Online-Based Kinetic Analysis of Higher Alcohol and Ester Synthesis During Winemaking Fermentations

The production of the major volatile carbon compounds corresponding to the predominant higher alcohols and esters synthesized during wine alcoholic fermentation was monitored using an online GC system. The accuracy and frequency of measurements made it possible to calculate kinetic parameters, in particular rates and specific rates of production. Using this original GC system and a model describing the evolution of the gas–liquid ratio during the fermentation process, kinetic gas–liquid balances of the synthesis of volatile compounds could be followed. This showed that, for esters—substantial proportions of which are lost in the off-gas (up to 40 % of the total production at 20 °C)—measurements of the liquid concentration, rather than of the total production (liquid content?+?losses), can lead to misinterpretations of yeast metabolism. The specific production rate of individual higher alcohols reached their maximum values before the exhaustion of the corresponding precursor amino acids. Isobutanol and isoamyl alcohol were formed from carbon metabolites and nitrogen metabolites and consequently were produced continuously throughout the fermentation process. In contrast, propanol synthesis was strongly correlated with the presence of assimilable nitrogen, during both the growth and stationary phases. Therefore, propanol appears to be a highly pertinent marker of nitrogen metabolism. Acetate ester concentrations correlated linearly with the concentrations of the corresponding higher alcohols, indicating that the availability of the precursors is the main limiting factor for the production of these esters. These results open possibilities for innovative approaches based on metabolic flux analysis and taking their dynamics into account.     

Positional distribution of Δ5-acids in triacylglycerols from conifer seeds as determined by partial chemical cleavage

The positional distribution of various Δ5-acids in the seed triacylglycerols from several conifer species has been established after partial chemical degradation with Grignard reagent. The species studied were representative of four conifer families and were specially selected for their particularly high Δ5-acid contents. These species were Taxus baccata (Taxaceae; 5,9-18:2 acid, 11.9%), Larix decidua (Pinaceae; 5,9,12-18:3 acid, 28.5%), Sciadopytis verticillata (Taxodiaceae; 5,11,14-20:3 acid, 16.7%), and Juniperus communis (Cupressaceae; 5,11,14,17-20:4 acid, 19.8%). Calculations from the fatty acid compositions of triacylglycerols and of the mixture of 1,2- and 2,3-diacylglycerols generated by the Grignard reagent indicated that, for the four species, there was a considerable enrichment of Δ5-acids (generally more than ten times) in the 1,3-positions as compared to the 2-position, where Δ5-acids represented always less than 2% of total fatty acids esterified to triacylglycerols. This distribution was practically independent from the species (four families studied), the chainlength (18 or 20 carbon atoms), and the number of ethylenic bonds (two to four) in the Δ5-acids. Similar distributions were established for triacylglycerols from the seeds of three pine species that are available on a ton-scale: Pinus pinea, P. koraiensis, and P. pinaster. These observations confirm and extend previous studies conducted with other conifer species by similar techniques or by ¹³C-nuclear magnetic resonance spectroscopy. Consequently, the almost exclusive location of Δ5-acids in the external positions of triacylglycerols is now well established and appears to be a general feature of conifer seed oils.     

Practicing engineering in a freshman introductory course

This paper discusses a teaching experience obtained in the undergraduate course of Control Engineering at the Federal University of Santa Catarina (UFSC), Brazil. The course endeavors to introduce the students to the university and to the real world of engineering and to develop an understanding of basic engineering concepts and foster professional skills. By introducing practicing engineering to the course from day one, student motivation is increased, and the relationship between theoretical and practical aspects of engineering is demonstrated more clearly. This "hands-on approach" allows the student a greater insight into the life of an engineer. It strengthens a weakness found in established teaching methods, allowing the individual to embark on his or her engineering education with greater confidence in his or her ability as an engineer.     

Influence of avocado oil processing on the nature of some unsaponifiable constituents

The unsaponifiable part of avocado pear oil, after heating during extraction and processing, contains an abundant fraction that has never been found in the unsaponifiable part of usual vegetable oils nor in cold-pressed avocado oil. Nine components were detected. Eight of them could be identified through chromatographic fractionations and spectroscopic analysis, mainly by mass spectrometry and proton nuclear magnetic resonance. These products are characterized by a homogeneous structure. A furyl nucleus is substituted in position 2 by an aliphatic, mono- or polyunsaturated chain. The chainlength varies from 13 to 17 carbon atoms. The carbon number is always odd. The significance of these components in the biological effects of avocado oil unsaponifiables is still being studied.     

A design-oriented method to build correct hypermedia documents

Over the years, different approaches to identify temporal and spatial conflicts in hypermedia applications has been proposed. Most of them are based on formal verification techniques and impose to the designers to follow a formal model or language to ensure application’s functional correctness. Furthermore, the error diagnose is hard to be interpreted by a non-specialist in this domain. In this paper, we present an approach which supports formal verification for documents written in markup languages. We proposed a method and built a verification toolchain that helps designers to verify time and spatial constraints in hypermedia applications. The input language is the designer language. Its translation towards the input of toolchain is automatic and transparent for the application designer. The errors scenarios provided by the verification tool are presented in a timeline way, easily understandable by the designer. The method and toolchain support different markup languages translated in the same intermediary language in order to facilitate the use of different verification tools in the same environment.

     

Triterpene alcohols, 4-methylsterols and 4-desmethylsterols of sal and illipe butters

Four 4-desmethylsterols, four 4-methylsterols and eight triterpene alcohols were isolated from sal and illipe butters and identified by¹H nuclear magnetic resonance and mass spectrometry. In addition to some components which had been shown to be present in these fats, several triterpene alcohols and one 4-methylsterol are described for the first time in these fats. An analytical method for detection of sal or illipe butters in foodstuffs is suggested.     

Hybrid simulation of a current fed asynchronous machine

In this article the authors present a hybrid simulation program for variable speed drives comprising an AC machine current fed by a static convertor. The examination here beare upon a current fed asynchronous machine. The authors give the details of the utilization of this program, and show the results obtained in comparison with experimental results. They also indicate the conditions for the use of this program.     

Enzymatic synthesis of fatty esters in 5‐caffeoyl quinic acid

The fatty esters of 5‐caffeoyl quinic acid were synthesized by direct esterification biocatalysed by an immobilised lipase obtained from Candida antarctica. Esterification yields (from 40 to 75%) depended on the carbon chain length of the fatty alcohols and whether or not solvent (2‐methyl 2‐butanol) was present in the reaction medium.     

Oxidation of Organic Pollutants of Water to Mineralization by Catalytic Ozonation

The oxidation of various organic compounds in aqueous solution was studied using catalytic ozonation (TOCCATA process) and conventional ozonation. The aim of the work is to assess catalytic ozonation efficiency for the mineralization of various organic compounds in order to envisage its application on real effluents. The selected organic compounds (about 30) are commonly found in industrial wastewaters. Comparative experiments were performed in batch mode at laboratory scale. Investigations were focused on ozone consumption rate, variations of total organic carbon, oxidation by-products and oxidation rate. Catalytic and conventional ozonation treatments were compared considering kinetic data, mineralization extent, and effect of organic functionalities. Catalytic ozonation system according to the TOCCATA process was able to convert organic compounds which were totally inert to ozone treatment and permitted considerably enhanced reaction rates when compounds were reactive to ozonation.