一种细菌糖脂的化学结构和物化性能

从土壤中分离得到一支假单孢菌, 当它生长在正烷烃或植物油中时分离得到两个具有表面活性的体外糖脂, 用柱层析及制备薄层层析得以纯化, 样品经负离子化学电离质谱、快原子轰击质谱以及^1H和^1^3C核磁共振谱鉴定其结构为鼠李糖脂1和2; 它们都具有降低表面张力、水与十六烷之间的界面张力, 以及良好的乳化性、发泡性及增溶性.     

铜在乳状液膜体系中的迁移行为

近年来膜分离技术在环境治理方面得到广泛应用。本文研究了铜在span80-TBP（磷酸三丁酯）-煤油-NH3液膜分离体系中的迁移行为。用TBP作为载体,在溶液中迁移时,在外相与膜相界面上形成中性络合物后穿过膜相,在膜相与内相界面上络合物再与NH3反应,生成铜氨络离子,释放出来的TBP又返回膜相。     

Permeation of hydrocarbons through liquid surfactant membranes and formation of liquid crystalline structures

The separation of benzene from its mixture with heptane can be achieved by emulsifying the feed mixture to form an oil-in-water emulsion and then dispersing this emulsion in kerosene. At high agitation intensity a gel-like structure develops which prevents phase separation and thereby interferes with the overall mass transfer process. These gel-like structures have very high viscosities, and show rheopectic behaviour; polarising microscopic examination of these gel-like structures revealed the existence of liquid crystalline structures on the surface of the emulsion globules dispersed in kerosene. A possible mode of development of such liquid crystalline structures is presented, 1-Pentanol added to kerosene prevents gel formation and assists phase separation. Its action is explained on the basis of Winsor's theory of solubilization. Typical results for selectivity and benzene yield are presented.     

Synthesis and primary biological evaluation of 188ReN-NEMPTDD

The recovery of uranium(VI) from chloride solution using a liquid emulsion membrane (LEM) technique was studied. The emulsion is constituted by the quaternary salt of benzyloctadecyldimethyl ammonium chloride (BODMAC, R₄NCl) as a carrier, kerosene as organic diluent, Span 80 as emulsifying agent and 0.5 mol/l Na₂CO₃ as stripping phase. The important variables affecting the LEM permeation process such as the concentrations of extractant, internal strip phase, types of organic diluent, and the presence of magnesium chloride or magnesium sulfate were investigated. It was found that, at a given condition, the maximum extraction rate of uranium(VI) reached 80%. The emulsion was stable at low pH in the presence of certain amounts of electrolytes such as NaCl and MgCl₂.     

Total synthesis,isolation, surfactant properties,and biological evaluation of ananatosides and related macrodilactone-containing rhamnolipids

Rhamnolipids are a specific class of microbial surfactants, which hold great biotechnological and therapeutic potential. However, their exploitation at the industrial level is hampered because they are mainly produced by the opportunistic pathogen Pseudomonas aeruginosa. The non-human pathogenic bacterium Pantoea ananatis is an alternative producer of rhamnolipid-like metabolites containing glucose instead of rhamnose residues. Herein, we present the isolation, structural characterization, and total synthesis of ananatoside A, a 15-membered macrodilactone-containing glucolipid, and ananatoside B, its open-chain congener, from organic extracts of P. ananatis. Ananatoside A was synthesized through three alternative pathways involving either an intramolecular glycosylation, a chemical macrolactonization or a direct enzymatic transformation from ananatoside B. A series of diasteroisomerically pure (1→2), (1→3), and (1→4)-macrolactonized rhamnolipids were also synthesized through intramolecular glycosylation and their anomeric configurations as well as ring conformations were solved using molecular modeling in tandem with NMR studies. We show that ananatoside B is a more potent surfactant than its macrolide counterpart. We present evidence that macrolactonization of rhamnolipids enhances their cytotoxic and hemolytic potential, pointing towards a mechanism involving the formation of pores into the lipidic cell membrane. Lastly, we demonstrate that ananatoside A and ananatoside B as well as synthetic macrolactonized rhamnolipids can be perceived by the plant immune system, and that this sensing is more pronounced for a macrolide featuring a rhamnose moiety in its native ¹C₄ conformation. Altogether our results suggest that macrolactonization of glycolipids can dramatically interfere with their surfactant properties and biological activity.

We show that macrolactonization of gluco- and rhamnolipids dramatically interfere with their surfactant properties and biological activity.     

