Amount Of EPS Research Articles

Extracellular Zn Detoxication by <i>Penicillium chrysogenum</i> and <i>Aspergillus niger</i>

Microfungi are promising objects for bioremediation due to their ability to convert metals into forms that are less mobile and accessible to organisms. The study showed that the fungi Penicillium chrysogenum and Aspergillus niger have physiological mechanisms of extracellular Zn detoxification at its initial concentration of 250 µmol – 2 mmol in the medium. At concentrations of 250–500 µmol Zn promotes the accumulation of biomass and abundant sporulation of A. niger and Penicillium chrysogenum, and at concentrations of 1–2 mmol inhibits the growth of fungi. Extracellular Zn detoxification in Aspergillus niger culture occurs by the formation of dihydrate zinc oxalate katsarosite, due to the active biosynthesis of oxalic acid in A. niger. The main mechanism of zinc detoxification in Penicillium chrysogenum culture was the formation of zinc phosphate hopeite. The formation of zinc phosphate hopeite under the action of the fungus was established for the first time. The key factors that determine the direction of the processes of formation of extracellular mineral phases are the amounts of EPS and oxalic acid produced by fungi, as well as changes in the pH of the medium during the growth of cultures.

IN VITRO EVALUATION OF PROBIOTIC POTENTIAL OF Lactiplantibacillus plantarum TRG1 ISOLATED FROM AN ALGERIAN’S GOAT RUMEN

This present paper is intended to demonstrate the desirable probiotic properties of Lactiplantibacillus plantarum TRG1 isolated from the Algerian goat rumen. The study focused on assessing the strain’s survival rate in stress conditions, namely in phenol 0.4%, bile salts 0.3%, in saliva and the Gastrointestinal tract (GIT) simulated conditions. The adhesion ability of the strain with GIT cells, cell surface properties, the production of EPS and β-galactosidase activity were also analyzed. Besides, biogenic amines production, sensitivity to antibiotics and hemolytic activity were evaluated as safety properties. The results showed that the strain can tolerate phenol 0.4% (13.88 ± 2.54%), bile salts 0.3% (10.91± 0.71%), and displayed good viability in saliva and different parts of the GIT. Viability rates were 99.26 % in saliva, 69.68 % in gastric juice, 37.4 % in the ileum. In the duodenum, 93.09 % of viability was attained after 90 min and 53.73% after 180 min of incubation. Furthermore, the strain displayed good adhesion and acceptable surface properties: hydrophobicity (76.94 ±3.36%), auto-aggregation (29.52% ± 6.95), and co-aggregation with E. coli (15.38 ± 05.43), P. aeruginosa (16.05 ± 2.14) and S. aureus (17.33 ± 2.31). A considerable amount of EPS (942.50 ± 32.78 mg/l) was noticed too. Results also showed that the strain did not present hemolytic activity while it can produce the β-galactosidase enzyme. The strain displaced sensitivity to nitroxolin and tetracycline and is resistant to other antibiotics.

Anti-Adhesion and Antibiofilm Activity of Eruca sativa Miller Extract Targeting Cell Adhesion Proteins of Food-Borne Bacteria as a Potential Mechanism: Combined In Vitro-In Silico Approach.

Bacterial cells have the ability to form biofilm onto the surfaces of food matrixes and on food processing equipment, leading to a source of food contamination posing serious health implications. Therefore, our study aimed to determine the effect of Eruca sativa Miller (E. sativa) crude extract against biofilms of food-borne bacteria along with in silico approaches to investigate adhesion proteins responsible for biofilm activity against the identified phytochemicals. The antibacterial potential of crude extract was evaluated using agar well diffusion technique and combinations of light and scanning electron microscopy to assess the efficacy of crude extract against the developed biofilms. Our results showed that crude extract of E. sativa was active against all tested food-borne bacteria, exhibiting a rapid kinetics of killing bacteria in a time-dependent manner. MIC and MBC values of E. sativa crude extract were found to be ranging from 125 to 500 µg/mL and 250 to 1000 µg/mL respectively. Furthermore, inhibition of developed biofilm by E sativa was found to be ranging from 58.68% to 73.45% for all the tested strains. The crude extract also reduced the viability of bacterial cells within biofilms and amount of EPS (ranging 59.73–82.77%) in the biofilm matrix. Additionally, the microscopic images also revealed significant disruption in the structure of biofilms. A molecular docking analysis of E. sativa phytochemicals showed interaction with active site of adhesion proteins Sortase A, EspA, OprD, and type IV b pilin of S. aureus, E. coli, P. aeruginosa, and S. enterica ser. typhi, respectively. Thus, our findings represent the first demonstration of E. sativa crude extract’s bioactivity and potency against food-borne bacteria in their planktonic forms, as well as against the developed biofilms. Therefore, a possible mechanistic approach for inhibition of biofilm via targeting adhesion proteins can be explored further to target biofilm producing food-borne bacterial pathogens.

