Production and Characteristics of an Enantioselective Lipase from Burkholderia sp. GXU56

The lipase production of Burkholderia sp. GXU56 was influenced by carbon and nitrogen sources, inorganic salts, initial pH of the medium and cultivation temperature. The maximum lipase production was 580.52 U/mL and reached 5 times the level of the basic medium in the optimum medium at pH 8.0, 32 °C, 200 rpm and 40–48 h. The lipase was purified 53.6 fold to homogeneity and the molecular weight was 35 KDa on SDS‐PAGE. The optimum pH and temperature of the lipase were 8.0 and 40 °C, respectively, and it was stable in the range of pH 7–8.5 and at temperatures below 45 °C. The lipase activity was strongly inhibited by Zn²⁺, Cu²⁺, Co²⁺, Fe²⁺, Fe³⁺ ions and SDS, while it was stimulated by Li⁺ and Ca²⁺ ions and in presence of 0.1 % CTAB, 0.1 % Triton X‐100 and 10 % DMSO. K_m and V_max of the lipase were calculated to be 0.038 mmol/L, and 0.029 mmol/L min^–1, respectively, with PNPB as the substrate. The GXU56 lipase showed enantioselective hydrolysis of (R,S)‐methyl mandelate to (R)‐mandelic acid, which is an important intermediate in the pharmaceutical industry.     

Some Biochemical Properties of Lipase from Bay Laurel (<Emphasis Type="Italic">Laurus nobilis</Emphasis> L.) Seeds

Lipase was isolated from bay laurel (Laurus nobilis L.) seeds, some biochemical properties were determined. The bay laurel oil was used as the substrate in all experiments. The pH optimum was found to be 8.0 in the presence of this substrate. The temperature optimum was 50 °C. The specific activity of the lipase was found to be 296 U mg protein⁻¹ in optimal conditions. The enzyme activity is quite stable in the range of pH 7.0–10. The enzyme was stable for 1 h at its optimum temperature, and retained about 68% of activity at 60 °C during this time. K _m and V _max values were determined as 0.975 g and 1.298 U mg protein⁻¹, respectively. Also, storage stability and metal effect on lipolytic activity were investigated. Enzyme activity was maintained for 9, 12, and 42 days at room temperature, 4 and −20 °C, respectively. Ca²⁺, Co²⁺, Cu²⁺, Fe²⁺, and Mg²⁺ lightly enhanced bay laurel lipase activity.     

Isolation and enzymatic characterization of the first reported hyaluronidase from Yak (Bos grunniens) testis

A novel hyaluronidase (BgHya1) from Yak Bos grunniens testis was isolated and shown to have comparatively high activity on sodium hyaluronate. However, surveys on BgHya1 are still limited. The enzyme was purified through gel filtration on Sephacryl S-100 and cation-exchange on SP Sepharose fast flow; the purity was confirmed by a reverse phase FPLC Shodex C₄ column. The specific activity of the purified BgHya1 was 20.4 U/mg assayed by the colorimetric method against 0.85 U/mg for the crude enzyme, representing a 24-fold purification. It was a monomeric protein of 55 kDa estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Sephacryl S-200. It exhibited maximum activity in the presence of 0.15 M NaCl at 37 °C, pH 3.8, and a specificity to sodium hyaluronate higher than that of chondroitin-4-sulfate, chondroitin-6-sulfate, and dermatan. The K _m value for BgHya1, using sodium hyaluronate as substrate, was 0.106 mg/mL. Activity of BgHya1 was inhibited mildly by Ca²⁺ and Fe²⁺, and significantly by Fe³⁺, Mg²⁺, EDTA, urea, heparin, and 0.5 M NaCl. It was not affected by Cu²⁺, Zn²⁺, Co²⁺, ascorbic acid, PMSF, DTT, glutathione (reduced), or L-cysteine. BgHya1 was shown to be heat unstable in the range of 4–45 °C. In terms of storage stability, 92% of the activity was retained after four weeks at 4 °C, and 58% at room temperature. In addition, adding BSA (1.0 mg/mL) to the enzyme sample prior to freezing resulted in complete retention of enzyme activity. This work yielded a high purity hyaluronidase, the first one isolated from Bos grunniens by-product.     