航空煤油替代燃料模型构建方法及HEF航空煤油替代燃料模型

本文在完善燃烧化学特性参数,发展更准确的混合物特性参数计算方法的基础上,提出一套完整的、精确的航煤替代燃料模型构建方法。并采用定容燃烧弹实验系统首次测量了初始温度420和460 K、压力0.1 MPa,实际HEF航煤以及代表性组分十氢萘的层流火焰传播速度,为本文发展和验证替代燃料模型提供充分的实验数据。依据该方法提出了摩尔分数为65%正十二烷、10%正十四烷、25%十氢萘三组分HEF航煤替代燃料模型。充分的的实验和计算结果验证表明,替代燃料模型与实际HEF航煤在物理特性和燃烧化学特性方面有很高的相似性。本文提出的HEF航煤替代燃料模型和实验测量的层流火焰传播速度,为后续化学反应机理的发展与验证奠定了基础。     

Analysis of Rhamnolipid Biosurfactants Produced Through Submerged Fermentation Using Orange Fruit Peelings as Sole Carbon Source

The fermentative production of rhamnolipid biosurfactant from Pseudomonas aeruginosa MTCC 2297 was carried out by submerged fermentation using various cost-effective waste materials such as orange peelings, carrot peel waste, lime peelings, coconut oil cake, and banana waste. The orange peel was found to be the best substrate generating 9.18 g/l of rhamnolipid biosurfactant with a surface tension reduction up to 31.3 mN/m. The production was growth independent, and optimum conditions were standardized. The emulsifying activity was highest against kerosene (73.3%). Rhamnolipid components were purified and separated by ethyl acetate extraction, preparative silica gel column chromatography, high-performance liquid chromatography and thin-layer chromatography. The major rhamnolipid components were characterized, by fast atom bombardment mass spectrometry, as a mixture of dirhamnolipids and monorhamnolipids.     

鼠李糖脂应用于微乳毛细管电动色谱快速测定化妆品中激素类物质

采用生物表面活性剂鼠李糖脂建立了无需助表面活性剂的微乳体系,并应用于微乳毛细管电动色谱快速分析化妆品中皮质类激素泼尼松、泼尼松龙和氢化可的松。考察了pH值、鼠李糖脂浓度、离子强度、油相种类和浓度、分离温度、分离电压及进样电压和时间的影响,得出微乳体系最佳组成为0.1%(w/w)鼠李糖脂+0.8%(w/w)正庚烷+99.1%(w/w)硼砂缓冲液(80 mmol/L,pH 9.2)。分离温度20℃,分离电压20kV,电动进样10 kV×3 s,泼尼松、氢化可的松和泼尼松龙在9.4 min内可基线分离。重复进样7次,迁移时间和峰面积的RSD分别小于0.2%和5.0%。3种分析物线性范围均为5～100 mg/L;检出限分别为1.0,1.1和1.3 mg/L(S/N=3)。仅需简单萃取即可用于化妆品样品测定,回收率为81.6%～108%;RSD均小于4.8%。     

Electron Microscopy of Rhamnolipid (Biosurfactant) Morphology: Effects of pH, Cadmium, and Octadecane

A rhamnolipid biosurfactant produced by Pseudomonas aeruginosa ATCC 9027 is reported to increase the aqueous dispersion and biodegradation of petroleum hydrocarbons and to complex heavy metals. These reports indicate the potential for application of rhamnolipids in remediation of contaminated sites. Effective use of rhamnolipids will require understanding of rhamnolipid morphology and the effects of pH and organic and inorganic contaminants on that morphology. We used cryo-transmission electron microscopy to investigate the morphology of vitrified, frozen hydrated suspensions of rhamnolipid over a pH range of 5.5 to 8.0, and to determine the effect of a model alkane, octadecane, and a model heavy metal, cadmium, on rhamnolipid morphology. Micrographs clearly showed that rhamnolipid morphology was a function of pH, changing from lamellar, to vesicular, to micellar as pH increased. The effect of cadmium and octadecane on rhamnolipid morphology was determined at pH 6.8 and 7.0, where maximum cadmium complexation and maximum octadecane dispersion occurs. Cadmium seemed to stabilize rhamnolipid vesicle structures as shown by an increase in vesicle number and a decrease in vesicle diameter. In contrast, octadecane favored the micellar structure as shown by the complete absence of vesicles.     

