High NaCl Concentrations Research Articles

Salinity-Induced Changes of Photosynthetic Performance, Lawsone, VOCs, and Antioxidant Metabolism in Lawsonia inermis L.

The present study aimed to elucidate the salinity influence on the bioactive metabolites of Lawsonia inermis L. (henna) plants. Young henna plants were cultivated under salinity stress with two NaCl concentrations (75 mM and 150 mM) in controlled environmental conditions and the leaves were investigated to check their adaptative responses. The modulation of photosynthetic performance to salinity stress was demonstrated by gas exchange and chlorophyll fluorescence parameters. The partial stomatal closure triggered an enhanced water-use efficiency, and a proline accumulation was observed, leading to an osmotic adjustment. The increased capacity to dissipate the excess excitation energy at photosystem II as heat was associated with changes in chlorophylls, anthocyanins, and carotenoids. The higher antioxidant activity at 150 mM salt level suggested its scavenger role on reactive oxygen species (ROS) dissipation and photoprotection. The reduced CO2 uptake and the higher metabolic costs necessary to sustain the henna tolerance mechanism against high NaCl concentration negatively affected lawsone production. Leaf volatile organic compounds (VOCs) showed changes in the amount and composition of VOCs with increasing salinity level. Overall, this study revealed efficient physiological and biochemical adaptations of henna leaves to salt stress despite an altered production of important economic metabolites such as lawsone.

Cytokinetic and anatomical analysis of Thellungiella botschantzevii meristem cells in high concentrations of NaCl and Na2SO4

The study of cytokinetic and anatomical properties of the extramophile plant Thellungiella botschantzevii (German) at high concentrations of NaCl and Na2SO4 and without them (control) allowed to identify structural and functional transformations at the cellular level and evaluate the effect of salinity. Cytophotometric method showed the accumulation of cells in the root meristem in G1 and S stages, which indicated the adaptation of Thellungiella botschantzevii to high concentrations of NaCl and Na2SO4. A high level of ploidy (up to 16C) and the maximum number of polyploid cells at the level of 4C and 8C gave the plant stability. Anatomical characteristics of Thellungiella botschantzevii root and leaf were obtained on semi-thin and ultra-thin sections, and accumulation of lipid and protein inclusions in the root cell was determined. The data obtained indicate that Thellungiella botschantzevii is a unique model for various kinds of research, including genetic research, and can help to develop proposals for increasing resistance in crops.

DNA Terminal-Specific Dispersion Behavior of Polystyrene Latex Microparticles Densely Covered with Oligo-DNA Strands Under High-Salt Conditions.

We prepared microspheres densely covered with oligo-DNA strands by immobilizing amino-terminated oligo-DNA strands on the surface of carboxylate polystyrene latex (PS) particles via the amide bond formation. The obtained microspheres (ssDNA-PS) stably dispersed in neutral pH buffer containing high concentrations of NaCl. For the ssDNA-PS ≥1 μm diameter, only 3 - 5% of surface-immobilized oligo-DNA could form a duplex with the complementary strands. Nevertheless, the resulting ssDNA-PS showed a distinct duplex terminal dependency in their dispersion behavior under neutral pH and high NaCl conditions; the microspheres with fully-matched duplexes on the surface spontaneously aggregated in a non-crosslinking manner. By contrast, the microspheres with terminal-mismatched duplexes remained dispersed under the identical conditions. These results suggest that the micrometer-scale particles covered with oligo-DNA strands also have high susceptibility to a duplex terminal sequence in their dispersion property, similar to previously reported DNA-functionalized nanoparticles. This property could potentially be used in various applications including analytical purposes.

An Endophytic Trichoderma Strain Promotes Growth of Its Hosts and Defends Against Pathogen Attack.

Plants host numerous endophytic microbes which promote plant performance, in particular under stress. A new endophytic fungus was isolated from the leaves of a deciduous wood tree Leucas aspera. Morphological inspection and multilocus phylogeny identified the fungus as a new Trichoderma strain. If applied to Arabidopsis thaliana and Nicotiana attenuata, it mainly colonizes their roots and strongly promotes initial growth of the plants on soil. The fungus grows on high NaCl or mannitol concentrations, and shows predatory capability on the pathogenic fungus Alternaria brassicicola. Colonized Arabidopsis plants tolerate higher salt stress and show lower A. brassicicola spread in roots and shoots, while arbuscular mycorrhiza formation in N. attenuata is not affected by the Trichoderma strain. These beneficial features of the novel Trichoderma strain are important prerequisites for agricultural applications.