Biocatalytic Properties of Lipase from Walnut Seed (<Emphasis Type="Italic">Juglans regia</Emphasis> L.)

Lipase (E.C. 3.1.1.3) from walnut seed was purified 28.6-fold with 31% yield using Sephadex G-100 gel chromatography. Olive oil served as good substrate for the enzyme. The optimum pH and temperature were 9.0 and 70 °C, respectively. The lipase was stable between 30 and 80 °C for 5 min. K _m and V _max values were determined as 48 mM and 23.06 × 10⁻³ U/min mg for triolein as substrate. Lipase activity was slightly reduced by Cu²⁺, Ca²⁺, Hg²⁺, Mn²⁺, and Ni²⁺ ions, while Mg²⁺ and Zn²⁺ had no effects. Anionic surfactant sodium dodecyl sulfate stimulated lipase activity while non-ionic surfactants Tween-80 and Triton X-100 had negligible effects on enzymatic activity. The enzyme activity was not affected by 50 mM urea and thioacetamide. Potassium ferricyanide, n-bromosuccinamide and potassium cyanide reduced the enzyme activity. The enzyme showed a good stability in organic solvents, the best result being in n-hexane (113% residual activity). The activity of dialysate was maintained approximately 80% for 1 year at −20 °C.     

Purification and partial characterization of milk-clotting enzyme extracted from glutinous rice wine mash liquor

Glutinous rice wine mash liquor is a traditional food of south of China and its ability to coagulate the milk has been proved. The aim of this work was to extract milk-clotting enzyme from glutinous rice wine mash liquor. A partial purified extract of enzyme was obtained by fractional precipitation with (NH₄)₂SO₄. The fractions obtained by precipitation, 40–90% possessed the milk-clotting activity (MCA) (145.72 U/mg). The 40–90% (NH₄)₂SO₄ fraction was further purified by sephadex G-100 and DEAE-sephadex A-50 with MCA (4,360±50 U/mg), which was confirmed by SDS-PAGE that showed only one band with a molecular mass of 36.0 kDa. Highest MCA was attained at 36 °C. The enzyme was completely inactivated by heating for 20 min at 60 °C. The MCA increased with the decreasing of milk pH from 8.0 to 5.5, and it was active at the wide range of pH 1 to 7. The metal ions Mg²⁺, Ca²⁺, Ba²⁺, Mn²⁺, Al³⁺, Fe²⁺ had a very clear function to accelerate milk coagulation whereas Na⁺ and K⁺ decelerated the activity slightly. The curd effect of the milk-clotting enzyme has primarily been studied.     

Production of ellagic acid from degradation of valonea tannins by Aspergillus niger and Candida utilis

