Activity of Laccase Immobilized on TiO2-Montmorillonite Complexes

The TiO₂-montmorillonite (TiO₂-MMT) complex was prepared by blending TiO₂ sol and MMT with certain ratio, and its properties as an enzyme immobilization support were investigated. The pristine MMT and TiO₂-MMT calcined at 800 °C (TiO₂-MMT800) were used for comparison to better understand the immobilization mechanism. The structures of the pristine MMT, TiO₂-MMT, and TiO₂-MMT800 were examined by HR-TEM, XRD and BET. SEM was employed to study different morphologies before and after laccase immobilization. Activity and kinetic parameters of the immobilized laccase were also determined. It was found that the TiO₂ nanoparticles were successfully introduced into the MMT layer structure, and this intercalation enlarged the “d value” of two adjacent MMT layers and increased the surface area, while the calcination process led to a complete collapse of the MMT layers. SEM results showed that the clays were well coated with adsorbed enzymes. The study of laccase activity revealed that the optimum pH and temperature were pH = 3 and 60 °C, respectively. In addition, the storage stability for the immobilized laccase was satisfactory. The kinetic properties indicated that laccase immobilized on TiO₂-MMT complexes had a good affinity to the substrate. It has been proved that TiO₂-MMT complex is a good candidate for enzyme immobilization.     

Influence of montmorillonite on cadmium accumulation in carp, Carassius auratus

The present study was designed to test the influence of montmorillonite (MMT) on cadmium accumulation in different tissues of Carassius auratus. 180 normal healthy C. auratus were randomly divided into four groups. They were fed with normal diet, normal diet supplemented with MMT (0.5%), high-cadmium (cadmium chloride, 120 mg/kg) diet and high-cadmium diet supplemented with MMT (0.5%). After 60 days, cadmium concentration in several tissues were measured by eletrothermic atomic absorption spectrophotometry, metallothionein contents were determined using the Cd-chelex assay and histopathological alterations of kidney were observed. MMT inhibited cadmium accumulation in kidney, intestine, liver, spleen, blood, gills, spermary, ovary, brain, bone and muscles of C. auratus. Metallothionein levels in liver, intestine and muscle decreased and pathological changes of kidney were reduced by MMT addition. Thus, MMT protected tissues of C. auratus from cadmium accumulation and damage.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Utilization of starch and montmorrilonite for the preparation of superabsorbent nanocomposite

Starch and montmorrilonite (MMT) were used as raw materials for synthesizing starch‐graft‐poly[acrylamide (AM)–acrylic acid (AA)]/MMT superabsorbent nanocomposite by graft and intercalation copolymerization reaction of starch, AM, and AA in the presence of organic MMT micropowder in aqueous solution. Major factors affecting water absorbency such as weight ratio of monomers to starch, weight ratio of AM to AA, neutralization degree of AA, amount of crosslinker, initiator, and MMT were investigated. The superabsorbent nanocomposite synthesized under optimal synthesis conditions exhibits absorption of 1120 g H₂O/g sample and 128 g H₂O/g sample in deionized water and in 0.9 wt % NaCl solution, respectively. IR spectra showed that the graft copolymerization between  OH groups on MMT and monomers took place during the reaction, and that crystal interlayer was pulled open in the superabsorbent nanocomposite. X‐ray diffraction analysis showed that the crystal interlayer of MMT was pulled open to 2.73 nm, and thus formed nanometer exfoliation composite material. Thermogravimetric analysis showed that starch‐graft‐poly (AM–AA) superabsorbent nanocomposite (8 wt % MMT) has good thermal stability. This superabsorbent nanocomposite with excellent water absorbency and water retention, being biodegradable in nature, economical and environment friendly, could be especially useful in industry, agricultural, and horticultural applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characterization and Toxicity of Amanita cokeri Extract

The nonprotein amino acids 2-amino-3-cyclopropylbutanoic acid and 2-amino-5-chloro-4-pentenoic acid were isolated from the mushroom Amanita cokeri. The cyclopropyl amino acid is toxic to the fungus Cercospora kikuchii, the arthropod Oncopeltus fasciatus (milk weed bug), and the bacteria Agrobacterium tumefaciens, Erwinia amylovora, and Xanthomonas campestris. Toxicity to bacteria was reversible by addition of isoleucine to the medium. No toxicity was observed for 2-amino-5-chloro-4-pentenoic acid.     