Optimization of dextran production from Leuconostoc strains isolated from different dairy products from Ouargla region Algeria

Leuconostoc (Ln) sp. belongs to a group of lactic acid bacteria, which has the capacity to produce dextran (an exopolysaccharides) in the presence of su-crose. dextran is industrially important, it was the first microbial exopolysac-charide affirmed for commercial use. This study aimed to optimize the pro-duction of the synthesized dextran by Ln strains species isolated from differ-ent dairy products. Morphological, cultural, physiological and biochemical characteristics were employed to identify 23 isolated strains. We have identi-fied the species: Ln. gelidum, Ln. carnosum, Ln. citreum, Ln. fallax, Ln. mesen-teroides subsp mesenteroides, Ln. mesenteroides subsp dextranicum, Ln. mesenteroides subsp cremoris. 20 strains had the capacity to produce dex-tran from sucrose. The precipitation and quantification of EPS on MRSs (Mark rogosa et sharpe sucrose) medium revealed a difference between the strains, by the total sugars assay method, the amount of EPS varied between 0.63 ± 0.19 and 2.41 ± 0.17 g / L of strains LnF70 and LnC1 (isolated from goat's milk), respectively. The dextran production from MRSs medium was better than from liquid MSE. The optimization of production on MRSs medi-um with different concentration of glucose, yeast extract and sucrose showed that the strains had good production with a concentration of 2% glucose, 0.3% yeast extract and 10% sucrose.

Biofilm formation of Ancylobacter sp. TS-1 on different granular materials and its ability for chemolithoautotrophic As(III)-oxidation at high concentrations

The oxidation of arsenic (As) is a key step in its removal from water, and biological oxidation may provide a cost-effective and sustainable method. The biofilm-formation ability of Ancylobacter sp. TS-1, a novel chemolithoautotrophic As oxidizer, was studied for four materials: polypropylene, graphite, sand, and zeolite. After seven days under batch mixotrophic conditions, with high concentrations of As(III) (225 mg·L−1), biofilm formation was detected on all materials except for polypropylene. The results demonstrate As(III)-oxidation of TS-1 biofilms and suggest that the number of active cells was similar for graphite, sand, and zeolite. However, the biofilm biomass follows the specific surface area of each material: 7.0, 2.4, and 0.4 mg VSS·cm−3 for zeolite, sand, and graphite, respectively. Therefore, the observed biofilm-biomass differences were probably associated with different amounts of EPS and inert biomass. Lastly, As(III)-oxidation kinetics were assessed for the biofilms formed on graphite and zeolite under chemolithoautotrophic conditions. The normalized oxidation rate for biofilms formed on these materials was 3.6 and 1.0 mg·L−1·h−1·cm−3, resulting among the highest reported values for As(III)-oxidizing biofilms operated at high-As(III) concentrations. Our findings suggest that biofilm reactors based on Ancylobacter sp. TS-1 are highly promising for their utilization in As(III)-oxidation pre-treatment of high-As(III) polluted waters.

