Ethanol production from cellulose by coupled saccharification/fermentation usingSaccharomyces cerevisiae and cellulase complex fromSclerotiun rolfsii UV-8 mutant

Using cellulase/hemicellulase complex of Sclerotium rolfsii UV-8 mutant and Saccharomyces cerevisiae for fermentation, the coupled saccharification/fermentation (CSF) of 15% AT-rice straw was carried out at 40 degrees C, pH 4.5 for the first 24 h and further incubation was performed at 30 degrees C for 72 h. Increasing the amount of cellulase activity from 3-12 IU FPA/g of substrate resulted in increased yields of ethanol from 1.5-3.6% in 96 h. It has been observed that the coupled system was advantageous over the two stage (separate hydrolysis/fermentation) system as it produced higher amounts of ethanol from cellulose (3.6% as compared to 2.3% ethanol from rice straw).     

Factors affecting glycerol production byPichia farinosa under alkaline conditions

Glycerol is an important and valuable chemical that can be produced from renewable resources by fermentation. The desirable features of a successful process are high values of substrate conversions and high yields and concentrations of glycerol in the product broth, coupled with rapid fermentation cycles. Of the various osmophilic and nonosmophilic yeasts tested for their ability to produce glycerol in the presence and absence of steering agents (sodium sulfite or sodium carbonate), an osmophilic yeastPichia farinosa (ATCC 20210) was found to give attractive yields. Important variables influencing glycerol production by this strain under alkaline conditions using sodium carbonate have been investigated. A rapid fermentation (less than 120 h), coupled with high glycerol yields (45%), has been obtained.     

Stability and recovery ofPenicillium funiculosum cellulase under use conditions

The stability ofPenicillium funiculosum cellulase has been investigated under the conditions used for cellulose hydrolysis. Fifty five percent of filter paper activity (FPA) was inactivated on incubation at 50°C for 24 h, whereas there was no loss in endoglucanase and β-glucosidase activity. The addition of 2% polyethylene glycol (PEG) during incubation stabilized the FPA. The influence of pH during fermentation on the thermal stability of the enzyme is discussed. The recovery of enzymes after hydrolysis of bagasse at 50°C was between 8 and 14%. Under the optimal conditions of elution, the recovery of enzyme was 35% (1). Increasing the enzyme to the substrate ratio fivefold and presence of PEG during hydrolysis resulted in 80, 83, and 95% recovery of β-glucosidase, FPA, and endoglucanase activity, respectively. Index Entries: Stability; recovery of cellulase P.funiculosum.     

Factors affecting the stability of foamed concentrated emulsions

This paper attempts to quantify the stability of three-phase systems generated by aerating concentrated water-in-oil emulsions. In such materials, which we call foamed emulsions, the continuous phase is itself a two-phase system. In this work, we modify and extend the method originally proposed by Iglesias et al. (Colloids and Surfaces A, 98 (1995) 167–174) to viscous three-phase foams. The modified method involves imparting a destabilising force to the sample to make the foam short-lived and measuring the change in height as a function of decay time. The change of height during decay represents the rate at which gas is evolved from the foamed emulsion and is logarithmic with time. The data treatment yields two values, the decay constant and half-life, which are used as a means of measuring and comparing stability. Two distinct decay mechanisms (smooth decay and catastrophic collapse) operate in foamed emulsions that are subjected to oscillations. For a given decay mechanism, the decay constant is an intrinsic property of the foamed emulsion and is independent of the imposed oscillations. Experimental results indicate that different bubble stabilising surfactants and emulsion morphology significantly affect the foam stability, and that the stability is inversely related to the initial expansion. Examination of the gas–emulsion interface shows a segregation of droplets, with smaller droplets found preferentially at the gas–emulsion interface.     

Factors affecting drug encapsulation and stability of lipid-polymer hybrid nanoparticles

Lipid-polymer hybrid nanoparticles are polymeric nanoparticles enveloped by lipid layers that combine the highly biocompatible nature of lipids with the structural integrity afforded by polymeric nanoparticles. Recognizing them as attractive drug delivery vehicles, antibiotics are encapsulated in the present work into hybrid nanoparticles intended for lung biofilm infection therapy. Modified emulsification-solvent-evaporation methods using lipid as surfactant are employed to prepare the hybrid nanoparticles. Biodegradable poly (lactic-co-glycolic acid) and phosphatidylcholine are used as the polymer and lipid models, respectively. Three fluoroquinolone antibiotics (i.e. levofloxacin, ciprofloxacin, and ofloxacin), which vary in their ionicity, lipophilicity, and aqueous solubility, are used. The hybrid nanoparticles are examined in terms of their drug encapsulation efficiency, drug loading, stability, and in vitro drug release profile. Compared to polymeric nanoparticles prepared using non-lipid surfactants, hybrid nanoparticles in general are larger and exhibit higher drug loading, except for the ciprofloxacin-encapsulated nanoparticles. Hybrid nanoparticles, however, are unstable in salt solutions, but the stability can be conferred by adding TPGS into the formulation. Drug-lipid ionic interactions and drug lipophilicity play important roles in the hybrid nanoparticle preparation. First, interactions between oppositely charged lipid and antibiotic (i.e. ciprofloxacin) during preparation cause failed nanoparticle formation. Charge reversal of the lipid facilitated by adding counterionic surfactants (e.g. stearylamine) must be performed before drug encapsulation can take place. Second, drug loading and the release profile are strongly influenced by drug lipophilicity, where more lipophilic drug (i.e. levofloxacin) exhibit a higher drug loading and a sustained release profile attributed to the interaction with the lipid coat.     

