Studies on polymers and composites from lignin and fiber derived from sugar cane

Sugarcane fiber (i.e. bagasse) lignin has a larger fraction of aromatics unsubstitution in the ortho position than hardwood or softwood lignin and hence has the greater ability to be derivatized. Furthermore, organosolv lignin has a higher purity than sulfonated and kraft lignins. This work examines the purification of organosolv lignin derived from bagasse and the physico‐chemical properties of the lignin and lignin‐phenol formaldehyde (PF) resin coatings, and composites. The wetability tests have shown that lignin and lignin‐PF resin films are effective water barrier coatings, though the contact angles of lignin‐PF resin films were considerably less than the wax films. The overall mechanical properties (i.e. peak stress, peak strain and modulus) of the bagasse fiber composites were lower than the values obtained with the composites without the inclusion of bagasse fiber. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of aliphatic acids, furfural, and phenolic compounds on Debaryomyces hansenii CCMI 941

Debaryomyces hansenii is a polyol overproducing yeast that can have a potential use for upgrading lignocellulosic hydrolysates. Therefore, the establishment of its tolerance to metabolic inhibitors found in hydrolysates is of major interest. We studied the effects of selected aliphatic acids, phenolic compounds, and furfural. Acetic acid favored biomass production for concentrations <6.0 g/L. Formic acid was more toxic than acetic acid and induced xylitol accumulation (maximum yield of 0.21 g/g of xylose). All tested phenolics strongly decreased the specific growth rate. Increased toxicity was found for hydroquinone, syringaldehyde, and 4-methylcatechol and was correlated to the compound’s hydrophobicity. Increasing the amount of furfural led to longer lag phases and had a detrimental effect on specific growth rate and biomass productivity.     

Reaction of alkenes with hydrogen peroxide and sodium iodide: a nonenzymatic biogenic-like approach to iodohydrins

An efficient protocol to synthesize iodohydrins from alkenes is presented. Reactions were conducted in aqueous media using safe and readily available sodium iodide (the most abundant form of the element), and a highly convenient oxidant such as hydrogen peroxide. Addition of a protic acid triggers a faster and efficient process, a role formally related to that played by haloperoxidase enzymes in naturally occurring transformations. The successful application of these conditions to multigram scale preparations and over natural products derivatives is also discussed.     

Comparative assessment of solid-phase extraction clean-up procedures, GC columns and perfluoroacylation reagents for determination of type B trichothecenes in wheat by GC-ECD

Various solid-phase extraction (SPE) procedures for clean-up, two perfluoroacylation reagents (pentafluoropropionic anhydride (PFPA) and heptafluorobutyric anhydride (HFBA)) and two chromatographic columns (HP-1701 and HP-5) have been assessed comparatively to achieve the determination of type B trichothecenes (deoxynivalenol (DON), nivalenol (NIV), 3- and 15-acetyldeoxynivalenol (3- and 15-ADON)) in wheat grain by gas chromatography (GC)-electron-capture detection (ECD). Spiked wheat samples were extracted with acetonitrile-water (84:16, v/v). Tested SPE procedures were MycoSep 225 column, Florisil and different cartridges prepared in the laboratory with mixtures of various sorbents like alumina, Celite 545, C18, silica and charcoal. We propose MycoSep 225 column, and cartridges made with alumina-charcoal-silica and alumina-charcoal-C18 silica mixtures as clean-up procedures on the basis of recovery values (89.6, 87.3 and 86.1% for deoxynivalenol, respectively, at 1.0 mg/kg spiking level). The two last procedures are less expensive. Pentafluoropropionic anhydride was more stable against moisture and less expensive, while recoveries were similar to those obtained with heptafluorobutyric anhydride. HP-1701 column can separate 3- and 15-acetyldeoxynivalenol derivatives while HP-5 cannot, although this last column provided lower bleed and better sensitivity.     