<Emphasis Type="Italic">Desmoscaris tripsinosa</Emphasis> and <Emphasis Type="Italic">Palaemonetes africanus</Emphasis> Responses to Concentrations of Neatex and Norust CR486 in Sediment

The assessment of water and sediment quality from chemical pollutants in the Nigerian Niger Delta were conducted using bioindicators (Desmoscaris tripsinosa and Palaemonetes africanus). The Organization for Economic Cooperation and Development (OECD) (2004), No.218 direct sediment toxicity assessment was employed. Shrimp were exposed to sediments treated with Neatex (liquid detergent) and Norust CR 486 (corrosion inhibitor) at concentrations of 31.25, 62.5, 125, 250 and 500 mg/kg. Percentage mortality was measured as the ecological endpoint. Mean % mortality and estimated lethal concentration LC50 values varied with species type, concentration and exposure duration. Observed % mean mortality of the test organisms in both chemicals were significantly different from that of the control test suggesting that mortality may be induced by the effect of the chemicals. LC50s were significantly different for both chemicals at p < 0.05, t = 6.06 (fresh water) and p < 0.05, t = 12.34 (brackish). The values from this study are an indication that the chemicals have the potential to cause acute lethal toxicity. It is a prediction of likely adverse effects on shrimp populations in benthic sediment of the Niger Delta ecological zone. Consequently, there is a great need to protect some of the more sensitive invertebrates representing the major proportion of the diet of many other species.

Characterization and Immobilization of Marine Algal 11-Lipoxygenase from Ulva fasciata

The lipoxygenase (LOX) of the marine green alga Ulva fasciata was purified and immobilized in order to improve the stability and reusability. The algal LOX was partially purified by fractionation with 35–55% saturation of ammonium sulfate and MacroPrep high Q anion exchange chromatography. The LOX was purified ten times using linoleic acid (C_18:2) or arachidonic acid (C_20:4) as substrate, the Michaelis constant (K _m) of LOX was 117.6, 31.3 μM, and maximum velocity (V _max) was 12.8, 23.3 μmol hydroperoxy fatty acid/min-mg protein, respectively. The algal LOX showed the highest activity towards C_18:4 followed by C_20:4, C_18:2 and methyl ester of C_18:4. LOX activity increased up to 10.5 times with increased concentration of Triton X-100 in the extraction medium reaching an optimum at 0.05%. Calcium chloride, glutathione and phenylmethylsulphonyl fluoride were found effective protectants to LOX during purification. Hydroperoxyeicosatetraenoic acid (HpETE) formed from arachidonic acid catalyzed by this purified algal LOX was reduced and identified as 11-hydroxy-5,8,12,14-eicosatetraenoic acid (11-HETE) by NP-HPLC and GC–MS. This algal 11-LOX was immobilized in alginate beads. The stability was sevenfold greater than that of the unbound lipoxygenase at 4 °C in 0.05 M Tris–HCl buffer (pH 7.5). This is the first report on immobilization of a marine algal lipoxygenase with a view to its potential role in seafood flavor formation.     

Molecular basis ofMorinda citrifolia (L.): Toxicity on drosophila

The ripe fruit ofMorinda citrifolia, host plant forDrosophila sechellia is highly toxic for three closely related species (D. melanogaster, D. simulans, andD. mauritiana). Green and rotten fruits are not toxic for all species tested. Short fatty acids were found to be present in large quantities in the extract of the ripe fruit. The most abundant (octanoic acid) was tested pure for its toxicity in a dose-dependent manner;D. sechellia is five to six times more resistant thanD. melanogaster to octanoic acid. Octanoic acid alone seems to be sufficient to explain the toxic effect of the pulp. It is less abundant in the rotten fruit and absent in the green fruit.     

Effect of oligomeric‐modified montmorillonite on morphology and properties of polycarbonate/montmorillonite nanocomposites

Low‐molecular‐weight copolymers of styrene and vinylbenzyl ammonium salts (oligomeric surfactant) were used to modify montmorillonite (MMT). The oligomeric‐modified MMT showed good thermal stability, which made it suitable to be used for preparing polycarbonate(PC)/MMT nanocomposites at high temperature. A different series of PC/MMT nanocomposites had been prepared by melt processing using a twin screw extruder. The effect of oligomeric surfactant structure and clay loading on the morphology, mechanical property, thermal stability, and color appearance of the nanocomposites were explored. The results of X‐ray diffraction and transmission electron microscopy analyses indicated that the PC/MMT nanocomposites had partially exfoliated structures. The PC/MMT nanocomposites were found to retain light colored, which was important for optical application. Compared to neat PC, the nanocomposites showed better properties of thermal stability and heat insulation. The mechanical properties of the nanocomposites are significantly enhanced by incorporating clay into the PC matrix. The tensile strength of nanocomposites with 2 wt% clay content was up to 55 MPa, which was much higher than that of the neat PC (37 MPa). The maximum tensile modulus value was 19% higher than that of neat PC. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Polypropylene/organically modified Sabah montmorillonite nanocomposites: Surface modification and nanocomposites characterization