Two fungal strains, effective in converting valonea (Quercus aegilops) tannins into ellagic acid (EA), were isolated from soil contaminated by valonea tannins, and were tentatively identified as Aspergillus niger and Candida utilis. Properties of EA accumulation by the two isolates from valonea tannins' fermentation were studied. Both the strains preferred sucrose to glucose as the additional carbon and energy source. The most suitable concentrations of valonea tannins in fermentation media for EA accumulation by A niger and C utilis were 5.0 and 9.0 g dm^?3 with EA yields of 12.1 and 8.9% (w/w), respectively. The optimal temperature for the two strains was 28 °C, while the preferred pH values of the fermentation media were 4.5–5.0 for A niger and 4.8–5.2 for C utilis. The tannin tolerances of A niger and C utilis were adapted to 20 and 25 g dm^?3 by gradually increasing the concentrations of valonea tannins in the culture media. The adapted strain of A niger was able to completely degrade 20 g dm^?3 valonea tannins with an EA yield of 14.3% in 9 days. Meanwhile, the adapted strain of C utilis decreased the valonea tannins' level from 25 to 9.1 g dm^?3 with an EA yield of 11.48%. The degradation ability of A niger came from tannase whose activity in the medium was 63 U cm^?3 at the ninth day of fermentation, and that of C utilis was due to both tannase and polyphenol oxidase (PPO) whose activities were 32 U cm^?3 and 29 U cm^?3 at the ninth day. The coculture of both the adapted strains could completely degrade 25 g dm^?3 valonea tannins in only 7 days with a remarkably increased EA yield (21%). The activities of tannase and PPO of the coculture at the seventh day were 66 U cm^?3 and 47 U cm^?3 respectively, which proved the synergistic effect of the two enzymes on valonea tannins' degradation and EA accumulation. Copyright © 2005 Society of Chemical Industry     

Thermodynamics of the silver—silver chromate electrode in water + 10, + 20, + 30 and + 40 mass percent of dioxane at different temperatures

The emf of the cell: Ag, AgCl, NaCl(m)?Na₂CrO₄(m/2), Ag₂CrO₄, Ag in water + 10, + 20, + 30, and + 40 mass percent of dioxane has been measured at 5°C intervals over the temperature range 15–45°C. The values of the standard potentials of the silver—silver chromate electrode have been determined in these mixed solvent media at these temperatures. The standard thermodynamic quantities (ΔG°, ΔH°, and ΔS°) for the cell reaction in water + dioxane mixtures have been evaluated at these temperatures. The results are discussed in terms of the preferential solvation of the ions.     

Purification and Biochemical Characterization of Lipase from Tunisian Euphorbia peplus Latex

Lipases from vegetable sources have been the focus of intense and growing research. The use of enzymes from plants has the advantage of employing industrial waste products. The lipase activity of Euphorbia peplus L. (Euphorbiaceae) was investigated for the first time. The Euphorbia peplus latex lipase (EpLL) was purified after ammonium sulfate fractionation and anion exchange chromatography on a DEAE-Cellulose column leading to 12.57-fold purification. The EpLL displayed a probable molecular weight of about 40 kDa. The lipase activity was optimum at a temperature of 40 °C and pH 8, the specific activities of EpLL were found to be 249 ± 12.45 and 161.4 ± 8.07 U/mg when tributyrin (TC₄) and olive oil were used as substrate respectively. The enzyme retained 80 % of its activity when incubated for 1 h at 50 °C. The EpLL was strongly destabilised by divalent metal ions (Fe²⁺, Mg²⁺, Zn²⁺ and Cu²⁺). Lipase was slightly stimulated by Triton X-100 and Tween-80, while strongly inhibited by sodium dodecyl sulfate. A good stability of the enzyme in the presence of organic solvents was reveled suggesting its industrial utility.     

Asymmetric Reduction of (R)-Carvone through a Thermostable and Organic-Solvent-Tolerant Ene-Reductase

Ene-reductases allow regio- and stereoselective reduction of activated C=C double bonds at the expense of nicotinamide adenine dinucleotide cofactors [NAD(P)H]. Biological NAD(P)H can be replaced by synthetic mimics to facilitate enzyme screening and process optimization. The ene-reductase FOYE-1, originating from an acidophilic iron oxidizer, has been described as a promising candidate and is now being explored for applied biocatalysis. Biological and synthetic nicotinamide cofactors were evaluated to fuel FOYE-1 to produce valuable compounds. A maximum activity of (319.7±3.2) U mg⁻¹ with NADPH or of (206.7±3.4) U mg⁻¹ with 1-benzyl-1,4-dihydronicotinamide (BNAH) for the reduction of N-methylmaleimide was observed at 30 °C. Notably, BNAH was found to be a promising reductant but exhibits poor solubility in water. Different organic solvents were therefore assayed: FOYE-1 showed excellent performance in most systems with up to 20 vol% solvent and at temperatures up to 40 °C. Purification and application strategies were evaluated on a small scale to optimize the process. Finally, a 200 mL biotransformation of 750 mg (R)-carvone afforded 495 mg of (2R,5R)-dihydrocarvone (>95 % ee), demonstrating the simplicity of handling and application of FOYE-1.     

