1M NaCl Research Articles

Thermo‐mechanical properties of rosin‐modified o‐cresol novolac epoxy thermosets comprising rosin‐based imidoamine curing agents

AbstractRosin‐modified o‐cresol novolac epoxy resin (AEOCN) was synthesized by condensation of rosin acid with o‐cresol formaldehyde novolac resin (AOCN). The AEOCN resin was further epoxidized using epichlorohydrin and sodium hydroxide. Rosin‐based imidoamine curing agents (IAMDK, IASDK, and IAEDK) were also prepared by reacting dimaleopimaryl ketone (DMPK), a dimerized rosin product with aromatic diamines. The chemical structures of all synthesized products were confirmed by FTIR,1H‐NMR,13C‐NMR, and DEPT‐135° spectroscopic techniques. The curing process of rosin‐modified epoxy cured with imidoamine crosslinkers was studied using differential scanning calorimetry (DSC) and the results were compared to o‐cresol novolac epoxy resin (EOCN) and some previously reported commercial‐based systems. The thermal and mechanical properties of the cured epoxy thermosets were determined using a thermogravimetric analyzer (TGA) and a universal testing machine (UTM), respectively. The chemical resistance analysis was carried out by immersing cured epoxy coated panels in 1M NaOH, 1MHCl, and 1M NaCl solutions. The results were evaluated in terms of % weight loss method and the morphological changes that appeared due to chemical exposure were also investigated via scanning electron microscopy (SEM). This study presents the economical synthetic approach towards high‐performance bio‐based epoxy coating materials impending to replace some of the petrochemical compounds in coating industries.

Experimental investigation of the adsorption and desorption of cellulase enzymes on zeolite-β for enzyme recycling applications.

The recyclability of cellulase enzymes using zeolite and polyethylene glycol (PEG) was investigated. The cellulase enzymes from cellulose hydrolysate suspensions were adsorbed onto zeolite-β under typical working conditions (pH 5). PEG having a molecular weight of 200Da and 20kDa was used as an eluent to desorb the cellulase enzymes from zeolite-β. Adsorption and desorption profiles of cellulase enzymes were studied by varying pH, PEG concentration, and salt concentration. Maximum binding capacity, qm of the zeolite decreased by increasing the pH, or by introducing PEG. At pH 5, the qm of the zeolite was determined to be 121 × 10-3 g/g. About 24%, 51% and 75% of the adsorbed enzyme can be recovered using 1M NaCl, PEG 200 and PEG 20000, respectively. The specific activity of the recovered enzyme increased by 57% due to the presence of residual PEG.

The possibility of using silochrome sorbents for proteinase inhibitor aprotinin

Background. Aprotinin is a polypeptide, a proteinase inhibitor of natural origin. It inhibits kallikrein, kininogenase, plasmin, trypsin, chymotrypsin; blocks the activator of profibrinolysin, which helps to stop bleeding. Aprotinin is obtained from the lungs of cattle.
 Objective. To study the sorption of aprotinin on silochromic sorbents.
 Materials and methods. Affinity sorbents based on silochrome were used in the work: p-chlorobenzyl-silochrome, active bright blue K-silochrome, aminopropyl silochrome, phenyl-diol-silochrome, phenyl-glutaryl-silochrome. The optical density was measured on KFK-3 (590 nm, 750 nm) and SF-46 (280 nm). An NP-3 peristaltic pump was used for chromatographic purification.
 Results and discussion. Based on the obtained data, it can be assumed that the mechanism of binding of aprotinin to all carriers is obviously the same and is based on the presence of hydrophobic sites in its molecule, which leads to hydrophobic interactions with sorbents. However, increasing the hydrophobicity of the eluent does not lead to desorption of the inhibitor. Obviously, in addition to hydrophobic, a significant role is played by the electrostatic interaction, which is eliminated by increasing the ionic strength. The sorbents under study have a high capacity, they do not change their volume when the ionic strength or hydrophobicity changes, and therefore may be suitable for large-scale applications.
 Conclusions. Affinity sorbents based on silochrome, containing as ligands aminobenzene, p-chlorobenzyl chloride and active chlorotriazine dye of the anthraquinone series “active bright blue K”, in contrast to the original matrix – silochrome aminopropyl water and effectively dissolve. Increasing the ionic strength or hydrophobicity of desorbing solutions does not lead to elution of aprotinin due to additional electrostatic interaction. Therefore, the desorption of aprotinin is achieved only if it is eliminated in the presence of 25 % isopropanol with 1M NaCl.