Factors affecting stability and equilibria of free radicals Steric factors in hydrazyls

The preparation of 1,1-diphenyl-2-(2,4- and 2,6-dinitrophenylhydrazine) is described. Lead peroxide converts them into hydrazyl free radicals, but only the latter may be isolated in crystalline form. Ultra-violet and visible absorption spectra of hydrazines and hydrazyls are compared.     

Use of a new membrane-reactor saccharification assay to evaluate the performance of celluloses under simulated ssf conditions

A new saccharification assay has been devised, in which a continuously buffer-swept membrane reactor is used to remove the solubilized saccharification products, thus allowing high extents of substrate conversion without significant inhibitory effects from the buildup of either cellobiose or glucose. This diafiltration saccharification assay (DSA) can, therefore, be used to obtain direct measurements of the performance of combinations of cellulase and substrate under simulated SSF conditions, without the saccharification results being complicated by factors that may influence the subsequent fermentation step. This assay has been used to compare the effectiveness of commercial and special in-house-producedTrichoderma reeSci. cellulase preparations in the saccharification of a standardized microcrystalline (Sigmacell) substrate and a dilute-acid pretreated lignocellulosic substrate. Initial results strongly suggest that enzyme preparations produced in the presence of the targeted lignocellulosic substrate will saccharify that substrate more effectively. These results call into question the widespread use of the “filter paper assay” as a reliable predictor of enzyme performance in the extensive hydrolysis of substrates that are quite different from filter paper in both physical properties and chemical composition.

     

Olefin hydrocarboxylation under mild conditions in nickel complex solutions

The hydrocarboxylation of α-olefins into carboxylic acids can be carried out in the presence of the dissolved complex NiCl₂(PPh₃)₂ at comparatively low CO pressures (below 0.8 MPa) with a fairly high product yield. Hexene-1 in acetic acid is converted into a mixture of heptanoic and 2-methylhexanoic acids, whose total yield is 40%. The molar ratio of the isomers is close to unity. However, the normal-chain product dominates at low CO pressures. Under the conditions examined, the catalyst is active only in the presence of a hydrogen (hydride ion) donor. The activity of the nickel complex can be markedly enhanced by preexposure of the reaction mixture to hydrogen pressure in the absence of CO. For the 0.8 MPa CO + 3.2 MPa H₂ gas mixture at 170°C, the turnover frequency of the catalyst is 28.5 and its activity is 4.8 h^?1.     

Palladium-catalysed reactions of 8-hydroxy- and 8-benzyloxy-5,7-diiodoquinoline under aminocarbonylation conditions

Various 5-carboxamido-7-iodo-8-benzyloxyquinolines were synthesised via selective aminocarbonylation of 5,7-diiodo-8-benzyloxyquinoline in the presence of ‘in situ’ generated palladium(0) catalysts. Under similar conditions (50 °C, 80 bar CO), 5,7-bis(N-tert-butyl-glyoxylamido)-8-hydroxyquinoline was obtained using tert-butylamine as N-nucleophile. The unprotected 5,7-diiodo-8-hydroxyquinoline underwent dehydroiodination resulting in 8-hydroxyquinoline as the major product.     

Factors affecting convergence in LMTO calculations of the electronic structure of complex crystals

This paper considers factors affecting the convergence of linear muffin- tin (MT) calculations in the atomic sphere approximation (LMTO- ASA) for the case of polyatomic compounds. Recommendations on choosing the radii of MT spheres, the initial energies (centers of gravity of the occupied bands), and the initial distribution of the atomic density of the charge are given. Methods to separate the correct and discard the false self- consistent result are suggested using the calculations of MgO and NaCl as examples. These approaches were tested and gave good results for the compounds ScPd, ScRh, LiH, WC, TlBr, CaO, MgO, KBr, CuPd, NaCl, LiF, CaS, ZnO, Cu₂O, TiO₂, YBa₂Cu₃O₇, Tl₂CaBa₂Cu₂O₈. Translated fromZhumal Strukturnoi Khimii, Vol. 38, No. 4, pp. 616–624, July–August, 1997.     

Determination of the stability constants of uranyl complex with 8-hydroxyquinolinium sulfate

8-Hydroxyquinoline (8-HOQ) is known as an important chelating agent for several metal ions. This compound is practically insoluble in water. For this reason, in this study its water soluble sulfate salt has been used for complexing uranyl ions and the stability constants of the complex have been determined. The Irving-Rosotti method computing the Calvin-Bjerrum pH-titration data, was applied. Finally, the stability constants of the complex formed between (8-HOQN-H)₂SO₄ and uranyl ions were found to be lgK₁=8.25 and lgK₂=4.15, the overall stability constant being {ie55-1}.     

