Geotrichum candidum gene expression and metabolite accumulation inside the cells reflect the strain oxidative stress sensitivity and ability to produce flavour compounds.

Geotrichum candidum is a fungus-like yeast widely used as a starter culture for cheese ripening for its proteolytic and lipolytic activities and its contribution to the cheese flavours. The sequenced strain G. candidum CLIB 918 was isolated from cheese Pont-L'Evêque. This strain's ability to produce volatile compounds was compared to the ability of a known strong sulphur compound producer G. candidum strain (Gc203). The aminotransferase-coding genes BAT2 and ARO8 were identified to be involved in methionine catabolism. The production of volatile compounds indicated that the sequenced strain was a moderate producer compared to the strong producer strain. The major volatile compounds were produced from sulphur amino acid, branched-chain amino acid and fatty acid metabolisms. Metabolite content of the cells showed that the ability of the strain to produce volatile compounds was inversely proportional to its ability to store amino acids inside the cells. Reduced glutathione, hypotaurine and taurine intracellular concentrations and volatile fatty aldehyde production indicated the role of oxidative stress sensitivity in flavour production. The increase in expression of several genes in a Reblochon-type cheese at the end of ripening confirmed that oxygen and iron were key factors regulating cheese flavour production.

Assessment of the beneficial combination of electrochemical and ultrasonic activation of compounds originating from biomass.

The electro-oxidation of organic molecules at the anode with simultaneous generation of hydrogen at the cathode in electrosynthesis reactors is considered as a promising and efficient process for the co-production of hydrogen and bio-sourced value-added chemicals. In this study and for the first time, we investigated the electro-oxidation of glucose and methylglucoside in 0.1 mol L-1 NaOH on polycrystalline Pt (real surface area = 14.5 ± 0.5 cm2, roughness ≈ 5) in the potential range [0; +1.20 V vs. rhe] under silent and ultrasonic (bath, 45 kHz, Pacous = 11.20 W) conditions. A series of linear sweep voltammograms, chronoamperograms and high-performance liquid chronoamperograms were generated. It was found that higher current densities were obtained under ultrasonic conditions over the potential range of +0.25 V to +1.10 V vs. rhe, indicating that higher oxidation rates were provided under ultrasonication. It was observed that the desorption of species from the Pt surface in the medium potential region was favoured, allowing free catalytic Pt sites for further adsorption and oxidation of reactants; and in the high potential region, high peak current densities in the presence of ultrasound was due to enhanced mass transport of the electroactive species from the bulk electrolyte to the Pt-polycrystalline electrode surface. HPLC studies confirmed that higher electrochemical activity was obtained in the presence of ultrasound than in the absence. In our conditions, it was also found that low frequency ultrasound did not change the selectivity of the glucose and methylglucoside electro-oxidation reactions but instead, a significant increase in the rate of conversion was observed.

Fluorescence in situ hybridization characterization of ider(20q) in myelodysplastic syndrome.

Isochromosome of the long arm of chromosome 20 with loss of interstitial material [ider(20q)] is a variant of deletion of chromosome 20q and a rare abnormality in myelodysplastic syndrome (MDS). We studied seven cases with an ider(20q) in MDS. Fluorescence in situ hybridization (FISH) studies showed all proximal breakpoints to be consistently located in 20q11.21 band whereas distal breakpoints were variable. Amplification of HCK, TNFRSF6B and DIDO1 genes included in retained regions associated with loss of tumour suppressor genes in deleted regions could explain cell tumour progression and possibly the less favourable prognosis of ider(20q) compared with del(20q).

Gaining deeper insight into aroma perception: An integrative study of the oral processing of breads with different structures.

