Elevated Salt Concentrations Research Articles

Biodegradation of chloro- and bromobenzoic acids: Effect of milieu conditions and microbial community analysis

Monohalogenated benzoic acids often appear in industrial wastewaters where biodegradation can be hampered by complex mixtures of pollutants and prevailing extreme milieu conditions. In this study, the biodegradation of chlorinated and brominated benzoic acids was conducted at a pH range of 5.0–9.0, at elevated salt concentrations and with pollutant mixtures including fluorinated and iodinated compounds. In mixtures of the isomers, the degradation order was primarily 4-substituted followed by 3-substituted and then 2-substituted halogenated benzoic acids. If the pH and salt concentration were altered simultaneously, long adaptation periods were required. Community analyses were conducted in liquid batch cultures and after immobilization on sand columns. The Alphaproteobacteria represented an important fraction in all of the enrichment cultures. On the genus level, Afipia sp. was detected most frequently. In particular, Bacteroidetes were detected in high numbers with chlorinated benzoic acids.

Rapid evolutionary adaptation to elevated salt concentrations in pathogenic freshwater bacteria Serratia marcescens.

Rapid evolutionary adaptions to new and previously detrimental environmental conditions can increase the risk of invasion by novel pathogens. We tested this hypothesis with a 133-day-long evolutionary experiment studying the evolution of the pathogenic Serratia marcescens bacterium at salinity niche boundary and in fluctuating conditions. We found that S. marcescens evolved at harsh (80 g/L) and extreme (100 g/L) salt conditions had clearly improved salt tolerance than those evolved in the other three treatments (ancestral conditions, nonsaline conditions, and fluctuating salt conditions). Evolutionary theories suggest that fastest evolutionary changes could be observed in intermediate selection pressures. Therefore, we originally hypothesized that extreme conditions, such as our 100 g/L salinity treatment, could lead to slower adaptation due to low population sizes. However, no evolutionary differences were observed between populations evolved in harsh and extreme conditions. This suggests that in the study presented here, low population sizes did not prevent evolution in the long run. On the whole, the adaptive potential observed here could be important for the transition of pathogenic S. marcescens bacteria from human-impacted freshwater environments, such as wastewater treatment plants, to marine habitats, where they are known to infect and kill corals (e.g., through white pox disease).

The lipid flippase heterodimer ATP8B1–CDC50A is essential for surface expression of the apical sodium-dependent bile acid transporter (SLC10A2/ASBT) in intestinal Caco-2 cells

Deficiency of the phospholipid flippase ATPase, aminophospholipid transporter, class I, type 8B, member 1 (ATP8B1) causes progressive familial intrahepatic cholestasis type 1 (PFIC1) and benign recurrent intrahepatic cholestasis type 1 (BRIC1). Apart from cholestasis, many patients also suffer from diarrhea of yet unknown etiology. Here we have studied the hypothesis that intestinal ATP8B1 deficiency results in bile salt malabsorption as a possible cause of PFIC1/BRIC1 diarrhea.Bile salt transport was studied in ATP8B1-depleted intestinal Caco-2 cells. Apical membrane localization was studied by a biotinylation approach. Fecal bile salt and electrolyte contents were analyzed in stool samples of PFIC1 patients, of whom some had undergone biliary diversion or liver transplantation.Bile salt uptake by the apical sodium-dependent bile salt transporter solute carrier family 10 (sodium/bile acid cotransporter), member 2 (SLC10A2) was strongly impaired in ATP8B1-depleted Caco-2 cells. The reduced SLC10A2 activity coincided with strongly reduced apical membrane localization, which was caused by impaired apical membrane insertion of SLC10A2. Moreover, we show that endogenous ATP8B1 exists in a functional heterodimer with transmembrane protein 30A (CDC50A) in Caco-2 cells. Analyses of stool samples of post-transplant PFIC1 patients demonstrated that bile salt content was not changed, whereas sodium and chloride concentrations were elevated and potassium levels were decreased.The ATP8B1–CDC50A heterodimer is essential for the apical localization of SLC10A2 in Caco-2 cells. Diarrhea in PFIC1/BRIC1 patients has a secretory origin to which SLC10A2 deficiency may contribute. This results in elevated luminal bile salt concentrations and consequent enhanced electrolyte secretion and/or reduced electrolyte resorption.

Draft Genome Sequence of Haloalkaliphilic Exiguobacterium sp. Strain AB2 from Manleluag Ophiolitic Spring, Philippines.

