Non-conventional Conditions Research Articles

Multi-scale Features in Recent Development of Enzymic Biocatalyst Systems

Functional relation among elements of different size scales in a system is probably a main challenge across the areas of the science of engineering ever since their emergence. Multi-scale time and size correlation for description and prediction of complex systems, however, has been systematically examined only recently with the aid of new computational tools. In the pursuit of efficient and sustainable chemical processing technologies, people have seen a growing emphasis on synthetic biotechnology in recent R&D efforts. In particular, industrial enzyme technologies are attracting enormous attention. Having been traditionally developed for food and detergent applications, industrial enzyme technologies are being re-examined and tested to their limits to keep abreast of the challenges in drug, biochemical, and the emerging biorenewable energy industries. Toward that, enzymes are required to function in non-conventional conditions, such as organic solvents, extreme pH, and temperatures; they also have to compete against alternative chemical technologies in terms of costs and efficiency. Accordingly, enzymic biocatalyst systems are being tackled dynamically at all size levels through efforts ranging from molecular level protein engineering and modification, nanoscale structure fabrication, and microenvironment manipulation to the construction of microchip devices and macroscopic industrial bioreactors and devices. These efforts are probably still on a case-to-case trial basis without much consideration of cross-scale correlations. Discovering, understanding, and controlling of the common features that relate functions of biocatalysts at different size scales may eventually be realized in future.

Performance of Statistical Process Control Tools under Different Plant Operation Strategies

The outputs of statistical process control (SPC) tools developed for fault detection are comparatively examined while applied to actual data collected in an industrial plant. The influence of added information gathered from the plant operation under different strategies is analyzed. Particularly, standard principal component analysis (PCA), kernel PCA and the Hotelling's T2 charts are inspected for a reported problem. The effect of training the tools either with an extended historic databank obtained under standard operation, or including also non-conventional conditions, is studied. The ability of the tools to provide a specific alarm and identify the responsible variable is examined by analyzing the contributions per variable to the SPE and the T2 statistics. In addition, the capacity of the tested tools to adapt to a new operation strategy is compared.

Characterization of Italian Cheeses Ripened Under Nonconventional Conditions

Four Italian cheeses (Casciotta di Urbino, Barricato San Martino, Vento d’Estate, and Ubriaco di Raboso) nonconventionally ripened under different plant materials (walnut leaves, herbs, hay, and wine by-products, respectively) were compared for compositional, microbiological, biochemical, and volatile profile characteristics. Mean values for gross composition were rather similar. Because primary starters were not used for manufacture, the endogenous lactic acid bacteria were mainly present (7.0 to 9.0 log10 cfu/g). Except for Lactobacillus paracasei and Leuconostoc mesenteroides, which were commonly identified in 3 cheeses, Lactococcus lactis, Enterococcus sanguinicola, Lactobacillus brevis, Enterococcus durans/Enterococcus faecium, Lactobacillus plantarum, and Weissella cibaria/Weissella confusa were variously found in the 4 cheeses. Random amplification of polymorphic DNA-PCR analysis showed the biodiversity among the strains, and the species of lactobacilli were in part grouped according to their origin. As shown by the principal component analysis of reverse-phase fast protein liquid chromatography data for the pH 4.6-soluble fractions and by the determination of free AA, the secondary proteolysis of Barricato San Martino and Vento d’Estate mainly differed from the other 2 cheeses. Purge-and-trap and solid-phase microextraction were coupled with gas chromatography-mass spectrometry to determine volatile compounds. Vento d’Estate showed the highest levels of almost all chemical classes, and Casciotta di Urbino was characterized by a very low level of volatile components. Esters, ketones, and terpenes were the chemical classes that mainly differentiated the cheeses. Several volatile compounds seemed to be released directly from the plant materials used for ripening, especially terpenes for Vento d’Estate cheese. The lowest level of volatile free fatty acids was found in Casciotta d’Urbino, in which rennet paste was not used during manufacture. The highest concentration of free fatty acids, especially butyric and caproic acids, was found in Vento d’Estate cheese.

