Freezing Step Research Articles

Delivery of Therapeutic siRNA to the Lung Endothelium via Novel Lipoplex Formulation DACC

Posttranscriptional gene silencing by RNA interference can be therapeutically exploited to inhibit pathophysiological gene expression. However, in contrast to the established effectiveness of RNAi in vitro, safe and effective delivery of siRNAs to specific organs and cell types in vivo remains the major hurdle. Here, we report the development and in vivo characterization of a novel siRNA delivery system (DACC lipoplex) suitable for modulating target gene expression specifically in the lung vasculature. Systemic administration of DACC in mice delivered siRNA cargo functionally to the lung pulmonary endothelium. A single dose of DACC lipoplexes administered by bolus injection or by infusion was sufficient to specifically silence genes expressed in pulmonary endothelial cells such as CD31, Tie-2, VE-cadherin, or BMP-R2. When tested in a mouse model for lung cancer, repeated treatment with DACC/siRNA(CD31) reduced formation of lung metastases and increased life span in a mouse model of experimental lung metastasis.

Development of lyophilized spherical particles of poly(epsilon-caprolactone) and examination of their morphology, cytocompatibility and influence on the formation of reactive oxygen species

A common limitation of using polymeric micro and nanoparticles in long-term conservation is due to their poor physical and chemical stability. Freeze-drying is one of the most convenient methods that enable further reconstitution of micro and nanoparticles for therapeutical use. Nevertheless, this process generates various stresses during freezing and desiccation steps. This paper underlines the combined outcomes of freeze drying method and physicochemical solvent/non-solvent approach to design biocompatible poly(epsilon-caprolactone) (PCL) nanospheres and evaluate influence of different cryoprotectants (glucose, saccharose, polyvinyl alcohol or polyglutamic acid) on the outcome of freeze-dried PCL particles. Samples were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and dynamic light scattering method (DLS). In vitro studies used, include MTT assay (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), testing cytotoxicity as the quality of being toxic to cells, and DCFH-DA assay (2’,7’-dichlordihydrofluorescein-diacetate), testing the possible increase in ROS levels. It was found that cryoprotection with 1% glucose solution is an optimal for obtaining uniform, spherical but also biocompatible PCL nanoparticles for biomedical purposes.

Challenges in the Development of an Immunochromatographic Interferon-Gamma Test for Diagnosis of Pleural Tuberculosis

Existing diagnostic tests for pleural tuberculosis (TB) have inadequate accuracy and/or turnaround time. Interferon-gamma (IFNg) has been identified in many studies as a biomarker for pleural TB. Our objective was to develop a lateral flow, immunochromatographic test (ICT) based on this biomarker and to evaluate the test in a clinical cohort. Because IFNg is commonly present in non-TB pleural effusions in low amounts, a diagnostic IFNg-threshold was first defined with an enzyme-linked immunosorbent assay (ELISA) for IFNg in samples from 38 patients with a confirmed clinical diagnosis (cut-off of 300pg/ml; 94% sensitivity and 93% specificity). The ICT was then designed; however, its achievable limit of detection (5000pg/ml) was over 10-fold higher than that of the ELISA. After several iterations in development, the prototype ICT assay for IFNg had a sensitivity of 69% (95% confidence interval (CI): 50-83) and a specificity of 94% (95% CI: 81-99%) compared to ELISA on frozen samples. Evaluation of the prototype in a prospective clinical cohort (72 patients) on fresh pleural fluid samples, in comparison to a composite reference standard (including histopathological and microbiologic test results), showed that the prototype had 65% sensitivity (95% CI: 44-83) and 89% specificity (95% CI: 74-97). Discordant results were observed in 15% of samples if testing was repeated after one freezing and thawing step. Inter-rater variability was limited (3%; 1out of 32). In conclusion, despite an iterative development and optimization process, the performance of the IFNg ICT remained lower than what could be expected from the published literature on IFNg as a biomarker in pleural fluid. Further improvements in the limit of detection of an ICT for IFNg, and possibly combination of IFNg with other biomarkers such as adenosine deaminase, are necessary for such a test to be of value in the evaluation of pleural tuberculosis.

