The distribution of brominated long-chain fatty acids in sponge and symbiont cell types from the tropical marine spongeAmphimedon terpenensis

The tropical marine spongeAmphimedon terpenensis (family Niphatidae, order Haplosclerida) has previously been shown to possess unusual lipids, including unusual fatty acids. The biosynthetic origin of these fatty acids is of interest as the sponge supports a significant population of eubacterial and cyanobacterial symbionts. The total fatty acid composition of the sponge was analyzed by gas chromatography/mass spectrometry of the methyl esters. Among the most abundant of the fatty acids in intact tissue were 16∶0, 18∶0 and 3,7,11,15-tetramethylhexadecanoic (phytanic) acid. In addition, three brominated fatty acids, (5E,9Z)-6-bromo-5,9-tetracosadienoic acid (24∶2Br), (5E,9Z)-6-bromo-5,9-pentacosadienoic acid (25∶2Br) and (5E,9Z)-6-bromo-5,9-hexacosadienoic acid (26∶2Br) were also present. The three brominated fatty acids, together with phytanic acid, were isolated from both ectosomoal (superficial) and choanosomal (internal) regions of the sponge. Analysis of extracts prepared from sponge/symbiont cells, partitioned by density gradient centrifugation on Ficoll, indicated that phytanic acid and the three brominated fatty acids were associated with sponge cells only. Further, a fatty acid methyl ester sample from intact tissue ofA. terpenensis was partitioned according to phospholipid class, and the brominated fatty acids were shown to be associated with the phosphatidylserine and phosphatidylethanolamine fractions that are commonly present in marine sponge lipids. The phosphatidylcholine and phosphatidylglycerol fractions were rich in the relatively shorter chain fatty acids (16∶0 and 18∶0). The association of brominated long-chain fatty acids (LCFA) with sponge cells has been confirmed. The findings allow comment on the use of fatty acid profiles in chemotaxonomy and permit further interpretation of LCFA biosynthetic pathways in sponges. The assignment of the sponge studied, which is currently placed asA. terpenensis, is being supported to some extent, but the species is unusual in having C₂₅ fatty acids as the major constituent in this group. Other factors, such as season or microenvironmental conditions, may influence observed fatty acid composition which tends to reduce the usefulness of fatty acid profiles as markers in sponge chemotaxonomy.     

Simulation of binary gas separation with asymmetric hollow fibre membranes and case studies of air separation

A mathematical model for high‐flux asymmetric hollow fibre membrane was developed considering the effect of permeate pressure build‐up inside the fibre bore. A new solution technique was developed to solve the model equations, which constitute a boundary value problem. The ordinary differential equations were solved as an initial value problem in two successive steps using the Gear's BDF method. The technique is advantageous since it requires minimum computational time and effort with improved solution stability, and the computational complexity does not multiply as the number of components increases. The model predictions and the robustness of the numerical technique were validated with experimental data for several membrane systems with different flow configurations. The model and the solution technique were applied to evaluate the separation characteristics of air using representative membranes with different configurations, including single‐stage, single‐stage with permeate recycle, single‐stage with retentate recycle, air blending, and two stages in series. The study demonstrates that the new solution technique can conveniently handle the high‐flux hollow fibre membrane problems with different module configurations. © 2011 Canadian Society for Chemical Engineering     

Callyspongynes A and B: New polyacetylenic lipids from a southern australian marine sponge, Callyspongia sp

A Callyspongia sp. collected by SCUBA off Barwon Heads, Australia, has afforded two new polyacetylenic lipids, callyspongynes A and B, the structures of which were assigned by spectroscopic analysis and chemical derivatization.     

Production and stability studies of the biosurfactant isolated from marine Nocardiopsis sp. B4

A potential biosurfactant producing strain, marine Nocardiopsis B4 was isolated from the West coast of India. Culture conditions involving variations in carbon and nitrogen sources were examined at constant pH, temperature and revolutions per min (rpm), with the aim of increasing productivity in the process. The biosurfactant production was followed by measuring the surface tension, emulsification assay and emulsifying index E24. Enhanced biosurfactant production was carried out using olive oil as the carbon source and phenyl alanine as the nitrogen source. The maximum production of the biosurfactant by Nocardiopsis occurred at a C/N ratio of 2:1 and the optimized bioprocess condition was pH 7.0, temperature 30° C and salt concentration 3%. The production of the biosurfactant was growth dependent. The surface tension was reduced up to 29 mN/m as well as the emulsification index E24 was 80% in 6 to 9 days. Properties of the biosurfactant that was separated by acid precipitation were investigated. The biosurfactant activity was stable at high temperature, a wide range of pH and salt concentrations thus, indicating its application in bioremediation, food, pharmaceutical and cosmetics industries.     