Exiguobacterium sp. AB2 is a haloalkaliphilic bacterium isolated from a hyperalkaline spring in Manleluag, Pangasinan, Philippines. Sequencing of bacterial DNA assembled a 2.85 MB draft genome. Analysis suggests the presence of genes for tolerance to stresses such as elevated pH and salt concentrations and toxic metals.

A simple colorimetric DNA detection by target-induced hybridization chain reaction for isothermal signal amplification

A novel DNA detection method is presented based on a gold nanoparticle (AuNP) colorimetric assay and hybridization chain reaction (HCR). In this method, target DNA hybridized with probe DNA modified on AuNP, and triggered HCR. The resulting HCR products with a large number of negative charges significantly enhanced the stability of AuNPs, inhibiting aggregation of AuNPs at an elevated salt concentration. The approach was highly sensitive and selective. Using this enzyme-free and isothermal signal amplification method, we were able to detect target DNA at concentrations as low as 0.5nM with the naked eye. Our method also has great potential for detecting other analytes, such as metal ions, proteins, and small molecules, if the target analytes could make HCR products attach to AuNPs.

Microstructure and inter-molecular forces involved in gelation-like protein hydrolysate from neutrase-treated male gonad of scallop (Patinopecten yessoensis)

Neutrase-hydrolyzed male gonad of scallop (Patinopecten yessoensis) displayed a gelation-like profile, whereas the underlying mechanism was unknown. In this study, the microstructure and inter-molecular forces involved in the gel network of scallop (P. yessoensis) male gonad hydrolysates (SMGHs) were investigated, by monitoring changes of its gel strength in presence of different chemicals. The results showed that SMGHs chiefly consisted of peptides both below 1000 Da (46.86%) and above 10,000 Da (30.30%), and exhibited a porous, three-dimensional network, with firmness of 40.49 ± 1.96 g, cohesiveness of 479.02 ± 37.04 g·s and adhesive force of 23.69 ± 1.92 g, which were similar with that of 1.0–1.5% guar gum, 1.5% carrageenan, 1.0–2.0% xanthan gum and 0.5–1.5% gelatin. Addition of urea, and propylene glycol (PG) decreased the gel strength of SMGHs with the increase of concentration, and only a very weak gel was observed when the concentration of urea reached 8 M. The overall gel properties of SMGHs were improved in the presence of 0.3 M NaCl, KCl, CH3COONa and NaSCN (p < 0.05). However, elevated salt concentration led to decreased gel properties of SMGHs, especially the inhibiting effect of NaSCN at 3 M. In addition, inclusion of dithiothreitol (DTT), 2-mercaptoethanol (2-ME), and N-ethylmaleimide (NEM) also diminished the gel properties at high concentration (p < 0.05), but not severely, and their addition did not change the gelation-like profiles of SMGHs. These results suggest that the gel network of SMGHs was primarily maintained by hydrophobic, electrostatic interactions and hydrogen bonds.

Stable Isotope Analysis of Saline Water Samples on a Cavity Ring-down Spectroscopy Instrument

The analysis of the stable hydrogen and oxygen isotope composition of water using cavity ring-down spectroscopy (CRDS) instruments utilizing infrared absorption spectroscopy have been comprehensively tested. However, potential limitations of infrared spectroscopy for the analysis of highly saline water have not yet been evaluated. In this study, we assessed uncertainty arising from elevated salt concentrations in water analyzed on a CRDS instrument and the necessity of a correction procedure. We prepared various solutions of mixed salts and separate solutions with individual salts (NaCl, KCl, MgCl2, and CaCl2) using deionized water with a known stable isotope composition. Most of the individual salt and salt mixture solutions (some up to 340 g L(-1)) had δ-values within the range usual for CRDS analytical uncertainty (0.1‰ for δ (18)O and 1.0‰ for δ (2)H). Results were not compromised even when the total load of salt in the vaporizer reached ∼38.5 mg (equivalent to build up after running ∼100 ocean water samples). Therefore, highly saline mixtures can be successfully analyzed using CRDS, except highly concentrated MgCl2 solutions, without the need for an additional correction if the vaporizer is frequently cleaned and MgCl2 concentration in water is relatively low.