Phase Transitions, Prominent Dielectric Anomalies, and Negative Thermal Expansion in Three High Thermally Stable Ammonium Magnesium–Formate Frameworks

We present three Mg-formate frameworks, incorporating three different ammoniums: [NH4][Mg(HCOO)3] (1), [CH3CH2NH3][Mg(HCOO)3] (2) and [NH3(CH2)4NH3][Mg2(HCOO)6] (3). They display structural phase transitions accompanied by prominent dielectric anomalies and anisotropic and negative thermal expansion. The temperature-dependent structures, covering the whole temperature region in which the phase transitions occur, reveal detailed structural changes, and structure-property relationships are established. Compound 1 is a chiral Mg-formate framework with the NH4(+) cations located in the channels. Above 255 K, the NH4(+) cation vibrates quickly between two positions of shallow energy minima. Below 255 K, the cations undergo two steps of freezing of their vibrations, caused by the different inner profiles of the channels, producing non-compensated antipolarization. These lead to significant negative thermal expansion and a relaxor-like dielectric response. In perovskite 2, the orthorhombic phase below 374 K possesses ordered CH3CH2NH3(+) cations in the cubic cavities of the Mg-formate framework. Above 374 K, the structure becomes trigonal, with trigonally disordered cations, and above 426 K, another phase transition occurs and the cation changes to a two-fold disordered state. The two transitions are accompanied by prominent dielectric anomalies and negative and positive thermal expansion, contributing to the large regulation of the framework coupled the order-disorder transition of CH3CH2NH3(+). For niccolite 3, the gradually enhanced flipping movement of the middle ethylene of [NH3(CH2)4NH3](2+) in the elongated framework cavity finally leads to the phase transition with a critical temperature of 412 K, and the trigonally disordered cations and relevant framework change, providing the basis for the very strong dielectric dispersion, high dielectric constant (comparable to inorganic oxides), and large negative thermal expansion. The spontaneous polarizations for the low-temperature polar phases are 1.15, 3.43 and 1.51 μC cm(-2) for 1, 2 and 3, respectively, as estimated by the shifts of the cations related to the anionic frameworks. Thermal and variable-temperature powder X-ray diffraction studies confirm the phase transitions, and the materials are all found to be thermally stable up to 470 K.

116 Applications of the ΔtBIG method of cooling rate quantification to cell therapy cryopreservation under GMP compliance

Cryopreservation is a commonly adopted method for preserving allogeneic cell therapies through long-term storage and distribution to end-users. For clinical and eventually commercial manufacturing of these products, the cooling leg of the cryopreservation cycle is performed within a manufacturing environment that is regulated for Good Manufacturing Practices (GMP). To comply with GMP, the cooling process is held to high standards for process characterization and control, including defining critical process parameters, specifying acceptable ranges for those parameters, and verifying that each parameter is consistently controlled to within its specified range during normal operation. For cell products of defined composition, cooling rate is the primary critical process parameter that drives the performance of the cooling process. To successfully describe product cooling, cooling rate should be quantified in a specific and relevant manner that is independent of scale and freezer model, and enables measurement of multiple unit containers across a freezer load of interest. To support process development, engineering, scale-up and validation of the controlled-rate freezing step for CLT-008, an “off-the-shelf” cryopreserved myeloid progenitor cell therapy for neutropenia, we have defined a term which quantifies product cooling rate and serves as the primary critical process parameter linking product cooling to recovery of function. This cooling rate term, Δt BIG , represents the time required for bulk ice growth and is defined as the time difference between product nucleation and achieving −20 °C: Δ t BIG = t - 20 - t n ′ . Δt BIG has been successfully applied to internal and external monitoring of cryobags and vials to determine cooling rates of multiple individual product containers across controlled-rate freezer loads. Δt BIG distributions have served as the basis for load configuration and cooling program engineering as well as a means of setting acceptable ranges for performance qualification of GMP manufacturing freezes. The application of this cooling rate quantification method to cell cryopreservation development and GMP manufacturing is described using CLT-008 as a case study. Source of funding: Biomedical Advanced Research and Development Authority (BARDA). Conflict of interest: Cellerant is developing CLT-008 as a commercial therapy for neutropenia. dfrey@cellerant.com