Rhamnolipid Production by <Emphasis Type="Italic">Pseudomonas Aeruginosa</Emphasis> GIM 32 Using Different Substrates Including Molasses Distillery Wastewater

A rhamnolipid production strain newly isolated from oil-contaminated soil was identified as Pseudomonas aeruginosa GIM32 by its morphology and 16S rDNA sequence analysis. The effect of carbon source and carbon to nitrogen (C/N) ratio on rhamnolipids production was investigated. Palm oil was favorable as a carbon source for rhamnolipid production. The maximum biomass and rhamnolipid concentration were 8.24 g/L and 30.4 g/L, respectively, with an optimization medium containing 50 g/L palm oil and 5 g/L sodium nitrate. Molasses distillery wastewater as an unconventional substrate for rhamnolipid production was investigated. It was found that 2.6 g/L of rhamnolipids was produced; this amount was higher than that of past reports using wastewater as a substrate. In addition, 44% of the chemical oxygen demand of wastewater was removed at the same time under the optimization condition. Eleven kinds of different molecular weight rhamnolipid homologues were identified in the rhamnolipids obtained from molasses distillery wastewater by P. aeruginosa GIM32 by LC–MS analysis.     

Encapsulation and characterization of flurbiprofen loaded poly(є-caprolactone)–poly(vinylpyrrolidone) blend micropheres by solvent evaporation method

Flurbiprofen loaded PCL/PVP blend microspheres were prepared by o/w solvent evaporation method using various concentrations of gelatin as emulsifying agent. Microsphere recovery decreased with a decrease in the concentration of the emulsifier in the dispersion. Encapsulation efficiency and drug loading of microspheres increased with decrease in concentration of emulsifying agent. Hydration rate, encapsulation efficiency and drug loading of microspheres increased with increase in concentration of PVP. Rheological properties showed free flowing nature of microspheres. SEM (Scanning electron microscope) revealed microspheres were discrete, spherical and became porous with decrease in concentration of emulsifying agent but smooth with higher concentration of emulsifying agent. FTIR (Fourier transform infrared spectroscopy) spectra of pure and encapsulated flurbiprofen in all formulation showed no significant difference in characteristic peaks, suggesting stability of flurbiprofen during encapsulation process. X-RD (X-ray powder diffractometry) of pure flurbiprofen shows sharp peaks, which decreases on encapsulation, indicating dispersion at molecular level and hence decrease in the crystallinity of drug in microspheres. Microspheres showed an enteric nature at pH 1.2 and a sustained release pattern at pH 6.8. Rapid drug release was observed in microspheres with higher concentration of PVP (polyvinylpyrrolidone), PVP acts as channeling agent. Formulation with low concentration of emulsifying agent also showed a fast release due to porous structure. Drug release kinetics followed zero order at pH 1.2 while at pH 6.8 Higuchi model was best fitted and was found non fickian.     

Comparison of stages in oil agglomeration process of quartz with sodium oleate in the presence of Ca(II) and Mg(II) ions

The oil agglomeration of quartz with sodium oleate in the presence of calcium and magnesium ions comprises three consecutive stages: adsorption of cations onto quartz surfaces, which leads to coagulation of the suspension, shear flocculation with sodium oleate and finally, agglomeration of flocs by kerosene. The effects of pH and cation concentration on these stages were investigated and the results were presented comparatively. It was found that all the stages of oil agglomeration of quartz exhibited sharp dependences on pH and cation concentration. That is, these stages generally took place in the pH and concentration ranges in which hydroxy complexes of the cations existed in the suspension. In the case of magnesium ion, the coagulation, shear flocculation and especially oil agglomeration of quartz improved after precipitation of hydroxide. These species of calcium and magnesium ions formed at high pH were adsorbed on the negatively charged surface of quartz, as a result of which the adsorption of sodium oleate became possible and thus the shear flocculation of the particles was achieved. Thereafter, the hydrophobic quartz flocs could be agglomerated by kerosene as bridging liquid. The increase in the shear flocculation efficiency depending on the increase of surface hydrophobicity enhanced the oil agglomeration of quartz with kerosene. The maximum recoveries for all the stages of the quartz were obtained in the presence of 10(-3) M magnesium and 5x10(-3) M calcium ions at pH 11. However, some differences in the behavior of shear flocculation and oil agglomeration of quartz suspension were observed above 10(-3) M concentration of magnesium ion.     

α‐Chymotrypsin–catalyzed direct C (Sp3)–H functionalization reactions for synthesis of azaarene derivatives in water

α‐Chymotrypsin from the bovine pancreas has been shown for the first time to display catalytic nonnatural catalytic ability toward the C (sp³)–H functionalization reaction of 2‐methylquinoline and aromatic aldehydes in water. α‐Chymotrypsin exhibited favorable catalytic activity with good adaptability to different substrates. The activity of the enzyme could be improved by adjusting the solvent, temperature, molar ratio of substrates, and protein loading. The products were obtained in moderate to excellent yields (51%‐93%) in 24 samples. This process afforded a potential biocatalytic approach as an alternative to chemical synthesis for azaarene derivatives.     