Investigations on mechanical and thermal properties of concrete with different proportions of insulation aggregates

AbstractInvestigation of mechanical properties and thermal behavior of expanded polystyrene concrete (EPS) and exfoliated vermiculite (EV) concrete has been accomplished in this research. It includes how EPS concrete is prepared by substituting the coarse aggregate with 0, 10, 15, and 20% with EPS aggregates. Similarly, EV concrete is prepared by replacing the fine aggregates with 0, 15, 45, and 60% with EV aggregates. The influence of EPS and EV proportion on mechanical and thermal properties was detected. Thermal properties were studied with an adiabatic box technique. Clear improvement in thermal behavior was observed in comparison with normal concrete and reduction in compressive strength was observed for an appreciable increase in the amount of EPS and EV. Also, the properties like split tensile strength, load–deflection curves, and durability properties of the EPS and EV concretes were experimented.

Effect of aeration rate on the anti-biofouling properties of cellulose acetate nanocomposite membranes in a membrane bioreactor system for the treatment of pharmaceutical wastewater

In this study, the effect of aeration rate in terms of specific aeration demand per membrane area (SADm) on the anti-biofouling properties of cellulose acetate (CA) nanocomposite membranes (CA/ND-NH2) in a membrane bioreactor system was investigated. The amount of EPS and soluble EPS under high aeration rate conditions was observed to be higher than under low aeration rate conditions. The results obtained showed that either lower or higher aeration rates had a negative impact on membrane permeability. The high aeration rate resulted in a severe breakage of sludge flocs, and promoted the release of soluble EPS from the microbial flocs to the bioreactor tank. By increasing the aeration rate, the COD removal increased and decreased respectively for the membranes and the activated sludge. It was finally concluded that higher anti-biofouling properties of neat CA and nanocomposite membranes were obtained under optimal aeration rate conditions (SADm = 1 m3 m−2 h−1).

Fabrication and characterization of emulsified and freeze-dried epoxy/cellulose nanofibril nanocomposite foam

Utilization of cellulose nanofibril (CNF) material for light weight and high strength structural composites has attracted considerable attention in the recent years. CNF aerogels have a microporous structure that could have potential properties, such as ultra-low density, high porosity, high specific surface area, high flexibility, and low thermal conductivity. However, producing such a product is still somewhat problematic. In this study, an epoxy/CNF (EP/CNF) nanocomposite foam with micro-rib structures has been developed using emulsification combined with freeze-dried processes. The microstructures of these new EP/CNF composite foams were observed using a scanning electron microscope. The surface morphology showed that CNF fiber walls were uniformly sealed with epoxy resin after curing. Mechanical properties, water resistance, and thermal stability of the EP/CNF composites foams were tested using the compression test, water absorption test, and thermogravimetric analysis. The results showed that the CNFs played an important role in forming a skeleton like structure within these composite foams. The amount of EP in the EP/CNF emulsions had significant effect on the compressive properties and water resistance. Samples fabricated with higher epoxy content had higher compressive properties, better water resistance, and thermal stability. The epoxy/CNF nanocomposites properties were significantly improved as compared to pure CNF aerogel. The glass transition temperature (Tg) of the nanocomposites was influenced by the EP/CNF composition. The mechanical and physical properties of EP/CNF nanocomposite foams could be optimized via changing the weight ratio of epoxy resin in EP/CNF emulsion according to the demanding of specific application.

Bedform migration in a mixed sand and cohesive clay intertidal environment and implications for bed material transport predictions

Many coastal and estuarine environments are dominated by mixtures of non-cohesive sand and cohesive mud. The migration rate of bedforms, such as ripples and dunes, in these environments is important in determining bed material transport rates to inform and assess numerical models of sediment transport and geomorphology. However, these models tend to ignore parameters describing the physical and biological cohesion (resulting from clay and extracellular polymeric substances, EPS) in natural mixed sediment, largely because of a scarcity of relevant laboratory and field data. To address this gap in knowledge, data were collected on intertidal flats over a spring-neap cycle to determine the bed material transport rates of bedforms in biologically-active mixed sand-mud. Bed cohesive composition changed from below 2 vol% up to 5.4 vol% cohesive clay, as the tide progressed from spring towards neap. The amount of EPS in the bed sediment was found to vary linearly with the clay content. Using multiple linear regression, the transport rate was found to depend on the Shields stress parameter and the bed cohesive clay content. The transport rates decreased with increasing cohesive clay and EPS content, when these contents were below 2.8 vol% and 0.05 wt%, respectively. Above these limits, bedform migration and bed material transport was not detectable by the instruments in the study area. These limits are consistent with recently conducted sand-clay and sand-EPS laboratory experiments on bedform development. This work has important implications for the circumstances under which existing sand-only bedform migration transport formulae may be applied in a mixed sand-clay environment, particularly as 2.8 vol% cohesive clay is well within the commonly adopted definition of “clean sand”.

