Naomi Shibasaki-Kitakawa

Viscosity of gaseous HFC-134a (1,1,1,2-tetrafluoroethane) under high pressures

The viscosity of gaseous HFC-134a (1,1,1,2-tetrafluoroethane) was measured with an oscillating disk viscometer of the Maxwell type from 298.15 to 398.15 K at pressures up to 5.5 MPa. Intermolecular potential parameters for the Lennard–Jones 12-6 model were determined from the viscosity data at 0.1 MPa. The viscosity equation developed by Krauss et al. was applied to correlate the present viscosity data. In addition, the correlations proposed by Stiel and Thodos and by Lee and Thodos were tested for fitting the experimental viscosity data.

Improvement of Catechin Productivity in Suspension Cultures of Tea Callus Cells

In the suspension cultures of tea callus cells, C.sinensiscv. Yabukita, the effects of the culture conditions, such as culture period and light irradiation, on cell growth and catechin production were investigated. The production of flavonoids (catechins + proanthocyanidins) was promoted by inoculating the cells into the fresh medium at the culture period giving the maximum flavonoid content in the cells. The cultivation under light irradiation was repeated several times by inoculating the cells with the maximum flavonoid content. The flavonoid production was significantly increased without inhibiting the cell growth. We obtained the maximum flavonoid production, 1.5 g/dm3 medium, and the maximum content, 150 mg/(g of dry cell weight (DCW)). The latter value was larger than that in the leaves of the tea plant.

Viscosity of Gaseous HFC-125 (Pentafluoroethane) Under High Pressures

This paper reports experimental results lor the viscosity of gaseous HFC-125 (pentafluoroethane) under high pressures. The measurements were carried out with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K and at pressures up to the saturated vapor pressures at each temperature at subcritical conditions or up to 9 MPa at supercritical temperatures. Intermolecular scaling parameters of HFC-125 for the extended corresponding states were determined from the viscosity data at 0.1 MPa. An empirical viscosity equation is proposed to interpolate the present experimental results as a function of temperature and density.

Viscosity of Gaseous HFC-143a (1,1,1-trifluoroethane) Under High Pressures

The viscosity of gaseous HFC-143a(1,1,1-trifluoroethane) was measured with an oscillating-disk viscometer of the Maxwell type at temperatures from 298.15 to 423.15 K and at pressures up to the saturated vapor pressure at each temperature under subcritical conditions or up to 9 MPa under supercritical conditions. Intermolecular potential parameters of HFC-143a for the extended corresponding states were determined from the viscosity data at 0.1 MPa. An empirical viscosity equation as functions of temperature and density is proposed to interpolate the present experimental results.

Kinetic model for synthesis of fructosyl-stevioside using suspended β-fructofuranosidase

The synthesis experiments of fructosyl-stevioside were conducted under the various conditions of the initial concentrations of the substrates and the enzyme. The transfructosylation of stevioside with sucrose and the hydrolyses of sucrose and fructosyl-stevioside simultaneously occurred. The fructosyl-stevioside synthesis was inhibited by the side products, glucose and fructose. A kinetic model was constructed by considering the Ping-Pong Bi Bi mechanism for the transfructosylation, the apparent Ordered Uni Bi mechanism for the hydrolysis and the competitive inhibition by the side products. The model constants were estimated by fitting the model equations with the experimental results for the sucrose hydrolysis and the fructosyl-stevioside synthesis. The model can predict not only the appropriate conditions to efficiently synthesize the fructosyl-stevioside, but also the reaction time giving the maximum conversion.

Intraparticle cell growth and cell leakage in cultures of Nicotiana tabacum cells immobilized in calcium alginate gel beads.

Immobilized Nicotiona tabacum cells in calcium alginate gel beads were prepared under various conditions and then were cultivated. The effects of different conditions of preparation, in relation to concentration of calcium ions (Ca2+), on intraparticle cell growth and cell leakage from beads were investigated experimentally. As the amount of Ca2+ incorporated into the beads increased, the numbers of cells leaked from the beads into the medium decreased. However, cell growth was inhibited by high Ca2+ concentrations in the beads. Optimal conditions existed, which prevented cell leakage without inhibiting intraparticle cell growth. The effect of adding CaCl2 to the culture medium was also studied. The Ca2+, used for the alginate crosslinking, gradually leached from the beads with increasing cultivation time, such that the beads gradually became brittle and fragile. The addition of CaCl2 was effective in preventing Ca2+ loss from the beads and cell leakage. n n n n© 2000 Society of Chemical Industry

Kinetic model for oligosaccharide hydrolysis using suspended and immobilized enzymes

Abstract A novel kinetic model that describes the hydrolysis of oligosaccharide using the suspended enzyme has been constructed by introducing the selectivity of the enzyme for cleaving each α-1,6 glycosidic bond of the substrate. The Michaelis-Menten type kinetic constants, K m and V max , and the selectivity coefficient, α, are estimated by fitting the model with the experimental data obtained under various conditions. The new constant, α, is estimated at 0.411, and almost the same as the experimental values. The model has been extended for the immobilized enzyme system by taking into account the intraparticle mass transfer resistance. The model constants are estimated similarly to the case of the suspended enzyme system. α imm ( α for the immobilized enzyme system) is a little higher than that in the suspended enzyme system. K m imm and V max imm , are much greater than those for the suspended enzyme system. The estimated values of the effective diffusivities in the support particle are a few order of magnitude smaller than those in aqueous solution. The model well simulates both experimental results obtained in the suspended and immobilized enzyme systems.

Topic: Liquid Biofuel Production

Liquid biofuels, bioethanol, and biodiesel (fatty acid methyl ester) are practical and offer attractive advantages over other forms of biomass energy resources in terms of high energy density and ease of storage and transport. However, there has been no significant increase in the production of these fuels in the past few years. The reason is that there is no profitability for producers owing to high production cost and no benefits for consumers because of unstable product quality and lower fuel economy and power. Moreover, emergence of next-generation automobiles (e.g., battery-powered and fuel cell electric vehicles) will lower the demand for gasoline. From this perspective, it seems as if there is no role left for biofuel production in Japan’s future energy system. However, from another perspective, biofuels may have a vital function under some circumstances, if appropriate and profitable technologies are developed. Using the example of a novel biodiesel production process using resin catalysts, this article discusses those technologies and circumstances in which biofuels can be a part of future sustainable energy systems.