The objective of this study was to investigate for the first time the influence of bread structure, volatile compounds, and oral processing on aroma perception. 3 types of French baguette were created using the same raw ingredients but different bread-making processes; they consequently varied in their crumb and crust structures. We characterized the initial volatile profiles of two bread structural subtypes-namely bread crumb and bread crumb with crust-using proton transfer reaction-mass spectrometry (PTR-MS) headspace analysis. Three types of bread were characterized by thirty-nine ion fragments from m/z 45 to 139. We then conducted a study in which 8 participants scored aroma attribute intensities for the different bread types and subtypes at 3 key stages of oral processing (10, 40, and 100% of individual swallowing time). At these 3 time points, we collected boli from the participants and characterized their volatile profiles using PTR-MS headspace analysis. The results suggest saliva addition dilutes volatile compounds, reducing volatile release during oral processing. Thus, a bread with high porosity and high hydration capacity was characterized by a low volatile release above boli. We examined the relationships between 4 aroma attributes of bread crumb with crust and 24 discriminatory fragment ions found in boli headspace. This study demonstrated for the first time that the perceived aroma of crumb with crust was influenced more by volatile profiles than by crumb texture. It thus contributes to our understanding of aroma perception dynamics and the mechanisms driving volatile release during oral processing in bread.

Structural alterations of lignins in transgenic poplars with depressed cinnamyl alcohol dehydrogenase or caffeic acid O-methyltransferase activity have an opposite impact on the efficiency of industrial kraft pulping

We evaluated lignin profiles and pulping performances of 2-year-old transgenic poplar (Populus tremula x Populus alba) lines severely altered in the expression of caffeic acid/5-hydroxyferulic acid O-methyltransferase (COMT) or cinnamyl alcohol dehydrogenase (CAD). Transgenic poplars with CAD or COMT antisense constructs showed growth similar to control trees. CAD down-regulated poplars displayed a red coloration mainly in the outer xylem. A 90% lower COMT activity did not change lignin content but dramatically increased the frequency of guaiacyl units and resistant biphenyl linkages in lignin. This alteration severely lowered the efficiency of kraft pulping. The Klason lignin level of CAD-transformed poplars was slightly lower than that of the control. Whereas CAD down-regulation did not change the frequency of labile ether bonds or guaiacyl units in lignin, it increased the proportion of syringaldehyde and diarylpropane structures and, more importantly with regard to kraft pulping, of free phenolic groups in lignin. In the most depressed line, ASCAD21, a substantially higher content in free phenolic units facilitated lignin solubilization and fragmentation during kraft pulping. These results point the way to genetic modification of lignin structure to improve wood quality for the pulp industry.

Diversity of Lactobacillus reuteri Strains in Converting Glycerol into 3-Hydroxypropionic Acid.

The present study aims at comparing the performances of three Lactobacillus reuteri strains (DSM 20016, DSM 17938, and ATCC 53608) in producing 3-hydroxypropionic acid (3-HP) from glycerol and at exploring inhibition phenomena during this bioconversion. Differences were highlighted between the three strains in terms of 3-HP production yield, kinetics of substrate consumption, and metabolite production. With a maximal productivity in non-optimal conditions (free pH) around 2 g.L(-1).h(-1) of 3-HP and 4 g.L(-1).h(-1) of 3-hydroxypropionaldehyde (3-HPA) depending on the strain, this study confirmed the potential of L. reuteri for the biotechnological production of 3-HP. Moreover, the molar ratios of 3-HP to 1,3-propanediol (1,3-PDO) obtained for the three strains (comprised between 1.25 and 1.65) showed systematically a higher 3-HP production. From these results, the DSM 17938 strain appeared to be the most promising strain. The impact of glycerol bioconversion on the bacteria's physiological state (a decrease of around 40 % in DSM 17938 cells showing an enzymatic activity after 3 h) and survival (total loss of cultivability after 2 or 3 h depending on the strains) was revealed and discussed. The effect of each metabolite on L. reuteri DSM 17938 was further investigated, displaying a drastic inhibition caused by 3-HPA, while 3-HP induced lower impact and only at acidic pH.

Abiotic and enzymatic degradation of wheat straw cell wall: a biochemical and ultrastructural investigation.