Synthesis and properties of polyurethane/epoxy copolymers by UV curing

ABSTRACTTo improve the mechanical and thermal properties of polyurethane, two prepolymers, polyurethane acrylate (PUA) and epoxy acrylate (EPA) which have acrylate-ended groups, were synthesized. The obtained prepolymers were homogeneously mixed with various compositions and cured by UV. After UV curing, the properties of PU/EP copolymers were investigated by using Fourier-transform infrared spectroscopy, universal testing machine, dynamic mechanical thermal analysis and thermogravimetric analysis. The thermal and tensile properties of PU/EP copolymers gradually increased with the amount of EP due to the intermolecular interaction whereas their elongation properties decreased. These results indicate that the copolymerization of PU with EP could control their mechanical properties.

Experimental Study of the Properties of EPS Concrete and Manufactured Sand-EPS Concrete

The compressive strength of two kinds of lightweight concrete was studied. The results show that the incorporation of EPS can improve the plastic deformation ability of concrete. The effect of EPS on the compressive strength of concrete depends on the amount and particle size of EPS foam. The incorporation of manufactured sand can improve the compressive strength of EPS concrete. The effect of the amount of manufactured sand on the compressive strength of EPS concrete depends on the amount of EPS in concrete.

Effect of pure oxygen fine bubbles on the organic matter removal and bacterial community evolution treating coal gasification wastewater by membrane bioreactor

A lab-scale study was investigated to evaluate the effect of pure oxygen fine bubbles on membrane bioreactor (O2-MBR) performance of treating coal gasification wastewater. Compared with conventional MBR using aeration source of air (CMBR), the removal efficiencies of COD and total phenols increased by 28% and 36%, and the organic compositions of treated effluent represented significant difference that was mainly attributed to the controlled the foam expansion and enhanced the enzymatic activities in O2-MBR. Moreover, membrane fouling mitigation was observed in O2-MBR, probably owing to the less EPS amount and larger PSD. It was notable that the pure oxygen with fine bubbles promoted marked evolution of bacterial community from CMBR to O2-MBR, particularly, the bacterial community richness and diversity in O2-MBR was lower than CMBR, and the genera Phycisphaera, Comamonas, Thauera and Ohtaekwangia composed the top four most relative abundance genera in O2-MBR, giving the total relative abundance of 26.7%.

Adsorption Kinetics and Surface Characterization of Microorganisms Grown under Different Conditions

The adsorption of bacteria onto minerals is the premise for bioleaching and plays an important role in minerals oxidation. Understanding of the adsorption kinetics onto the surface will give information on the effectiveness of bioleaching. Three kinds of mixed bacteria (Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Sulfobacillus) were cultured in different substrates - copper concentrate, elemental sulfur and ferrous iron and adsorbed onto different solid surface of elemental sulfur, silica and copper concentrate. Adsorption kinetics was examined and surface properties were investigated by Zeta-potential and FT-IR spectroscopy. Bacterial adsorption equilibrium data for bacteria grown on three different substrates were well fitted to Freundlich isotherms, indicating inhomogeneous and selective adsorption. Microorganisms grown on copper concentrate and S0 showed similar adsorption kinetics whereby cell adsorptions proceeded rapidly and reached equilibrium within 30 mins of interaction. With the average KF value of 46.2, most copper concentrate-grown cells were strongly adsorbed to three solid surfaces. Microorganisms grown on copper concentrate and S0 also showed higher hydrophobicity and higher isoelectric point (IEP) (pH 3.4-3.8) as compared to the soluble Fe2+-grown cells (pH 2.1), indicating higher amount of EPS and proteins on the surfaces. The FT-IR spectra indicated the presence of COOH, NH2, OH and PO4 groups on all cell surfaces. However, more proteinaceous compounds were found on cells grown on copper concentrate and S0 substrates.