Selectivity Sequence of Multivalent Lanthanides for their Separation on Antimonate Based Exchangers

The adsorption of trivalent lanthanide ions, Ln³⁺ (La³⁺, Pr³⁺, Nd³⁺, Gd³⁺, and Er³⁺), using two antimonate based exchangers, namely, silicon antimonate (SiSb) and poly(acrylamide titanium antimonate), PAmTA, was studied from their nitrate solutions at pH 3.5 ± 0.1. The formation constants in Ln³⁺/SiSb and Ln³⁺/PAmTA systems, logK _S1 and logK _S2 , were calculated for the above mentioned lanthanides. The K _d values of the selected lanthanides were calculated at 30, 40, 50, and 60°C reaction temperatures. A fractionation is observed that due to the selective sorption between the heavy rare earths (HREEs) and the light rare earths (LREEs) at various reaction temperatures, the HREEs are being more sorbed than the LREEs. The selectivity order increased with increasing atomic number of these ions. Log K _d -Z plots revealed the presence of the M-type tetrad phenomenon in the system. Furthermore, the calculated separation factors showed that, binary separations for Er⁺³/La⁺³, Er⁺³/Pr⁺³, Er⁺³/Nd⁺³, and Gd⁺³/La⁺³ on SiSb, while, Er⁺³/Gd⁺³, Gd⁺³/Pr⁺³, Gd⁺³/Nd⁺³, Nd⁺³/La⁺³, and Nd⁺³/Pr⁺³, side by side to the mentioned separations could be accomplished on PAmTA at 30°C. The separation efficiency was found to increase with increasing in reaction temperatures. On PAmTA (at 40°C and 50°C) and on SiSb (at 50°C), Er⁺³/(La⁺³, Pr⁺³, Nd⁺³, Gd⁺³), Gd⁺³/(La⁺³, Pr⁺³, Nd⁺³), Nd⁺³/(La⁺³, Pr⁺³) fractionations were also noticed, while on the surface of SiSb at 40°C, Gd⁺³/La⁺³ and Gd⁺³/Pr⁺³ could be added to the list of binary separations at 30°C. Nevertheless, La⁺³/Pr⁺³ break through could not be obtained at any reaction temperature. Kinetic investigations were carried out; drawing an analogy, the pseudo second-order model was more agreeable to fit the data.     

Purification and characterization of thermophilic and alkalophilic tributyrin esterase fromBacillus strain A30-1 (ATCC 53841)

An extracellular esterase (EC 3.1.1.1) from a thermophilicBacillus A30-1 (ATCC 53841) was purified 139-fold to homogeneity by sodium chloride (6 M) treatment, ammonium sulfate fractionation (30–80%) and phenyl-Sepharose CL-6B column chromatography. The native enzyme was a single polypeptide chain with a molecular weight of about 65,000 and an isoelectric point at pH 4.8. The optimum pH for esterase activity was 9.0, and its pH stability range was 5.0–10.5. The optimum temperature for its activity was 60°C. The esterase had a half-life of 28 h at 50°C, 20 h at 60°C and 16 h at 65°C. It showed the highest activity on tributyrin, with little or no activity toward long-chain (12–20 carbon) fatty acid esters. The enzyme displayed K_m and K_cat values of 0.357 mM and 8365/min, respectively, for tributyrin hydrolysis at pH 9.0 and 60°C. Cyclodextrin (α, β, and γ), Ca²⁺, Co²⁺, Mg²⁺ and Mn²⁺ enhanced the esterase activity, and Zn²⁺ and Fe²⁺ acted as inhibitors of the enzyme activity. The enzyme activity was not affected by ethylenediaminetetraacetic acid, p-chloromercuribenzoate andN-bromosuccinimide. This paper was presented in part at the 82nd Annual Meeting and Exposition of the American Oil Chemists’ Society, held May 12–15, 1991, in Chicago, Illinois.     

