NaCl Conditions Research Articles

Studies on Beneficial Yeasts Isolated from Some Egyptian Dairy Products

Yeasts constitute large groups of microorganisms that are recently attracting attention of industry and scientists. Different biological activities make them favorable candidates for numerous applications not limited to the food sector. The aim of this study was to examine beneficial yeasts associated with some traditional Egyptian dairy products and to evaluate their microbiological and technological properties. One hundred samples of locally produced yoghurt, Kariesh, Domiatti and Mish cheeses were collected from different localities at Sharkia Governorate, Egypt. Seventy-seven (77%) of the examined samples were positive for the presence of yeasts. Kariesh cheese had the highest total yeast count compared with other examined dairy products. From these positive samples, a total of 154 yeast isolates were screened for their antibacterial activities against the common foodborne pathogens ( Staphylococcus aureus and Escherichia coli ). Yeast isolates showing highest antibacterial activity were identified and then investigated for some technological properties (growth ability at different temperature, low pH and different NaCl conditions). Only 30 strains corresponding to Saccharomyces cerevisiae, Debaryomyces hansenii and Candida zeylanoides were found to be effective against S. aureus and/ or E. coli strains. These strains have also technological properties that allow them attractive for use in food industry and for further evaluation.

The lysine-peptoid hybrid LP5 maintain activity under physiological conditions and affects virulence gene expression in Staphylococcus aureus

The antimicrobial peptide, LP5, is a lysine-peptoid hybrid, with antimicrobial activity against clinically relevant bacteria. Here, we investigated how various environmental conditions affect the antimicrobial activity of LP5 against Staphylococcus aureus (S. aureus). We found that LP5 maintained activity under host physiological conditions of NaCl, MgCl2 and pH. However, when exposed to serum, LP5 lost activity. Furthermore, when increasing NaCl concentration and lowering pH, the peptide showed reduces activity. When investigating the tolerance mechanisms of S. aureus toward antimicrobial peptides, we found that LP5 was protease resistant. However, the dltA and vraF genes, involved in reducing the net anionic charge of the bacterial cell envelope and sensing of antimicrobial peptides, respectively, played a role in the tolerance of S. aureus against LP5. In addition, the exposure of S. aureus to sub-inhibitory concentrations of LP5 affected the expression of the major virulence factors of S. aureus, revealing a potential as anti-virulence compound. Thus, these results show how environmental factors affect the peptide efficiency and further add to the knowledge on how the peptide affects S. aureus, which is crucial information for designing new peptides for optimizing antimicrobial therapy.

Quantifying the Impact of Biological and Experimental Variability Near the Growth Boundaries on the Stochastic Responses of Growth, Gene Transcription and Acid Resistance of Listeria monocytogenes

Hereby, we showed that the experimental and biological variability in culture preparation had little effect on the stochastic outcome of: (i) growth, (ii) relative transcription of stress- (gad2, sigB) and virulence- (prfA) associated genes and (iii) subsequent acid resistance of Listeria monocytogenes, across growth/ no growth boundaries regarding combinations of pH (4.8-7.2) (HCl) and NaCl (0-8% w/v) at 7oC. Variability of bacterial response, as described by the coefficient of variation (CV) and root mean square error (RMSE) was affected mainly by the previously pH and NaCl conditions that the pathogen had experienced. High biological variability regarding growth potential of the pathogen, was observed in conditions across growth boundaries (at 7oC), such as pH 5.5-6.4 and NaCl 2-8% w/v, as manifested by the highly ranged growth parameters (CVareas 18.3% - 49%, RMSEareas 8.7-13.9, RMSElagtime 9.3-31.2), while acid resistance (pH 2.0, HCl, 37 °C) was highly variable when pathogen habituated pH (5.0-5.2) and NaCl (2% w/v) resulting in average D1 (3-6min) and D2 (14-16min) of high variability (CVD1 28-35%; CVD2 35-60%). Moreover at the same conditions the highest upregulation of gad2 was observed with high biological variability of RMSEgad2 2.8, while relative transcription levels of pfrA ranged from 0.60 to 4.22, indicating the potential risk derived from the stochastic bacterial response (up- or down- regulation) regarding induction of virulence mechanisms in growth boundary conditions.