Simultaneous hexavalent chromium removal, water reclamation and electricity generation in osmotic bio-electrochemical system

For the first time, an osmotic microbial fuel cell (OsMFC) was employed for simultaneous hexavalent chromium [Cr(VI)] removal, organic contaminant removal, energy production, and water reclamation. In this system, draw solutions were prepared from 0 to 1 M NaCl mixed with 12 mg/L Cr(VI). Cr(VI) reduction and power generation at different pH were studied. In terms of power generation, the results revealed that the highest power density of 6.6 mW/m2 (170 mW/m3) was obtained using the 1 M NaCl catholyte at pH 7. However, the greater Cr(VI) reduction of 44.5% and 97.6% was achieved using the 0.2 M NaCl/Cr(VI) based catholyte at pH 7 and 2, respectively. This can be attributed to the competition between Cr(VI) and oxygen reduction due to the high rate of dilution at higher concentrations of NaCl. Additionally, the highest open-circuit voltage of 0.752–0.845 V was recorded at 0.2 M NaCl/Cr(VI) as a proof to support that 0.2 M NaCl was a favorite condition for reducing Cr(VI). Moreover, through cyclic voltammetry, the signals of oxidation-reduction peaks were observed in the case of 0.2 M NaCl/Cr(VI), while, reduction peaks mostly disappeared in other cases. Additionally, more precipitate [Cr(OH)3(s)] was observed to be deposited on the surface of the cathode electrode when 0.2 M NaCl was used as the draw solution. Hence, 0.2 M NaCl was the optimal catholyte concentration for Cr(VI) reduction. The Cr(VI) removal efficiency was 97.6% for an initial pH of 2 with the 0.2 M NaCl catholyte because low pH is thermodynamically favored for Cr(VI) reduction.

Experimental Study on Corrosion of J55 Casing Steel and N80 Tubing Steel in High Pressure and High Temperature Solution Containing CO2 and NaCl

The downhole casing and tubing in thermal recovery wells are the main channels for fluid flow. The corrosion for casing and tubing in high pressure (5 MPa) and high temperature (200 °C) (HPHT) fluid can cause string failure due to wall thinning, deformation, and fracture. In order to study the corrosion characteristics of J55 casing steel and N80 tubing steel in HPHT environment containing CO2 and NaCl, corrosion and corrosion inhibition experiments were carried out using a rotating autoclave at a pressure of 5 MPa and 50–200 °C environment. Morphologies and compositions of corrosion products were analyzed by SEM and XRD. HPHT corrosion process was discussed by Arrhenius equation and the transition state equation. Results showed that the corrosion rates of the two materials increased with CO2 partial pressure while increased initially and then decreased with increasing temperature. In CO2–NaCl solution, the saturate NaCl decreased the CO2 corrosion rates at low temperature (inhibition) and increased CO2 corrosion rates at high temperature. Meanwhile, SEM results showed that the surfaces of CO2 corrosion became more dense and uniform at high temperature. The increase of NaCl leaded to pitting and high concentration NaCl solution causes granular products to appear on the CO2 corrosion surface. The carbon steel corrosion rate is mainly controlled by kinetic parameters of activation; the activation parameters were increased by the increase in temperature and NaCl concentration. Oil-soluble imidazoline acts as a good inhibitor for corrosion of J55 and N80 in this work.

Antagonistic activity of strains of lactic acid bacteria isolated from Carpathian cheese

