of-the-art methodologies for characterizing metal–EPS binding are summarized.•Major mechanisms of metal–EPS interaction are elucidated.•Influential factors for metal adsorption by EPS are ...discussed.•Future research needs to further advance metal biosorption processes are proposed.
Biosorption presents a potent technology to remediate metal-contaminated aqueous environment or even to recover precious metals. Extracellular polymeric substances (EPS) are believed to play an important role in metal biosorption by microorganisms, but the reported results have been rather contradictory and the underlying mechanisms remain largely unclear so far. This review aims to clarify why large discrepancies existed for different EPS–metal systems through systematically exploring into the adsorption mechanisms and influential factors, and to offer some implications for advancing the implementation of metal biosorption technologies. The state-of-the-art methodologies for characterizing metal–EPS binding are summarized; several interaction mechanisms, including ion exchange, complexation and surface precipitation, are analyzed; the major influential factors such as EPS composition, metal species, solution chemistry and operating conditions are discussed; and lastly future research needs to advance the investigations and implementations of such biosorption processes are proposed.
In this study, we investigated the adsorption of Cd(II) and the biosynthesis of CdS quantum dots (QDs) mediated by cells of sulfate-reducing bacteria before and after the removal of EPS to determine ...whether EPS or the cell wall plays a major role. Potentiometric titration revealed that the concentration of proton-active binding sites on cells with EPS (EPS-intact) was notably higher than that on cells without EPS (EPS-free) and that the sites were predominantly carboxyl, phosphoryl, hydroxyl, and amine groups. The protein content in EPS-intact cells was higher, and thus the Cd(II) adsorption capacity was stronger. The CdS QDs biosynthesized using EPS-intact possessed better properties, including uniform size distribution, good crystallinity, small particle size, high fluorescence, and strong antimicrobial activity, and the yields were significantly higher than those of EPS-free by a factor of about 1.5–3.7. Further studies revealed that alkaline amino acids in EPS play a major role and serve as templates in the biosynthesis of QDs, whereas they were rarely detected in the cell wall. This study emphasizes the important role of EPS in the bacterial binding of metals and efficient recycling of hazardous waste in water.
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•Successful preparation of EPS-intact and EPS-free cells.•EPS play a more dominant role in mediating the synthesis of CdS QDs than cell wall.•EPS-mediated synthesis of CdS QDs has stronger ability and higher yield.•Alkaline amino acids act as biological templates in the synthesis of CdS QDs.
Secondary metabolites produced by bacteria and fungi are an important source of antimicrobials and other bioactive compounds. In recent years, genome mining has seen broad applications in identifying ...and characterizing new compounds as well as in metabolic engineering. Since 2011, the 'antibiotics and secondary metabolite analysis shell-antiSMASH' (https://antismash.secondarymetabolites.org) has assisted researchers in this, both as a web server and a standalone tool. It has established itself as the most widely used tool for identifying and analysing biosynthetic gene clusters (BGCs) in bacterial and fungal genome sequences. Here, we present an entirely redesigned and extended version 5 of antiSMASH. antiSMASH 5 adds detection rules for clusters encoding the biosynthesis of acyl-amino acids, β-lactones, fungal RiPPs, RaS-RiPPs, polybrominated diphenyl ethers, C-nucleosides, PPY-like ketones and lipolanthines. For type II polyketide synthase-encoding gene clusters, antiSMASH 5 now offers more detailed predictions. The HTML output visualization has been redesigned to improve the navigation and visual representation of annotations. We have again improved the runtime of analysis steps, making it possible to deliver comprehensive annotations for bacterial genomes within a few minutes. A new output file in the standard JavaScript object notation (JSON) format is aimed at downstream tools that process antiSMASH results programmatically.
A Sequencing Batch Reactor (SBR) with activated sludge was operated with synthetic wastewater containing ibuprofen (IBU) to investigate the biomass stress-responses under long-term IBU exposure. ...There were 3 different phases: phase I as the control without IBU for 56 days, phase II (40 days), and phase III (60 days) containing IBU at 10 and 5 mg L−1 each. The overall performance of the SBR as well as the extracellular polymeric substances (EPS) in terms of polysaccharides, proteins, and humic acid substances were estimated. Morphological parameters of microbial aggregates in the presence of IBU (phase II and phase III) were assessed by quantitative image analysis (QIA). Removal efficiencies of chemical oxygen demand (COD) and ammonium (NH4+) were significantly reduced by IBU. Loosely bound EPS (LB-EPS) decreased during phase II and phase III, and tightly bound EPS (TB-EPS) was slightly higher in phase II than phase I. TB-EPS proteins were greater in phase II, perhaps to protect microbial cells from IBU exposure. These findings provided insight into both activated sludge stress-responses and EPS composition under long-term IBU exposure. Spearman correlation showed that EPS and morphological parameters significantly affected sludge settleability and flocculation. QIA also proved to be a powerful technique in investigating dysfunctions in activated sludge under IBU exposure.