Production of Sludge in a Submerged Membrane Bioreactor and Dewatering Aspects

In wastewater treatment, the membrane bioreactor (MBR) holds the potential to become one of the new generation processes, ensuring effluent quality and disinfection of sufficiently high levels to allow water reuse and recycle. Furthermore, the possibility to operate with high biomass concentrations (2 to 5 times higher than in conventional activated sludge process, CAS) allows to impose high solid retention times(SRT) that can be beneficial to a sludge production reduction and so to a reduction of disposal costs. These non-conventional operating conditions (high SRT) can also induce different sludge characteristics and dewatering aptitude, which are essential parameters for the optimization of the sludge post-treatment, like mechanical dewatering. The objective of this work was to study the performances of a complete sludge retention membrane bioreactor, in terms of organic removal efficiency, sludge production and sludge dewaterability. The adaptability of Activated Sludge Model 3 (ASM3) to provide good prediction results of high SRT-MBR was studied. Typical parameters adopted to describe sludge dewaterability were quantified and compared with the conventional activated sludge process (CAS).

Roles of adsorbed OH and adsorbed H in the oxidation of hydrogen and the reduction of UO2+2 ions at Pt electrodes under non-conventional conditions

The roles of adsorbed hydroxyl radicals, OH, at a high temperature and adsorbed hydrogen atoms, H, in an acidic solution were investigated in the electrochemical reactions on Pt electrode by using potentiodynamic polarisation experiment, cyclic voltammetry and constant-potential electrolysis combined with UV/VIS analysis. From the analysis of the polarisation curves obtained from Pt electrode in a 0.185 M H3BO3 solution at 473 K, it was found that the reducing capability of dissolved hydrogen is significantly enhanced due to the increases of the mass transfer and the electron transfer rates. Especially, it is suggested that the stable Pt-OHad plays a significant role in the passivation reaction in the potential range from 0.60 to 0.75 VSHE. From the analyses of the experimental results for the electrochemical reduction of UO 2 2+ ions on Pt surface in a 1.0 M HClO4 solution, it is recognised that the reduction reaction of UO 2 2+ to U4+ ions is strongly dependent on the hydrogen atoms adsorbed on Pt electrode (indirect reduction of UO 2 2+ ) as well as on the electrons transferred from Pt electrode (direct reduction of UO 2 2+ ). In addition, the reduction mechanism of UO 2 2+ ions involved in Pt-Had is also proposed.

Asymmetric Synthesis of 1,3‐Aminoketals.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Recent Advances in the Industrial Enzymatic Synthesis of Semi-Synthetic βLactam Antibiotics

The production, under environmentally benign conditions, of efficient and more cost-effective anti-infective agents (available to the whole mankind) is one of most ambitious dreams of the industrial medicinal chemistry. Semi-synthetic βlactam antibiotics are very effective anti-infective agents. They are very stable and can be used via oral delivery. They exhibit a very wide spectrum of anti-bacterial activity and minimal side effects after being massively used for a very long time. In this way, we can assume that semi-synthetic β-lactam antibiotics are going to be one of the key anti-infective agents in the next years. The condensation of natural or modified antibiotic nuclei with different acyl donor chains is one of the key steps for the industrial synthesis of these anti-infective agents. Up to now, these condensations are mainly carried out through classical chemical methods and this implies a number of economical, ecological and technological drawbacks (high energy requirements, many protection and deprotection steps, utilization of toxic methylene chloride as solvent, etc). Enzyme biocatalysts may be very useful to catalyse these selective condensations under very mild experimental and environmental conditions. In fact, the possibility of using enzymes to carry out such biotransformations, at laboratory scale, has been discussed and demonstrated a long time ago. However, industrial synthesis of βlactamic antibiotics is still carried out via unfavorable chemical routes. In fact, enzymes have not been produced in the nature to act in industrial reactors; so they are usually very unstable, inhibited by substrates and products and they may not have ideal catalytic properties for industrial uses (high reaction rates, required selectivity, ability to reach quantitative synthetic yields, stable enough to run a number of reaction cycles, etc). These limitations of enzyme biocatalysis become even more significant mainly when the enzyme is going to be used with non-natural substrates, catalysing non-natural processes and working under non-conventional conditions. However, in the last ten years, a great number of papers have reported substantial improvement of these enzymatic synthetic approaches (new enzymes, better enzyme derivatives, improved reaction designs and so on) and it seems that a massive industrial implementation of enzymes in antibiotic synthesis is approaching. In this review, we would like to make a critical discussion of these very interesting advances in the application of enzyme biocatalysts for the industrial synthesis of semi-synthetic antibiotics. Keywords: bioactive molecules, penicillin g, reactor design, solid synthesis, hydrolysis, organic solvents, phenylacetic acid (paa), antibiotics, thermodynamically controlled synthesis (tcs), thermostable enzymes

