Physiological aspects involved in production of xylanolytic enzymes by deep-sea hyperthermophilic archaeon Pyrodictium abyssi

Xylanases (EC3.2.1.8) catalyze the hydrolysis of xylan, the major constituent of hemicellulose. The use of these enzymes could greatly improve the overall economics of processing lignocellulosic materials for the generation of liquid fuels and chemicals. The hyperthermophilic archaeon Pyrodictium abyssi, which was originally isolated from marine hot abyssal sites, grows optimally at 97°C and is a prospective source of highly thermostable xylanase. Its endoxylanase was shown to be highly thermostable (over 100 m in at 105°C) and active even at 110°C. The growth of the deep-sea archaeon P. abyssi was investigated using different culture techniques. Among the carbohydrates used, beech wood xylan, birch wood glucuronoxylan and the arabinoxylan from oats pelt appeared to be good inducers for endoxylanase and β-xylosidase production. The highest production of arabinofuranosidase, however, was detected in the cell extracts after growth on xylose and pyruvate, indicating that the intermediate of the tricarboxylic acid cycle acted as a nonrepressing carbon source for the production of thi enzyme. Electron microscopic studies did not show a significant difference in the cell surface (e.g., xylanosomes) when P. abyssi cells were grown on different carbohydrates. The main kinetic parameters of the organism have been determined. The cell yield was shown to be very low owing to incomplete substrate utilization, but a very high maximal specific growth rate was determined (μ_max=0.0195) at 90°C and pH 6.0. We also give information on the problems that arise during the fermentation of this hyperthermophilic archaeon at elevated temperatures.     

Thermal degradation of α-pinene using a Py–GC/MS

Mediterranean forest fires may be accelerated, partly due to biogenic volatile organic compounds produced by vegetation, mainly monoterpenes largely represented by α-pinene. To model the propagation of biomass combustion, it is necessary to study the flammability of the produced gas mixture, and thus, necessary to identify the emitted volatile compounds. However, thermal degradation of monoterpenes is rarely experimented above 300 °C, whereas forest fires reach higher temperatures. Thus, in this work, we experimented a 2-min pyrolysis of α-pinene at temperatures from 300 to 800 °C using a Py–GC/MS device. Less than 1% of pyrolysis products were detected at 300 and 400 °C. The pyrolysis products increased then from 14 compounds at 500 °C to 31 compounds at 800 °C. Degradation of α-pinene started with its isomerization at 500 °C. At 800 °C, alkenes detected increased as well as aromatics produced through the Diels–Alder mechanism. These results are consistent with the literature on thermal degradation of α- and β-pinene presented in our article.

     

A Convenient Synthesis of 2′- OR 4′-Hydroxycocaine

Abstract: A short, convenient and efficient synthesis of 2′- or 4′-hydroxycocaine is described. The key step involved selective hydrolysis/transesterification of the acetoxy group of 2′- or 4′-acetoxycocaine in methanol saturated with dry HCl gas.     

The He(I) photoelectron spectra of some γ-substituted Co(III) acetylacetonate complexes

The He(I) photoelectron spectra of the complexes of Co(III) with acetylacetone and several derivatives are reported. The ionization potentials of metal-localized d-electrons and ligand π-orbitals are used to probe the extent of metal-to-ligand π-bonding and possible aromatic character in the chelate ring.     

Acuminatanol, the first 2′,2?-bis-dihydrobiflavonol from the aqueous extract of Trichoscypha acuminata

One new 3′,4′,5′,5,7-pentahydroxy-2′,2?-bis-dihydrobiflavonol, acuminatanol (1), was obtained from the aqueous extract of Trichoscypha acuminata. The structure elucidation process was performed primarily utilizing a capillary scale NMR probe. Acuminatanol (1) is the first example of a bis-dihydroflavonol linked exclusively via the B-rings at C-2′ and C-2? positions. To date, it is the first naturally-occurring compound reported from the genus Trichoscypha, and the first new natural product published from our compound libraries generated from the aqueous extracts of American and African plants.     

Numerical simulation of soot optical diagnostics in non-optically thin media

The global aim of this paper consists of quantifying the effect of optically thick media on LII measurements. The paper emphasises in a simple, general two-phase case, the potential “signal trapping” due to the multiple scattering of light by soot particles. A statistical Monte Carlo approach has been used in the frame of a parametric study. This method allows testing separately the distinct influences of parameters like soot volume fraction, sphere diameter, optical path length or aggregate shape. As a first result of this numerical study, the theoretical validity range of experimental techniques can be determined when applied to a larger domain than the strictly optically thin one. A numerical tool for a better understanding of mixed and complex phenomena has been realised. Here the approach is validated on the simplest geometrical configuration; it will be applied to a real combustion chamber configuration later. PACS 78.70.-g