The action of an abiotic lignin oxidant and a diffusible xylanase on wheat straw was studied and characterized at the levels of the molecular structures by chemical analysis and of the cell wall ultrastructure by transmission electron microscopy. While distinct chemical changes in the target polymers were observed when each system was used separately, a combination of the two types of catalysts did not significantly increase either lignin oxidation or hemicellulose hydrolysis. Microscopic observations however revealed that the supramolecular organization of the cell wall polymers was significantly altered. This suggests that the abiotic Mn-oxalate complex and the xylanase cooperate in modifying the cell wall architecture, without noticeably enhancing the degradation of the constitutive polymers.

The phenolic fraction of maize bran: evidence for lignin-heteroxylan association.

Maize bran heteroxylan samples were extracted in various conditions of severity. Their ferulate and diferulate content was investigated by GC-MS of methyl ester-TMSi derivatives. When extracted by 0.5 M NaOH in mild conditions, the heteroxylan sample contained a low level of ferulic acid (0.032% by wt.) and the main diferulate surviving alkaline extraction was found to be the 8-8' diferulate. On peroxidase treatment, this sample nevertheless produced a firm and brittle gel without any change in the diferulate profile. Typical lignin structures, mainly comprising syringyl units interconnected through beta-O-4, beta-1 and beta-beta interunit bonds, were evidenced in the maize bran sample. More importantly, these lignin structures were found to be tightly associated with the alkali-extracted heteroxylans. Thioacidolysis revealed the occurrence of 0.1-0.5% (by wt.) lignin structures in heteroxylan fractions extracted in mild or severe conditions, before and after purification of the polysaccharides. The gelling potential of the heteroxylan fractions was not only dependent on their ferulate level, but also influenced by associated lignin structures. These results argue for the occurrence of covalent linkages between heteroxylan chains and lignin structures which could participate in the peroxidase-driven gelation of feruloylated polysaccharides. They demonstrate the role of low lignin levels in the organization of native or reconstructed polysaccharide networks.

Repression of O-methyltransferase genes in transgenic tobacco affects lignin synthesis and plant growth.

Among the different enzymatic steps leading to lignin biosynthesis, two methylation reactions introduce the methyl groups borne by guaiacyl (G) and syringyl (S) units. Tobacco possesses a complex system of methylation comprising three classes of CCoAOMTs (caffeoyl-CoA-O-methyltransferases) and two classes of COMTs (caffeic acid OMTs). Antisense plants transformed with the CCoAOMT sequence alone or fused to COMT I sequence have been produced and compared to ASCOMT I plants in order to study the specific role of each OMT isoform in lignin biosynthesis, plant development and resistance to pathogens. Tobacco plants strongly inhibited in OMT activities have been selected and analyzed. Whereas antisense COMT I plants exhibited no visual phenotype, CCoAOMT repression was shown to strongly affect the development of both single and double transformants: a reduction of plant growth and the alteration of flower development were observed in the most inhibited plants. Lignin analysis performed by Klason and thioacidolysis methods, showed a decrease in the lignin quantity and changes in the lignin structure of ASCCoAOMT and ASCCoAOMT/ASCOMT I transgenics but not in ASCOMT I plants. Inhibition of COMT I in single as well as in double transformed tobacco was demonstrated to decrease S unit synthesis and to provoke the accumulation of 5-hydroxyguaiacyl lignin units. ASCCoAOMT/ASCOMT I tobacco was affected in lignin amount and composition, thus demonstrating additive effects of inhibition of both enzymes. The changes of lignin profiles and the phenotypical and molecular alterations observed in the different transgenic lines were particularly prominent at the later stages of plant development.

Lignin structure in a mutant pine deficient in cinnamyl alcohol dehydrogenase.

Cinnamyl alcohol dehydrogenase (CAD) activity is deficient in loblolly pine (Pinus taeda L.) harboring a mutated allele of the cad gene (cad-n1). We compared lignin structure of CAD-deficient and wild-type pines, both types segregating within full-sib families obtained by controlled crosses. The type and frequency of lignin building units and distribution of interunit bonds were determined from the GC-MS analysis of thioacidolysis monomers and dimers. While the lignin content was only slightly reduced, the lignin structure was dramatically modified by the mutation in both mature and juvenile trees. Lignins from CAD-deficient pine displayed unusually high levels of coniferaldehyde and dihydroconiferyl alcohol. In addition, biphenyl and biphenyl ether bonds were in large excess in these abnormal lignins. These results suggest that the CAD-deficient pines efficiently compensate for the shortage in normal lignin precursors by utilizing nontraditional wall phenolics to construct unusual lignins particularly enriched in resistant interunit bonds.

