Production of antitumoral retamycin during fed-batch fermentations of Streptomyces olindensis

Fed-batch runs were performed in order to correlate the production of retamycin, an anthracycline antibiotic produced by Streptomyces olindensis in submerged cultures, with the specific growth rate. Maximum retamycin production was achieved with an exponential feed rate, controlling the specific growth rate at a low value (0.03 h-1, about 10% of the maximum specific growth rate). Control of the specific growth rate at higher values (0.10 and 0.17 h-1) caused a decrease in antibiotic production. Morphology, assessed by image analysis, was shown to be highly relevant in this process. Cell growth mainly in the form of clumps (90% clumps and 10% free filaments) led to better results than growth as clumps (75%) and free filaments (25%).     

Preliminary characterization of anhydrous ethanol used in Brazil as automotive fuel

This work reports preliminary studies on the characterisation of anhydrous ethanol (AEA) used as an automotive fuel mixed with gasoline in Porto Alegre (South Brazil). Pre-concentration of the impurities contained in 1000 ml of AEA was carried on through solid-phase extraction using XAD4 resin. The main compounds in the extract were identified by means of spectral data from the library of the equipment. The concentrate was then fractionated using a preparative liquid chromatographic column filled with activated silica gel and the elution procedure was carried out with, n-hexane, n-hexane-benzene (1:1, v/v) and dichloromethane. Prior to analysis by GC-MS, each fraction was reduced to 1 ml with a gentle stream of nitrogen. Saturated linear hydrocarbons and aromatic hydrocarbons eluted in the first fraction and oxygenated compounds such as aldehydes. ketones and alcohols, eluted in the second one. were the main compounds detected in the sample.     

NMR-Spektren vontrans—Chalcon-oxim,-semicarbazon und-thiosemicarbazon und ihren cyclischen Isomeren (3,5-Diphenyl-2-isoxazolin und 1-substituierte 3,5-Diphenyl-2-pyrazoline)

Zusammenfassung Frühere Strukturvorschläge für dastrans-Chalcon-oxim, semicarbazon und thiosemicarbazon¹ werden mit Hilfe von NMR-Spektren richtiggestellt: Die sauer katalysierte Reaktion führt zwar zum Oxim, Semicarbazon und Thiosemicarbazon destrans-Chalcons; basische Katalysatoren bewirken dagegen eine interne Cyclisierung zu 3,5-Diphenyl-2-isoxazolin bzw. zu 1-substituierten 3,5-Diphenyl-2-pyrazolinen. Die Zuordnungen in den NMR-Spektren wurden durch Vergleich mittrans-Dypnon und seinem Semicarbazon getroffen.

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NMR spectra of trans-chalcone oxime, semicarbazone and thiosemicarbazone and their cyclic isomers (3,5-diphenyl-2-isoxazoline and 1-substituted 3,5-diphenyl-2-pyrazolines)

Earlier tentatively assigned structures fortrans-chalcone oxime, semicarbazone and thiosemicarbazone, resp., have been corrected by means of NMR spectra: open-chain structures have been found for the title compounds formed in the acid catalyzed reaction, whereas basic catalysts lead to intramolecular cyclization with formation of 3,5-diphenyl-2-isoxazoline and 1-substituted 3,5-diphenyl-2-pyrazolines resp. Assignments in the NMR spectra were made by comparison with those from authentic samples oftrans-dypnone and its semicarbazone.

     

Functionalization of single-walled carbon nanotubes via the Bingel reaction

Single-walled carbon nanotubes have been cyclopropanated under Bingel reaction conditions, and the functionalized nanotubes have been characterized by atomic force microscopy using "chemical tagging" techniques.     

Study of process parameters for starch,gluten, and glycerol mixtures

This work involved a study of the effect of processing variables (temperature, water content, rotor speed, and time) on the mechanical properties of starch:gluten:glycerol mixtures in the weight ratio of 40:40:20. The properties of the materials were affected by the processing variables. The torque decreased with water content, indicating that water facilitates the plasticization of mixtures, whereas the increase in temperature accelerated the evaporation of water, thus increasing the torque. Ultimate tensile strength was achieved at the lowest temperature (110°C) and the highest water content (20%), whereas maximum elongation was achieved for the material processed at the highest temperature, 150°C, and the fastest rotor speed, 70 rpm. Copyright © 2007 John Wiley & Sons, Ltd.     

Behaviour of Pluronic P84 block copolymer micelles above the gelification temperature as probed by positron annihilation lifetime spectroscopy

The new method based on positron annihilation lifetime spectroscopy (PALS) to determine both the mean core radius, R(core), and aggregation number, N(ag), of micelles is applied to the study of aqueous solutions of the triblock Pluronic P84 copolymer as a function of temperature (T), beyond the gelification point (334 K). Two long-lived components appear in the PALS spectra, ascribed to triplet positronium in the water bulk (o-Ps(aq)) and in the organic core of the micelles (o-Ps(org)). Of the various fitting parameters, only the lifetime of the latter species, tau4, and the micellar parameters, R(core) and N(ag), disclose the occurrence of gelification by first increasing up to 334 K, then decreasing. By contrast to what is known in case of phase transition, none of the parameters shows any abrupt change at 334 K, whereas the macroscopic viscosity of the solutions suffers a drastic increase. This is attributed to the fact that positronium is sensitive to the microviscosity of the solutions. At the transition point, the properties of the polyoxipropylene aggregates forming the organic core of the P84 micelles are not greatly affected. Furthermore, the fact that the experimental N(ag) values coincide with those calculated for spheres, from the R(core) values, indicates that the shape of the P84 cores does not change significantly after gelification. The onset of gelification results from a decrease in the hydrogen bonding interactions in the solution with an ensuing relative increase in the interactions between the polyoxipropylene (PPO) groups, initially forming the corona of the P84 micelles, in an intermicellar mode. This increased solicitation of the PPO groups outside their initial location would result in depletion in the number of surfactant molecules forming the micelles, viz. a decrease in both R(core) and N(ag) above 334 K. From the data, additional information can be gained regarding the local viscosity and surface tension in the micellar cores.     

A New ent‐Kaurane Diterpene from Stems of Alibertia macrophylla K. Schum. (Rubiaceae)

Phytochemical investigations of the stems of a specimen of Alibertia macrophylla led to the isolation and characterization of the new diterpene ent‐kaurane‐2β,3α,16α‐triol ( 1 ), along with triterpenes 2 – 8 , iridoids 9 – 12 , and phenolic acids 13 – 15 . The structure of 1 was established based on spectroscopic studies (¹H‐ and ¹³C‐NMR, IR, and HR‐ESI‐MS). This is the first report of the isolation of a diterpene from the Alibertia genus in Rubiaceae.