Recent Advances in Spectral Nodal Methods for Numerically Solving Neutron‐Diffusion Eigenvalue Problems

In this paper we present the recent advances in spectral nodal methods for numerically solving neutron-diffusion eigenvalue problems in Cartesian geometry. For one‐dimensional two‐energy group diffusion criticality problems, we describe the use of nonconventional albedo boundary conditions that substitute approximately the reflective properties of the nonmultiplying media around the core. We also present the Chebyshev acceleration scheme for the power method used in the outer iterations. For three‐dimensional one‐speed diffusion eigenvalue problems, we present a spectral nodal method that is based on transverse‐integrating the diffusion equation separately in X, Y, and Z directions, and then considering flat approximations for the transverse leakage terms. Numerical results for typical model problems are given to illustrate the accuracy.

Stabilization of alpha-chymotrypsin by ionic liquids in transesterification reactions.

Five different ionic liquids, based on dialkylimidazolium and quaternary ammonium cations associated with perfluorinated and bis (trifluoromethyl) sulfonyl amide anions, were used as reaction media to synthesize N-acetyl-L-tyrosine propyl ester by transesterification with alpha-chymotrypsin at 2% (v/v) water content at 50 degrees C. The synthetic activity was reduced by the increase in alkyl chains length of cations and by increases in anion size, which was related to the decrease in polarity. Incubation of the enzyme (with and without substrate) in ionic liquids exhibited first-order deactivation kinetics at 50 degrees C, allowing determination of deactivation rate constants and half-life times (1-3 h). Ionic liquids showed a clear relative stabilization effect on the enzyme, which was improved by increased chain length of the alkyl substituents on the imidazolium ring cations and the anion size. This effect was 10-times enhanced by the presence of substrate. For example, 1-butyl-3-methylimidazolium hexafluorophosphate increased the alpha-chymotrypsin half-life by 200 times in the presence of substrate with respect to the 1-propanol medium. These results show that ionic liquids are excellent enzyme-stabilizing agents and reaction media for clean biocatalysis in non-conventional conditions.

Characterisation of nonoriented electric alloys under nonconventional conditions

The variations of magnetic and loss characteristics of nonoriented cobalt-iron and silicon-iron sheets have been investigated using an Epstein frame. Cobalt-iron alloys have been tested under sinusoidal magnetic flux density with respect to frequency and temperature. Both kinds of alloys have also been investigated with respect to frequency, time constant wavefront and temperature under trapezoidal flux density. The qualitative behaviour is identical under both flux density conditions for all these alloys. These investigations have made it possible to model the variations of iron losses with experimental parameters, except the temperature. These quantitative evolutions differ with alloy and flux-density conditions and do not confirm several propositions of different authors.

ChemInform Abstract: Nonconventional Reaction Conditions: Ultrasound, High Pressure, and Microwave Heating in Organic Synthesis

ChemInform Abstract: Nonconventional Reaction Conditions: Ultrasound, High Pressure, and Microwave Heating in Organic Synthesis

Langevin and Fokker-Planck equation with nonconventional boundary conditions for the description of domain-wall dynamics in ferromagnetic systems.

Langevin and Fokker-Planck equation with nonconventional boundary conditions for the description of domain-wall dynamics in ferromagnetic systems.