Cell membrane localization of sterols with conventional and unusual side chains in two marine demonsponges

Subcellular fractionation by differential centrifugation was performed on two previously unstudied marine sponges that predominantly contain either conventional (Reniera sp.) or unconventional (Pseudaxinyssa sp.) sterols. Direct evidence for the presence of unconventional sterols with C₂₄ alkylated side chains in the cellular membranes ofPseudaxinyssa sp. is provided, but the presence of unconventional sterols in sponge membranes is shown not to be a universal feature of the Porifera. Possible structural and functional roles of unconventional lipid molecules in sponge cell membranes are discussed. Part 5 of “Sterols in Marine Invertebrates”. Fort Part 58 in this series, see Cho, J.-H., and Djerassi, C. (1987)J. Org. Chem. 52, 4517–4521.     

Computational simulation of gas separation using nonporous polymeric membranes: Experimental and theoretical studies

In this study, preparation and simulation of polydimethylsiloxane (PDMS) membranes for gas separation is carried out. The membranes are synthesized by solution‐casting method via silicon oil as precursor. Gas permeation experiments for single gases of CH₄ and N₂ were conducted at different feed pressures (2–10 bars). PDMS membrane as a rubbery polymer showed that are more permeable toward more condensable gases, i.e., CH₄ compared to N₂. It was indicated that increasing feed pressure enhances permeability of CH₄ through the membrane slightly, but the permeability of nitrogen was almost constant over enhancement of feed pressure. Moreover, a mathematical model was developed to predict the permeation of gases across PDMS membrane. The model is based on solving conservation equations for gases in the membrane phase. Finite element analysis was utilized for numerical simulation of the governing equations. The simulation results were used to predict the concentration of gases inside the membrane. POLYM. ENG. SCI., 55:54–59, 2015. © 2014 Society of Plastics Engineers     

The distribution of lipids and sterols in cell types from the marine spongePseudaxinyssa sp

The sponge Pseudaxinyssa sp., unique in sterol and fatty acid composition, was cellularly dissected into fractions enriched in each of the major cell types present in the sponge: microbial symbionts (cyanobacteria), small sponge cells (pinacocytes and choanocytes), and large sponge cells (archeocytes and cyanophytes). Three phototrophic microbial symbionts were also isolated from the cell fractions and grown in culture. An unsymmetrical distribution of fatty acids and sterols was observed for the sponge cells: small cells contained larger quantities of long chain fatty acids (greater than C24) and smaller quantities of sterols than were present in the larger sponge cells. Moreover, the rare sterols 24-isopropylcholesterol predominated in the smaller sponge cells, whereas its 22-dehydro analog predominated in the larger sponge cells. Long chain fatty acids and sterols were not detected in the cultured microbial symbionts. This constitutes the first report of lipid variability according to cell type for this most primitive group of Metazoa.     

游离细胞膜生物反应器法与固定化细胞法在丙烯酰胺微生物转化中的比较

研究和介绍了一种新的分离方法———游离细胞法 ,并用膜生物反应器分离细胞和产品 ,使其在丙烯酰胺微生物转化中得到了成功的应用。比较了它和固定细胞法的生产工艺、生产效率、产品质量以及生产成本等因素。研究表明 ,在丙烯酰胺微生物转化中 ,游离细胞法优于固定化细胞法。     

Microporous polypropylene and polyethylene hollow fiber membranes. Part 3. Experimental studies on membrane distillation for desalination

Three polypropylene (PP) and one polyethylene (PE) microporous hollow-fiber membranes were used in direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD) for the desalination of simulated seawater. The influence of feed temperature and feed flow on distillate pure water flux was investigated. The comparison of the PP and PE membranes in DCMD and VMD was carried out. It was found that the water flux increased with the feed temperature and feed flow in both DCMD and VMD. The data also showed that, compared with the PP membranes, higher water flux could be obtained by using PE membranes in both the DCMD and VMD processes.     