STABILITY OF BIOSURFACTANT PRODUCED BY PSEUDOMONAS TAENENSIS

Biosurfactants are one of the microbial bioproducts that are naturally synthesized and are applicable for many industrial purposes. In this study, antibacterial, stability and antibiotic susceptibility of biosurfactant was evaluated. Biosurfactants produced from different substrates (groundnut cake, cassava flour waste, pome, cooking oil, engine oil, cassava waste water, molasses, cassava peel, potato) by Pseudomonas taenensis were evaluated for antibacterial activity using agar well diffusion method. Antibiotics susceptibility of Pseudomonas taenensis was carried out using different antibiotics (augmentin, ofloxacin, tetracyclin and ciprofloxacin, cotrimoxazole, pefloxacin, amoxylin, ceftriazone, nitrofuranton and gentamycin). The stability of the biosurfactant was evaluated by adjusting the biosurfactant to: pH (2, 4, 6, 8, 10 and 12) using 1M NaOH and 1M HCl, temperature (4, 30, 37, 55, 75 and 100 °C) and NaCl (0, 5, 10, 15, 20 and 25 %). Results showed that only biosurfactant produced using cassava waste water as substrate was sensitive to Escherichia coli while biosurfactant produced using cassava flour waste, pome and molasses were sensitive to Staphylococcus aureus. Biosurfactant-producing isolate (Pseudomonas taenensis) was sensitive to four antibiotics (augmentin, ofloxacin, tetracyclin and ciprofloxacin) and resistant to six antibiotics (cotrimoxazole, pefloxacin, amoxylin, ceftriazone, nitrofuranton and gentamycin). Biosurfactant was stable over all the wide ranges of pH, temperature and sodium chloride concentrations investigated. This study therefore revealed that biosurfactant have good stability, thus, could survive environmental stress; Not all biosurfactant and biosurfactant producers have antimicrobial and antibiotic property.
 

A novel thermostable serine protease from a metagenomic library derived from marine sediments in the East China Sea.

Thermal activity and stability are important characteristics for proteases applied in the detergent, pharmaceutical, food, and other green industries. With the intent to discover thermostable novel proteases, we constructed a fosmid metagenomic library from marine sediments in the East China Sea and isolated a clone endowed with high proteolytic activity from this library. Sequence analysis of the positive subclones allowed the identification of a coding region of 1254bp related to protease activity. The unrooted phylogenetic tree and alignment results revealed that the sequence might be derived from Anaerolineaceae bacterium and encodes a new member of the peptidase S8A subfamily with the typical catalytic triad Asp119/His150/Ser325. The fusion protein, named pF1AL2, was expressed in Escherichia coli and showed a molecular weight of 35kDa. pF1AL2 was active in the pH range of 5.0-11.0 with an optimal pH at 10.0 and had high stability under alkaline conditions, retaining more than 95% of its activity after 24h at pH11.0. The optimal temperature of pF1AL2 was 80°C, and it retained nearly 80% of its activity after 6h at 70°C, showing great thermal activity and stability. In addition, the enzyme had great salt tolerance (the residual activity when kept in 3M NaCl was 40%). Its thermal activity and stability, along with its halotolerance and pH-tolerance, indicate the high potential value of pF1AL2 in industrial applications. The exploitation of pF1AL2 could lay the foundation for the development and utilization of proteases with special features from marine resources by a metagenomic strategy. KEY POINTS: • A novel protease, pF1AL2, from marine sediments, was screened out by a metagenomic strategy. • The protease pF1AL2 analyzed in silico, cloned, and characterized. • pF1AL2 had an optimal temperature of 80°C and retained nearly 80% of activity after 6h at 70°C. • pF1AL2 had great tolerance for high-temperature and acid, alkaline, and high salt environments.

Molecular Characterization of a Novel 1,3-α-3,6-Anhydro-L-Galactosidase, Ahg943, with Cold- and High-Salt-Tolerance from Gayadomonas joobiniege G7.

