Kinetic study of a hen-egg white lysozyme-based oenological preparation

The catalytic activity of a lysozyme-based oenological preparation toward the specific substrates i) glycol chitosan, as a non-cellular synthetic substrate, and ii) Oenococcus oeni, as a microbial substrate for muramidase activity, was investigated in wine-like acidic medium (tartaric buffer, pH 3.2). The good reproducibility and reliability of results revealed that both substrates are useful for lysozyme kinetics studies. Both the chitinolytic and muramidase activity of lysozyme were affected by uncompetitive substrate inhibition. However, the O. oeni effect occurred at very high concentration with respect to the typical wine bacterial content, even when microbial population reaches its maximum growth level during malolactic fermentation. The optimum pH and temperature for lysozyme activity were very far from the usual wine handling conditions, but residual enzyme activity was observed at pH 3.2 and 20°C, confirming that the oenological application of lysozyme is a useful practice.     

Development of a biosensor for monitoring of glycerol during alcoholic fermentation

A biosensor for the measurement of glycerol in FIA was constructed using covalently immobilized glycerokinase and glycerol-3-phosphate oxidase in conjunction with a Pt based hydrogen peroxide probe. Different immobilization strategies have been studied including random and asymmetric immobilization onto a polymeric support and immobilization onto two different membranes. The latter resulted in the best configuration for batch measurement. The most effective configuration for measurement in FIA was the immobilization of glycerokinase in a glass beads reactor coupled with glycerol-3-phosphate oxidase on a preactivated Immobilon AV membrane kept at the electrode surface. Using a 250-microliter injection loop, 3 mmol ATP(Mg+2) in 0.1 M borate buffer pH 8.5 and a flow rate of 0.5 ml/min, a linear response in the 2 x 10(-6)/10(-3) mol/l range and a detection limit of 5 x 10(-7) mol/l were obtained for glycerol. Lifetime of the glycerol-3-phosphate membrane was extended up to 1 month by storage in the working buffer containing 1% DEAE-dextran and 5% lactitol. More than 350 samples can be assayed with this system. The biosensor was used to monitor off-line glycerol production during alcoholic fermentations carried out at different pHs and temperatures.     

Effect of the matrix volatile composition in the headspace solid-phase microextraction analysis of extra virgin olive oil

The effectiveness of headspace solid-phase microextraction (HS-SPME) for the quantitative analysis of extra virgin olive oil volatiles was investigated on 44 standard compounds, using an adsorbent polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber. The method’s sensitivity was satisfactory, as was its repeatability. However, when the extraction was carried out on mixtures containing all the standard analytes, phenomena of coating saturation and competition between components caused losses in linearity at lower levels of concentration, thus distorting the quantitative evaluation. Coating saturation or displacement between components was also found to be responsible for the bias in the quantitative determinations when extra virgin olive oil samples were analysed. These limitations were overcome by diluting the oil at concentrations not exceeding the total capacity of the fiber coating and until the quantity of displacing compounds was reduced to sufficiently low levels.     

A first step to the rational design of an organometallic catalyst: RhxHySnz (CH3)n

V/P/O catalysts were prepared using isobutanol as solvent, which contained either cobalt or iron as the dopant (Me/V 0.01). The catalysts were characterized with several techniques, both after thermal treatment and after reaction in n-pentane/air. The catalytic performance was compared for the selective oxidation to maleic and phthalic anhydrides under conditions at which results were stable (i.e., after at least 200 h time-on-stream). It was found that iron had a dramatic effect on the structural evolution of the catalyst both during calcination and during aging; in contrast, the effect of cobalt was much less marked. Doping with 1% cobalt remarkably improved the selectivity to the phthalic anhydride at the expense of the maleic anhydride with respect to the undoped catalyst, while doping with iron led to a catalyst less selective to phthalic anhydride and more selective to carbon oxides. This revised version was published online in July 2006 with corrections to the Cover Date.     