Study of the synthesis of chitosan derivatives containing benzo‐21‐crown‐7 and their adsorption properties for metal ions

Three new chitosan crown ethers, N‐Schiff base‐type chitosan crown ethers (I, III), and N‐secondary amino type chitosan crown ether (II) were prepared. N‐Schiff base‐type chitosan crown ethers (I, III) were synthesized by the reaction of 4′‐formylbenzo‐21‐crown‐7 with chitosan or crosslinked chitosan. N‐Secondary amino type chitosan‐crown ether (II) was prepared through the reaction of N‐Schiff base type chitosan crown ether (I) with sodium brohydride. Their structures were characterized by elemental analysis, infrared spectra analysis, X‐ray diffraction analysis, and solid‐state ¹³C NMR analysis. In the infrared spectra, characteristic peaks of C?N stretch vibration appeared at 1636 cm^?1 for I and 1652 cm^?1 for II; characteristic peaks of N? H stretch vibration appeared at 1570 cm^?1 in II. The X‐ray diffraction analysis showed that the peaks at 2θ = 10° and 28° disappeared in chitosan derivatives I and III, respectively; the peak at 2θ = 10° disappeared and the peak at 2θ = 28° decreased in chitosan‐crown ether II; and the peak at 2θ = 20° decreased in all chitosan derivatives. In the solid‐state ¹³C NMR, characteristic aromatic carbon appeared at 129 ppm in all chitosan derivatives, and the characteristic peaks of carbon in C?N groups appeared at 151 ppm in chitosan crown ethers I and III. The adsorption and selectivity properties of I, II, and III for Pd²⁺, Au³⁺, Pt⁴⁺, Ag⁺, Cu²⁺, and Hg²⁺ were studied. Experimental results showed these adsorbents not only had good adsorption capacities for noble metal ions Pd²⁺, Au³⁺, Pt⁴⁺, and Ag⁺, but also high selectivity for the adsorption of Pd²⁺ with the coexistence of Cu²⁺ and Hg²⁺. Chitosan‐crown ether II only adsorbs Hg²⁺ and does not adsorbs Cu²⁺ in an aqueous system containing Pd²⁺, Cu²⁺, and Hg²⁺. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1886–1891, 2002     

Methacrylic acid and dodecyl methacrylate (MAc‐DMA) hydrogel for enhanced catalytic activity of lipase of Bacillus coagulans MTCC‐6375

An alkaline thermotolerant bacterial lipase of Bacillus coagulans MTCC‐6375 was purified and immobilized on a methacrylic acid and dodecyl methacrylate (MAc‐DMA) hydrogel. The lipase was optimally bound to the matrix after 20 min of incubation at 55°C and pH 9 under shaking conditions. The matrix‐bound lipase retained approximately 50% of its initial activity at 70–80°C after 3 h of incubation. The immobilized lipase was highly active on medium chain length p‐nitrophenyl acyl ester (C: 8, p‐nitrophenyl caprylate) than other p‐nitrophenyl acyl esters. The presence of Fe³⁺, NH₄⁺, K⁺, and Zn²⁺ ions at 1 mM concentration in the reaction mixture resulted in a profound increase in the activity of immobilized lipase. Most of the detergents partially reduced the activity of the immobilized lipase. The immobilized lipase performed ～62% conversion in 12 h at temperature 55°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1420–1426, 2006     

Effect of temperature on viscosity of amylose

Viscosity parameters were obtained for maize maylose (molecular weight of 107,000) in 1N KOH at 25, 30, 35, and 40°C. Intrinsic viscosity continuously decreased and Huggins' constant k' continuously increased with increasing temperature. The temperature dependence of intrinsic viscosity, d[η]/dT, was ?2.12 × 10^?2/°C.     