Investigations on Polyplex Stability During the Freezing Step of Lyophilization Using Controlled Ice Nucleation—The Importance of Residence Time in the Low-Viscosity Fluid State

The aim of the study was to comprehensively investigate the influence of the freezing step during lyophilization on the stability of gene-delivery particles in order to better understand particle stabilization during freezing. Particle size of plasmid/linear polyethylenimine (LPEI) polyplexes at two DNA concentrations and at increasing sucrose-DNA ratios was investigated separately as a function of freezing procedure, ice-nucleation temperature, residence time of the particles in a partially frozen state, or incomplete freezing. Using a numerical model, the increase in sucrose concentration and system viscosity and corresponding bimolecular reaction rates were theoretically estimated. Freezing with a temperature-hold step after ice nucleation negatively influenced particle stability. Ice-nucleation temperature had an impact only at low DNA concentrations. Particle stability was highly reduced during the early part of freezing (<-3°C), especially at low shelf-ramp rates. In this phase, bimolecular reaction rates increase greatly at still low system viscosity. Below a critical temperature (≤∼-18°C) and at high system viscosity, no further particle aggregation occurred. In conclusion, the initial sample viscosity rather than the unfrozen volume and the residence time of particles in the low-viscosity state are the predominant factors in particle stabilization, which likely apply to aggregation in any system.

Enzymatically degradable oxidized dextran–chitosan hydrogels with an anisotropic aligned porous structure

Enzyme-degradable hydrogels with aligned pores were prepared via unidirectional freezing of a mixed solution of oxidized dextran (oxDex) and chitosan (CHI) followed by cryo-gelation. At the frozen state, imine bonds as the crosslinking points of the hydrogels were formed as a result of the reaction between the aldehyde groups on the oxDex and the amino groups on the CHI. The morphologies of the obtained hydrogels were studied by confocal laser scanning microscopy (CLSM). Microtubular pores aligned along the freezing direction were obtained in the swollen state of the hydrogels. The pore size was adjustable ranging from 20 to 100 μm by controlling the freezing temperature in the unidirectional freezing step. Upon exposure of the hydrogels to chitosanase solution, chitosan can be hydrolyzed into short oligosaccharide fragments leading to collapse and degradation of the gel network. The degradation rate can be tuned by adjusting the gel composition and enzyme concentration.

A New Approach to Achieve Controlled Ice Nucleation of Supercooled Solutions During the Freezing Step in Freeze‐Drying