Basic Results in Automatic Transformations of Shared Memory Parallel Programs into Sequential Programs

We study the problem of developing a set of syntax-driven transformations for automatic translation of shared memory parallel programs into sequential programs. The result is a sequential program that is semantically equivalent to the original program. Consequently, the problem of debugging parallel programs is reduced to the problem of debugging sequential programs. Moreover, the efficiency of parallel programs can be increased by sequentializing code segments that include extra parallelism.The main difficulty in developing such a system is to preserve the fairness property of any actual parallel execution, which states that no process can wait forever unserved. Thus, non termination of the sequential version (namely an infinite loop) is allowed only if there is at least one fair parallel execution that does not halt as well (i.e., a process that executes an infinite loop whose termination is not dependent on any other process).We show that it is sufficient to consider the case of two sequential programs executed in parallel in order to solve the general case. We then describe several types of transformations and check their ability to preserve fairness. The results, with regards to the existence of such a transformation for general parallel programs are not conclusive; however, we do show that restricted cases (which are likely to appear in the reality) can be sequentialized using this set of transformations.     

Natural antioxidants in the unsaponifiable fraction of virgin olive oils from different cultivars

An investigation on carotene, α-tocopherol and squalene contents of olives from six different cultivars and 15 virgin olive oils produced in Molise region in 1995 was carried out. Olives were harvested at different stages of ripeness and oil was extracted in industrial plants by pressure or centrifugation systems. The concentration of carotenes, α-tocopherol and squalene have been correlated, both in fruit and oil samples, with the olive ripeness index. In particular a significant linear correlation (R²=0·95) has been found between olive ripeness index and olive carotene content. In order to evaluate the stability of the extracted oil, a 6 month storage test at room temperature in the dark has been carried out. In addition to the nutritional relevance of β-carotene and α-tocopherol, the compounds studied are also characterised by antioxidant activities. Within the same cultivar, tocopherol and squalene stability was inversely related to the degree of ripeness. In general, storage losses ranged, probably due to different antioxidant mechanisms, from 0 to 10% for carotene, from 14 to 32% for tocopherol and from 26 to 47% for squalene. © 1998 SCI.     

Cellular pathology and histopathology of hypo-salinity exposure on the coral Stylophora pistillata

Coral reefs can experience extreme salinity changes, particularly hypo-salinity, as a result of storms, heavy rainy seasons (e.g., monsoons), and coastal runoff. Field and laboratory observations have documented that corals exposed to hypo-saline conditions can undergo extensive bleaching and mortality. There is controversy in the literature as to whether hypo-saline conditions induce a pathological response in corals, and if there is a relationship between decreasing salinity treatment and pathological responses. To test the hypothesis that hypo-salinity exposure does not have a pathological effect on coral, we used histological and cellular diagnostic methods to characterize the pathology in hypo-salinity-exposed corals. Colonies of Stylophora pistillata were exposed to five salinity concentrations [39 parts per thousand (ppt), 32 ppt, 28 ppt, 24 ppt, and 20 ppt] that may realistically occur on a reef. Histological examination indicated an increasing severity of pathomorphologies associated with decreasing salinity, including increased tissue swelling, degradation and loss of zooxanthellae, and tissue necrosis. Pulse-amplitude modulated chlorophyll fluorimetry kinetics demonstrated a decreasing photosynthetic efficiency with decreasing salinity conditions. Cytochrome P450 levels were affected by even slight changes in salinity concentration suggesting that detoxification pathways, as well as several endocrine pathways, may be adversely affected. Finally, these studies demonstrated that hypo-saline conditions can induce an oxidative-stress response in both the host and in its algal symbiont, and in so doing, may synergistically increase oxidative-stress burdens. As with other types of environmental stresses, exposure to hypo-saline conditions may have long-term consequences on coral physiology.     

Polysaccharide and volatile composition of Cabernet wine affected by different over-lees ageing

The influence of different over-lees ageing conditions on the soluble polysaccharides?? glycosyl residue and volatile composition of Cabernet wine was addressed in this work. Specific operating conditions have been considered: wine ageing on fine white lees, wine ageing on fine red lees, wine ageing on fine second-passage white lees and short ageing on rough red lees, which were compared with ageing without lees. The ageing on lees led to an increase in all wine polysaccharide glycosyl residues, with the exception of glucose, xylose and myo-inositol, and to volatile profile modifications. Different behaviours could be observed between the four types of lees, giving important hints for a rational use of them in winemaking. In particular, the use of red grape-derived lees caused the major release of polysaccharides; on the other hand, white grape-derived lees were more effective in enhancing ester content. Second-passage lees did not lead to any increase in wine polysaccharides, whereas they allowed aroma changes, and short ageing on rough red lees caused the greatest adsorption of several volatiles.