1,3-α-3,6-anhydro-L-galactosidase (α-neoagarooligosaccharide hydrolase) catalyzes the last step of agar degradation by hydrolyzing neoagarobiose into monomers, D-galactose, and 3,6-anhydro-Lgalactose, which is important for the bioindustrial application of algal biomass. Ahg943, from the agarolytic marine bacterium Gayadomonas joobiniege G7, is composed of 423 amino acids (47.96 kDa), including a 22-amino acid signal peptide. It was found to have 67% identity with the α-neoagarooligosaccharide hydrolase ZgAhgA, from Zobellia galactanivorans, but low identity (< 40%) with the other α-neoagarooligosaccharide hydrolases reported. The recombinant Ahg943 (rAhg943, 47.89 kDa), purified from Escherichia coli, was estimated to be a monomer upon gel filtration chromatography, making it quite distinct from other α-neoagarooligosaccharide hydrolases. The rAhg943 hydrolyzed neoagarobiose, neoagarotetraose, and neoagarohexaose into D-galactose, neoagarotriose, and neoagaropentaose, respectively, with a common product, 3,6- anhydro-L-galactose, indicating that it is an exo-acting α-neoagarooligosaccharide hydrolase that releases 3,6-anhydro-L-galactose by hydrolyzing α-1,3 glycosidic bonds from the nonreducing ends of neoagarooligosaccharides. The optimum pH and temperature of Ahg943 activity were 6.0 and 20°C, respectively. In particular, rAhg943 could maintain enzyme activity at 10°C (71% of the maximum). Complete inhibition of rAhg943 activity by 0.5 mM EDTA was restored and even, remarkably, enhanced by Ca2+ ions. rAhg943 activity was at maximum at 0.5 M NaCl and maintained above 73% of the maximum at 3M NaCl. Km and Vmax of rAhg943 toward neoagarobiose were 9.7 mg/ml and 250 μM/min (3 U/mg), respectively. Therefore, Ahg943 is a unique α-neoagarooligosaccharide hydrolase that has cold- and high-salt-adapted features, and possibly exists as a monomer.

Contribution of the mitogen-activated protein kinase Hog1 to the halotolerance of the marine yeast Debaryomyces hansenii

Halotolerant species are adapted to dealing continually with hyperosmotic environments, having evolved strategies that are uncommon in other organisms. The HOG pathway is the master system that regulates the cellular adaptation under these conditions; nevertheless, apart from the importance of Debaryomyces hansenii as an organism representative of the halotolerant class, its HOG1 pathway has been poorly studied, due to the difficulty of applying conventional recombinant DNA technology. Here we describe for the first time the phenotypic characterisation of a null HOG1 mutant of D. hansenii. Dhhog1Δ strain was found moderately resistant to 1M NaCl and sensitive to higher concentrations. Under hyperosmotic shock, DhHog1 fully upregulated transcription of DhSTL1 and partially upregulated that of DhGPD1. High osmotic stress lead to long-term inner glycerol accumulation that was partially dependent on DhHog1. These observations indicated that the HOG pathway is required for survival under high external osmolarity but dispensable under low and mid-osmotic conditions. It was also found that DhHog1 can regulate response to alkali stress during hyperosmotic conditions and that it plays a role in oxidative and endoplasmic reticulum stress. Taken together, these results provide new insight into the contribution of this MAPK in halotolerance of this yeast.

Low-resolution molecular shape, biochemical characterization and emulsification properties of a halotolerant esterase from Bacillus licheniformis.

Bacterial esterases are highly versatile enzymes, currently widely used in detergents, biosurfactants, bioemulsifiers and as biocatalysts in paper and food industries. Present work describes heterologous expression, purification, and biophysical and biochemical characterization of a halotolerant esterase from Bacillus licheniformis (BlEstA). BlEstA preferentially cleaves pNP-octanoate and both activity and stability of the enzyme increased in the presence of 2M NaCl, and also with several organic solvents (ethanol, methanol and DMSO). Furthermore, BlEstA has considerable emulsifying properties, particularly with olive oil as substrate. Our studies also show that the enzyme is monomeric in solution and its small-angle X-ray scattering low-resolution molecular envelope fits well its high-resolution homology model.