Screening and Characterization of Potential Bacillus Starter Cultures for Fermenting Low-Salt Soybean Paste (Doenjang).

The bacterial strains were screened as potential starters for fermenting low-salt doenjang (a Korean traditional fermented soybean paste) using Korean doenjang based on proteolytic and antipathogenic activities under 6.5-7.5% NaCl conditions. Phylogenetic analysis based on 16S rRNA gene sequences showed that they all belonged to the genus Bacillus. Proteolytic and antipathogenic activities against Escherichia coli, Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, and Aspergillus flavus, as well as fibrinolytic, amylase, and cellulase activities of the 10 strains were quantitatively evaluated. Of these, strains D2-2, JJ-D34, and D12-5 were selected, based on their activities. The functional, phenotypic, and safety-related characteristics of these three strains were additionally investigated and strains D2-2 and D12-5, which lacked antibiotic resistance, were finally selected. Strains D2-2 and D12-5 produced poly-γ-glutamic acid and showed various enzyme activities, including α-glucosidase and β-glucosidase. Growth properties of strains D2-2 and D12-5 included wide temperature and pH ranges, growth in up to 16% NaCl, and weak anaerobic growth, suggesting that they facilitate low-salt doenjang fermentation. Strains D2-2 and D12-5 were not hemolytic, carried no toxin genes, and did not produce biogenic amines. These results suggest that strains D2-2 and D12-5 can serve as appropriate starter cultures for fermenting low-salt doenjang with high quality and safety.

Synergistic interactions between Bradyrhizobium japonicum and the endophyte Stenotrophomonas rhizophila and their effects on growth, and nodulation of soybean under salt stress

Understanding the interactions between endophytic bacteria, rhizobia, free living root associated bacteria and their host plants under stressed conditions remains a significant challenge for proposing strategies to improve the efficacy of PGPR. In this study we analyzed the role of the endophytic bacterium Stenotrophomonas rhizophila in alleviating salinity stress in plants. The nodulation efficiency, plant growth, nitrogen and phosphorus uptake of soybean under hydroponic salt stress conditions were determined. Soybean seedlings were inoculated with Bradyrhizobium japonicum BDYD1 and S. rhizophila ep-17 were grown in hydroponic plastic pots containing 2 l of Hoagland solution for 42 days. Salinity conditions were established by adding 50 and 75 mM NaCl to the nutrient solution. The results showed that the salinity decreased the colonization of B. japonicum BDYD1 in the rhizosphere of soybean, inhibited shoot, root growth, and nodulation compared with those of unstressed plants. We found synergistic interactions between compatible salt tolerant S. rhizophila ep-17 and B. japonicum BDYD1 strains which were manifested themselves as improved root, shoot length, dry weight, N and P uptake and number of nodules compared with the uninoculated plants grown under 75 mM NaCl condition. S. rhizophila and Bradyrhizobium build beneficial association in the rhizosphere and can act synergistically on promoting plant growth, nutrient uptake and fitness of hydroponically grown soybean under salt stress condition.

ABA-induced CCCH tandem zinc finger protein OsC3H47 decreases ABA sensitivity and promotes drought tolerance in Oryza sativa

Water deficit causes multiple negative impacts on plants, such as reactive oxygen species (ROS) accumulation, abscisic acid (ABA) induction, stomatal closure, and decreased photosynthesis. Here, we characterized OsC3H47, which belongs to CCCH zinc-finger families, as a drought-stress response gene. It can be strongly induced by NaCl, PEG, ABA, and drought conditions. Overexpression of OsC3H47 significantly enhanced tolerance to drought and salt stresses in rice seedlings, which indicates that OsC3H47 plays important roles in post-stress recovery. However, overexpression of OsC3H47 reduced the ABA sensitivity of rice seedlings. This suggests that OsC3H47 is a newly discovered gene that can control rice drought-stress response, and it may play an important role in ABA feedback and post-transcription processes.