A promising area for improving probiotics is the search for new sources of strains and the development of complex preparations which would include different types of bacterial cultures that complement each other. Sources of selection may be traditional dairy products, in particular, cheeses made from raw milk. Wild strains can be endowed with antibacterial properties. The antagonistic action of lactic acid bacteria (LAB) has long attracted the attention of researchers and scientists. The aim of the study was to investigate the antagonistic activity against pathogenic and opportunistic microorganisms of LAB strains isolated from traditional Carpathian cheese. Three samples of cheese were selected for the research – one sample of brynza and budz (brynza before salting), made in the highlands of the Carpathians, and one sample of budz, made in the foothills. LAB were identified using classic microbiological and modern molecular genetic methods (RAPD-PCR, RFLP-PCR, 16S rRNA gene sequencing). The objects of our studies were five strains of LAB: Lactococcus lactis IMAU32258, L. garvieae JB2826472, Enterococcus durans FMA8, E. faecium L3-23, E. faecium IMAU9421. Technological parameters such as acid-forming activity of milk fermentation, resistance to high concentrations of NaCl and temperature optimums of cultivation were taken as the main criteria for assessing the suitability of LAB for inclusion in fermentation preparations. Antagonistic activity was determined by agar diffusion (agar well method) and optic density of test cultures using a Multiscan FC microplate reader (Thermo scientifiс, USA) at the wave of 620 nm. There were four reference strains of pathogenic and opportunistic microorganisms were test cultures: Listeria monocytogenes PCM 2191, Staphylococcus aureus PCM 458, Escherichia coli PCM 2208, Salmonella typhimurium PCM 2182. Strains of the test cultures were received from the collection of microorganisms of the Institute of Biology and Biotechnology the (University of Rzeszów, Poland). According to the ability of LAB strains to form lactic acid, L. lactis IMAU32258 was the best acid-forming agent with an acid-forming energy of 94 °T. E. faecium was characterized by moderate levels of active and titratable acidity. Less pronounced acid-forming ability was determined for the species E. durans and L. garvieae. Cultures of the genus E. faecium, L. garvieae and E. durans were the most resistant to high concentrations of NaCl (6.5%). Regarding temperature optimums, we found that strains of E. faecium and E. durans species grew both at temperatures of 10, 15 and 45 °C, whereas no growth of L. lactis IMAU32258 and L. garvieae JB282647 2 was observed at 45 °C. Among the studied bacteria, the strains of E. durans FMA8 and E. faecium L3-23 were characterized by the highest antagonistic activity in producing the largest zones of growth inhibition and optic density of pathogenic and opportunistic microorganisms. The strain L. garvieae JB282647 2 exhibited the lowest level of antagonistic activity against pathogenic and opportunistic microorganisms.

RpoB mutations conferring rifampicin-resistance affect growth, stress response and motility in Vibrio vulnificus.

Rifampicin is a broad-spectrum antibiotic that binds to the bacterial RNA polymerase (RNAP), compromising DNA transcription. Rifampicin resistance is common in several microorganisms and it is typically caused by point mutations in the gene encoding the β subunit of RNA polymerase, rpoB. Different rpoB mutations are responsible for various levels of rifampicin resistance and for a range of secondary effects. rpoB mutations conferring rifampicin resistance have been shown to be responsible for severe effects on transcription, cell fitness, bacterial stress response and virulence. Such effects have never been investigated in the marine pathogen Vibrio vulnificus , even though rifampicin-resistant strains of V. vulnificus have been isolated previously. Moreover, spontaneous rifampicin-resistant strains of V. vulnificus have an important role in conjugation and mutagenesis protocols, with poor consideration of the effects of rpoB mutations. In this work, effects on growth, stress response and virulence of V. vulnificus were investigated using a set of nine spontaneous rifampicin-resistant derivatives of V. vulnificus CMCP6. Three different mutations (Q513K, S522L and H526Y) were identified with varying incidence rates. These three mutant types each showed high resistance to rifampicin [minimal inhibitory concentration (MIC) >800 µg ml−1], but different secondary effects. The strains carrying the mutation H526Y had a growth advantage in rich medium but had severely reduced salt stress tolerance in the presence of high NaCl concentrations as well as a significant reduction in ethanol stress resistance. Strains possessing the S522L mutation had reduced growth rate and overall biomass accumulation in rich medium. Furthermore, investigation of virulence characteristics demonstrated that all the rifampicin-resistant strains showed compromised motility when compared with the wild-type, but no major effects on exoenzyme production were observed. These findings reveal a wide range of secondary effects of rpoB mutations and indicate that rifampicin resistance is not an appropriate selectable marker for studies that aim to investigate phenotypic behaviour in this organism.