Developing novel thin film composite membrane on a permeate spacer backing fabric for forward osmosis

A repeatable method was introduced for developing liable flat sheet thin-film forward osmosis (FO) membranes on spacer backing fabric support. Pasting of a water-soluble polymer (Polyvinylpyrrolidone (PVP)) on the backside of the fabric was investigated to prevent the penetration of the polymer dope (Polyethersulfone (PES)) into the backing fabric during phase inversion. All samples were prepared on spacer fabric with a 250μm in thickness. First, PVP as a water-soluble polymer was cast in 100μm thickness on a glass plate and then the spacer fabric was pulled from the top on the pasted PVP to fill the bottom side of the fabric. The lower bottom side of the fabric was filled with PVP. This helped to limit PES polymer penetration and to achieve a thinner polymeric support layer during phase inversion. After interfacial polymerization and forming rejection, thin-film composite (TFC) FO membranes were obtained. Water flux of 17.1 Lm−2h−1 and reverse solute flux (RSF) of 9.2gm−2h−1 were achieved when 1M NaCl as draw solution and deionized water as feed solution (FS) were used under pressure retarded osmosis (PRO) operating mode for TFC2 sample.

Influence of surface condition on the current densities rendering nucleation loop during cyclic voltammetry for electrodeposition of Pd thin films

ABSTRACT Cyclic voltammetry (CV) for Pd electrodeposition on Au from PdCl2+HCl solution between +1.100 and –0.400 V vs Ag/AgCl (3M NaCl) was performed. The CVs exhibit nucleation loop (NL), which can be characterized by higher cathodic current density (j) in the reverse scan rather than that in the forward scan. The reasons for the appearance of NL are investigated by making use of the surface condition of electrode and overpotential (η). Since it is difficult to estimate η during CV, it was obtained by potentiostatic electrodepositions (ED) on the substrates with similar surface conditions as those within NL. These substrates were produced by a potential sweep in (i) forward (FS) and (ii) forward+reverse (RS) scans from open circuit potential up to a representative potential (+0.330 V) within NL. These FS and RS substrates possess partial and significant Pd coverage, respectively. ED at +0.330 V on these substrates shows similar j trends in the initial stages as in NL. η during ED is estimated from the equilibrium potentials and the potential drop due to solution resistance (Rs). Rs is obtained from electrochemical impedance spectroscopy at +0.330 V. The estimated η is higher on RS, supporting higher j during electrodeposition on RS and reverse scan of CV within NL. Electrochemical and morphological analyses suggest that Pd deposition on the FS is nucleation driven whereas that on the RS is growth driven with the surface condition playing an important role in the appearance of NL during CV.

Evaluación de seguridad del ácido benzoico complejado empleando ensayos de permeación in vitro con piel de cerdo en celdas de Franz

Las celdas de Franz son una de las herramientas para evaluar la permeación transepitelial de compuestos mediante la realización de ensayos in vitro, estos permiten inferir el comportamiento de seguridad de un compuesto en la piel. El objetivo de esta investigación fue determinar el comportamiento de permeación del ácido benzoico a partir de complejos con polielectrolitos () en comparación con el ácido benzoico sin complejar, para inferir su comportamiento de seguridad. En una primera fase, se establecieron las condiciones de almacenamiento de la piel comparando los parámetros de difusión (flujo y constante de permeación) y pérdida de agua transepitelial, empleando piel de orejas de cerdos recién sacrificados, almacenadas en NaCl 1M a -2°C por 3 días; se trabajó bajo condiciones de dosis infinitas. Posteriormente, se realizó el ensayo de permeación de dos complejos entre ácido benzoico y Eudragit E, en comparación con el ácido benzoico, bajo condiciones de dosis finitas. La cuantificación del ácido benzoico fue realizada con un método analítico validado por HPLC-DAD. Los resultados evidenciaron que las muestras biológicas pueden almacenarse durante 72 h en las condiciones descritas. El comportamiento de permeación del ácido benzoico complejado respecto al ácido benzoico libre demostró tener un mejor perfil de seguridad, puesto que hubo una menor permeación para el primer caso. Estos resultados demuestran que la complejación del ácido benzoico podría disminuir las reacciones de sensibilidad que normalmente este presenta, basándose en la disminución de su permeación.

