Comparative ethanol productivities of different Zymomonas recombinants fermenting oat hull hydrolysate

Iogen Corporation of Ottawa, Canada, has recently built a 50 t/d biomass-to-ethanol demonstration plant adjacent to its enzyme production facility. Iogen has partnered with the University of Toronto to test the C6/C5 cofermentation performance characteristics of National Renewable Energy Laboratory's metabolically engineered Zymomonas mobilis using its biomass hydrolysates. In this study, the biomass feedstock was an agricultural waste, namely oat hulls, which was hydrolyzed in a proprietary two-stage process involving pretreatment with dilute sulfuric acid at 200–250°C, followed by cellulase hydrolysis. The oat hull hydrolysate (OHH) contained glucose, xylose, and arabinose in a mass ratio of about 8:3:0.5. Fermentation media, prepared from diluted hydrolysate, were nutritionally amended with 2.5 mL/L of corn steep liquor (50% solids) and 1.2 g/L of diammonium phosphate. The estimated cost for large-scale ethanol production using this minimal level of nutrient supplementation was 4.4c/gal of ethanol. This work examined the growth and fermentation performance of xyloseutilizing, tetracycline-resistant, plasmid-bearing, patented, recombinant Z. mobilis cultures: CP4:pZB5, ZM4:pZB5, 39676:pZB4L, and a hardwood prehydrolysate-adapted variant of 39676:pZB4L (designated asthe “adapted” strain). In pH-stat batch fermentations with unconditioned OHH containing 6% (w/v) glucose, 3% xylose, and 0.75% acetic acid, rec Zm ZM4:pZB5 gave the best performance with a fermentation time of 30h, followed by CP4:pZB5 at 48h, with corresponding volumetric productivities of 1.4 and 0.89 g/(L·h), respectively. Based on the available glucose and xylose, the process ethanol yield for both strains was 0.47 g/g (92% conversion efficiency). At 48 h, the process yield for rec Zm 39676:pZB4L and the adapted strain was 0.32 and 0.34 g/g, respectively. None of the test strains was able to fermentarabinose. Acetic acid tolerance appeared to be a major determining factor in cofermentation performance.     

On the number of generators of Cohen-Macaulay ideals

Several bounds on the number of generators of Cohen-Macaulay ideals known in the literature follow from a simple inequality which bounds the number of generators of such ideals in terms of mixed multiplicities. Results of Cohen and Akizuki, Abhyankar, Sally, Rees and Boratynski-Eisenbud-Rees are deduced very easily from this inequality.

     

Room-temperature phosphorescence,sensitized phosphorescence and fluorescence of licit and illicit drugs enhanced by organized media

The ability of microscopically organized media, in the form of surfactant micelles and α- and β-cyclodextrins, to enhance the luminescence phenomena of several licit and illicit drugs is discussed. Because physiological samples are not often amenable to direct spectrometric measurements without pretreatment, the applicability of these organized media to liquid chromatography is also considered. Fluorescence enhancements for certain hallucinogenic drugs such as N,N-dimethyltryptamine, mescaline and ibogaine are seen in cyclodextrin media compared to conventional, homogeneous solutions. Heavy-atom substituted sodium dodecyl sulfate micelles induce phosphorescence from cationic and/or hydrophobic drugs at room temperature in fluid solution; drugs such as propranolol, diflunisal, naphalozine, and selected quinoline derivatives can be determined conveniently. Sensitized phosphorescence is observed for several drugs including brethine, cocaine, didrate, estradiol, meprobarbital, methaqualone, phenobarbital, and sulfanilamide; it can be enhanced markedly when micellar solutions are used as the solvent. The energy-transfer step is facilitated by the organizing ability of the micelle; limits of detection can be decreased by over two orders of magnitude compared to homogeneous solvents. Sensitized phosphorescence can also be measured in cyclodextrin solutions, but the detectability is inferior to that in micellar media. Which form of organized medium is superior for determination of drugs is discussed.     

A study of the analytical behaviour of selected synthetic and naturally occurring coumarins using liquid chromatography, ion trap mass spectrometry, gas chromatography and polarography and the construction of an appropriate database for coumarin characterisation

The aim of this paper is to provide analytical chemical information on a range of naturally occurring and synthetic coumarins. This analytical chemical information on liquid chromatography-electrospray ionisation-mass spectrometry (HPLC-ESI-MS), ion trap mass spectrometry (ESI-MSⁿ), gas chromatography-flame ionisation detection (GLC-FID) and polarographic behaviour is then incorporated into a database which is of use in identifying unknown coumarins isolated from natural sources. This paper is also concerned with understanding the effect of functional groups in coumarins on their analytical chemical behaviour using the above techniques.     

Kinetics of ethylene polymerization reactions with chromium oxide catalysts

Principal kinetic data are presented for ethylene homopolymerization and ethylene/1‐hexene copolymerization reactions with two types of chromium oxide catalyst. The reaction rate of the homopolymerization reaction is first order with respect to ethylene concentration (both for gas‐phase and slurry reactions); its effective activation energy is 10.2 kcal/mol (42.8 kJ/mol). The r₁ value for ethylene/1‐hexene copolymerization reactions with the catalysts is ～30, which places these catalysts in terms of efficiency of α‐olefin copolymerization with ethylene between metallocene catalysts (r₁ ～ 20) and Ti‐based Ziegler‐Natta catalysts (r₁ in the 80–120 range). GPC, DSC, and Crystaf data for ethylene/1‐hexene copolymers of different compositions produced with the catalysts show that the reaction products have broad molecular weight and compositional distributions. A combination of kinetic data and structural data for the copolymers provided detailed information about the frequency of chain transfer reactions for several types of active centers present in the catalysts, their copolymerization efficiency, and stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5315–5329, 2008     

Numerical solution of a free surface problem by a boundary element method

This paper describes a method for the numerical solution of a Riabouchinsky cavity flow. Application of a boundary element method leads to a system of non-linear equations. The mild singularity appearing at the separation point is treated with the introduction of a curved boundary element, which satisfies the exact behaviour of the free boundary in that neighbourhood.     

Clausal resolution for normal modal logics

We present a clausal resolution-based method for normal modal logics. Differently from other approaches, where inference rules are based on the syntax of a particular set of axioms, we focus on the restrictions imposed on the binary accessibility relation for each particular normal logic. We provide soundness and completeness results for all fifteen families of multi-modal normal logics whose accessibility relations have the property of being non-restricted, reflexive, serial, transitive, Euclidean, or symmetric.