Development of biosensor for phenol detection using agarose–guar gum based laccases extracted from Pleurotus ostreatus

Laccases from Pleurotus ostreatus was extracted from the Shaken flask cultures of Pleurotus ostreatus grown at 25°C with continuous agitation (110 rpm.) in baffled 1000 mL Erlenmeyer flasks containing 200 mL medium. The basal GYP medium used for cultures contained 20 g glucose l^?1, 5 g yeast extract l^?1, 5 g peptone from casein l^?1, and 1 g MgSO₄.7H₂O l^?1. The pH was adjusted to 5.0 with H₃PO₄ before sterilization. The kinetics of oxidation reactions catalyzed by laccases was studied using 2,2′‐azino‐bis (3‐ethylbenzthiazoline‐6‐sulphonic acid). The laccases showed lower specific activity and higher activity in nonpolar organic solvents. A biosensor using laccases was constructed for the determination of phenol. The enzyme was extracted from Pleurotus ostreatus and entrapped in agarose–guar gum composite biopolymer matrix. Phenol was determined by direct reduction of biocatalytically liberated quinone species at ?0.1 V versus Ag/AgCl (3M KCl). The response was found to be linear and concentration dependent.It has a shelf life of more than 2 months when stored at 4°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Formation of BaFe12−xNbxO19 and its high electromagnetic wave absorption properties in millimeter wave frequency range

BaFe_12?xNb_xO₁₉ (BFNO, x=0‐0.6) powders with Nb⁵⁺ substituting for Fe³⁺ were prepared by sol‐gel method. The formation process and electromagnetic (EM) wave absorption properties of the BFNO are investigated in detail. With Nb⁵⁺ content increasing from x=0 to x=0.6, the formation temperature of barium ferrite phase without heat time increases from ~700°C to ~900°C, while the appearance temperature of typical plate grains decreases from ~1300°C to ~1100°C, and the crystallization ability decreases at 600°C‐900°C, while the grain size increases gradually at 1100°C‐1300°C. Increasing sintering temperature and time promote the formation of barium ferrite phase and grain growth in all the samples. The ε′ and ε″ of the sample with x=0.6 sintered at 1300°C for 3 hours reach highest of ~7.9 and ~0.95 over 26.5‐40 GHz. Multiresonance peaks in permeability decrease from 40+ GHz to ~30 GHz with x rising from 0 to 0.6. Ultimately, small RL_min of ~?42 dB, thin d_m of ~0.76 mm, and broad bandwidth of >12 GHz can be exhibited simultaneously around millimeter wave atmospheric window of 35 GHz.     

Preparation of goat milk powder with Lactobacillus casei L61 and antioxidant peptides: optimization of the composite thermal protectants and evaluation of storage stability

Abstract

The Lactobacillus casei L61 has great ability for producing antioxidant peptides. For reducing the mortality of L. casei L61 in spray drying process, the Box-Behnken design (BBD) was adopted to optimize the composite thermal protective agent formula. The results exhibited that the composite thermal protective agent formula of L. casei L61 contained glucose at 6.03% (w/v), skim milk at 18.98?g/L, and glycerol at 12.50?mL/L. Under the optimal conditions, the average survival of L. casei L61 in the fermented goat milk reached 14.58?±?0.72% after heat treatment at 75?°C for 10?min, which was higher than the control (13.14%). The average hydroxyl free radical scavenging activity of L. casei L61 reached 85.09?±?0.98%, which was not significantly different from the predicted value (86.83%). Therefore, the BBD is feasible for optimizing the composite thermal protective agent formula of L. casei L61. Under the optimal conditions with the inlet air temperature of 130?°C and feed rate of 4.5?mL/min, the maximum viable counts and survival rate of L. casei L61 were 7.46?×?10⁸ cfu/g and 23.41?±?1.28%, respectively. More importantly, the storage stability of antioxidative probiotic goat milk powder was predicted by temperature acceleration test. The shelf life of antioxidative probiotic goat milk powder was estimated to be 352?days at 4?°C and 117?days at 25?°C, embodying the great long-term stability. This study provides a technical reference for industrialized production of probiotic goat milk powder.     