A novel angular geometry for the sonochemical silver recovery process at cylinder electrodes.

In order to obtain maximum ultrasonic effect upon electrochemical silver recovery, mass transfer measurements were investigated. The effect on limiting current of changing the position of an ultrasonic horn tip (i.e. vertical and horizontal) and using a cylinder electrode (CE), was studied in an attempt to find the optimum position required for maximum sonoelectrochemical effect. The importance of the ultrasonic intensity, the electrode-horn distance and positioning (angle) in assigning limiting currents was also investigated. For the CE placed at an angle of 45 degrees with respect to the ultrasonic horn, it was suggested that the 50% increase in limiting current for the 'face-on' geometry is caused by an approximately 50% decrease in diffusion layer thickness for the 'face-on' geometry compared to the 'angular' geometry due to the difference in the sonicated areas for both geometries.

The development and evaluation of ultrasound in the biocidal treatment of water.

The effect of ultrasound upon the destruction of micro-organisms has been studied and reported here. The results obtained from the work carried out has shown that ultrasound can be used effectively for water disinfection and has several advantages. When used in conjunction with chlorine it significantly reduces the number of bacteria present in water samples. Ultrasound also reduces the amount of chlorine required for disinfection. Increasing the power of ultrasound leads to greater efficiency in the destruction of bacterial cells. High frequency ultrasound is more beneficial than low frequency in the disinfection of water.

Double-structured ultrasonic high frequency reactor using an optimised slant bottom.

The present work has been carried out in order to design a new type of ultrasonic reactor consisting of a double-structured tank. The inner working compartment is built with a slant bottom to allow a better ultrasonic transmission. This paper reports the effect of the inclination angle on acoustic efficiency for several different plates, e.g. two plates made of glass (2 mm and 3 mm thickness) and one made of PVC (3 mm thickness). The acoustic efficiency was determined as the ratio of the signal measured by a hydrophone in the presence of the plate to that signal in the absence of the plate. Having optimised the system, the ultrasonic powers in the inner and the outer compartments of the slant bottom reactor were determined by hydrogen peroxide dosimetry.

The effect of ultrasound upon the oxidation of thiosulphate on stainless steel and platinum electrodes.

Ultrasound was found to increase the oxidation peak current and hence the decomposition rate of thiosulphate 50-fold compared to silent conditions. The effects of the ultrasonic frequency (20 and 38 kHz) and power upon the electrochemical oxidation of thiosulphate in aqueous KCl (1 mol dm-3) at stationary stainless steel and platinum electrodes were studied chronoamperometrically and potentiostatically (at various scan rates). No sigmoidal-shaped voltammograms were observed for the redox couple S4O6(2-)/S2O3(2-) in the presence of ultrasound. However, application of ultrasound to this redox couple provided an increase in the oxidation peak current at the frequencies employed, the magnitude of which varied with concentration, scan rate and ultrasonic power. Under sonication at 20 and 38 kHz, the oxidation peak potential shifted anodically with increasing ultrasonic power. This anodic shift in potential may be due to the formation of hydroxyl radicals, changes in electrode surface composition and complex adsorption phenomena. The large increase in oxidation peak currents and the rates of decomposition of thiosulphate, in the presence of ultrasound, are explained in terms of enhanced mass transfer at the electrode due to cavitation and acoustic streaming together with microstreaming coupled with adsorption phenomena. It is also shown that changes in macroscopic temperature throughout the experiment are insufficient to cause the observed enhanced diffusion.

Management of psoteriorly dislocated crystalline lenses or lens fragments.