Insertion of a Specific Fungal 3′-phosphoadenosine-5′-phosphatase Motif into a Plant Homologue Improves Halotolerance and Drought Tolerance of Plants

Soil salinity and drought are among the most serious agricultural and environmental problems of today. Therefore, investigations of plant resistance to abiotic stress have received a lot of attention in recent years. In this study, we identified the complete coding sequence of a 3′-phosphoadenosine-5′-phosphatase protein, ApHal2, from the halotolerant yeast Aureobasidium pullulans. Expression of the ApHAL2 gene in a Saccharomyces cerevisiae hal2 mutant complemented the mutant auxotrophy for methionine, and rescued the growth of the hal2 mutant in media with high NaCl concentrations. A 21-amino-acids-long region of the ApHal2 enzyme was inserted into the Arabidopsis thaliana homologue of Hal2, the SAL1 phosphatase. The inserted sequence included the META motif, which has previously been implicated in increased sodium tolerance of the Hal2 homologue from a related fungal species. Transgenic Arabidopsis plants overexpressing this modified SAL1 (mSAL1) showed improved halotolerance and drought tolerance. In a medium with an elevated salt concentration, mSAL1-expressing plants were twice as likely to have roots in a higher length category in comparison with the wild-type Arabidopsis and with plants overexpressing the native SAL1, and had 5% to 10% larger leaf surface area under moderate and severe salt stress, respectively. Similarly, after moderate drought exposure, the mSAL1-expressing plants showed 14% increased dry weight after revitalisation, with no increase in dry weight of the wild-type plants. With severe drought, plants overexpressing native SAL1 had the worst rehydration success, consistent with the recently proposed role of SAL1 in severe drought. This was not observed for plants expressing mSAL1. Therefore, the presence of this fungal META motif sequence is beneficial under conditions of increased salinity and moderate drought, and shows no drawbacks for plant survival under severe drought. This demonstrates that adaptations of extremotolerant fungi should be considered as a valuable resource for improving stress-tolerance in plant breeding in the future.

Responses of nutrient dynamics in barley seedlings to the interaction of salinity and carbon dioxide enrichment

The effects of elevated CO2 on the content of several nutrients in plants have been well studied, but few studies have investigated plant nutrient dynamics under future environmental conditions, which are expected to include elevated CO2 and elevated soil salt concentrations. This study investigated whether high salt and CO2 conditions, singly or in combination, might affect nutrient dynamics, and the underlying mechanisms. We measured macro- and micronutrient uptake and translocation rates, nutrient content and concentrations in whole seedlings and in each plant organ. We estimated whole-plant nutrient use efficiencies in barley subjected to 0, 80, 160, or 240mM NaCl and grown at either 350 (ambient) or 700 (elevated) μmolmol−1 CO2. Under non-saline conditions, plants grown at elevated CO2 adjusted their root size and activity to change nutrient uptake and transport efficiency in response to the demand for a given nutrient. Under high saline conditions, salt stress reduced K, Ca, N, B, and S uptake rates and concentrations in tissues, which caused growth reduction. Nevertheless, barley had the ability to increase the selectivity of K over Na, and Ca over Na. Under combined conditions of salt stress and elevated CO2, barley seedlings were able to maintain higher uptake and translocation rates of almost all nutrients. This ability allowed the plants to adapt to higher demands under elevated CO2; they could grow more rapidly by allocating more C to root growth and by increasing active nutrient uptake and translocation. Our results indicated that salinity generally increased nutrient use efficiency under both CO2 conditions. However, we found no consistent evidence that nutrient use efficiency was affected by CO2 concentration, either under non-saline or saline conditions.

A dileucine motif is involved in plasma membrane expression and endocytosis of rat sodium taurocholate cotransporting polypeptide (Ntcp)

The sodium taurocholate cotransporting polypeptide (Ntcp) is the major uptake transporter for bile salts into liver parenchymal cells, and PKC-mediated endocytosis was shown to regulate the number of Ntcp molecules at the plasma membrane. In this study, mechanisms of Ntcp internalization were analyzed by flow cytometry, immunofluorescence, and Western blot analyses in HepG2 cells. PKC activation induced endocytosis of Ntcp from the plasma membrane by ~30%. Endocytosis of Ntcp was clathrin dependent and was followed by lysosomal degradation. A dileucine motif located in the third intracellular loop of Ntcp was essential for endocytosis but also for processing and plasma membrane targeting, suggesting a dual function of this motif for intracellular trafficking of Ntcp. Mutation of two of five potential phosphorylation sites surrounding the dileucine motif (Thr225 and Ser226) inhibited PKC-mediated endocytosis. In conclusion, we could identify a motif, which is critical for Ntcp plasma membrane localization. Endocytic retrieval protects hepatocytes from elevated bile salt concentrations and is of special interest, because NTCP has been identified as a receptor for the hepatitis B and D virus.