Controlled ice nucleation of supercooled solutions has recently attracted a lot of interest in the field of freeze‐drying. 1. CPPR. 2012. Freeze‐drying of pharmaceuticals and biologicals. Conference program. Accessed on 08‐25‐2012, at: http://nipte.org/docs/FreezeDrying%20Revised%20Program.pdf. Google Scholar , 2. Konstantinidis A.K. Kuu W. Otten L. Nail S.L. Sever R.R. Controlled nucleation in freeze‐drying: Effects on pore size in the dried product layer, mass transfer resistance, and primary drying rate. J Pharm Sci. 2011; 100: 3453-3470 Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar , 3. Patel S. Bhugra C. Pikal M. Reduced pressure ice fog technique for controlled ice nucleation during freeze‐drying. AAPS PharmSciTech. 2009; 10: 1406-1411 Crossref PubMed Scopus (71) Google Scholar , 4. Kasper J.C. Friess W. The freezing step in lyophilization: Physico‐chemical fundamentals, freezing methods and consequences on process performance and quality attributes of biopharmaceuticals. Eur J Pharm Biopharm. 2011; 78: 248-263 Crossref PubMed Scopus (321) Google Scholar Ice nucleation is a stochastic event and the probability of spontaneous ice crystal formation is, among others, dependent on the presence of foreign particles. 5. Rambhatla S. Ramot R. Bhugra C. Pikal M. Heat and mass transfer scale‐up issues during freeze drying: II. Control and characterization of the degree of supercooling. AAPS PharmSciTech. 2004; 5: 54-62 Crossref Scopus (190) Google Scholar Thus, ice nucleation becomes a major issue during scale‐up from laboratory‐scale to almost particle‐free clean room production environment. 6. Roy M.L. Pikal M.J. Process control in freeze drying: Determination of the end point of sublimation drying by an electronic moisture sensor. PDA J Pharm Sci Technol. 1989; 43: 60-66 Google Scholar Controlling ice nucleation at a certain product temperature is expected to lead to a more uniform product because the degree of supercooling and nucleation temperature is influencing product parameters, for example, cake resistance, 5. Rambhatla S. Ramot R. Bhugra C. Pikal M. Heat and mass transfer scale‐up issues during freeze drying: II. Control and characterization of the degree of supercooling. AAPS PharmSciTech. 2004; 5: 54-62 Crossref Scopus (190) Google Scholar specific surface area, and residual moisture. 2. Konstantinidis A.K. Kuu W. Otten L. Nail S.L. Sever R.R. Controlled nucleation in freeze‐drying: Effects on pore size in the dried product layer, mass transfer resistance, and primary drying rate. J Pharm Sci. 2011; 100: 3453-3470 Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar Reduction of cake resistance is greatly reducing primary drying time 6. Roy M.L. Pikal M.J. Process control in freeze drying: Determination of the end point of sublimation drying by an electronic moisture sensor. PDA J Pharm Sci Technol. 1989; 43: 60-66 Google Scholar and therefore saves energy, time, and money because primary drying usually is the longest step in a freeze‐drying cycle.

Effects of freezing and thawing on the microstructure of latex paints

Freeze–thaw (FT) cycles can aggregate particles in aqueous paint suspensions. To understand the mechanism of particle aggregation, cryogenic scanning electron microscopy (cryoSEM) was used to visualize the microstructure after the freezing and thawing steps of the FT cycle. After the freezing step, cryoSEM images show that the microstructure contains ice crystals and particle-rich regions. Adding propylene glycol, a FT stabilizing additive, leads to formation of larger ice crystals. After thawing, the dispersion structure revealed by cryoSEM shows that the particles redisperse only in the paint with the highest amount of propylene glycol. The other paints contain clusters that are different from the particle-rich regions found after the freezing step. Increasing the thawing rate leads to a more dispersed microstructure even in the absence of propylene glycol. Analysis of the cryoSEM results shows that particle aggregation into these clusters occurs during the thawing stage, and slow thawing conditions lead to more aggregation. The cryoSEM results reported here are used to propose a mechanism of aggregation of particles in the paint.

Fractal Analysis and Biophysical Investigation of Muscular Tissue Damaged due to Low Temperature: A Pilot Study

Severe damage is produced in tissues by freezing and thawing. Until now, a great majority of the studies are performed qualitatively, lacking any quantitative approach. An important step is to choose the best option among different freezing methods. To approach the complex problem of damage produced in tissues by freezing, in this paper we present the classical mechanics approach and a quantitative study making use of a fractal methodology (evaluation of fractal dimension by box-counting method). A comparative fractal analysis between two different steps of freezing the human thoracic diaphragm muscle has been performed to quantify the voids and cracks produced by freezing (samples were placed in a cryostat chamber). Moreover, a standard Euclidean morphometry was performed to determine area and shape of the muscle nuclei after the two steps of freezing. Fractal dimension of the ice-tissue interface structures increased with decreasing temperature (p&lt;0.0001), percentage of cell muscle decreased (p&lt;0.01), while standard morphometry of the nuclei didnt show any modifications. Our results show the ability of the fractal approach to accurately quantify the damage produced by freezing and reveals that the lowest temperature produces the most damage.