Functional Properties of Lactic Acid Bacteria Isolated from Romanian Fermented Vegetables

A total of 139 lactic acid bacterium (LAB) strains isolated from Romanian traditionally fermented vegetables were screened for the ability to produce exopolysaccharides and for their antagonistic activity against a set of nine LAB strains, three Bacillus strains, and four Gram-negative bacteria. Eighty-five of the tested strains showed a variable antimicrobial activity against Listeria monocytogenes ATCC 1911, 35 of the strains showed a limited inhibition zone against Escherichia coli ATCC25922, and 26 strains against Salmonella enterica ATCC 14024, while 19 strains showed inhibition against one or all three Bacillus strains used as indicators. None of the tested strains showed an antimicrobial activity against Staphylococcus aureus ATCC 25923. Several strains showed antibacterial activity against more than one indicator strain. For instance, Lactobacillus plantarum 307, Lactobacillus brevis 308, and Lactobacillus plantarum/pentosus 358 were active against five of the indicator strains used, while other 23 LAB were active against three indicator strains. In the case of two strains, namely Leuconostoc citreum 344 and Lactobacillus brevis 183, the activity was maintained after neutralizing the pH of the cell-free supernatant likely due to the production of bacteriocins. The gel permeation chromatography-based screening revealed seven EPS-producing LAB strains. Two of the positive strains, namely Leuconostoc citreum 177 and Leuconostoc citreum 52, have been shown to produce large amounts of EPS, of about 20 g/L. All isolated EPS have a high molecular mass, of above 1400 KDa, and a monomer composition dominated by the presence of glucose.

Characterization of the inclusion complex of 16,17α-epoxyprogesterone with randomly methylated β-cyclodextrin in aqueous solution and in the solid state

The inclusion complex between 16,17α-epoxyprogesterone (EP) and randomly methylated β-cyclodextrin (RM-β-CD) was prepared by freeze-drying method and subsequently characterized by means of differential scanning calorimetry, X-ray powder diffractometry, scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The results clearly revealed that EP molecules were included in the cavity of RM-β-CD, thus giving rise to the solubility enhancement of EP in aqueous solution. The effect of RM-β-CD on the aqueous solution of EP was evaluated by the phase solubility diagram. The amount of EP increased linearly with the addition of RM-β-CD according to an AL type plot, indicating the formation of 1:1 stoichiometric inclusion complexes. Thermodynamic study showed the complexation process between EP and RM-β-CD (ΔG = −34.4 kJ mol−1) was driven by both favorable enthalpy (ΔH = −21.4 kJ mol−1) and entropy (ΔS = 43.2 J mol−1 K−1) changes. Dissolution studies showed that such inclusion complex offered a marked improvement in the dissolution rate compared to EP alone and the physical mixture.

Phenotypic variation in Azospirillum brasilense exposed to starvation

Bacteria have developed mechanisms that allow them maintaining cell viability during starvation and resuming growth when nutrients become available. Among these mechanisms are adaptive mutations and phase variation, which are often associated with DNA rearrangements. Azospirillum brasilense is a Gram-negative, nitrogen-fixing, plant growth-promoting rhizobacterium. Here we report phenotypic variants of A. brasilense that were collected after exposure to prolonged starvation or after re-isolation from maize roots. The variants differed in several features from the parental strains, including pigmentation, aggregation ability, EPS amount and composition and LPS structure. One of the phenotypic variants, overproducing EPS and showing an altered LPS structure, was further characterized and showed differential response to several stresses and antibiotics relative to its parental strain. Characterization of the variants by repetitive-PCR revealed that phenotypic variation was often associated with DNA rearrangements.