Purification and characterization of a thermophilic chitinase produced by <Emphasis Type="Italic">Aeromonas</Emphasis> sp. DYU-Too7

An extracellular chitinase, produced by Aeromonas sp. DYU-Too7, was purified in the following procedures: ammonium sulfate precipitation, ultrafiltration, chromatographic separation of DEAE-sepharose CL-6B and sephacrylS-100HR. The resulting chitinase has a molecular mass of 36 kDa, an optimal reaction pH of 5.0, and an optimal reaction temperature of 70°C. It retains almost 100% activity in the pH range of 5.0–8.0. This chitinase has a high thermal tolerance and retained 90% of its activity at 50°C and 75% at 60°C. Enzyme activity was inhibited by Ba²⁺, Hg²⁺, Mg²⁺ and Ag⁺ cations, but was not substantially inhibited by the K⁺ cation nor the chelating agent EDTA. The K _m and V _mα , using colloidal chitin as a substrate, are 6.3 g/L and 18.69 μmol/min/mg-protein, respectively. The 36 kDa chitinase of Aeromonas sp. DYU-Too7 is an exo-type enzyme, because chitobiose was the main hydrolysate in hydrolysis of colloidal chitin.     

Characterization of two polypentadienes of differing tacticity by physical methods

The preparation of isotactic and syndiotactic 1,4-polypentadienes with a cis content of at least 70%–75% using i-Bu₂AlH/Ti(i-OPr)₄ and AlEtCl₂/thiophene/Co(acetylacetonate)₂ catalysts, respectively, is reported. Physical characterization of the vulcanizates, prepared by a common recipe, involving infrared analysis, DTA, simple stress–strain and swelling measurements, and dynamic mechanical measurements over a frequency range of 2 decades and temperature range of ?60°C to +20°C indicated that no isomerization had taken place during vulcanization and that stereoregularity of the polymer chains affected the resultant cure: the isotactic form was found to have a greater crosslink density than the syndiotactic form. Master curves covering an extended frequency range were constructed from the reduced dynamic mechanical data and the calculated quantities—thermal expansion coefficients of free volume and the fractional free volumes at the glass transition temperatures—agree with the accepted values. Glass transition temperatures of the isotactic and syndiotactic polymers are ?37°C and ?42°C, respectively, and for their vulcanizates, ?33°C and ?40°C, respectively.     

Biosorption of a Basic Dye from Aqueous Solutions by Euphorbia rigida

Abstract

In this study, the biosorption of Basic Blue 9 (BB9) dye from aqueous solutions onto a biomass of Euphorbia rigida was examined by means of the initial biosorbate concentration, biosorbent amount, particle size, and pH. Biosorption of BB9 onto E. rigida increases with both the initial biosorbate concentration and biosorbent amount, whereas decreases with the increasing particle size. The experimental data indicated that the biosorption isotherms are well‐described by the Langmuir equilibrium isotherm equation at 20, 30, and 40°C. Maximum biosorption capacity was 3.28×10^?4 mol g^?1 at 40°C. The biosorption kinetics of BB9 obeys the pseudo‐second‐order kinetic model. The thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated to estimate the nature of biosorption. These experimental results have indicated that E. rigida has the potential to act as a biosorbent for the removal of Basic Blue 9 from aqueous solutions.