On the Nucleation Loop in Cyclic Voltammetry for Electrodeposition of Pd Thin Films

Pd is an excellent catalyst layer for Mg-based thin films for hydrogen storage. Cyclic voltammetry (CV) for Pd deposition on Au in PdCl2+HCl solution between +1.100 and –0.400 V vs Ag/AgCl (3M NaCl) exhibits nucleation loop (NL). NL is characterized by higher cathodic current density (j) in reverse scan versus that in forward scan. This work addresses the question “Why does nucleation loop occur during CV?” using substrate conditions and overpotential (η). Since it is difficult to estimate η during CV, the substrate conditions similar to those within NL are reproduced by potential sweep in (i) forward and (ii) complete forward+reverse scans up to a representative potential (+0.330 V) within NL. These scans produce substrates FS and RS with partial and significant Pd coverage, respectively. Eventual potentiostatic electrodepositions (ED) at +0.330 V on these substrates initially show similar j trends as in NL, replicating Pd deposition during CV. η during ED is estimated by equilibrium potentials and potential drop due to solution resistance (R s) from electrochemical impedance spectroscopy at +0.330 V. The estimated η is higher on RS, supporting higher j during electrodeposition on RS and reverse scan of CV within NL. Electrochemical and morphological analyses together suggest that Pd deposition on FS is nucleation driven; that on RS is growth driven, which help in revealing the metal deposition mechanisms.

Characterization of Halophilic Isolates Producing Bioactive Metabolites Against Pathogens

Halophiles are salt loving microorganisms that are able to survive in high salt conditions. Halophiles are highly diverse group belongs to all three domains of life, Archaea, bacteria and Eucarya. Halophiles adapted themselves through various strategies to maintain their osmotic balance in order to survive in high salt concentrations. Likewise halophiles are also able to produce bioactive molecules such as carotenoids, polyhydroxy-alkanoates, ectoine, bioplastics, and enzymes that have commercial importance. In current study halophiles were isolated at 1M NaCl concentration and characterized, and check its antibacterial activity against pathogenic E.coli, Pseudomonas aeruginosa and Klebsiella pneumonae. Two halophilic strains showed activity against pathogenic E.coli and Klebsiella pneumonae only. Antimicrobial activity was further analyzed through disc diffusion method and by using extracted filtrate. The activity only observed against E.coli after 48 hours old cultures that were served as filtrate extracts and discs against. Furthermore optimization as well as detailed characterization of the secondary metabolites will be needed to find the source of antibacterial metabolites against specific pathogens.

Rhizosphere Bacteria with the Potential of Forming Biofilm and Plant Growth Promotion Under Salt Stress

Bacteria develop microbial communities as biofilm under different environmental stress factors like salinity, temperature, pH and antimicrobial agents and help in the adherence of bacteria to different surfaces. The growth of microorganisms is inhibited in the presence of salinity. An objective of the present research work was to check the growth response and biofilm behavior of indigenous bacteria isolated from plant rhizosphere in the presence of salt. Bacterial strains were named as TAK, TAF and SY. Biofilm formation response was also observed at different molar concentration (0M, 1M, 2M and 3M) of NaCl following test tube assay after 24, 48 and 72 hours of culture incubation. Results showed that TAK has the best biofilm forming ability on abiotic surface as compared to isolate TAF and SY, however, isolate SY showed growth and form biofilm under saline conditions. Bacterial plant growth promoting response was also determined on the basis of improvement in seed germination, shoot length and root length. In general, bacterial biofilm was best at 1M to 3M NaCl stress and 72 hours of culture incubation . Inoculation with SY improved (shoot length 3 % and root length 10.41 %) at 100 mM when compared to inoculated seedlings at 0 mM NaCl stress. It was concluded that among all three isolates, isolate SY used for broad perspective to increase soil fertility. While working to strive for the most promising isolates involved in plant growth promotion, the indigenous isolates showed the promising ability to improve germination of seeds in saline soil while helping the seeds to grow in salt stress conditions.

Characterization of an Intracellular Alkaline Serine Protease from Bacillus velezensis SW5 with Fibrinolytic Activity.