Palladium complex catalyst immobilized on epoxy support under supercritical conditions

The aim of this research was to obtain a new-generation complex catalyst under supercritical carbon dioxide. A new complex catalyst based on epoxy resin cured with multifunctional polythiourethane was prepared. The use of polythiourethane as a hardener allowed us to introduce linking groups into the structure of the polymer without further functionalization of the resin. Additionally, the use of supercritical CO₂ enabled a more accurate and better distribution of the metal complex in the polymer matrix. The presence of the functional groups allowed us to obtain a catalyst wherein the metal centers had a different electronic structure and various degrees of oxidation, so that such a system was characterized by its high selectivity. The catalytic properties of the prepared catalysts were tested in the hydrogenation reaction. Research methods like time-of-flight secondary-ion mass spectrometry (ToF–SIMS), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and nitrogen BET surface area measurements were used to characterize polymeric support and heterogenized catalysts.     

Determination of complex forming conditions of 8-hydroxyquinoline with technetium-99m

Complex forming conditions of 8-hydroxyquinoline with^99mTc have been specified.^99mTcO₄ ^– has been reduced by SnCl₂ to a lower oxidation level. Labeling yields have been determined by ITLC (Instant Thin Layer Chromatography). Various parameters, such as pH, temperature, reaction time, ligand to SnCl₂ ratio, which can affect the labeling yields, have been determined. Optimum conditions are 4–7 for pH; 15–20°C (room) for temperature; 1.55 for ligand to SnCl₂ ratio and 5 min for reaction time.     

Assessment of polyelectrolyte coating stability under dynamic buffer conditions in CE

Dynamic buffer conditions are present in many electrophoretically driven separations. Polyelectrolyte multilayer coatings have been employed in CE because of their chemical and physical stability as well as their ease of application. The goal of this study is to measure the effect of dynamic changes in buffer pH on flow using a real-time method for measuring EOF. Polyelectrolyte multilayers (PEMs) were composed of pairs of strong or completely ionized polyelectrolytes including poly(diallyldimethylammonium) chloride and poly(styrene sulfonate) and weak or ionizable polyelectrolytes including poly(allylamine) and poly(methacrylic acid). Polyelectrolyte multilayers of varying thicknesses (3, 4, 7, 8, 15, or 16 layers) were also studied. While the magnitude of the EOF was monitored every 2 s, the buffer pH was exchanged from a relatively basic pH (7.1) to increasingly acidic pHs (6.6, 6.1, 5.5, and 5.1). Strong polyelectrolytes responded minimally to changes in buffer pH (<1%), whereas substantial (>10%) and sometimes irreversible changes were measured with weak polyelectrolytes. Thicker coatings resulted in a similar magnitude of response but were more likely to degrade in response to buffer pH changes. The most stable coatings were formed from thinner layers of strong polyelectrolytes.     

Physical and chemical stability of marine lipid-based liposomes under acid conditions

Liposomes made from a marine lipid extract containing a high polyunsaturated fatty lipid ratio were submitted to large pH variations, ranging from 1 to 8. Shape transformations were followed by video microscopy using giant liposomes and micromanipulation experiments. Acidification induced a decrease of the vesicle size simultaneous to the appearance of invaginations. These pH-dependent structural rearrangements were interpreted in terms of osmotic shocks and chemical modifications of the membranes. Liposomes produced by direct filtration were studied using turbidity measurements and optical microscopy observations. A low pH led to an instantaneous vesicle aggregation and to complex supramolecular and/or morphological changes as a function of time. The subsequent buffer neutralization of the liposome suspensions induced a partial reversion of the aggregation phenomenon while the structural membrane rearrangements were persisting. Furthermore, weak chemical degradations (oxidation and hydrolysis) were evidenced when the vesicles were incubated at low pH up to a 24-h incubation time. Thus, although acidification revealed liposome size and shape changes, the bilayer structure was maintained indicating that marine lipid-based liposomes could be used as oral administration vectors.     

Hydrolytic stability of nitrogenous-heteroaryltrifluoroborates under aqueous conditions at near neutral pH

The hydrolytic stability of heteroaryltrifluoroborates under physiological conditions has been analyzed by ¹⁹F NMR spectroscopy and is found to be greatly enhanced by the presence of endocyclic ring nitrogens. Stability is further enhanced by the presence of exocyclic electron withdrawing substituents. As with aryltrifluoroborates, NMR analysis suggests that the hydrolysis proceeds via single rate-determining step reflecting loss of the first fluoride atom. The stability of these complexes is significant both in terms of metal catalyzed cross-coupling reactions as well as the potential for generating boronic acid based ¹⁸F-PET imaging agents.     

Factors affecting stability and equilibria of free radicals—VIII : 1-Cyano-2,2-diphenylhydrazyl

The oxidation of 3,3-diphenylcarbazonitrile (1-cyano-2,2-diphenylhydrazine) with lead dioxide or tetraacetate affords the stable violet free radical 1-cyano-2,2-diphenylhydrazyl whose ESR spectra in solution and solid state are reported and discussed.