Polyunsaturation in cell membranes and lipid bilayers and its effects on membrane proteins

The effect of variation of the degree ofcis-unsaturation on cell membrane protein functioning was investigated using a model lipid bilayer system and protein kinase C (PKC). This protein is a key element of signal transduction. Furthermore it is representative of a class of extrinsic membrane proteins that show lipid dependent interactions with cell membranes. To test for dependence of activity on the phospholipid unsaturation, experiments were devised using a vesicle assay system consisting of phosphatidylcholine (PC) and phosphatidylserine (PS) in which the unsaturation was systematically varied. Highly purified PKCα and ε were obtained using the baculovirus-insect cell expression system. It was shown that increased PC unsaturation elevated the activity of PKCα. By contrast, increasing the unsaturation of PSdecreased the activity of PKCα, and to a lesser extent PKCε. This result immediately rules out any single lipid bilayer physical parameter, such as lipid order, underlying the effect. It is proposed that while PC unsaturation effects are explainable on the basis of a contribution to membrane surface curvature stress, the effects of PS unsaturation may be due to specific protein-lipid interactions. Overall, the results indicate that altered phospholipid unsaturation in cell membranes that occurs in certain disease states such as chronic alcoholism, or by dietary manipulations, are likely to have profound effects on signal transduction pathways involving PKC and similar proteins.     

Studies with thin membranes. II. Measurement of membrane potentials and evaluation of membrane fixed charge density

Membranes prepared from 5% Parlodion solution have been characterized. These and other membranes prepared from 0.38, 0.5, 1.0, 2.0, and 3.0% Parlodion solutions and already characterized, have been used severally to estimate the number of anionic sites present in them by two different methods. The potentiometric method, which is indirect, gave values of X?_P which were higher than X?_T, the values obtained by a direct isotopic method. The order was reversed for well-characterized ion-exchange membranes. These discrepancies were attributed to the shortcomings of the Teorell, Meyer, and Sievers theory of membrane potentials from which the potentiometric method was derived.     

A new hybrid membrane separation process for enhanced ethanol recovery: Process description and numerical studies

Ethanol is a biofuel, produced through the fermentation of sugars derived from biomass. Its usefulness as a fuel is limited by the energy intensive nature of the ethanol separation process. The ethanol recovery process is inefficient due to the dilute nature of the fermentation product and the presence of the ethanol?water azeotrope. This investigation presents a new hybrid separation process for energy efficient ethanol recovery. The new process is a hybrid of distillation and pervaporation. However, as opposed to most other hybrid processes, the distillation and pervaporation processes are combined into single unit. An overview of the proposed system was provided and differences to the conventional separation process were highlighted. A mathematical model was derived to explain the transport phenomena occurring in the hybrid process. The model was then used to compare the process to distillation. It was shown that the hybrid process is capable of breaking the ethanol-water azeotrope. It was also demonstrated that the pervaporation process, which is associated with both material and energy transfer, induces partial condensation of the vapor and thereby affects the efficiency of vapor?liquid contacting. Simulations were presented to show the impact of reflux ratio and pervaporation flux on the performance of the process.     

Accumulation of an alkyl lysophospholipid in tumor cell membranes affects membrane fluidity and tumor cell invasion

Tumor cells grown in the presence of 1-O-alkyl-2-O-methylglycero-3-phosphocholine (AMG-PC) accumulated this ether lipid in their membranes. Depending on the cell type and the dose of the compound, up to 17% of the total phospholipids of the purified plasma membranes consisted of authentic AMG-PC. Extensive incorporation of the agent resulted in a decrease in plasma membrane fluidity and inhibition of tumor cell invasiveness in embryonic chick heart fragments. The extent of AMG-PC incorporation and fluidity change was not strictly correlated with the degree to which tumor cell invasion was inhibited.     

Pervaporation separation of pentane-alcohol mixtures through ionically crosslinked blended membranes. I. Thermal measurements,electron microscopy and tensile studies

Ionically crosslinked blended membranes were prepared from blends of nylon 6 and poly(acrylic acid) (PAA) with the proportion of PAA ranging from 25 to 45 wt.-%. The technique consists of casting a film of the blend, followed by drying and immersion in an aluminum salt crosslinking solution for a predetermined time. The glass transition temperature (T_g) of the membranes was determined by differential scanning calorimetry (DSC). All the samples exhibited a single T_g, which is higher than that of either polymer. There is also a shift in the T_g with increasing scanning time. This phenomenon is attributed to the elimination of water molecules and the formation of anhydrides in the non-crosslinked PAA portion of the membrane. The membrane morphology was studied using scanning electron microscopy (SEM) and shows a dense structure without any pores. No phase separation is observed by scanning cross-sections of the samples, indicating that nylon 6 and PAA are completely miscible in the ranges studied. The membrane material strength lies in the range of 5 to 26 MPa and varies with the amount of PAA in the membrane. Samples with higher PAA content show lower tensile strength in spite of increased crosslinking density. This is due to the inherent low strength of PAA, coupled with increasing swelling of the membrane with increasing PAA content. The latter is confirmed by the measurement of water uptake into a dry membrane which increases from 23.6% to 76.3% with the membrane PAA content increasing from 25 to 45 wt.%.     