Stabilization and improved properties of Salipaludibacillus agaradhaerens alkaline protease by immobilization onto double mesoporous core-shell nanospheres

In this study, serine alkaline protease from halotolerant alkaliphilic Salipaludibacillus agaradhaerens strain AK-R was purified and immobilized onto double mesoporous core-shell silica (DMCSS) nanospheres. Covalent immobilization of AK-R protease onto activated DMCSS-NH2 nanospheres was more efficient than physical adsorption and was applied in further studies. DMCSS-NH2 nanospheres showed high loading capacity of 103.8 μg protein/mg nanospheres. Relative to free AK-R protease, the immobilized enzyme exhibited shifts in the optimal temperature and pH from 60 to 65 °C and pH 10.0 to 10.5, respectively. While the soluble enzyme retained 47.2% and 9.1% of its activity after treatment for 1 h at 50 and 60 °C, the immobilized protease maintained 87.7% and 48.3%, respectively. After treatment for 2 h at pH 5 and 13, the immobilized protease maintained 73.6% and 53.4% of its activity, whereas the soluble enzyme retained 32.9% and 1.4%, respectively. Furthermore, the immobilized AK-R protease showed significant improvement of enzyme stability in high concentration of NaCl, organic solvents, surfactants, and commercial detergents. In addition, the immobilized protease exhibited a very good operational stability, retaining 79.8% of its activity after ten cycles. The results clearly suggest that the developed immobilized protease system is a promising nanobiocatalyst for various protease applications.

Isolation and Characterization of Bacillus cereus Phage vB_BceP-DLc1 Reveals the Largest Member of the Φ29-Like Phages.

Bacillus phage φ29 and its relatives have been considered as one of the most important model organisms for DNA replication, transcription, morphogenesis, DNA packaging studies, and nanotechnology applications. Here, we isolated and characterized a new member of the φ29-like phage, named Bacillus cereus phage vB_BceP-DLc1. This phage, with a unique inserted gene cluster, has the largest genome among known φ29-like phages. DLc1 can use the surface carbohydrate structures of the host cell as receptors and only infects the most related B. cereus strains, showing high host-specificity. The adsorption rate constant and life cycle of DLc1 under experimental conditions were also determined. Not only stable under temperatures below 55 °C and pH range from 5 to 11, the new phage also showed tolerance to high concentrations of NaCl, 75% ethanol, chloroform, and mechanical vortex, which is preferable for practical use in the food and pharmaceutical industries.

Carbon Nanotubes Inhibit the Pepsin Activity at High Ionic Strength

Background: Gastroesophageal reflux disease (GERD) is a common chronic gastrointestinal disorder in adults that occurs as the stomach contents reflux and come up into the esophagus due to a dysfunction in the lower oesophageal sphincter. One approach commonly used to treat GERD is inhibition of the activity of pepsin enzyme. Carbon nanotubes (CNTs) are nanoparticles of carbon atoms that possess numerous interesting physical and chemical properties. CTNs functionalization expands the range of their properties to make them soluble in biological fluids and to confer the property of carrying drug or biological macromolecules which increase the scope of their applications in biomedical science. Objective: This study aims to utilize CNTs as a pepsin inhibitor and as a new medication for the treatment of GERD. Methods: The pepsin activity before and after the addition of an exact amount of the CNTs to the reaction mixture was measured colorimetrically. Results: The results showed that both Vmax and Km changed after the addition of CNTs to the pepsin solution indicating a mixed inhibition of pepsin activity. This finding pointed to the ability of CNTs to bind with the pepsin molecule and pepsin-protein complex, therefore inhibiting the enzyme activity. Conclusion: The findings also demonstrated a complete inhibition of pepsin activity by CNTs when increasing the ionic strength of the reaction mixture. It can be inferred that using CNTs at a high concentration of NaCl at 37°C is the optimal condition for pepsin inhibition.

Novel Sources of Variation in Grain Yield, Components and Mineral Traits Identified in Wheat Amphidiploids Derived from Thinopyrum bessarabicum (Savul. & Rayss) Á. Löve (Poaceae) under Saline Soils in India