Suaeda salsa is Adaptive to Chilling Stress under Salinity at Stages of Seed Germination and Seedling Establishment

Suaeda salsa L., a C3 euhalophytic herb, is a native of saline soils. This herb displays high resistance to salinity stress. In the present study, we investigated the interaction between low temperature and salinity on seed germination and seedling establishment. Low temperature (4 oC) conditions severely inhibited seed germination at 0 and 200 mM NaCl. The percent germination at 200 mM NaCl was higher than that at 0 mM NaCl. After 24 h of chilling stress, the fresh weight and dry weight of S. salsa seedlings at 0 mM NaCl was reduced, but the fresh weight and dry weight of S. salsa seedlings at 200 mM NaCl increased. APX and CAT activities decreased during chilling stress at both 0 and 200 mM NaCl, yet the activity of both enzymes was not affected as strongly at 200 mM NaCl compared to 0 mM NaCl. After a 12 h chilling treatment, the unsaturated fatty acid content and the double bond index (DBI) of DGDG, SQDG and PG major membrane lipids was significantly increased at 200 mM NaCl. The level of PG and the ratio of DGDG/MGDG in seedling leaves were also increased in the presence of 200 mM NaCl. These results suggest that S. salsa is more adaptive to chilling stress under 200 mM NaCl conditions at stage of seed germination and during seedling establishment.

Supplementation with solutions of lipo-chitooligosacharide Nod Bj V (C18:1, MeFuc) and thuricin 17 regulates leaf arrangement, biomass, and root development of canola (Brassica napus [L.

Recent work has shown that plant-to-microbe signals can enhance the growth of a wide range of crops. Nevertheless, canola (Brassica napus L.), which forms neither arbuscular mycorrhizal nor nitrogen-fixing symbioses, has not been rigorously evaluated for its capacity to perceive and respond to microbe-to-plant signals. It was shown previously that the Bradyrhizobium japonicum lipo-chitooligosaccharide (LCO) and Bacillus thuringiensis bacteriocin thuricin 17 enhance the germination and growth of other crop species. To evaluate canola’s response, B. napus plants were grown in controlled environment chambers, in either peat pellets or large plant culture vessels. In the peat pellet system, plants that were irrigated with 10−6 M LCO, and grown at 30 °C, produced one more leaf than water- or signal-treated plants that were grown at 25/20 °C. The numbers of cotyledons (seed leaves) produced by thuricin 17-treated plants was greater than LCO treated plants and the control treatment. Among the plants grown in vessels, those grown with 0.2 M NaCl and 10−9 M thuricin 17 were taller than either treated or untreated plants that were grown with 10−5 M NaCl. Under 10/4 °C and 4 × 10−5 M NaCl conditions, only seeds treated with thuricin 17 produced roots. Among the plants grown in vessels at 30/30 °C, those treated with 10−11 M thuricin 17 resulted in approximately one more leaf per plant than nM. Root lengths were shortened with 10−5 M NaCl and 10−9 M thuricin 17, compared to lower salinities. At 30/30 °C, plants grown with 10−5 M NaCl and 10−9 M thuricin 17 were heavier than plants grown in nonsaline media without thuricin 17. Where LCO supplementation may stimulate a competitive form, thuricin 17 supplementation triggers a reduction in the plant’s surface area, which may reduce the plant’s vulnerability to prohibitive salinity levels.

Systematic analysis of maize class III peroxidase gene family reveals a conserved subfamily involved in abiotic stress response