ISP-SW5 is an intracellular alkaline serine protease gene from Bacillus velezensis SW5 that was heterologously expressed in Escherichia coli BL21 (DE3). Sequence analysis indicated that the ISP-SW5 gene has 960bp open reading frame and encodes a protein of 319 amino acid residues. Three-dimensional structure of ISP-SW5 with the fibrinolytic activity from Bacillus velezensis was predicted by in silico analysis. Gly219 was the most likely active site for the fibrinolytic activity of ISP-SW5. The recombinant enzyme ISP-SW5 was purified by Ni-NTA Superflow Column. SDS-PAGE showed that this enzyme had a molecular mass of 34kDa. The result of native-PAGE and N-terminal sequencing showed that the N-terminal propeptide of ISP-SW5 was cleaved during the maturation of protease. The optimum pH and temperature were 8.0 and 40°C, respectively. Enzyme activity was markedly inhibited by PMSF and EDTA but enhanced by 5mM Ca2+ and 2mM Zn2+ by up to 143% and 115%, respectively. Additionally, ISP-SW5 retained 93%, 78%, and 49% relative enzyme activity after incubation with 0.5M, 1M and 2M NaCl, respectively, at 4°C for 12h. The enzyme activity determined by casein as substrate was 1261U/mg. ISP-SW5 could degrade fibrin at an activity of 3428 U/mg, and its properties reflect its potential application in developing a novel biological catalyst for efficient fibrin hydrolysis in medical treatment.

Electrochemical redox behavior of organic quinone compounds in aqueous metal ion electrolytes

Organic quinone compounds are promising electrode materials for aqueous rocking-chair batteries due to chemical inert toward aqueous solutions and wide feasibility of various charge carriers. However, in aqueous electrolytes, the ion-pairing effect of different charge carriers on the electrochemical properties of organic quinone compounds remains unclear. Herein, we selecte a small molecule 9,10-anthraquinone as a study model and propose that the proton assisted metathesis reaction between anthrahydroquinone and M n+ results in stabilizing electrode reaction. Meantime, the possibility of anthraquinone as anode for aqueous multivalent metal-ion (Al 3+ , Mg 2+ , Zn 2+ ) batteries is illustrated. Typically for aluminum-ion battery, a reversible capacity of 211.4 mA h g -1 at 800 mA g -1 after 500 full cycles with a capacity retention of 94.5% can be obtained. This work may provide guidance to design and explore more organic quinone compounds for aqueous batteries. Here, two redox mechanisms of AQ in different aqueous metal ion electrolytes were proposed. In 1 M LiCl, NaCl, KCl, CaCl 2 and BaCl 2 , AQ molecule obtains an electron and becomes a radical anion [AQ] - , then a metal ion pairs with radical anion to form red [AQ-M n+ ] (n-1)+ ; In 1 M AlCl 3 , MgCl 2 and ZnCl 2 , AQ molecules undergoes one step two-electron redox process assisted by protons in electrolyte. Then metathesis reactions between AQ-H2 and metal-ions occur and induce morphology evolution in electrode. • Different electrochemical redox behaviors of AQ in different aqueous electrolytes were observed. • The spin density distribution of red species result in poor redox stability of AQ in 1M LiCl, NaCl, KCl, CaCl 2 and BaCl 2 . • Metathesis reactions assisted by protons induce the reversible redox reaction of AQ in 1 M AlCl 3 , MgCl 2 and ZnCl 2 . • The possibility of AQ as anode for aqueous multivalent metal-ion (Al 3+ , Mg 2+ , Zn 2+ ) batteries was demonstrated.

Pollution reduction and electricity production from dairy industry wastewater with microbial fuel cell.

Taguchi L9 orthogonal array was implemented to select optimum values of process parameters and to attain the maximum removal of pollutants and power generation from dairy industry wastewater using double chambered salt bridge microbial fuel cell. The maximum chemical oxygen demand reduction, current, voltage, power, current density and power density in double chambered salt bridge microbial fuel cell from dairy industry wastewater was found to be 86.30 %, 16.10 mA, 886.34 mV, 14.27 mW, 1219.69 mA/m2 and 1081.06 mW/m2 respectively for the optimum value of 1M NaCl concentration, 10 % agar concentration and 0.10 m salt bridge length. Double chambered salt bridge microbial fuel cell was not only removed chemical oxygen demand and produced power, but it also removed other pollutants at the maximum level against the best optimum value of process parameters from the dairy industry wastewater. The proposed regression model was used to select the right combination of process parameters for obtaining a maximum reduction of pollutants and simultaneous power production from the dairy industry wastewater.