Characterization of xylitol dehydrogenase from debaryomyces hansenii

The xylitol dehydrogenase (EC 1.1.1.9) from xylose-grown cells ofDebaryomyces hansenii was partially purified in two Chromatographic steps, and characterization studies were carried out in order to inves tigate the role of the xylitol dehydrogenase-catalyzed step in the regu lation of D-xylose metabolism. The enzyme was most active at pH 9.0–9.5, and exhibited a broad polyol specificity. The Michaelis con stants for xylitol and NAD⁺ were 16.5 and 0.55 mM, respectively. Ca²⁺, Mg²⁺, and Mn²⁺ did not affect the enzyme activity. Conversely, Zn²⁺, Cd²⁺, and Co²⁺ strongly inhibited the enzyme activity. It was concluded that NAD⁺-xylitol dehydrogenase from D.hansenii has similarities with other xylose-fermenting yeasts in respect to optimal pH, substrate specificity, and K_m value for xylitol, and therefore should be named L-iditol:NAD⁺-5-oxidoreductase (EC 1.1.1.14). The reason D.hansenii is a good xylitol producer is not because of its value of K_m for xylitol, which is low enough to assure its fast oxidation by NAD⁺ xylitol dehydrogenase. However, a higher K_m value of xylitol dehydro genase for NAD⁺ compared to theK _m values of other xylose-ferment ing yeasts may be responsible for the higher xylitol yields.     

PHOTOSENSITIZATION BY FENOFIBRATE. II. In vitro PHOTOTOXICITY OF THE MAJOR METABOLITES

Fenofibric acid, the major metabolite of fenofibrate, was found to be photolabile. Its irradiation in aqueous solution gave rise to two photoproducts, whose formation involves photodecarboxylation of the dissociated acid to an aryloxy-substituted carbanion, which is directly protonated or, alternatively, undergoes a Wittig rearrangement. A comparative in vitro phototoxicity study has been carried out on the anti-hyperlipoproteinemic drug fenofibrate, its metabolites and the photoproducts of fenofibric acid. Fenofibrate, fenofibric acid and its two photoproducts were found to be active when examined by the photohemolysis test and were able to photosensitize peroxidation of linoleic acid, as evidenced by the UV monitoring of dienic hydroperoxides. In summary, the major metabolite of fenofibrate (fenofibric acid), as well as its photoproducts, are phototoxic in vitro . This behavior can be attributed to the fact that the four compounds retain the benzophenone chromophore present in fenofibrate and is indicative of free radicalmediated photosensitization. In agreement with this rationalization, the metabolites with a reduced ketone functionality exhibit no detectable in vitro phototoxicity.     

A ferrocene-based heteroditopic ligand for electrochemical sensing of cations and anions

A ferrocene-based heteroditopic receptor containing urea and crown ether units shows electrochemical responses to dihydrogenphosphate and fluoride anions. K+ cations can only be detected in the presence of dihydrogenphosphate.     

Constant neutral loss scanning for the characterization of glycerol phosphatidylcholine phospholipids

The product-ion spectra of the sodiated molecules of glycerol phosphatidylcholine phospholipids (GPC) were obtained, using fast-atom bombardment (FAB) as the ionization method, in a tandem mass spectrometer. The product-ion spectra of these sodiated molecules of GPCs were found to differ significantly from those of the protonated GPC molecules. This difference is due to the absence of the ion of m/z 184 (protonated-phosphocholine moiety) and to the presence of an ion resulting from the loss of trimethylamine (m=59 Da) from the polar head group, which is the dominant fragmentation. This characteristic neutral loss provides a means of identification of this class of phospholipids and of differentiation from other phospholipid classes in complex mixtures by performing a constant-neutral-loss scan of 59.     

Michael additions of benzoins versus Michael-Stetter additions of aldehydes

Triethylamine catalyzed Michael additions of benzoins to chalcone can prevail over the expected Michael-Stetter additions when certain thiazolium ion conjugate bases - prepared $\text{in situ}$ from the pertinent thiazolium salts and triethylamine- are used as catalysts.