Seizure and wear rate testing of wheel–rail contacts under lubricated conditions using pin-on-disc methodology

An increased wear rate and a shift of wear mechanism in the wheel–rail contact has been observed in tight curves, mainly due to the change from an almost pure rolling contact to more of a sliding contact. The wheel flange–rail gauge contact is commonly known to experience the toughest conditions of the overall wheel–rail contact in terms of contact pressure and sliding velocity. The wheel flange–rail gauge contact is preferably lubricated to reduce the wear rate and to minimise the risk of transition to severe wear or seizure. The amount and type of lubrication are therefore important parameters if one is to control the wear rate. In this study, a flange contact is experimentally simulated using pin-on-disc testing, to determine the difference in wear rate among a selection of lubricants under different contact conditions. The selection of lubricants consisted of environmentally adapted oils, mineral oils, and greases containing different amounts of EP and AW additives. The results of the pin-on-disc testing indicate that both the amount and type of lubrication applied is decisive for the wear rate and active wear mechanism. Tests have also been performed to simulate either on-board or wayside lubrication, by applying the lubricant at different intervals. A general observation is that under starved lubrication conditions a transition to severe wear is initiated and the wear rate increases rapidly, i.e., all tests indicate that the contact between wheel and rail must be lubricated to avoid high wear rates.

Ultrastructural and genetic characteristics of endolithic cyanobacterial biofilms colonizing Antarctic granite rocks

The precise identification of the cyanobacteria that comprise an endolithic biofilm is hindered by difficulties in culturing the organisms found in these biofilms and a lack of previous molecular and ultrastructural data. This study characterizes, both at the ultrastructural and molecular level, two different cyanobacterial biofilms found in fissures of granite from continental Antarctica. Electron microscopy revealed structural differences between the two biofilms. One was only loosely adhered to the substrate, while the other biofilm showed a closer association between cells and rock minerals and was tightly attached to the substrate. Cells from both biofilms where ultrastructurally distinct, displaying, for instance, clear differences in their sheaths. The amounts of EPS and their organization associated with the cyanobacteria may determine the differences in adhesion and effects on the lithic substrate observed in the biofilms. By sequencing part of the 16S rRNA gene, the two cyanobacteria were also genetically characterized. The gene sequence of the cells comprising the biofilm that was tightly attached to the lithic substrate showed most homology with that of an endolithic cyanobacterium from Switzerland (AY153458), and the cyanobacterial type loosely adhered to the rock, clustered with Acaryochloris marina, the only organism unequivocally known to contain chlorophyll d. This study reveals the presence of at least two different types of endolithic biofilm, dominated each by a single type of cyanobacterium, able to withstand the harsh conditions of the Antarctic climate.

Exopolymeric production by bacterial strains isolated from activated sludge of paper industry

The bacteria originated from the paper mill sludge were identified, isolated and cultured. Enterobacter (E) and Klebsiella (K) represented 70% of the culturable aerobic flora. Kinetics of EPS production in isolated culture and in arbitrary 1:1 mixture was investigated by high-pressure size exclusion chromatography (HPSEC). In isolated culture, Enterobacter produced regularly and gradually during 24h of culture, while Klebsiella produced the total amount of EPS already after 4h without any changes later. The chromatographic profiles of the EPS production of the 1:1 mixture after 4, 8 and 24h of culture could be fitted as a linear combination of the profiles of exopolymers produced by pure Enterobacter and Klebsiella strains. After 24h of culture, Enterobacter was predominant in term of population (82%) and produced about 77% EPS amount, in spite of competition phenomena observed during culture.

Effect of Coagulant Dosing on Physicochemical and Microbiological Characteristics of Activated Sludge and Foam Formation

AbstractThe paper examines the effect of coagulant dosing on stable biological foam formation and occurrence of filamentous microorganisms. Physicochemical (surface charge, extracellular polymers concentration and composition) and biological parameters (sedimentation characteristics, microscopical analysis) were determined for this purpose. Coagulant dosing was found to suppress biological foam formation and filamentous microorganisms Microthrix parvicella presence in activated sludge.Close connection between sludge volume index and EPS amount was detected during experiment.