Synthesis and electrochemical characterization of sol–gel-derived RuO2/carbon nanotube composites

Ruthenium oxide was coated on multiwalled carbon nanotubes (MWCNTs) to obtain nanocomposite electrode which has a good response to the pH. To synthesize this electrode, gold and cobalt were coated on a stainless steel 304 substrates, respectively, and then, vertically aligned carbon nanotubes were grown on the prepared substrates by chemical vapor deposition. Gold reduced activity of the stainless steel, while cobalt served as a catalyst for growth of the carbon nanotube. Ruthenium oxide was then coated on MWCNTs via sol–gel method. At last, different techniques were used to characterize the properties of synthesized electrode including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction, and cyclic voltammetry. SEM results showed that the length of the carbon nanotubes varied with reaction time, and in this research, it was maintained around 9 μm with a diameter about 100 nm. Electrochemical analysis revealed that optimum sol concentration and heat treatment temperature to meet the best pH sensing response were 0.1 M RuCl₃ sol and 200 °C, respectively. Moreover, the obtained electrode represented a linear and near-Nernstian response (about ?63 mV/pH) throughout the whole pH range (2–12) of Britton–Robinson buffer solutions.     

Effect of electrolytes on the surface behavior of rhamnolipids R1 and R2

The surface behavior of solutions of the rhamnolipids, R1 and R2, were investigated in the absence and presence of an electrolyte (NaCl) through surface tension measurements and optical microscopy at pH 6.8. The NaCl concentrations studied are 0.05, 0.5 and 1 M. Electrolytes directly affect the carboxylate groups of the rhamnolipids. The solution/air interface has a net negative charge due to the dissociated carboxylate ions at pH 6.8 with strong repulsive electrostatic forces between the rhamnolipid molecules. This negative charge is shielded by the Na⁺ ions in the electrical double layer in the presence of NaCl, causing the formation of a close-packed monolayer, and a decrease in CMC, and surface tension values. The maximum compaction is observed at 0.5 M NaCl concentrations for R1 and R2 monolayers, with the R1 monolayer more compact than R2. The larger spaces left below the hydrophobic tails of R1 with respect to that of R2, due to the missing second rhamnosyl groups are thought to be responsible for the higher compaction. The rigidity of both R1 and R2 monolayers increases with the electrolyte concentration. The rigidity of the R1 monolayer is greater than that of R2 at all NaCl concentrations due to the lower hydrophilic character of R1. The variation of CMC values as a function of NaCl concentration obtained from the surface tension measurements and critical packing parameter (CPP) calculations show that spherical micelles, bilayer and rod like micelles are formed in the rhamnolipid solutions as a function of the NaCl concentration. The results of optical microscopy supported these aggregation states indicating lamellar nematic liquid crystal, cubic lamellar and hexagonal liquid crystal phases in R1 and R2 solutions depending on the NaCl concentration.     

Interfacial and emulsifying properties of designed β-strand peptides

The structural and surfactant properties of a series of amphipathic β-strand peptides have been studied as a function of pH. Each nine-residue peptide has a framework of hydrophobic proline and phenylalanine amino acid residues, alternating with acidic or basic amino acids to give a sequence closely related to known β-sheet formers. Surface activity, interfacial mechanical properties, electronic circular dichroism (ECD), droplet sizing and zeta potential measurements were used to gain an overview of the peptide behavior as the molecular charge varied from ±4 to 0 with pH. ECD data suggest that the peptides form polyproline-type helices in bulk aqueous solution when highly charged, but may fold to β-hairpins rather than β-sheets when uncharged. In the uncharged state, the peptides adsorb readily at a macroscopic fluid interface to form mechanically strong interfacial films, but tend to give large droplet sizes on emulsification, apparently due to flocculation at a low droplet zeta potential. In contrast, highly charged peptide states gave a low interfacial coverage, but retained good emulsifying activity as judged by droplet size. Best emulsification was generally seen for intermediate charged states of the peptides, possibly representing a compromise between droplet zeta potential and interfacial binding affinity. The emulsifying properties of β-strand peptides have not been previously reported. Understanding the interfacial properties of such peptides is important to their potential development as biosurfactants.     