A validated ultra-high performance liquid chromatography coupled to high resolution mass spectrometry analysis for the simultaneous quantification of the three known boar taint compounds

Boar taint is an off-odour that can occur when meat or fat from entire male pigs is heated. Most of the currently available analytical methods are not capable of detecting the three known boar taint compounds (indole, skatole and androstenone) simultaneously, which renders their analysis often labour-intensive and time-consuming as separate analyses are required. In this study a validated U-HPLC–HR-Orbitrap-MS analysis method is described for the quantitative determination of the three boar taint compounds in fat. The sample pre-treatment involves a melting step followed by extraction with methanol and clean-up consisting of a freezing step and solid phase extraction (HLB cartridges). The analytes are then chromatographically separated and detected with an Exactive™ high-resolution mass spectrometer. Due to the absence of guidelines for the analysis of boar taint in fat, the Commission Decision 2002/657/EC [18] and ISO 17025 [19] guidelines were used as guideline for validation of the developed detection method. This resulted in limits of detection and limits of quantification between 2.5 and 7μgkg−1 and between 5 and 10μgkg−1 for the three compounds, respectively, which is far below the threshold values set at 100μgL−1 for indole, 200μgL−1 for skatole and 1000μgL−1 for androstenone in pig fat samples. The method obtained for the three compounds a repeatability (RSD) lower then 12.7% and a within-laboratory reproducibility (RSD) lower than 16.9%. The recovery of the three compounds ranged between 99 and 112 and an excellent linearity (R2≥0.99) was found. In the future, this method may be extended with other compounds that turn out to be correlated with boar taint.

Effect of Cholesterol-loaded-cyclodextrin in Presence and Absence of Egg Yolk during Freezing Step on Quality of Markhoz Buck’s Spermatozoa

Cryopreservation protocols induce partially irreversible damage to mammalian sperm plasma membranes. Previous studies have indicated that adding cholesterol to the plasma membrane, as cholesterol-loaded-cyclodextrins, improves cryosurvival of sperm. Therefore, the purpose of this study was to determine if treating sperm of Markhoz bucks with cholesterol-loaded-cyclodextrins (CLC) (0, 0.75, 1.5, 2.25 and 3 mg/ml diluted sperm/ml) in Tris-citric acid-glucose diluents with and without egg yolk (containing 5% glycerol) would improve the post-thaw sperm quality. The motion characteristics were evaluated with a Computer Assisted System Analyzer (CASA); acrosome integrity and vitality were measured with the triple-stain technique. Samples were recovered before and after freezing by means of putting straws into water for 30 sec and then parameters were assessed. The results showed that the treatments significantly affected motility, progressive motility, recovery rate, curvilinear velocity, beat cross frequency, live sperm with reacted acrosome, live sperm with unreacted acrosome, dead sperm with reacted acrosorne, and dead sperm with unreacted acrosome during freezing (p0.05). The best results were observed for extender containing 2.25 mg/ml ( sperm/ml) CLC supplemented with 2.6% egg yolk. In conclusion, the findings of this study indicate improved Markhoz sperm viability and motility following treatment in the presence of egg yolk.

