Search results for "hydration"
showing 10 items of 217 documents
Immobilisation increases yeast cells' resistance to dehydration-rehydration treatment.
2014
This study was performed with the goal of revealing if the dehydration procedure used in our new immobilisation method noticeably decreases the viability of yeast cells in immobilised preparations. Various yeasts were used in this research: Saccharomyces cerevisiae cells that were rather sensitive to dehydration and had been aerobically grown in an ethanol-containing medium, a recombinant strain of S. cerevisiae grown in aerobic conditions which were completely non-resistant to dehydration and an anaerobically grown bakers' yeast strain S. cerevisiae, as well as a fairly resistant Pichia pastoris strain. Experiments performed showed that immobilisation of all these strains essentially incre…
Cryopreservation of white mulberry (Morus alba L.) by encapsulation-dehydration and vitrification
2011
Shoot apices of in vitro-grown plantlets of white mulberry, Morus alba L. cv Florio, were cryopreserved using either encapsulation-dehydration or vitrification. For encapsulation-dehydration, alginate beads containing apices were dehydrated for 1, 3, 5 or 7 days in a liquid medium containing various sucrose concentrations (0.5, 0.75, 1.0 or 1.25 M). Bead desiccation was performed using silica gel for either 0, 4, 6, 8, 9 or 14 h. For vitrification, apices were directly immersed for either 5, 15, 30 or 60 min in a vitrification solution (PVS2). Following encapsulation-dehydration, treatment of alginate beads with 0.75 M sucrose was more effective in promoting re-growth of explants after imme…
Dehydration and crystallization of trehalose and sucrose glasses containing carbonmonoxy-myoglobin
1999
We report a study wherein we contemporarily measured 1) the dehydration process of trehalose or sucrose glasses embedding carbonmonoxy-myoglobin (MbCO) and 2) the evolution of the A substates in saccharide-coated MbCO. Our results indicate that microcrystallization processes, sizeably different in the two saccharides, take place during dehydration; moreover, the microcrystalline structure is maintained unless the dry samples are equilibrated with a humidity >/=75% (>/=60%) at 25 degrees C for the trehalose (sucrose) sample. The evolution of the parameters that characterize the A substates of MbCO indicates that 1) the effects of water withdrawal are analogous in samples dried in the presenc…
Role of the support on the activity of H3PW12O40 supported on SiO2 or TiO2 in Catalytic and Photocatalytic propene hydration: An EPR Study
2016
Catalytic and catalytic photo-assisted hydration of propene to 2-propanol in gas-solid regime at atmospheric pressure and 85°C were carried out by using the Keggin heteropolyacid (HPA) H3PW12O40 (PW12) supported on home prepared SiO2, WO3, TiO2 or N-doped TiO2. The HPA played the key role both in catalytic and photocatalytic reactions; however, the support strongly influenced the binary material performance. The contemporary presence of heat and UV light improved the activity of the (photo)catalysts. EPR (Electron Paramagnetic Resonance) has been used to understand the intimate mechanism underlying the photoactivity of the supported heteropolyacid and the role played by the support.
Glycerol selective oxidation to lactic acid over AuPt nanoparticles; Enhancing reaction selectivity and understanding by support modification
2020
2 Schemes, 3 Tables, 5 Figures.
Adsorption and Dehydration of Water Molecules from α, β and γ Cyclodextrins — A Study by TGA Analysis and Gravimetry
2015
The adsorption and desorption of water molecules from α, β and γ-cyclodextrins were studied by gravimetric and thermogravimetric analysis. Cyclodextrins like all the other carbohydrates have tendency to adsorb water molecules. However, their cyclic nature tends to affect the adsorption patterns. The cyclic nature of the cyclodextrins facilitates the formation of hydrogen bondings between OH groups of the neighbouring glucose units. The C2(1)-OH forms hydrogen bonding with C3(2)-OH. The extent of the hydrogen bond formation and strength of the hydrogen bond affect the way the adsorption and dehydration of water molecules from cyclodextrins take place.
Dehydration of Fructose to 5-HMF over Acidic TiO2 Catalysts
2020
Different solid sulfonic titania-based catalysts were investigated for the hydrothermal dehydration of fructose to 5-hydroxymethylfurfural (5-HMF). The catalytic behavior of the materials was evaluated in terms of fructose conversion and selectivity to 5-HMF. The surface and structural properties of the catalysts were investigated by means of X-ray diffraction (XRD), N2 adsorption isotherms, thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and acid capacity measurements. Special attention was focused on the reaction conditions, both in terms of 5-HMF selectivity and the sustainability of the process, choosing water as the solvent. Among the various process condition…
The Effect of Calcium on the Cohesive Strength and Flexural Properties of Low-Methoxyl Pectin Biopolymers.
2019
Abstract: Pectin binds the mesothelial glycocalyx of visceral organs, suggesting its potential role as a mesothelial sealant. To assess the mechanical properties of pectin films, we compared pectin films with a less than 50% degree of methyl esterification (low-methoxyl pectin, LMP) to films with greater than 50% methyl esterification (high-methoxyl pectin, HMP). LMP and HMP polymers were prepared by step-wise dissolution and high-shear mixing. Both LMP and HMP films demonstrated a comparable clear appearance. Fracture mechanics demonstrated that the LMP films had a lower burst strength than HMP films at a variety of calcium concentrations and hydration states. The water content also influe…
Foodborne pathogens inactivation in low-water activity foods
2016
Dried food products are common in food industry. Nevertheless, their safety is not well insured, involving numerous outbreaks every years around the world. Particularly, two pathogenic bacteria are of interest, one of them due to its number of cases, Salmonella enterica, and the other one due to its ability to survive environmental perturbations, Cronobacter spp.. A deeper comprehension of drying and heat treatment in dried state impact could lead to an optimization of drying and heating processes, insuring food safety. In the first instance, drying was considered as a supplementary decontamination step by optimizing its conditions of use. In a second phase, the rehydration impact was studi…
Identification and transcriptional profile of Lactobacillus paracasei genes involved in the response to desiccation and rehydration
2020
International audience; Lactobacillus paracasei is able to persist in a variety of natural and technological environments despite physico-chemical perturbations, in particular alternations between desiccation and rehydration. However, the way in which it adapts to hydric fluctuations and the genetic determinants involved are not clearly understood. To identify the genes involved in adaptation to desiccation, an annotated library of L. paracasei random transposon mutants was screened for viability after desiccation (25% relative humidity, 25 °C). We found 16 genes that have not been described as being involved in this response. Most of them are linked to either the transport of molecules or …