Polymer membranes for high temperature proton exchange membrane fuel cell: Recent advances and challenges

Proton-exchange membrane fuel cells (PEMFCs) are considered to be a promising technology for efficient power generation in the 21st century. Currently, high temperature proton exchange membrane fuel cells (HT-PEMFC) offer several advantages, such as high proton conductivity, low permeability to fuel, low electro-osmotic drag coefficient, good chemical/thermal stability, good mechanical properties and low cost. Owing to the aforementioned features, high temperature proton exchange membrane fuel cells have been utilized more widely compared to low temperature proton exchange membrane fuel cells, which contain certain limitations, such as carbon monoxide poisoning, heat management, water leaching, etc. This review examines the inspiration for HT-PEMFC development, the technological constraints, and recent advances. Various classes of polymers, such as sulfonated hydrocarbon polymers, acid-base polymers and blend polymers, have been analyzed to fulfill the key requirements of high temperature operation of proton exchange membrane fuel cells (PEMFC). The effect of inorganic additives on the performance of HT-PEMFC has been scrutinized. A detailed discussion of the synthesis of polymer, membrane fabrication and physicochemical characterizations is provided. The proton conductivity and cell performance of the polymeric membranes can be improved by high temperature treatment. The mechanical and water retention properties have shown significant improvement., However, there is scope for further research from the perspective of achieving improvements in certain areas, such as optimizing the thermal and chemical stability of the polymer, acid management, and the integral interface between the electrode and membrane.     

Studies on syntheses and permeabilities of special polymer membranes. X. Effects of conditions of membrane preparation on permeation characteristics of cellulose acetate membranes in separation of aqueous polymer solutions

The effects of casting solvents, dissolution temperature of casting solution, and pH and temperature of gelation solution, etc. on the permeation characteristics of cellulose acetate membranes in the separation of polymers from their aqueous solutions were investigated, using aqueous solutions of poly(ethylene glycol) and poly(vinyl alcohol) as feed. The permeation characteristics were influenced significantly by the conditions of membrane preparation and of the permeation. It was found that a concentration polarization at the membrane surface occurred with poly(vinyl alcohol) molecules, but it was very small with poly(ethylene glycol). The above results were discussed in detail from points of view of structure of the resulting membranes and the interactions between the solvent, the solute in the feed and the cellulose acetate molecules.     

Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. I. The effects of salts on the permselectivity of cellulose membrane in pervaporation

In the separation of water/alcohol mixtures through cellulose membranes, the addition of trace amounts of specific salts to the feed mixture (10^?5?5 × 10^?3 mol/kg) caused the marked increase of the separation factor and only the salts composed of a multivalent metal ion and a multivalent counteranion were effective for the increase of the selectivity. For example, when 1.5 × 10^?3 mol/kg CoSO₄ was added to water/ethanol mixture (35/65 wt/wt), the separation factor was 194 and the permeation rate was 5.14 kg/m² h. But, in the absence of the salt, the separation factor was only 6.7 and the permeation rate was 5.63 kg/m² h. We presumed that the increase of the selectivity by the addition of specific salts would be attributed to the contraction of the “holes” produced by the thermal motion of polymer chains and this contraction would be correlated with the conformation change of cellulose molecule.     

Polyurethane and sulfonated polysulfone blend ultrafiltration membranes: II. Application studies

Ultrafiltration membranes are largely being applied for macromolecular and heavy metal ion separations from aqueous streams. Polyurethane‐ and sulfonated‐ polysulfone‐based membranes prepared in the absence and presence of the polymeric additive, poly(ethylene glycol) 600, in various compositions, were subjected to the rejection of macromolecular proteins, such as bovine serum albumin, egg albumin, pepsin and trypsin. Toxic heavy metal ions such as Cu²⁺, Ni²⁺, Cd²⁺ and Zn²⁺ were subjected to rejection by the blend membranes by complexing them with a polymeric ligand, polyethyleneimine. The effects of polymer blend compositions and additive concentrations on the rejection and permeate flux of both proteins and metal ions are discussed. The rejection and permeate flux efficiencies of the blend membranes are compared with pure sulfonated polysulfone membranes. © 2003 Society of Chemical Industry