The authors conducted a retrospective study during a 4-year period (jan. 91-dec. 94) of the charts of 26 patients (27 eyes) treated by pars plana vitrectomy for posteriorly dislocated crystalline lenses or lens fragments. One patient had a spontaneous lens luxation on both eyes and 3 patients presented with a posttraumatic dislocation of their lens. Twenty one eyes had retained intravitreal lens material after cataract surgery and 1 after perforating injury. Six eyes received an intraocular lens (IOL) at the end of the vitrectomy procedure; in 11 eyes an IOL had already been inserted at the time of primary cataract surgery. Ten eyes were left aphakic. Surgical details and visual outcome are discussed.

Electrophoresis and stability of nano-colloids: history, theory and experimental examples.

The paper contains an extended historical overview of research activities focused on determining interfacial potential and charge of dispersed particles from electrophoretic and coagulation dynamic measurements. Particular attention is paid to nano-suspensions for which application of Standard Electrokinetic Model (SEM) to analysis of experimental data encounters difficulties, especially, when the solutions contain more than two ions, the particle charge depends on the solution composition and zeta-potentials are high. Detailed statements of Standard Electrokinetic and DLVO Models are given in the forms that are capable of addressing electrophoresis and interaction of particles for arbitrary ratios of the particle to Debye radius, interfacial potentials and electrolyte compositions. The experimental part of the study consists of two groups of measurements conducted for Pt/C nano-suspensions, namely, the electrophoretic and coagulation dynamic studies, with various electrolyte compositions. The obtained experimental data are processed by using numerical algorithms based on the formulated models for obtaining interfacial potential and charge. While analyzing the dependencies of interfacial potential and charge on the electrolyte compositions, conclusions are made regarding the mechanisms of charge formation. It is established that the behavior of system stability is in a qualitative agreement with the results computed from the electrophoretic data. The verification of quantitative applicability of the employed models is conducted by calculating the Hamaker constant from experimental data. It is proposed how to explain the observed variations of predicted Hamaker constant and its unusually high value.

Respective contribution of cavitation and convective flow to local stirring in sonoreactors.

The knowledge of respective parts of convection and cavitation to the stirring induced by ultrasound at one exact position into a sonoreactor is useful for all processes implementing surfaces exposed to sonication. PIV measurement allows real fluid motion determination, whereas the electrochemical technique gives an equivalent flow velocity considered as the sum of all stirring contributions to the electrode. Thus, by a simple subtraction between real fluid velocity and equivalent flow velocity, it is possible to identify the contribution of each phenomenon. Applied to low frequency reactors, it had been observed that cavitation is the preponderant phenomenon, with a contribution of stirring close to the electrode always more than 90%. High frequency reactors, frequently known to produce less cavitation, have shown that at the focal zone, if it concerns HIFU, cavitation becomes preponderant and reaches similar values to those close to the ultrasonic horn in low frequency sonoreactors.

Sonoelectrochemical recovery of silver from photographic processing solutions

This paper describes the effect of ultrasound upon the electrochemical recovery of silver from photographic processing solutions using a newly designed electrochemical cell--SonoEcoCell. Rates of deposition of silver (obtained potentiostatically) were studied in the model 'fix' solutions (dilute aqueous Na2S2O3/NaHSO3 at a stainless steel cylinder electrode in both the absence and the presence of ultrasound. Under silent conditions, the magnitude of the cathodic potential is a major factor in the removal of silver. Under 20 kHz sonication, the rate of deposition of silver increases with increasing ultrasonic intensity. The cathode efficiency is also enhanced under insonation. The position of the ultrasonic probe with respect to the rotating cylinder electrode (RCE) was studied. It was found that for a 'face-on' geometry (probe parallel to the electrode) led to higher rate constants compared with a 'side-on' geometry (probe perpendicular to the electrode). The effect of coupling an RCE with ultrasound upon these rate constants employing the two geometry was also investigated. It was found that, employing either the face-on or the side-on geometry alone, improved rate constants were obtained below approximately 1500 and 2000 rpm, respectively.