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•Reactor performance was significantly reduced during long-term IBU exposure.•EPS influenced both the aggregates structure and the settling ability.•Quantitative image analysis revealed disfunctions during long-term IBU exposure.•A greater impact on both EPS and microbial structure was caused by IBU at 10 mg L−1
Mild steel (MS) coated with protective bilayer hybrid coatings of polyetherimide, and ZnO/CuO was exposed to artificial treated wastewater (ATWW) inoculated with Desulfovibrio sp. (biotic system). ...Proteins from the extracellular polymeric substances (EPS) matrix of Desulfovibrio sp. responded to the coatings. PEI-CuO offered the highest performance against biocorrosion. The higher PEI-CuO resistivity value of $2.17\times 10^{6}~\Omega {\cdot }\mathrm{cm}^{2}$ contrasted with the decrease to $1.5\times 10^{5}$ and $1.6\times 10^{3}~\Omega {\cdot }\mathrm{cm}^{2}$ for PEI-ZnO and PEI coatings, respectively. The one order of magnitude increased resistance of the biotic system, compared to sterilized ATWW (abiotic system), resulted from the protective nature of the bacterial biofilm.
The phylum Acidobacteria is one of the most widespread and abundant on the planet, yet remarkably our knowledge of the role of these diverse organisms in the functioning of terrestrial ecosystems ...remains surprisingly rudimentary. This blatant knowledge gap stems to a large degree from the difficulties associated with the cultivation of these bacteria by classical means. Given the phylogenetic breadth of the Acidobacteria, which is similar to the metabolically diverse Proteobacteria, it is clear that detailed and functional descriptions of acidobacterial assemblages are necessary. Fortunately, recent advances are providing a glimpse into the ecology of members of the phylum Acidobacteria. These include novel cultivation and enrichment strategies, genomic characterization and analyses of metagenomic DNA from environmental samples. Here, we couple the data from these complementary approaches for a better understanding of their role in the environment, thereby providing some initial insights into the ecology of this important phylum. All cultured acidobacterial type species are heterotrophic, and members of subdivisions 1, 3, and 4 appear to be more versatile in carbohydrate utilization. Genomic and metagenomic data predict a number of ecologically relevant capabilities for some acidobacteria, including the ability to: use of nitrite as N source, respond to soil macro-, micro nutrients and soil acidity, express multiple active transporters, degrade gellan gum and produce exopolysaccharide (EPS). Although these predicted properties allude to a competitive life style in soil, only very few of these prediction shave been confirmed via physiological studies. The increased availability of genomic and physiological information, coupled to distribution data in field surveys and experiments, should direct future progress in unraveling the ecology of this important but still enigmatic phylum.
► FTIR and 3D-EEM are used to analyse the main components of EPS in aerobic granule. ► Results indicate the importance of aromatic protein-like substances in the stable granular sludge. ► The isomers ...of carbohydrates (1110–1047cm−1) can be attributed to the aerobic sludge granulation.
In recent years, lots of the extracellular polymeric substances (EPS) related researches have focused on its role in the granulation and structural stability of aerobic sludge. Three-dimensional fluorescence spectrum (3D-EEM) and fourier transform infrared spectroscopy (FTIR) technologies were used to analyse the main components of sludge EPS during aerobic sludge granulation in this study. Results showed that the components of sludge EPS tended to be stable during aerobic sludge granulation. The peak F (Ex/Em=230/308.5) from 3D-EEM and the predominant spectral band at approximately 1517cm−1 from the FTIR spectra of the matured granular sludge indicated the importance of aromatic protein-like substances together, especially tyrosine in maintaining the stable structure of the granular sludge. Furthermore, the differences in the occurrence position and frequency of C–O bonds (1110–1047cm−1) observed during aerobic sludge granulation showed that the transformations between the isomers and other forms of carbohydrates may be attributed to the formation of aerobic granule.
Oxidative damage caused by free radicals is an inevitable and pervasive phenomenon that leads to cell damage and the emergence of diseases including ageing, cancer, diabetes, cardiovascular disease ...and neurodegenerative disorders. In this context, antioxidants play a significant role in encountering free radicals by delaying or reducing the oxidative damage of cells. Evidence suggests that synthetic antioxidants are double-edged swords wherefore the requirement for natural antioxidants is increasing globally. Exploring non-toxic, biodegradable and compatible natural molecules like exopolysaccharides can favour the current antioxidant limitations. Microbial exopolysaccharides represent a structurally diverse class of carbohydrate molecules secreted at the cell wall. Recently, bioprospecting exopolysaccharides for their astounding physiochemical properties and the reliable structure-activity relationship have motivated more research towards the investigation of their antioxidant properties. Here we propose that structural features of exopolysaccharides such as monosaccharide residues, branching, molecular weight, glycosidic linkage, functional groups, protein, selenium, and chemical modifications are likely to influence their antioxidant activity. To support this hypothesis we review the interdependence of structural features of exopolysaccharides to the observed antioxidant activity. In light of its importance, this review focuses on the understanding of the elimination of free radicals by microbial exopolysaccharides derived from marine and nonmarine sources during the last six years.
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•Structural features such as monosaccharides, uronic acid, carboxyl, sulfate and hydroxyl groups are effectively involved in the scavenging, metal chelating and reducing activity of EPS.•EPS protects the cells against free radical accumulation and inhibits lipid peroxidation in vitro.•Chemical modifications like acetylation, carboxymethylation, sulfonation and phosphorylation enhances the antioxidant properties of EPS.•Thermostability, non-toxicity, and biocompatibility of EPS makes it preferable for wide range of biomedical applications.
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