Biosurfactant production by Rhodococcus erythropolis grown on glycerol as sole carbon source

The production of biosurfactant by Rhodococcus erythropolis during the growth on glycerol was investigated. The process was carried out at 28°C in a 1.5-L bioreactor using glycerol as carbon source. The bioprocess was monitored through measurements of biosurfactant concentration and glycerol consumption. After 51 h of cultivation, 1.7 g/L of biosurfactant, surface, and interfacial tensions values (with n-hexadecane) of 43 and 15 mN/m, respectively, 67% of Emulsifying Index (E ₂₄), and 94% of oil removal were obtained. The use of glycerol rather than what happens with hydrophobic carbon source allowed the release of the biosurfactant, originally associated to the cell wall.     

Evaluation of the orientation coefficient for the c axis in poly(ethylene terephthalate) fibers

The literature methods for the determination of the mean of the crystallite orientation distribution for the c axis, that is of the orientation coefficient f_c, for poly(ethylene terephthalate) (PET), based on the azimuthal scan of the (1 05) reflection, are reviewed. These methods appear unsuitable for samples presenting the “tilted orientation”; that is, the molecular chain axis inclined by some degrees with respect to the fiber axis, as frequently occurs for PET fibers. A new method for the determination of f_c for PET, also based on the azimuthal scan of the (1 05) reflection (which can be applied also to samples with “tilted orientation”), is proposed. This method implies as a first step the determination of the tilt angle, for which the complete fiber pattern is required. A possible simplifying assumption, which allows use of the sole azimuthal (1 05) profile and makes the method also applicable to poorly oriented samples (for which the determination of the tilt angle is not easy), is also discussed. © 1995 John Wiley & Sons, Inc.     

Density-functional theory structures of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complexes for ions across the lanthanide series

The use of organically chelated lanthanides in diagnosis and treatment is a rapidly growing field in medicine. In order to gain a deeper understanding into the properties of these chelates, particularly spectroscopic, density-functional calculations have been performed on a series of lanthanide ions chelated with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid. Based on the results of these calculations, it has been concluded that the local symmetry experienced by the chelated lanthanide ion may be treated as being axial, which will make the interpretation of their spectroscopic properties greatly simplified. It has also been suggested that the so-called "capping" water molecule at the ninth coordination position of the lanthanide is hydrogen bonded to the acetate oxygens of the sidearms, rather than coordinated as the ninth ligand of the lanthanide.     

Biohydrolysis of urea from urea-bearing wastewater

Biological stabilization of urea is a two staged process; (i) urea hydrolysis and (ii) ammonia stripping/nitrification-denitrification. Ammonia thus produced is either stripped off by usual methods or after converting into nitrate using chemoautotrophic bacteria. On denitrification, nitrate is finally converted into nitrogen gas by means of heterotrophic bacteria. Details of stabilization of urea from urea bearing wastewater using urea biohydrolyser are presented in this paper.     

pH-stat techniques in titrimetric analysis: IV. pH-stat monitoring of chelatometric titrations

The theory of pH-stat chelatometric titrations recently developed [Anal. Chim. Acta 456 (2002) 313] is experimentally substantiated here. The titrations of four representative doubly charged cations having different behaviour (copper, zinc, calcium, magnesium) are taken as examples. Copper is titratable between pH 3 and 5, zinc between 3 and 6, calcium between 6 and 10, and magnesium between 7 and 10. The shapes of the titration plots agree well with the theory, accounting for simultaneous equilibria involving proton exchange. The technique yields accurate and precise results, which compare favourably with those of other instrumental techniques, in particular photometric titrations.     

Matrix-assisted laser desorption/ionisation mass spectrometry in the study of polycondensation of Ti(OBun)4 in the presence of Si(OEt)4

The hydrolysis-polycondensation behaviour of alcoholic solutions containing Si(OEt)4 and Ti(OBun)4, in different molar ratios (Si/Ti = 10-0.2), was analysed by laser desorption/ionisation (LDI) and matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry. The solutions were prepared using operating conditions usually employed in the sol-gel synthesis of SiO2-TiO2 materials. In accord with the well-known procedures for controlling the different chemical reactivities of the alkoxides, the pre-hydrolysis of the slower reacting silicon ethoxide and the chelation by acetylacetone of the faster reacting titanium butoxide were performed before mass spectrometric analysis. While LDI-MS did not provide evidence for the presence of mixed Si-Ti species in samples obtained from these reactions, MALDI-MS of samples diluted with chloroform and using 2,5-dihydroxybenzoic acid (DHB) as matrix led to detection of various oligomers with different contents of Si and Ti atoms. The results suggest that the formation of Si-Ti mixed oligomers seems to be the favoured process, especially for solutions in which one of the two components is diluted.     

A "catch and release" strategy for the parallel synthesis of 2,4,5-trisubstituted pyrimidines

A resin capture and release strategy for making a combinatorial array of 2,4,5-trisubstituted pyrimidines is demonstrated by capturing beta-ketoesters and beta-ketoamides on a solid-supported piperazine. Through a cyclocondensation reaction, the solid-supported enaminone is reacted with several guanidines under heating or microwave irradiation affording the corresponding pyrimidines in good yield and chemical purity directly on solution. After this final step, the support can be effectively recycled.     

Aromatic polyamides with pendent acetoxybenzamide groups and thin films made therefrom

New aromatic polyamides containing 1,3,4-oxadiazole or benzonitrile units in the main chain and 5-(4-acetoxybenzamido) groups in the side chain have been synthesized and their properties have been characterized and compared with those of related polyamides and polyoxadiazole-amides. These polymers show good thermal stability, with initial decomposition temperature being at about 300 °C and glass transition temperature in the range of 260-280 °C. They are easily soluble in certain solvents such as N-methylpyrrolidinone (NMP), N,N^′-dimethylacetamide (DMA) and N,N^′-dimethylformamide (DMF) and can be cast from solutions into thin flexible films. The polymer films had tensile strengths in the range of 77-97 MPa, tensile moduli in the range of 2.3-2.6 GPa and elongation at break values ranging from 6% to 24%. One of the polymers containing the 1,3,4-oxadiazole ring exhibited blue fluorescence.