Remoção de cor de efluentes têxteis com cogumelos Agaricus bispora

Decolorization of textile effluent with mushroom Agaricus bispora. The direct application of Agaricus bispora mushroom was evaluated for decolorization of a synthetic mixture of reactive dyes. The effects of particle size (0.5 or 1.0 cm cubes and triturated mushroom), mushroom mass (10, 20, 40, 60 or 80 g in 250 mL of solution) and different mushroom tissue treatments were analyzed regarding color removal efficiency of dyes Reactive Yellow 37, Reactive Black 5 and Reactive Red in a synthetic solution of 13.3 mg L -1 concentration of each dye. The best results were found with larger superficial contact area between mushroom particle (triturated mushroom) and colored effluent under continuous aeration. Acetone addition during mushroom trituration process followed by a freezing step contributed to decolorization improvement, leading to best results: 73% after 6h, with 20 g of biocatalyst 250 mL -1 of effluent. The use of different mushroom batches and brands resulted in different enzymatic activities and similar levels of color removal, such result confirmed that decolorization does not have any direct relation with enzyme activity.

Determination of the different components of cadmium short‐term uptake by roots

AbstractAs the various components of the cadmium (Cd) root sink have not been clearly described, there is a need to precisely measure the respective contributions of apoplast and symplast to short‐term root Cd uptake and to explain the linear component of the absorption isotherms. A new method of fractionating Cd in roots was applied to two plant species with contrasting abilities to accumulate Cd: maize (Zea mays) and a Cd‐hyperaccumulating ecotype of alpine pennycress (Noccaea caerulescens). Their roots were exposed for 1 h to increasing concentrations of labeled Cd. Series of desorption baths were used to obtain the root apoplastic Cd in combination with a brief freezing step in liquid nitrogen to separate the intracellular metal from the apoplastic one. The apoplastic uptake accounted for 15% to 82% and for 48% to 96% of the total Cd uptake of maize and of alpine pennycress roots, respectively. In the case of maize, the concentration‐dependent symplastic net flux fitted a biphasic Michaelis‐Menten function, while in the case of alpine pennycress, a Michaelis‐Menten‐plus‐linear function proved a better fit. The second component of the symplastic net flux may reflect absorption through a low‐affinity transport system. Short‐term Cd uptake by roots is dominated by the high‐affinity transport system for exposure concentrations below 1 μM for maize and 0.2 μM for alpine pennycress, while cell‐wall binding prevailed for higher exposure concentrations.

Simulation of freezing step in vial lyophilization using finite element method

Determination of heat transfer and temperature profile during freezing step is fundamental to predict the final structure of a lyophilized product. The aim of this study was to develop and optimize a dynamic model based on finite element method for simulation of freezing step in order to study final product morphology in both vertical and radial directions. Different factors have been taken into account: chamber pressure, shelf temperature, vial shape, initial solution temperature, nucleation temperature and phase changes. The dynamic axisymmetric model proposed could simulate temperature of each point in the vial and position of liquid–solid interface, without necessity of fitting parameters or questionable assumptions. In addition, the model was extended to predict the average crystal size in each element and the influence of different factors was examined.

Gluten-free frozen dough: Influence of freezing on dough rheological properties and bread quality

The freezing process at different steps of breadmaking is widely used to improve fresh bread availability for the consumer. The consequences of a freezing step on wheat dough and bread, and the way to reduce its negative impacts have been studied for years. Nevertheless, few works report studies on gluten-free doughs and breads. This work investigates the effect of unfermented frozen dough process on the properties of gluten-free dough and the quality of bread. Rheological oscillation tests showed that viscoelastic properties were unchanged for fresh and thawed doughs. However flow tests exhibit an effect of freezing on consistency index and flow behaviour index. Regarding the quality of bread, gluten-free breads obtained by frozen dough process had lower specific volumes and harder crumbs than conventional gluten-free breads (unfrozen breads). Distribution of gas cells was more homogeneous with a freezing step. Crust colour characteristics were also modified by the freezing step.