Studies on Productivity and Characterization of Polygalacturonase from <Emphasis Type="Italic">Aspergillus giganteus</Emphasis> Submerged Culture Using Citrus Pectin and Orange Waste

Polygalacturonases are part of the group of enzymes involved in pectin degradation. The aim of this work was to investigate some of the factors affecting polygalacturonase production by an Aspergillus giganteus strain and to characterize this pectinolytic activity. Several carbon sources, both pure substances and natural substrates, were tested in standing cultures, and the best results were obtained with orange bagasse and purified citrus pectin. On citrus pectin as sole carbon source, the highest extracellular activity (9.5 U/ml and 40.6 U/mg protein) was obtained in 4.5-day-old cultures shaken at 120 rpm, pH 3.5 and 30°C, while on orange bagasse, the highest extracellular activity (48.5 U/ml and 78.3 U/mg protein) was obtained in 3.5-day-old cultures shaken at 120 rpm, pH 6.0 and 30°C. Optimal polygalacturonase activity was observed in assays conducted at pH 5.5–6.5 and 55–60°C. The activity showed good thermal stability, with half-lives of 90 and 30 min when incubated at 55 and 60°C, respectively. High stability was observed from pH 4.5 to 8.5; more than 90% of the activity remained after 24 h in this pH range.     

Cr(VI) ion removal from artificial waste water using supported liquid membrane

In this study, a novel flat-type synergic-supported liquid membrane was evaluated with a mixture of N-methyl-N,N,N-trioctylammonium chloride (Aliquat 336) and tributyl phosphate (TBP) as the carrier and kerosene as the diluent to remove Cr(VI) from synthetic waste water. The main parameters involved in the process were identified and optimised. The parameters were divided into two groups, those that were independent and those having an interaction. The parameters of the carrier/kerosene volumetric proportion and stirring rate were optimised individually due to their nature. The optimal values of these parameters were 0.5 and 500 min^?1, respectively, for a constant carrier/kerosene ratio and stirring rate in the designed experiments using the response surface method (RSM). The four parameters of TBP/Aliquat 336, chromium concentration in the feed phase, feed and product pH were optimised using RSM; it was observed that the TBP/Aliquat 336 ratio, feed pH, pH of the stripping phase and interaction of this parameter with feed concentration have the most important effects on the removal of Cr(VI). The optimal levels of these parameters were 0.61, 71.75 mg L^?1, 3.5 and 12.66 for the ratio of TBP/Aliquat 336, feed chromium concentration, pH of the feed and pH of the product, respectively. An experimental removal rate of 94.63 % at the optimized levels was obtained.     

Acetone powder from dormant seeds of Ricinus communis L

The influence of several factors on the hydrolytic activity of lipase, present in the acetone powder from dormant castor seeds (Ricinus communis) was evaluated. The enzyme showed a marked specificity for short-chain substrates. The best reaction conditions were an acid medium, Triton X-100 as the emulsifying agent and a temperature of 30 degrees C. The lipase activity of the acetone powder of different castor oil genotypes showed great variability and storage stability of up to 90%. The toxicology analysis of the acetone powder from genotype Nordestina BRS 149 showed a higher ricin (toxic component) content, a lower 2S albumin (allergenic compound) content, and similar allergenic potential compared with untreated seeds.     

Optimization of beta-carotene production from synthetic medium by Blakeslea trispora: a mathematical modeling

The effect of inoculum, pH, carbon and nitrogen source, natural oils, fatty acids, antioxidant, and precursors on beta-carotene production by Blakeslea trispora in shake-flask culture was investigated. The highest concentration of beta-carotene was obtained in the medium (pH 7.0) inoculated with one loop of each culture. Sucrose, glycerol, cornmeal, soy protein acid hydrolysate, and distiller's solubles did not improve the production of beta-carotene. By contrast, glucose, corn steep liquor, antioxidant, olive oil, soybean oil, cottonseed oil, oleic and linoleic acids, and kerosene significantly increased the beta-carotene production. A central composite design was employed to determine the maximum beta-carotene production at optimum values for the process variables (linoleic acid, kerosene, and antioxidant). The fit of the model was found to be good. Linoleic acid, kerosene, and antioxidant had a strong linear effect on beta-carotene production. The concentration of beta-carotene was significantly affected by linoleic acid-kerosene and linoleic acid-antioxidant interactions as well as by the negative quadratic effects of these variables. The interaction between kerosene and antioxidant had no significant linear effect. The maximum beta-carotene concentration (2.88 g/L) was obtained at concentrations of 17.15 g/L of linoleic acid, 39.25 g/L of kerosene, and 9.04 g/L of antioxidant.