Salt-affected soils constrain wheat production globally. A wild wheat species, Thinopyrum bessarabicum (Savul. & Rayss) Á. Löve (Poaceae), and its derivatives are tolerant of high external NaCl concentrations but have not been tested yet in field conditions. The aim of this study was to study the performance of amphidiploids derived from T. bessarabicum for grain yield (GYD), yield components and grain mineral composition traits under normal and saline soil conditions. Field experiments were conducted at Karnal (pH(water) = 7.3) and Hisar (pH(water) = 8.3) sites in 2014–2015 and 2015–2016 in India. Grain samples were analysed using inductively coupled plasma–mass spectrometry (ICP-MS). Yield and yield component traits of amphidiploids were typically greater at Karnal than Hisar. The GYD was greater at Karnal (1.6 t ha−1) than Hisar (1.2 t ha−1) in 2014–2015. However, GYD was greater at Hisar (1.7 t ha−1) than Karnal (1.1 t ha−1) in 2015–2016. Mean grain zinc (Zn) concentration of eight amphidiploids, averaged across sites and years, varied from 36 to 43 mg kg−1. Some amphidiploids derived from T. bessarabicum showed greater GYD and grain Zn concentration under saline soils (Hisar) than normal soils (Karnal). These might be potential new sources for the development of salt-tolerant wheat varieties with increased grain Zn concentration under salt-affected soils.

Novel molecular level insights into forward osmosis membrane fouling affected by reverse diffusion of draw solutions based on thermodynamic mechanisms

Forward osmosis membrane bioreactor (FOMBR) has a more intricate membrane fouling mechanism than MBR because of the special existence of the reverse diffusion of draw solution. The mechanisms of membrane fouling affected by reverse diffusion of draw solution and ion content in gel layer were investigated from thermodynamic perspective and molecular level in this study. Phase-contrast microscopy non-invasively observed that the molecular chain structure of the gel layer containing low content of reverse diffused solute (NaCl) was sparse, while the alginate molecular chains with high NaCl content were parallel and compact. Density functional theory (DFT) further simulated the formation mechanism of different alginate chain structures, that is, the reverse diffused solute shortened the distance between hydrogen bonds and reduced the interaction energy at the terminals of alginate chains. This proved that the NaCl trapped in alginate layer directly affected its structure. Heating experiments indicated that gel layer acted as a “chemical potential barrier” that prevented bound water from turning into free water. Accordingly, the “chemical potential barrier” described by Flory-Huggins theory was proposed, which was confirmed to account for the filtration of alginate gels affected by reverse diffusion of draw solution. To the best of our knowledge, this is the first membrane fouling study that explores the effect of reverse diffusion of draw solution on the “chemical potential barrier” of gel layer from perspective of molecular chain structure. This study investigated FOMBR fouling mechanism at molecular level and provided a new strategy for FOMBR system fouling quantification.

Optimization of biomass and some metabolites productivity of Merismopedia tenuissima and Spirulina (Arthrospira) platensis grown under stress conditions

The attention to using cyanobacteria as a nutrient supplement has increased due to their nutritional value and high bioactive metabolites contents. The reason behind designing such a study is to illustrate and clarify stress conditions effects like nitrogen and phosphorus supplementation and deficiency, salinity stress, and different pH values on the biomass, lipid, protein, amino acid, and carbohydrate productivities of Merismopedia tenuissima and Spirulina (Arthrospira) platensis.  The obtained results revealed that an increase in sodium nitrate by 100% caused an improvement in biomass, protein, and amino acid’s productivity of S. platensis  and M. tenuissima by 7.02 % and 7.05, 9.2% and 47.5%, 11.8% and19.5, respectively while 100% nitrogen deficiency enhanced lipid productivity of S. platensis  and M. tenuissima to 41% and 94%. Moreover, phosphorus limitation led to a reduction in biomass, protein, amino acid, and carbohydrate S. platensis to 24.3%, 21.1%, 43.3%, and 28.1%, respectively. However, phosphorus-free medium showed an increase in lipid productivity of S. platensis and M. tenuissima by 46.8% and 81.8%, respectively. The addition of 0.05 M NaCl concentration to S. platensis  medium stimulates the biomass, protein, and carbohydrate productivity by 6%, 7.75%, and 18.1%, respectively, whilst, among all concentration, zero M NaCl (control) resulted in increasing biomass, protein, and amino acids, whilst, high concentration (0.3M) of NaCl enhanced lipid productivity to 125.9% and 153.5% at S. platensis  and M. tenuissima, respectively. Applications of high alkalinity (pH 9) increased the productivities of all studied metabolites in S. platensis and reduction of all mention metabolites in M. tenuissima.

Effect of NaCl Concentration on Microbiological Properties in NaCl Assistant Anaerobic Fermentation: Hydrolase Activity and Microbial Community Distribution.