Effects of cholesterol-loaded cyclodextrin during freezing step of cryopreservation with TCGY extender containing bovine serum albumin on quality of goat spermatozoa

The susceptibility of mammalian spermatozoa to cold shock and freezing damage is due to changes in membrane lipid composition, particularly cholesterol depletion in plasma membrane during cryopreservation. The aim of this study was to investigate the effects of different concentrations of cholesterol-loaded cyclodextrin (CLC) and bovine serum albumin (BSA) on the cryopreservation of goat spermatozoa in tris-citrate egg yolk extender. Semen was collected from four mature goats and divided into seven aliquots prior to cryopreservation. The first aliquot remained untreated and was mixed with TCG, the second aliquot was mixed with TCG and egg yolk (TCGY), third aliquot was mixed with TCGY and 2.5% BSA (TCGYB) and other aliquots were mixed with TCGYB containing 0.75, 1.5, 2.5 and 3 mg/ml CLC. All samples were cryopreserved in straws over liquid nitrogen vapor and sperm motion Kinetics were measured by computer-assisted semen analysis (CASA) (percent motility (MOT), curvilinear velocity (VCL), straight-line velocity (VSL), average path velocity (VAP), linearity (LIN), and amplitude of lateral head displacement (ALH)). Acrosome status and vitality was observed by the triple-stain technique. CLC addition to extender resulted in significant ( p < 0.05) enhancement of MOT, STR, and VCL of post-thawing sperm. Post-thawed motility, progressive motility and recovery rate were significantly ( p < 0.05) higher in 1.5 mg/ml CLC with 2.5% BSA in TCGY extender compared to other groups. The 1.5 CLC sperm yielded a significant increase in percentage of spermatozoa with intact acrosome ( P > 0.05). These results indicate that treating goat sperm with CLC and BSA in TCGY extender improved motility and vitality after freezing and thawing.

Freeze-thawing as a path to concentrate aqueous solution

Phenol-dye aqueous ternary solutions were employed as model eutectic solution, and concentration phenomena during freezing and thawing were investigated. The freeze-concentration level during freezing step and the concentration profiles of the melt fractions during thawing step were examined. It was found that the present freezing conditions did not effectively separate the solutes from frozen zone. Phenol component was slightly concentrated in the top frozen layer though the dye was almost equivalently distributed in the frozen domain. However, the concentrations of melt fractions obtained during thawing step were clearly higher than the concentration level of the frozen domains. Approximately 50% of the both solutes could be recovered from the initial 30% of the melt fraction. It was suggested that concentration behaviour during thawing would be controlled by thawing condition as explained by the kinetics of mass transfer of solutes in the frozen domain and at the frozen interface.

E231 木質系バイオマスからの糖抽出方法に関する研究(OS-10:バイオマスエネルギー(III)・一般講演)

This study focused on the pre-process of extracting sugar that is very essential in bioethanol production system to promote its efficiency. To do it, the freezing step was introduced into the first process. Furthermore, the effect of the kind of wood, the size of wood chips on the extracting efficiency of sugar was also investigated. As a result, there is a little difference in sugar concentration sue to the kind of wood. The bigger is the size of wood chips, the higher is sugar concentration with the short time. The effect of freezing step introduced was not seen.

Freeze-Drying Conditions Non-Altering to Ettringite Contained in Hardened Cement and the Pore Size Distribution

The freeze drying process for hardened bodies of cement consists of a freezing step by liquid nitrogen and a drying step by vacuum. The use of liquid nitrogen during the process involves the risk of cracking due to heat impact. The authors made improvement to existing freeze-drying equipment to minimize heat impact on specimens and tested various freezing conditions and drying temperatures in the current study. The specimens used in this experiment were hardened bodies of hauyne-containing cement with ettringite, which was susceptible to structural destruction by drying. As the result of comparative study, the authors determined optimum conditions for drying where peak area measured by the powder X-ray diffraction remained almost unreduced successfully. This revealed that the proposed conditions were almost non-altering to ettringite. The pore size distribution of the specimens prepared by this method was found to differ significantly in major pore diameter and total pore volume from those of specimens dried by other common methods : D-drying or drying at 105°C. The pore size distribution data for ettringite obtained by the freeze drying under the conditions proposed in the current study further allowed prediction that the data would represent the extremely fresh condition in which most of ettringite remained intact.