The aim of the work is to extract, purify, and organically modify montmorillonite (MMT) of Lahad Datu, Sabah bentonite. The octadecylamine treated Sabah MMT (S‐OMMT) (2–8 wt%) was then melt blended with polypropylene (PP) and maleated polypropylene (PPgMAH) (10 wt%) via single screw nanomixer extruder followed by injection molding into test samples to examine the mechanical, thermal, and morphological properties of PP/S‐OMMT nanocomposites. Unmodified Sabah MMT (S‐MMT) and commercial grade MMT (Nanomer 1.30P) filled PP nanocomposites were also characterized for comparison purpose. X‐ray diffraction results showed that the interlayer spacing of S‐MMT increased after organic modification as Fourier transform infra‐red and elemental analysis evidenced the presence of octadecylamine. PP/S‐OMMT nanocomposites showed a better dispersion and strength compared to PP/Nanomer 1.30P nanocomposites due to its smaller MMT platelet size. differential scanning calorimetry and Thermogravimetry analysis revealed that the thermal stability and crystallinity of neat PP improved with the addition of all types of MMT. Dynamic mechanical analyzer showed that PP nanocomposites have higher storage modulus (E′) values than the neat PP over the whole temperature range. The new PP/S‐OMMT nanocomposites showed a comparable performance with PP/Nanomer 1.30P nanocomposites exhibiting promising future applications of S‐MMT in polymer/MMT nanocomposites. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Hyperbranched polyester‐modified montmorillonite: a novel phase change material for energy storage

Hyperbranched polymer, montmorillonite (MMT) and phase change material (PCM) were used in the preparation of a novel energy storage clay material (H‐PCM). 1,3‐Diamino‐2‐propanol and methyl acrylate were firstly used in the synthesis of an AB2 intermediate. Then, Na‐MMT was modified by an intercalation agent, l‐glutamic acid. Third, hyperbranched polymer‐modified Na‐MMT (H‐MMT) was successfully fabricated using the amino acid‐modified Na‐MMT and AB2 intermediate. Subsequently, liquid paraffin was incorporated into H‐MMT, and non‐corrosive organic H‐PCM was prepared. This H‐PCM was systematically characterized using various methods, such as diffusion‐oozing circle test, differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and X‐ray diffraction (XRD). The diffusion‐oozing circle and DSC results revealed that H‐PCM possessed good heat storage and release capacity. In XRD analysis, expansions of the spacings in the plane were observed for all samples. TG analysis of this clay illustrated that it could be suitable for industrial applications due to its high thermal stability. © 2017 Society of Chemical Industry     

Chemical inhibition of fire-prone grasses by fire-sensitive shrub,Conradina canescens

In an investigation of potential chemical activity of fire-sensitive shrubs in Florida's sand pine scrub community, bioassays of foliar washes ofConradina canescens showed significant inhibitory activity on three native grasses that are known to fuel frequent surface fires; inhibition was concentrated seasonally in spring and summer. Application of runoff fromConradina leaves to one of the grasses caused a 50% reduction in growth over a 20-week period. Isolation of the biologically active fractions from the fresh leaves ofC. canescens yielded numerous monoterpenes, a number of which were identified from a GC-MS reference library and/or MS comparison to authentic compounds: 11 from the diethyl ether extract, 11 from steam distillation, and four from the foliar leaf wash. Numerous other monoterpenes present in the extractions were unknown. The terpenoid fraction completely inhibited seed germination of one of the native grasses and of lettuce. Saturated aqueous solutions of nine of the monoterpenes inhibited germination and radicle growth of two native grasses. SEM views of the leaf surfaces ofConradina reveal secretory trichomes that appear to be the source of the monoterpenes as well as the triterpene, ursolic acid. The biological activity ofC. canescens as a fire-sensitive component of the scrub community is reviewed in light of the chemical evidence.     