Previous studies have demonstrated that sludge hydrolysis and short-chain fatty acids (SCFAs) production were improved through NaCl assistant anaerobic fermentation. However, the effect of NaCl concentrations on hydrolase activity and microbial community structure was rarely reported. In this study, it was found that α-glucosidase activity and some carbohydrate-degrading bacteria were inhibited in NaCl tests, owing to their vulnerability to high NaCl concentration. Correspondingly, the microbial community richness and diversity were reduced compared with the control test, while the evenness was not affected by NaCl concentration. By contrast, the protease activity was increased in the presence of NaCl and reached the highest activity at the NaCl concentration of 20 g/L. The protein-degrading and SCFAs-producing bacteria (e.g., Clostridium algidicarnis and Proteiniclasticum) were enriched in the presence of NaCl, which were salt-tolerant.

Identification of potential key genes affecting soybean growth under salt stress via transcriptome study

Soybean is one of the most important economic crops in the world. However, the salinization of soil results in the decrease of soybean yield as it is only a moderately salt-tolerant crop. We treated three soybean cultivars with low and high concentrations of NaCl. The differentially expressed genes between the control group and the salt treatment group were identified by mRNA sequencing and analyzed by gene ontology and Kyoto encyclopedia of genes and genomes annotations. We performed weighted gene co-expression network analysis on all samples and found genes most related to the phenotype. After verifying the results of differentially expressed genes by quantitative PCR, we finally identified Glyma06G01990, Glyma08G22730, Glyma019G05140, and Glyma06G20160 as key genes affecting the soybean growth under salt stress.

α or β?-hemihydrates transformed from dihydrate calcium sulfate in a salt-mediated glycerol–water solution

α-and β-hemihydrate calcium sulfate (HH), the most important calcium sulfate phases, are usually achieved by autoclave hydrothermal reaction and calcination in air, respectively. Herein, we report an investigation on preparation of HH from dihydrate calcium sulfate(DH) in a salt-mediated glycerol-water solution. We found that both α-HH and β-HH in forms of apparently single crystals could be obtained at 110 ℃ only by tuning the concentrations of glycerol, Na2EDTA, and NaCl. TG-DSC, XRD, SEM, and Raman spectroscopy were used to identify and characterize the product crystals. The results indicate that the high relative supersaturation of HH could be the key factor determining the generation of β-HH crystal in solution. Glycerol and NaCl generally decrease the water activity, enhance the crystallization kinetics, and therefore allow the presence of a metastable HH phase (especially for compact α-HH bulk crystal). But too high concentration of glycerol (i.e., ≥70%) and NaCl (i.e., ≥0.2 M) would be favorable for β-HH crystallization with obviously defective crystal morphology due to the dramatically increased local relative supersaturation. Na2EDTA could retard the recrystallization but well regulate the morphology of HH bulk crystals.

Differential Contribution of P5CS Isoforms to Stress Tolerance in Arabidopsis.

Proline accumulation is a widespread response of plants to salt stress as well as drought and cold stress. In most plant species, two isoforms of pyrroline-5-carboxylate synthetase (P5CS) catalyze the first step in proline biosynthesis from glutamate. In Arabidopsis, these isoforms differ in their spatial and temporal expression patterns, suggesting sub-functionalization. P5CS1 has been identified as the major contributor to stress-induced proline accumulation, whereas P5CS2 has been considered important for embryo development and growth. In contrast to previous results, our analysis of P5CS1- and P5CS2-GFP fusion proteins indicates that both enzymes were exclusively localized in the cytosol. The comparison of the susceptibility of p5cs1 and p5cs2 mutants to infection with Pseudomonas syringae and salt stress provided novel information on the contribution of the two P5CS isoforms to proline accumulation and stress tolerance. In agreement with previous studies, salt-stressed p5cs1 mutants accumulated very little proline, indicating that P5CS1 contributed more to stress-induced proline accumulation, whereas its impact on stress tolerance was rather weak. Germination and establishment of p5cs2 mutants were impaired under ambient conditions, further supporting that P5CS2 is most important for growth and development, whereas its contribution to stress-induced proline accumulation was smaller than that of P5CS1. In contrast to p5cs1 mutants or wildtype plants, p5cs2 mutants were only weakly affected by sudden exposure to a high NaCl concentration. These findings show that proline content, which was intermediate in leaves of p5cs2 mutants, was not directly correlated with stress tolerance in our experiments. In rosettes of NaCl-exposed p5cs2 mutants, nearly no accumulation of Na+ was observed, and the plants showed neither chlorosis nor reduction of photosynthesis. Based on these data, we suggest a function of P5CS2 or P5CS2-mediated proline synthesis in regulating Na+ accumulation in leaves and thereby salt stress tolerance.