Removal of the nonionic surfactant Eumulgin ES from protein solutions by means of adsorption and ultrafiltration

Aqueous micellar two-phase extraction (AMTPE) is a promising technique for large-scale protein purification, however, it is unavoidable that a certain surfactant load will remain in the product stream. Therefore, an industrial application of AMTPE requires efficient and economic ways for the removal of surfactants as a polishing step. In view of this demand, the removal of the nonionic surfactant Eumulgin ES has been investigated by means of fixed bed adsorption and cross-flow ultrafiltration. The critical micelle concentration of an aqueous Eumulgin ES solution is 9.2mg/L with a hydrodynamic diameter of a micelle of approximately 15nm at 22°C. The adsorption of Eumulgin ES to hydrophobic polystyrene beads leads to high loading capacities, but proteins also bind with high affinity to the beads, making the technique of limited use. A better way is to remove the surfactant by means of ultrafiltration through a hydrophobic polyethersulfone membrane. In the course of the filtration process a viscous micelle phase at the membrane forms, by which the flux through the membrane is decreased drastically. While elevated temperatures and salt concentrations decrease the flux and the overall separation performance, the opposite conditions lead to improved surfactant removal efficiencies. Cross-flow ultrafiltration is finally applied for the separation of Eumulgin ES from a proteinaceous solution originating from a technical-scale AMTPE investigation. The filtration results in a total surfactant removal of >98.8% from the target protein solution within 8 exchanged volumes.

Barley Growth and Its Underlying Components are Affected by Elevated CO2 and Salt Concentration

The future environment will exhibit increases in soil salt concentrations and atmospheric CO2. In general, plant growth is inhibited by salt stress and stimulated by elevated CO2. This study investigated whether elevated CO2 could improve plant growth under salt stress and the mechanisms involved. We measured functional and morphological components of growth in barley (cv. Iranis) subjected to 0, 80, 160, or 240 mM NaCl and grown at either 350 (ambient) or 700 (elevated) μmol mol−1 CO2. Under nonsaline conditions, elevated CO2 stimulated growth by increasing the relative growth rate (RGR). Maximum CO2 stimulation was observed within the first 10 days of development, before the start of the salt treatment. Afterwards, salt stress caused reductions in biomass production and RGR by decreasing the photosynthetic rate and increasing the respiration rate; this resulted in a reduced net assimilation rate (functional component). In addition, salt stress caused nutritional imbalances, which reduced the leaf expansion capacity, and changed the root-to-shoot ratio. This resulted in reductions in the specific leaf area and leaf weight ratio (morphological components). However, the functional component became more relevant with increasing salt stress. Under elevated CO2 conditions, salt stress inhibited growth less than that observed at ambient CO2. This occurred because (1) more dry biomass was synthesized for a given leaf area due to higher photosynthetic rates, and (2) greater leaf area and root biomass were maintained for photosynthesis and water and mineral uptake, respectively.

Agl16, a Thermophilic Glycosyltransferase Mediating the Last Step of N -Glycan Biosynthesis in the Thermoacidophilic Crenarchaeon Sulfolobus acidocaldarius

Recently, the S-layer protein of Sulfolobus acidocaldarius was shown to be N-linked with a tribranched hexasaccharide, composed of Man2Glc1GlcNAc2 and a sulfated sugar called sulfoquinovose. To identify genes involved in the biosynthesis and attachment of this glycan, markerless in-frame deletions of genes coding for predicted glycosyltransferases were created. The successful deletion of agl16, coding for a glycosyltransferase, resulted in the S-layer protein and archaellins having reduced molecular weights, as visualized by Coomassie staining or immunoblotting. This analysis indicated a change in the N-glycan composition. Nano-liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses confirmed that the glycan of the S-layer protein from the agl16 deletion mutant was a pentasaccharide, which was missing a terminal hexose residue. High-performance liquid chromatography (HPLC) analyses of the hydrolyzed N-glycan indicated that the missing hexose is a glucose residue. A physiological characterization of the agl16 deletion mutant revealed a significant effect on the growth at elevated salt concentrations. At 300 mM NaCl, the doubling time of the Δagl16 mutant was increased 2-fold compared to that of the background strain. Furthermore, the incomplete glycan structure of the Δagl16 deletion strain affected the assembly and function of the archaellum, as exemplified by semisolid Gelrite plate analysis, in which the motility is decreased according to the N-glycan size.