Zosteric acid—An effective antifoulant for reducing fresh water bacterial attachment on coatings

Zosteric acid, a natural product present in eelgrass, has been found to prevent the attachment of some bacteria and barnacles. The results indicate that it may also be effective at reducing the early stages of biofouling, such as the attachment of bacteria that lead to a biofilm. In this study, the ability of zosteric acid in reducing the early stages of fouling was evaluated using attachment studies of fresh water bacteria via two approaches. First, plain coatings were submersed in water containing zosteric acid and either enriched Lake Erie bacteria or Pseudomonas putida, a model fresh water bacteria. It was found that zosteric acid with a concentration one-tenth of its EC₅₀ (the concentration eliminates 50% of the bacteria) was able to reduce bacterial attachment by more than 90%. The second approach incorporated zosteric acid into silicone coatings in the presence of a common solvent to achieve the slow release of zosteric acid; such coatings were then subjected to the bacterial attachment. A ～75% reduction in bacterial attachment was found for 1 wt% zosteric acid entrapped Sylgard^® 184, a model silicone coating, but the reduction only achieved ～55% for 1 wt% zosteric acid entrapped in a commercial silicone coating, RTV11.     

An environmentally compatible synthesis of polyesters derived from 5‐(2‐phthalimidoethanesulfonamido) isophthalic acid as a novel diacid monomer

A biologically active diacid monomer, 5‐(2‐phthalimidoethanesulfonamido) isophthalic acid (6), based on taurine, was easily prepared in three steps. Also a series of novel biologically active polyesters ( PE )s were synthesized by the reaction of this monomer with several aromatic diols by step growth polymerization using tosyl chloride (TsCl)/dimethylformamide (DMF)/pyridine (Py) system as a condensing agent. The resulting new polymers were obtained in good to high yields with moderate inherent viscosities. All of the PE s were characterized by FTIR and some of them were also characterized by ¹H‐NMR and elemental analyses methods. The thermal stability of PE s was evaluated with thermogravimetric analysis and differential scanning calorimetry techniques under a nitrogen atmosphere and it was found that they have moderate stability. Wheat seedlings were normally grown in the presence of 6 and it's derived PE s in soil. Also the high dehydrogenase activities in treated soils with obtained compounds showed biodegradability of polymers under soil burial in natural environments. It can be concluded that the synthesized compounds derived from taurine are possibly biologically active and environmentally nontoxic for soil microorganisms. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polyimide/montmorillonite nanocomposites based on thermally stable, rigid-rod aromatic amine modifiers

The preparation and processing of most of polymer/clay nanocomposites need high temperature. This limited the application of commonly used organic modifiers of long carbon-chain alkyl ammonium salts because of their low thermal stability. In this study, we synthesized two novel thermally stable, rigid-rod aromatic amines. Montmorillonite (MMT) treated by these amines exhibited larger layer-to-layer spacing, higher thermal stability than that treated by commonly used 1-hexadecylamine and also high ion-exchange ratio (>95%). They were applied to prepare nanocomposites with polyimide (PI) by in situ polymerization. XRD, TEM were used to obtain the information on morphological structure of PI/MMT nanocomposites. DMA, TGA, DSC, universal tester were applied to characterize the mechanical and thermal properties of the nanocomposites. When the MMT content was below 3 wt%, the PI/MMT nanocomposites were strengthened and toughened at the same time. The introduction of a small amount of MMT also led to improvement in thermal stability, slight increase in glass transition temperature, marked decrease in coefficient of thermal expansion and decrease in solvent uptake. MMT treated by these aromatic amines exhibited better dispersibility and (probably) interfacial interaction with PI matrix than that treated by 1-hexadecylamine. The nanocomposites based on these MMT resultantly exhibited better mechanical, thermal and solvent resistance properties than those based on 1-hexadecylamine treated MMT.     

The positional and fatty acid selectivity of oat seed lipase in aqueous emulsions

The positional and fatty acid selectivities of oat (Avena sativa L.) seed lipase (triacylglycerol hydrolase EC 3.1.1.3) were examined. Pure triacylglycerols were used as substrates. The products of lipolysis were examined by thin-layer chromatography and gas-liquid chromatography. Only symmetrical triacylglycerols were used as substrates; thus potential complications arising from stereobias were avoided. Controls were carried out with a lipase specific for primary positions. The lipase from oat seeds catalyzed the hydrolysis of both primary and secondary esters. When the lipase was tested upon mixtures of homoacid triacylglycerols (triacylglycerols composed of the same three fatty acids), the lipase acted most rapidly upon those containing oleate, elaidate, linoleate and linolenate. Strong intermolecular selectivity against homoacid triacylglycerols containing palmitate, petroselinate and stearate was observed. Comparison of assays performed at 26°C with those performed at 45°C showed that selectivity was temperature-independent. When mixed-acid triacylglycerols containing both oleate and stearate were treated with lipase, intramolecular selectivity was observed, with oleate hydrolysis predominating. From this work and earlier work, it can be concluded that the selectivity exhibited by the oat seed lipase is similar to that of the lipase fromGeotrichum candidum, except that the oat seed lipase attacks elaidate, a fatty acyl group with atrans double bond, whereas theG. candidum lipase strongly discriminates against elaidate.     

