Search results for "Freeze Drying"

Influence of freezing temperatures prior to freeze-drying on viability of yeasts and lactic acid bacteria isolated from wine

2017

Aims To determine the effect of three different freezing temperatures on post-freeze-drying survival rates of wine yeasts and lactic acid bacteria (LAB). To know if a similar freeze-drying protocol can be used for both micro-organisms. Methods and Results Cells from liquid culture media were recovered and concentrated in appropriate lyoprotectants. Aliquots of each strain were frozen at −20, −80 and −196°C before vacuum drying. Viable cell counts were done before freezing and after freeze-drying. Survival rates were calculated. Freezing temperatures differently affected yeast and bacteria survival. The highest survival rates were obtained at −20 and −80°C for yeasts, but at −196°C for LAB. …

The Use of Frozen-Thawed Platelet-Derived Phospholipids as a Confirmatory Test for the Diagnosis of Lupus Anticoagulants. Comparison with Two Commerc…

1999

Lupus anticoagulants (LAs) belong to acquired circulating anticoagulants interfering with phospholipid-dependent coagulation tests. Owing to the remarkable variability among patients, SSC guidelines recommend more than one test to detect and confirm the presence of LAs. However, this is an expensive procedure and greatly raises the work load of the laboratory. A standardised platelet-derived phospholipid preparation was obtained and platelet neutralisation (PNP) procedures with APTT and DRVVT reagents were performed on plasmas from 16 patients with LAs and from 41 control subjects. In comparisons, STAclot-PNP and DVVconfirm clotting assays were conducted. PNP by using APTT or DRVVT reagents…

Evaluation of biological and antimicrobial properties of freeze-dried whey fermented by different strains ofLactobacillus plantarum

2018

The aim of this study was to evaluate the biological and antimicrobial activities of commercial freeze-dried whey fermented by lactic acid bacteria in order to valorize this high polluting liquid waste of the dairy industry. Freeze-dried whey was fermented by different strains of Lactobacillus plantarum (CECT 220, 221, 748) at three different times of fermentation (24, 48, 72 h). Afterwards, the extract was purified on centricon amicon with a cut-off of 3 kDa to obtain a permeate consisting of small bioactive compounds reported in the literature to show greater bioactivity. The purified and diluted samples were subjected to the biological and antimicrobial tests for the evaluation of antiox…

Design, characterization and in vitro evaluation of 5-aminosalicylic acid loaded N-succinyl-chitosan microparticles for colon specific delivery

2011

The objective of this study was to prepare NS-chitosan microparticles for the delivery of 5-aminosalicylic acid (5-ASA) to the colon. Microparticles can spread out over a large area of colon allowing a more effective local efficacy of 5-ASA. N-Succinyl-chitosan was chosen as carrier system because of its excellent pharmaceutical properties in colon drug targeting such as poor solubility in acid environment, biocompatibility, mucoadhesive properties, and low toxicity. It was prepared by introducing succinic group into chitosan N-terminals of the glucosamine units. 5-ASA loaded NS-chitosan microparticles were prepared using spray-drying. As a control, a matrix obtained by freeze-drying techni…

Lyophilization of lepidopteran midguts: a preserving method for Bacillus thuringiensis toxin binding studies

2004

Binding assays with brush border membrane vesicles (BBMV) from insect midguts are commonly used in the study of the interactions between Bacillus thuringiensis Cry toxins and their receptors. Collaboration between laboratories often require that frozen insect samples are sent in dry ice. Because of customs restrictions and delays, sample thawing is always a risk and often the biological material becomes ruined during shipping. We have tested lyophilization as an alternative method for preserving insect midguts for binding studies with B. thuringiensis Cry toxins. For this purpose, BBMV were prepared from both frozen and lyophilized midguts from three lepidopteran species: Spodoptera exigua,…

Competitive Binding of Aroma Compounds by β-Cyclodextrin

2001

Retention of six aroma compounds has been studied after dehydration of ternary mixtures of aroma water and beta-cyclodextrin. A maximal retention of a mole of aroma per mole of beta-cyclodextrin has been observed for five of the aroma compounds, whereas retention of benzyl alcohol can be twice as high. Retention of a mixture of aroma compounds has also been studied. It has been noted that when volatile compounds compete for the same binding sites on beta-cyclodextrin, ethyl hexanoate, 2-methylbutyric acid, and benzyl alcohol are, respectively, better retained than ethyl propionate, hexanoic acid, and hexanol. Preferential retention observed with esters can be simply explained by their diffe…

Dissolution enhancement and in vitro performance of clarithromycin nanocrystals produced by precipitation–lyophilization–homogenization method

2014

The gastroduodenal diseases caused by Helicobacter pylori were commonly treated with antibiotic clarithromycin as a standard regimen. According to the poorly water-soluble of clarithromycin, the nanocrystal formulation was prepared. The aim of this study was to investigate an enhancement effect of clarithromycin nanocrystals produced by precipitation-lyophilization-homogenization (PLH) method on the saturation solubility, dissolution velocity, antibiotic activity, permeability through the gastric mucus and cellular permeability. Poloxamer 407 and sodium lauryl sulfate (SLS) were chosen as combined stabilizers in the nanocrystal system. The obtained clarithromycin nanocrystals were identifie…

Spray Freeze Dried Lyospheres® for Nasal Administration of Insulin

2021

Pharmacologically active macromolecules, such as peptides, are still a major challenge in terms of designing a delivery system for their transport across absorption barriers and at the same time provide sufficiently high long-term stability. Spray freeze dried (SFD) lyospheres® are proposed here as an alternative for the preparation of fast dissolving porous particles for nasal administration of insulin. Insulin solutions containing mannitol and polyvinylpyrrolidone complemented with permeation enhancing excipients (sodium taurocholate or cyclodextrins) were sprayed into a cooled spray tower, followed by vacuum freeze drying. Final porous particles were highly spherical and mean diameters r…

Toxicity assessment of pesticides using the microtox test: application to environmental samples.

1997

Application of accelerated solvent extraction followed by gel performance chromatography and high-performance liquid chromatography for the determina…

2005

Accelerated solvent extraction (ASE) has been evaluated as a fast alternative to methanolic saponification for the extraction of 12 polycyclic aromatic hydrocarbons (PAHs) from mussel tissue. Several solvent systems and different operating conditions were investigated. The mixture dichloromethane-acetone (1:1, v/v) gave the best recoveries at 125 degrees C and 1500 psi, in a total time of 10 min. No yield difference was found between freeze-drying (Fd) or drying the wet mussel with diatomaceous earth (Ded) prior to extraction. The ASE method was validated using the standard reference material SRM 2977, a freeze-dried mussel tissue with naturally present organic contaminants. The performance…