A Study on Chitosan Coated Polycaprolactone (Ch-PCL) Microspheres Prepared via Double Emulsion Solvent Evaporation Method

Polycaprolactone coated with chitosan microspheres have the potential to be used as delivery systems and biosensors. Polycaprolactone (PCL) is, however hydrophobic, to improve the biofunctional and potential immobilization of PCL polymer, chitosan-coated PCL microspheres (MSs) were prepared using a double emulsion solvent evaporation method. Different particle sizes were prepared by altering five parameters. When the MSs were prepared using oil to water phase ratio or oil fraction (ϕo) of ϕo = 0.95 to ϕo = 0.38, the MSs average diameter (Dv) reduced from 3.86 to 3.53 µm along with its coefficient of variation (CV), reduced from 18.1 to 12.3 respectively. The MSs prepared with higher polymer concentration of 6wt.% shows higher Dv (4.51 µm) and CV (25.2) compared to 1.2wt.% of PCL, which Dv = 3.86 µm with CV of 18.1. The first homogenizer speed (H1) was increased in order to prepare smaller MSs. When H1 increased from 6 000 to 10 000 rpm, MSs Dv reduced from 3.86 to 3.45 µm along with its CV reduce from 18.1 to 16.6 for ϕo = 0.95. It is also the same case for ϕo = 0.52, where the Dv reduced from 3.70 to 3.19 µm and its CV reduce from 25.8 to 25.2. The effect of NaCl concentration on MSs preparation shows, higher NaCl concentration (1.8wt.%) produced smaller Dv(Dv = 3.86 µm) compared to lower concentration of 0.9wt.%, produced Dv = 4.51 µm for ϕo = 0.95. The trend also follows when the MSs were prepared for ϕo = 0.52. The delay in adding the NaCl shows distinct effect on Dv. For both 0.9 and 1.8 wt.% of NaCl, the Dv increase from 4.51 to 6.40 µm and 4.31 to 6.17 µm respectively. Therefore, the targeted Dv for certain application could be achieved by altering the parameters above. Finally, to study the Ch-PCL potential as enzyme immobilizer, horseradish peroxidase (HRP) was used to be immobilized on to the Ch-PCL MSs. After 7 days, the HRP enzyme still show 51% activity under robust storage condition.

Donnan Contribution and Specific Ion Effects in Swelling of Cationic Hydrogels are Additive: Combined High-Resolution Experiments and Finite Element Modeling.

Finite element modeling applied to analyze experimentally determined hydrogel swelling data provides quantitative description of the hydrogel in the aqueous solutions with well-defined ionic content and environmental parameters. In the present study, we expand this strategy to analysis of swelling of hydrogels over an extended concentration of salt where the Donnan contribution and specific ion effects are dominating at different regimes. Dynamics and equilibrium swelling were determined for acrylamide and cationic acrylamide-based hydrogels by high-resolution interferometry technique for step-wise increase in NaCl and NaBr concentration up to 2 M. Although increased hydrogel swelling volume with increasing salt concentration was the dominant trend for the uncharged hydrogel, the weakly charged cationic hydrogel was observed to shrink for increasing salt concentration up to 0.1 M, followed by swelling at higher salt concentrations. The initial shrinking is due to the ionic equilibration accounted for by a Donnan term. Comparison of the swelling responses at high NaCl and NaBr concentrations between the uncharged and the cationic hydrogel showed similar specific ion effects. This indicates that the ion non-specific Donnan contribution and specific ion effects are additive in the case where they are occurring in well separated ranges of salt concentration. We develop a novel finite element model including both these mechanisms to account for the observed swelling in aqueous salt solution. In particular, a salt-specific, concentration-dependent Flory–Huggins parameter was introduced for the specific ion effects. This is the first report on finite element modeling of hydrogels including specific ionic effects and underpins improvement of the mechanistic insight of hydrogel swelling that can be used to predict its response to environmental change.