Development and evaluation of terminally epoxidized triglycerides for coatings applications

Epoxidized 10-undecenoic acid triglyceride, an experimental seed oil derivative that has a terminal epoxy group on each of the three acyl glyceride segments, has been found to have good reactivity with amine curatives and allows room temperature cures to be obtained. Coatings based on epoxidized 10-undercenoic acid triglyceride have also shown excellent UV stability. As an example, coatings samples placed in a QUVA chamber exhibit no loss in gloss after 3000 hr of a cycled exposure to high intensity UV lamps and moisture at temperatures of 50–60°C. In comparison, coatings based on standard liquid epoxy resins (LERs) and commercially available hydrogenated LERs lose gloss due to chalking/decomposition within 200–800 hr. Presented at the 81 st Annual Meeting of the Federation of Societies for Coatings Technology, November 12–14, 2003, in Philadelphia, PA.     

Ozonolysis of cyclododecene

Ozonolysis of cyclododecene was carried out to produce an w-formyl carboxylic acid (12-oxododecanoic acid) which is derived from zwitterion and aldehyde moiety that are formed during the reaction. The ozonolysis was performed to examine the product distribution under such reaction variables as temperature, kinds of solvent, and presence of catalyst. The yield of polymeric ozonide, which is undesirable product, was measured to be dominantly 86% without pyridine catalyst, whereas, only 10.25% with the catalyst. The optimum reaction condition was to be in MC (methylene chloride) solvent, and in the presence of equimolar olefin and pyridine catalyst at O°C, at which the yields of polymeric ozonide, 1,12-dodecanedialdehyde, 1,12-dodecanedicarboxylic acid, and 12-oxo-dodecanoic acid were 10.25%, 26.72%, 26.31%, and 36.72%, respectively.     

A novel high polymer nanocomposite inhibitor for coal gangue spontaneous combustion prevention: A case study of Yangquan coal gangue in China

Coal gangue spontaneous combustion produces toxic and harmful gases. This research aims to study a new type of polymer nanocomposite inhibitor to prevent and control coal gangue spontaneous combustion. Nanomodification of montmorillonite (MMT) was carried out on high polymer emulsion inhibitor polyacrylamide (PAM) to improve its thermal stability and overcome the short inhibition duration problem. First, through scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), and proximate analysis experiments, it was found that the coal gangue in the Yangquan mining area was prone to spontaneous combustion. Then, PAM/MMT was produced by an intercalation method. The results of X-ray diffraction (XRD) and differential scanning calorimetry (DSC) showed that the interval spacing of MMT increased, which was sufficient for the insertion of acrylamide monomer. The vitrification temperatures of PAM and PAM/MMT prove that PAM/MMT exhibited higher thermal stability. The results of Fourier transform infrared spectroscopy (FTIR) experiments indicated that the PAM/MMT composite inhibitor agent effectively inhibited the oxidative activity of reactive groups on the coal gangue surface. As a result, PAM/MMT could suppress coal gangue oxidative spontaneous combustion, so as to reduce environmental problems caused by coal gangue spontaneous combustion. Furthermore, a spraying process is designed for the application of the inhibitor.     

Influence of the structure of the onium iodide salts on the properties of modified montmorillonite

Dialkyl imidazoline, alkyl pyridine and alkyl quinoline containing salts have been synthesized and used as new surfactants for cationic exchange of layered silicates, such as montmorillonite (MMT) in order to evaluate their role in the formation of intercalated MMT clays. The new salts have been characterized by FTIR, ¹H, ¹³C‐NMR spectra. These compounds have been intercalated into the layers of MMT via a solution dispersion technique and the extent of the interlayer space expansion was confirmed by using wide angle X‐ray diffraction and FTIR spectra. Thermogravimetry analysis shows that these salts can be used in place of ammonium salts to produce organophilic clays with higher thermal stability than commercial alkyl ammonium‐treated MMT. Moreover, the results also show that the imidazolium‐modified clays have a greater thermal stability compared to the quinolinium and the pyridinium‐modified clay. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013