Class III peroxidases (PRXs) are plant-specific enzymes that play key roles in the responses to biotic and abiotic stress during plant growth and development. In this study, we identified 119 nonredundant PRX genes (designated ZmPRXs). These PRX genes were divided into 18 groups based on their phylogenetic relationships. We performed systematic bioinformatics analysis of the PRX genes, including analysis of gene structures, conserved motifs, phylogenetic relationships and gene expression profiles. The ZmPRXs are unevenly distributed on the 10 maize chromosomes. In addition, these genes have undergone 16 segmental duplication and 12 tandem duplication events, indicating that both segmental and tandem duplication were the main contributors to the expansion of the maize PRX family. Ka/Ks analysis suggested that most duplicated ZmPRXs experienced purifying selection, with limited functional divergence during the duplication events, and comparative analysis among maize, sorghum and rice revealed that there were independent duplication events besides the whole-genome duplication of the maize genome. Furthermore, microarray analysis indicated that most highly expressed genes might play significant roles in root. We examined the expression of five candidate ZmPRXs under H2O2, SA, NaCl and PEG stress conditions using quantitative real-time PCR (qRT-PCR), revealing differential expression patterns. This study provides useful information for further functional analysis of the PRX gene family in maize.

Photosynthetic capacity of canola ( Brassica napus L.) plants as affected by glycinebetaine under the salt stress

Salinity causes reduction in growth and severe losses of crop productivity by affecting various biochemical and physiological processes including photosynthesis. Plants sense and adapt to salt stress by modulating different physiological processes including accumulation of osmoprotectants. Glycinebetaine (GB) is an important osmoprotectant and found to have ameliorative effects on the growth of plants by altering ion homeostasis, photosynthetic and antioxidant capacity. In this study, it was attempted to reveal how GB improves photosynthetic activity and salt tolerance of two canola cultivars which differ in degree of salt tolerance. Two cultivars (Dunkled and Cyclone) of canola ( Brassica napus L.) were grown under non-saline or saline (150 mM NaCl) conditions. Glycinebetaine (100 mM) was foliarly applied to both non-stressed and salt stressed plants of both canola cultivars at the vegetative growth stage. Salt stress reduced growth of both canola cultivars, however, cv. Dunkled was superior to cv. Cyclone. Foliar application of GB improved leaf relative water contents (RWC), osmotic potential and proline accumulation in salt stressed plants. The chlorophyll fluorescence transient (CFT) remained unchanged at O and J phase while at I and P phase it was affected by salt stress in both cultivars that was ameliorated by GB application. The positive values of K band after 1000 µs under salt stress revealed the reduced efficiency of oxygen evolving complex (OEC). The GB application enhanced electron transport chain and decreased heat dissipation under salt stress. This effect was more in cultivar Cyclone as compared to Dunkled. Furthermore, a considerable proteomic variation was noted in canola cultivars after application of GB under both saline and non-saline condition. The results suggested that exogenous foliar application of GB ameliorated the adverse effects of salt stress on both cultivars of canola by osmotic adjustment, growth improvement, increased light absorption by reaction centers, efficient energy trapping and enhanced electron transport chain in both cultivars of canola.

Involvement of nitrogen in salt resistance of Atriplex portulacoides is supported by split‐root experiment data and exogenous application of N‐rich compounds

AbstractUsing a split‐root system, we aimed to identify the limiting factors for the growth of the halophyte Atriplex portulacoides L. under extreme salinity (800 mM NaCl) conditions. One half of the root system was immersed in complete nutrient solution at 0 or 800 mM NaCl and the other half was immersed in NaCl‐free medium, containing all nutrients or deprived of potassium (K+) or calcium (Ca2+) or nitrogen (N). Data indicate that at high salinity levels A. portulacoides growth is limited by the restrictions imposed by NaCl on N uptake. Next, the alleviation of the adverse impact by salt stress (800 mM NaCl) on plant growth was investigated through urea (U) and/or thiourea (TU) external addition through foliar application. Whether separately or supplied together, both components mitigated the negative impact of salinity on the plant growth by significantly improving the photosynthetic activity parameters [CO2 assimilation rate, stomatal conductance and maximum quantum efficiency of PSII photochemistry (Fv/Fm)], as well as shoot N concentration and the photosynthetic nitrogen‐use efficiency (PNUE). A concomitant increase of protein and free amino acid concentrations was also observed. As a whole, the present study highlights the significance of N in A. portulacoides response to high salinity and suggests that combined application of U and TU could promote the growth of this halophyte potentially useful for saline soil reclamation and revegetation purposes.