Conditions associated with Clostridium sporogenes growth as a surrogate for Clostridium botulinum in nonthermally processed canned butter

The objective of this study was to better understand the effect of butter composition and emulsion structure on growth and survival of Clostridium sporogenes, used as a surrogate for C. botulinum in canned butter. The lack of a thermal process step in commercially available canned butter raises questions of potential safety, because it is hermetically sealed and generally exhibits anaerobic growth conditions, which are optimal for Clostridium botulinum growth. Without thermal processing, low-acid canned foods must have inhibitory factors present to prevent C. botulinum growth. Some potential intrinsic inhibitory factors, or hurdles, within butter include: reduced water activity, acidity in cultured products, elevated salt content, and the micro-droplet nature of the aqueous phase in the butter emulsion. It was hypothesized that a normal, intact butter emulsion would have sufficient hurdles to prevent C. botulinum growth, whereas a broken butter emulsion would result in a coalesced aqueous phase that would allow for C. botulinum growth. Batch-churned butter was inoculated with C. sporogenes; butter samples with varying salt contents (0, 0.8, 1.6, and 2.4% wt/wt NaCl) were prepared and stored in coated steel cans for varying times (1 or 2 wk) and temperatures (22 or 41°C) to determine temperature and emulsion structure effects on C. sporogenes growth. Samples stored at 41°C showed a significant increase in C. sporogenes growth compared with those stored at 22°C. Furthermore, NaCl addition was found to have a significant effect on C. sporogenes growth, with 0.8% NaCl promoting more growth than 0%, but with decreases in growth observed at 1.6 and 2.4%. Uninoculated control plates were also found to have bacterial growth; this growth was attributed to other anaerobic bacteria present within the cream. It was concluded that removal of the hurdle created by the micro-droplet size of the emulsion aqueous phase could result in C. botulinum growth even at elevated salt levels and, therefore, home preparation of canned butter is not advisable. It is also possible that commercially canned butter, if heat abused, could potentially allow for C. botulinum growth and, therefore, consumption is not recommended.

Chimeric Beta-Defensin Analogs, Including the Novel 3NI Analog, Display Salt-Resistant Antimicrobial Activity and Lack Toxicity in Human Epithelial Cell Lines

Human beta-defensins (hBDs) are crucial peptides for the innate immune response and are thus prime candidates as therapeutic agents directed against infective diseases. Based on the properties of wild-type hBD1 and hBD3 and of previously synthesized analogs (1C, 3I, and 3N), we have designed a new analog, 3NI, and investigated its potential as an antimicrobial drug. Specifically, we evaluated the antimicrobial activities of 3NI versus those of hBD1, hBD3, 1C, 3I, and 3N. Our results show that 3NI exerted greater antibacterial activity against Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis than did hBD1 and hBD3, even with elevated salt concentrations. Moreover, its antiviral activity against herpes simplex virus 1 was greater than that of hBD1 and similar to that of hBD3. Subsequently, we investigated the cytotoxic effects of all peptides in three human epithelial carcinoma cell lines: A549 from lung, CaCo-2 from colon, and Capan-1 from pancreas. None of the analogs significantly reduced cell viability versus wild-type hBD1 and hBD3. They did not induce genotoxicity or cause an increase in the number of apoptotic cells. Using confocal microscopy, we also investigated the localization of the peptides during their incubation with epithelial cells and found that they were distributed on the cell surface, from which they were internalized. Finally, we show that hBD1 and hBD3 are characterized by high resistance to serum degradation. In conclusion, the new analog 3NI seems to be a promising anti-infective agent, particularly given its high salt resistance--a feature that is relevant in diseases such as cystic fibrosis.

Salt stress, signalling and redox control in seeds.

Abiotic stresses, including salt stress, can impair electron transport chains, thereby increasing the production of reactive oxygen species (ROS). An excess of ROS can damage macromolecular and cellular structure, but ROS are also key components of signalling networks, through which they regulate developmental processes. Surprisingly little is known about the effects of salt stress upon seeds given their pivotal role in plant reproduction and dispersal. This review provides information on tolerance mechanisms and redox control in relation to seed metabolism and performance. First, the effects of salt stress throughout the seed life cycle are discussed, comprising salt effects on the mother plant and its implications on seed development, salt uptake upon seed imbibition and effects on seed germination. Then, responses to elevated salt concentrations are discussed according to a recently proposed triphasic seed stress model comprising the phases alarm, resistance and exhaustion. Implications of redox control in seeds on the physiological, biochemical and molecular level are considered and the review concludes with a perspective on future research in relation to salt stress and seed biology.