A Mesohaline Thraustochytrid Produces Extremely Halophilic Alpha-Amylases.

Halophilic bacteria are well known to produce highly salt-tolerant enzymes that have unusual applications in biotechnology. Production of halophilic proteins is generally not expected in mesohaline microorganisms. Ulkenia sp. AH-2, a mesohaline, marine straminipilan thraustochytrid isolated from waters of a mangrove ecosystem, produces halophilic alpha-amylases. Four enzyme fractions, viz.., A, B, C, and D, were obtained upon ammonium sulfate fractionation and gel filtration. These had a broad salinity tolerance ranging from 0 to 4M NaCl, with an optimum at 3M NaCl. Pools A, C, and D each resolved as a single band on PAGE and zymogram analysis, and the purified proteins were designated Amy a, Amy c, and Amy h. The major activity resided in "pool B," consisting of several amylases which could not be further resolved into pure fractions. Together, these had an optimum at 2M NaCl. All the enzymes were stable to storage for 2 to 24h at 4°C in a range of salt concentrations and even showed enhanced activity following such incubations. True to halophilic enzymes, the complex of "pool B" amylases showed improved activity in the presence of a wide range of organic solvents at 20% concentration. These enzymes are of particular interest by virtue of their constitutive nature as well as production under culture conditions that do not require salinity beyond that of seawater.

Sensory discrimination between aversive salty and bitter tastes in an haematophagous insect.

Sensory aversion is essential for avoiding prospective dangers. We studied the chemical perception of aversive compounds of different gustatory modalities (salty, bitter) in the haematophagous bug, Rhodnius prolixus. Over a walking arena, insects avoided a substrate embedded with 1M NaCl or KCl if provided with water as an alternative. However, no preferences were expressed when both salts were opposed to each other. A pre-exposure to amiloride interfered with the repellency of NaCl and KCl equally, suggesting that amiloride-sensitive receptors are involved in the detection of both salts. Discriminative experiments were then performed to determine whether R.prolixus can distinguish between these salts. An aversive operant conditioning involving either NaCl or KCl modulated the repellency of the conditioned salt, but also of the novel salt. Repellency levels of both salts were rigid to a chemical pre-exposure to any of both salts. When gustatory modalities were crossed by presenting as a choice NaCl and a bitter molecule as caffeine (Caf), no innate preferences were expressed. Aversive operant conditionings with either NaCl or Caf rendered unspecific changes in the repellency of both compounds. A chemical pre-exposure to Caf modulated the response to Caf but not to NaCl, suggesting the existence of two independent neural pathways for the detection of salts and bitter compounds. Overall results suggest that R.prolixus cannot discriminate molecules of the same gustatory modality (i.e. salty), but can distinguish between salty and bitter tastes. The potential use of aversive gustatory stimuli as a complement of commercially available olfactory repellents is discussed.

High performance thin-film nanocomposite forward osmosis membrane based on PVDF/bentonite nanofiber support

In this study, PVDF electrospun nanofibers impregnated with bentonite nanoclay based highly hydrophilic thin-film nanocomposite (TFN) membranes were synthesized by interfacial polymerization of a polyamide selective layer for forward osmosis (FO) applications. It was revealed that the bentonite nanoclay can tune the properties of the PVDF nanofiber supported TFN membranes, including the key parameters, such as hydrophilicity, the β-phase fraction (polar phase), and its mechanical properties. The PVDF/bentonite nanoclay mixture resulted in a significant improvement in FO performance. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDX) analysis confirmed the successful integration of bentonite nanoclay into the electrospun nanofiber. The prepared TFN membranes showed higher hydrophilicity, mechanical strength and water permeability compared to the pristine PVDF electrospun nanofiber TFN membrane due to an increase in the β-phase fraction (hydrophilicity) by the synergetic effect of electrospinning and addition of bentonite nanoclay. A TFN membrane with the highest nanoclay content (2.0wt%) showed an exceptionally high FO water flux of 40.64L/m2 h at 1M NaCl draw solution, without a considerable increase in reverse solute flux (RSF).