Exogenous 24-Epibrassinolide Elevates the Salt Tolerance Potential of Pea (Pisum sativum L.) by Improving Osmotic Adjustment Capacity and Leaf Water Relations

Salinity, as a wide spread problem around the globe, can drastically limits the crop growth and productivity. Therefore, there is a growing need to mitigate the drastic effects of this abiotic stress through the use some sustaiable short-term or long term approaches. An investigation was carried out to assess the potential role of 24-epibrassinolide (EBL) in mitigating the drastic effects of salt stress on growth, water relations, osmolytes, and ions accumulation of salt-tolerant and salt-sensitive pea genotypes. EBL treatment significantly altered the leaf water status and accumulation of osmolytes and various ions in salt-stressed [with sodium chloride (+NaCl)] plants. The plants of both salt-tolerant and salt-sensitive genotypes, subjected to +NaCl conditions had a significant reduction in plant fresh and dry weights, internodal distance, leaf area (LA), leaf water potential (w), leaf osmotic potential (o), leaf turgor potential (t), relative water content (RWC), number of seeds pod−1, seed weight, root/leaf inorganic osmolytes (Ca2+, K+ and Mg2+), while increased the levels of root/leaf proline, glycinebetaine, total free amino acids, total soluble sugars, sodium (Na+), and chloride (Cl−). There was non-significant effect of EBL on number of pods plant−1 both under saline and non-saline conditions. However, the foliar application of EBL significantly alleviated the deleterious effects of salinity by improving the plant biomass, water relations and concentration of organic/inorganic osmolytes and yield attributes. However, EBL minimized the drastic effects of salt stress by limiting the root/leaf Na+ and Cl− contents. It can be concluded that EBL efficiently alleviated the salinity-induced drastic effects by improving the water status of plant tissues, which led to salt dilution within plant tissues, thus minimized the ion-toxicity, ultimately elevated the plant growth by minimizing the toxic action of Na+ and Cl−. Secondly, EBL augmented the salt-tolerance capacity of tested pea genotypes by enhancing their osmotic adjustment potential, in terms of high accumulation of organic and inorganic osmolytes within leaf and root tissues.

Expression analysis of photosynthesis genes in Dunaliella salina grown at different NaCl concentrations

The expression of five genes involved in photosynthesis was investigated under different salinity conditions in Dunaliella salina. These genes encodes ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo) large and small subunits, major light-harvesting chlorophyll (chl) a/b protein of photosystem II, carbonic anhydrase and adenosine tri phosphate synthase alpha subunit. As D. salina grows in hypersaline conditions, it is important to study expression of these genes in relation to different salinity levels. Changes in the mRNA level under different NaCl conditions were determined using the comparative CT method. Cell number and chl a content were estimated to determine optimal growth at different NaCl concentrations. Real-time PCR results showed enhanced expression of photosynthesis genes upon exposure of D. salina cells from Sambhar Lake to 1.7 M NaCl containing medium. This salinity corresponds to only one-third of the salinity of the Sambhar Lake habitat. In another salt condition, the expression level of all genes was found to be down -regulated at 1.0 M (sub-optimal concentration for growth of D. salina), 2.5 M and 3.0 M NaCl (supra-optimal concentration for growth) when compared with 1.7 M NaCl containing medium as a control. The present study will help in understanding the salinity tolerance in D. salina as a model microalga.

Selection of reliable reference genes for quantitative real-time RT-PCR in alfalfa.