Effect of zinc and copper on cultivable populations of soil fungi with special reference to entomopathogenic fungi

The effect of copper and zinc on cultivable soil fungi populations was investigated in a laboratory experiment. Samples of four different soils (arable sandy soil and loam clay; forest sandy soil and forest peat) were collected from sites located in Vilnius district, Lithuania. Metals’ effect was elaborated by addition of metal salts (CuSO4 and ZnSO4) at appropriate concentrations into the growth medium (Czapek's agar) and evaluating cultivable fungi abundance and species diversity changes. Zinc or copper salt was added to the medium after its sterilization; zinc concentration varied from 0.05 to 0.20 M (by 0.05 M concentration range) and copper concentration – from 0.5 to 3.0 mM (by 0.15 mM concentration range). At elevated metal salt concentrations, the abundance of cultivable fungi decreased with a marked elimination of some fungi species as compared with a control medium (without metal addition) fungi cultures. Irrespective of a fungi community structure in different type soils, Cu was a stronger inhibitor of soil fungi population abundance than Zn, however, both metals showed a comparable effect on the fungi species diversity. The most resistant fungi belonged to common insect pathogens (Beuveria bassiana, Metarhizium anisopliae, Lecanicillium lecanii and Isaria spp.), which dominated comprising up to 90% of all recovered from the soils isolates, due to the metal salt concentration.

Preservation Status and Priorities for In Situ Monitoring of the Weapon Sacrifice in Illerup Ådal, Denmark

Excavations of the southern part of a very rich sacrificial bog in Illerup Ådal, Denmark between 1950 and 1985 recovered approximately 15,000 Iron Age artefacts. At the time, 60 per cent of the area was left unexcavated and thousands of objects are now preserved in situ, but the present preservation status has not been investigated for approximately twenty-five years. Extensive in situ monitoring was carried out for one year in order to present a prioritized plan for further monitoring of the unexcavated areas, producing documentation of groundwater table variations, water quality and vegetation in the area. Results show that the remaining artefacts are generally well preserved in a waterlogged and anaerobic environment. However, in the north-eastern part of the bog, the groundwater table is too low even in a year when net precipitation and hydrological conditions were near normal. In the centre of the bog elevated salt concentrations have been measured in the groundwater.

Estimation of the cation balance of soil solutions for vegetable cultivation

Recently, in Japan, the amount of sodium and potassium in composts has tended to increase. This study clarified the effects of composts with elevated salt content on the soil and on mini tomato (Solanum lycopersicum) and komatsuna (Brassica rapa var. peruviridis) growth by investigating the time course of changes in soil solution composition and cation balance. Because the application of elevated-salt compost drastically increased the concentration of potassium and sodium in the soil solution, the relative ratio of bivalent cations to monovalent cations was a key factor causing poor-growth symptoms in mini tomato and komatsuna. By introducing a new index for the activity ratio for potassium plus sodium, i.e. ARK+Na, the composition of cations in the soil solution could be evaluated quantitatively. Based on ARK+Na index, it was found that blossom-end rot occurred when the ARK+Na value was too low and exceeded a specified level (−1.25 in the present case) while mini tomato fruit still grew on the first branch. Komatsuna was successively cultivated 4 times in an Andosol and a Fluvisol with ordinary compost or elevated-salt compost. The value of ARK+Na decreased to a steady level by the beginning of the third cropping in the case of the elevated-salt compost.

Performance enhancement and scaling control with gas bubbling in direct contact membrane distillation

This study incorporates gas bubbling into direct contact membrane distillation (DCMD) and examines its effect on the MD performance especially at elevated salt concentrations in the feed steam. Process optimization in the bubbling assisted DCMD process was carried out which involved varying operating conditions and module configurations. Also, observations were performed for the scaling status on the membrane surface with operating time in different modules to further understand the role of gas bubbling in affecting the behavior of crystal deposition when the salt concentration has reached super-saturation.Due to intensified local mixing and physical flow disturbance in the liquid boundary layer on the feed side, a higher flux enhancement could be achieved in a bubbling system with either a higher feed operating temperature, lower feed and permeate flow velocities, inclined module orientation, shorter fiber length or lower packing density. It was also found that gas bubbling not only enhanced the permeation flux by average 26% when concentrating feed solution from 18% salt concentration to saturation, but also delayed the occurrence of major flux decline due to crystal deposition when compared to the module with spacers. These results were confirmed by membrane surface autopsy at different operating stages using SEM.