Real-time quantitative RT-PCR (qRT-PCR) is the most commonly used method for accurately detecting gene expression patterns. As part of qRT-PCR analysis, normalization of the data requires internal control gene(s) that display uniform expression under different biological conditions. However, no invariable internal control gene exists, and therefore more than one reference gene is needed to normalize RT-PCR results. In this study, we assessed the expression of eight candidate internal control genes, namely 18S ribosomal RNA (18S rRNA), elongation factor-1alpha, β-Actin, E2 ubiquitin-conjugating enzyme, β-Tubulin (TUB), ACTIN2, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and Msc27 of unknown function, in a diverse set of 16 alfalfa (Medicago sativa) samples representing different tissues and abiotic stress challenges, using geNorm and BestKeeper software. The results revealed that the eight candidate genes are inconsistently expressed under different experimental conditions. Msc27 and 18S rRNA are suitable reference genes for comparing different tissue types. Under different abscisic acid and NaCl conditions, three reference genes are necessary. Finally, GAPDH, TUB and β-Actin are unsuitable for normalization of qRT-PCR data under these given conditions in alfalfa. The relative expression level of MsWRKY33 was analyzed using selected reference genes. These results provide an experimental guideline for future research on gene expression in alfalfa using qRT-PCR.

Growth enhancing effect of exogenous glycine and characterization of its uptake in halotolerant cyanobacterium Aphanothece halophytica.

Alkaliphilic halotolerant cyanobacterium Aphanothece halophytica showed optimal growth in the medium containing 0.5 M NaCl. The increase of exogenously added glycine to the medium up to 10 mM significantly promoted cell growth under both normal (0.5 M NaCl) and salt stress (2.0 M NaCl) conditions. Salt stress imposed by either 2.0 or 3.0 M NaCl retarded cell growth; however, exogenously added glycine at 10 mM concentration to salt-stress medium resulted in the reduction of growth inhibition particularly under 3.0 M NaCl condition. The uptake of glycine by intact A. halophytica was shown to exhibit saturation kinetics with an apparent K s of 160 μM and V max of 3.9 nmol/min/mg protein. The optimal pH for glycine uptake was at pH 8.0. The uptake activity was decreased in the presence of high concentration of NaCl. Both metabolic inhibitors and ionophores decreased glycine uptake in A. halophytica suggesting an energy-dependent glycine uptake. Several neutral amino acids showed considerable inhibition of glycine uptake with higher than 50 % inhibition observed with serine, cysteine and alanine whereas acidic, basic and aromatic amino acids showed only slight inhibition of glycine uptake.

Structural and agonist properties of XCL2, the other member of the C-chemokine subfamily

Known for its unusual metamorphic native state structure, XCL1 has been the focus of most efforts to elucidate the structural, functional, and physiological properties of chemokines in the C subfamily. By comparison, its closely related paralog XCL2 remains virtually uncharacterized. Based on the importance of the chemokine N-terminus in receptor activation, it was hypothesized that two amino acid differences in XCL2 would alter its agonist activity relative to XCL1 for their shared receptor XCR1. This present study reveals several properties of XCL2 that were unexamined until now. Structurally, XCL1 and XCL2 are very similar, exchanging between the monomeric chemokine fold and an unrelated dimeric state under physiological NaCl and temperature conditions. Ca2+ flux, chemotaxis, and heparin binding assays showed that the monomer form of XCL2 is responsible for G protein-coupled receptor activation while the dimeric form is important for GAG binding. Despite their high structural similarity, XCL2 displays a slightly higher affinity for heparin than XCL1. Because their in vitro functional profiles are virtually identical, distinct physiological roles for XCL1 and XCL2 are probably encoded at the level of expression.

English

The present study was conducted to optimize the media composition through response surface methodology (RSM) for extracellular polysaccharide (EPS) production in Halobacillus trueperi AJSK strain isolated from the salt pan. Halobacillus trueperi was identified with morphological, biochemical characteristics as well as 16S rRNA gene sequencing method. Production medium was optimized through central composite design. In the present study, the maximum EPS production was achieved under the optimal culture conditions of peptone, glucose, NaCl and MgSO4 and they were 15.50, 22.24, 61.56 and 2.33 g/L, respectively at pH 9.0, 35°C in 72 h. An EPS production of 12.93 (g/L) which was well in agreement with the predicted value was achieved by this optimized procedure. Results of the present study proved that statistical media composition analysis with RSM enhanced the EPS production in Halobacillus trueperi.   Key words: Extracellular polysaccharide, Halobacillus trueperi, response surface methodology, salt pan bacteria. &nbsp

High temperature-short time glycation to improve heat stability of whey protein and reduce color formation

Glycation of whey protein isolate (WPI) improves functionalities such as heat stability. Conventionally, glycation is achieved by heating at <∼90 °C for hours up to several days, which favors the formation of Maillard reaction products such as 5-hydroxymethyl-2-furaldehyde (HMF) that is linked to undesirable color and flavor. In this work, we report for the first time that glycating WPI with lactose or maltodextrin at 130 °C for <30 min and 79% relative humidity simultaneously reduced the color formation and improved the heat stability. Maltodextrin was less reactive than lactose, as a longer (30 vs. 20 min) glycation at 130 °C was needed to obtain heat stability at all acidity (pH 3.0–7.0) and ionic (0–150 mM NaCl or CaCl2) conditions. However, WPI glycated with maltodextrin had a lighter color and a lower content of HMF. Our findings indicate high temperature-short time glycation favors the industrial production of high quality WPI ingredients.

Fermentative hydrogen production by a new alkaliphilic Clostridium sp. (strain PROH2) isolated from a shallow submarine hydrothermal chimney in Prony Bay, New Caledonia

The hydrogen-producing strain PROH2 pertaining to the genus Clostridium was successfully isolated from a shallow submarine hydrothermal chimney (Prony Bay, New Caledonia) driven by serpentinization processes. Cell biomass and hydrogen production performances during fermentation by strain PROH2 were studied in a series of batch experiments under various conditions of pH, temperature, NaCl and glucose concentrations. The highest hydrogen yield, 2.71 mol H2/mol glucose, was observed at initial pH 9.5, 37 °C, and glucose concentration 2 g/L, and was comparable to that reported for neutrophilic clostridial species. Hydrogen production by strain PROH2 reached the maximum production rate (0.55 mM-H2/h) at the late exponential phase. Yeast extract was required for growth of strain PROH2 and improved significantly its hydrogen production performances. The isolate could utilize various energy sources including cellobiose, galactose, glucose, maltose, sucrose and trehalose to produce hydrogen. The pattern of end-products of metabolism was also affected by the type of energy sources and culture conditions used. These results indicate that Clostridium sp. strain PROH2 is a good candidate for producing hydrogen under alkaline and mesothermic conditions.

Salicylic acid alleviates the adverse effects of salt stress in Torreya grandis cv. Merrillii seedlings by activating photosynthesis and enhancing antioxidant systems.

BackgroundSalt stress is a major factor limiting plant growth and productivity. Salicylic acid (SA) has been shown to ameliorate the adverse effects of environmental stress on plants. To investigate the protective role of SA in ameliorating salt stress on Torreya grandis (T. grandis) trees, a pot experiment was conducted to analyze the biomass, relative water content (RWC), chlorophyll content, net photosynthesis (Pn), gas exchange parameters, relative leakage conductivity (REC), malondialdehyde (MDA) content, and activities of superoxide dismutase (SOD) and peroxidase (POD) of T. grandis under 0.2% and 0.4% NaCl conditions with and without SA.Methodology/Principal FindingsThe exposure of T. grandis seedlings to salt conditions resulted in reduced growth rates, which were associated with decreases in RWC and Pn and increases in REC and MDA content. The foliar application of SA effectively increased the chlorophyll (chl (a+b)) content, RWC, net CO2 assimilation rates (Pn), and proline content, enhanced the activities of SOD, CAT and POD, and minimized the increases in the REC and MDA content. These changes increased the capacity of T. grandis in acclimating to salt stress and thus increased the shoot and root dry matter. However, when the plants were under 0% and 0.2% NaCl stress, the dry mass of the shoots and roots did not differ significantly between SA-treated plants and control plants.ConclusionsSA induced the salt tolerance and increased the biomass of T. grandis cv. by enhancing the chlorophyll content and activity of antioxidative enzymes, activating the photosynthetic process, and alleviating membrane injury. A better understanding about the effect of salt stress in T. grandis is vital, in order gain knowledge over expanding the plantations to various regions and also for the recovery of T. grandis species in the future.