Enhanced anthocyanin production from grape callus in an air-lift type bioreactor using a viscous additive-supplemented medium

An N-medium containing carboxymethyl cellulose (CMC) was applied to an air-lift type bioreactor culture of grape (Vitis vinifera cv. Bailey alicant A.) callus, and anthocyanin production was investigated. Grape callus grew well at an air flow rate of 80 ml/min and anthocyanin production was significantly increased in the N-medium, reaching 17 mg/l after 7 d of culture. The anthocyanin content of the N-medium was about two times higher than that of the conventional medium without CMC. The effect of air flow rate was also investigated within the range from 40 to 160 ml/min. A twofold increase in anthocyanin content was obtained at all the air flow rates tested in the N-medium. The distribution of grape callus size obtained after 7 d of the bioreactor culture was investigated. The average callus size was 490 mum which was 1.6 times larger than that obtained in the conventional medium. It was found that large calli with a relatively high anthocyanin pigment content were formed in the bioreactor culture using the N-medium. The fluid dynamics in the bioreactor was also investigated at three points (top, middle and bottom) in the bioreactor by laser doppler velocimetry. The average axial velocity of the circulated medium was 0.4 times lower than that of the conventional medium while their average radial velocities were almost the same (zero). The standard deviation of radial velocity fluctuation in the N-medium was also 0.4 times less than that in the conventional medium. These results suggest that turbulent flow occurred in the bioreactor culture using the conventional medium and the degree of turbulent flow decreased significantly when 0.8% CMC was added to the medium to prepare the N-medium. A change of the flow pattern is considered to be the cause of the decrease in hydrodynamic stress, resulting in enhanced pigment production due to the enlargement of the callus.     

Degradation of cell wall materials from sweetpotato, cassava, and potato by a bacterial protopectinase and terminal sugar analysis of the resulting solubilized products

Cell wall materials (CWMs) from sweetpotato, cassava, and potato starch residues were degraded using a crude enzyme solution from the culture filtrate of a Bacillus sp. isolated from soil, Bacillus sp. M4. This organism has been found to secrete polygalacturonic acid lyase (PGL) and glycan depolymerase activities, especially arabinanase, but cellulase activity was nearly absent. Sugar analysis of the solubilized product after enzyme treatment at pH 7.0 revealed that it is mainly composed of galacturonic acid, galactose, and arabinose, the sugars found commonly in the pectin fraction. This suggested the presence of a protopectinase (PPase) activity in the culture filtrate. The presence of EDTA completely inhibited PGL but PPase activity was almost retained, suggesting that the PGL is not the primary activity responsible for pectin solubilization. The mode of action of the crude enzyme was determined by terminal sugar analysis using HPAEC-PAD after hydrolysis of the reduced products. Results revealed that galactose is the main neutral sugar at the reducing terminal of the products, although rhamnose was also present in the higher molecular weight component. This suggested that at neutral pH, the primary activity in the culture filtrate of Bacillus sp. M4 is a B-type PPase, which attacked the galactan as well as rhamnogalacturonan moieties of the protopectin, resulting in the release of a soluble pectin fraction.     

The effect of surfactant solutions on the growth rate of environmental stress cracking of low-density polyethylene

The growth rate of environmental stress cracking (ESC) of low-density polyethylene (PE) specimens bent and immersed in surfactant solutions has been measured. In the temperature range 25 to 60° C, the values of the growth rate are almost independent of the amount of deformation varying in a narrow range but dependent on it below 25° C. They are changed over a few hundredfold by the changes of temperature and of surfactant solutions. The growth of ESC of PE is assumed to be a stress-assisted thermal activation process. In the temperature range 25 to 60° C, the values of activation enthalpy obtained depend on the surfactants used, but are almost independent of their concentrations. The growth rate was measured under hydrostatic pressure up to 2.25×10⁷ N m^–2 (220 atm). A few of the values of the dilation activation volume were evaluated. The nature of the mixture-like (surfactant and PE) region developed on PE surfaces at crack tips and the increase in the mobility of PE segments there seem to be essential to ESC of PE.     

Surface Friction of Poly(dimethyl Siloxane) Gel and Its Transition Phenomenon

The surface sliding friction of chemically cross-linked poly(dimethyl siloxane) (PDMS) swollen with linear PDMS as an oligomer is investigated. The friction force f increases with the normal pressure P in a power-law relation fP , where the exponent changes in a range of 0-1, depending on the degree of polymerization, N _poly, of the linear PDMS oligomer. When N _poly is in a range of 240-320, a dramatic decrease in friction force is observed at a critical normal pressure, P _c, leading to a very low friction coefficient on the order of 10^–3 at high-pressure ranges. The P _c increases with decreasing network size N _netof the gel and also with increasing polymer length related to N _poly. One possible explanation for this transition phenomenon in friction is that linear PDMS molecules are exuded from the gel network beyond a certain pressure and behave as polymer brushes, which are able to reduce the friction.     

Reactivities of oxo and peroxo intermediates studied by hemoprotein mutants

A series of myoglobin mutants, in which distal sites are modified by site-directed mutagenesis, are able to catalyze peroxidase, catalase, and P450 reactions even though their proximal histidine ligands are intact. More importantly, reactions of P450, catalase, and peroxidase substrates and compound I of myoglobin mutants can be observed spectroscopically. Thus, detailed oxidation mechanisms were examined. On the basis of these results, we suggest that the different reactivities of P450, catalase, and peroxidase are mainly caused by their active site structures, but not the axial ligand. We have also prepared compound 0 under physiological conditions by employing a mutant of cytochrome c 552. Compound 0 is not able to oxidize ascorbic acid.     

Heat deterioration of phospholipids. V. A new rearrangement reaction of sugars and phosphatidylethanolamine

Novel four 2,3-dihydro-1H-imidazo[1,2-a]pyridine-4-ylium derivatives were obtained with increase of UV absorption at 350 nm and browning of the solution by heating paste lecithin from soybean (SL) in octane. These four derivatives were formed by reaction of one molar of any sugar except 2-deoxysugars with two molar of phosphatidylethanolamines (PE) in SL. To confirm the reaction mechanism, several (13)C-labeled-sugars were reacted with 1,2-di-O-stearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE), respectively. These reactants clearly showed that five carbons of the pyridinium ring and one carbon of the substituted group were based on those of a sugar and that the formation of the pyridinium derivatives was accompanied with cleaving between the carbons of 1- and 2-positions in the sugar and rearrangement. This reaction is a new rearrangement reaction and we named it "new pseudo Maillard rearrangement reaction".     

Slip casting molds produced by hot isostatic process

Slip casting can produce large green bodies of fairly complex shape with high homogeneity. In this work, porous alumina produced by hot isostatic process (HIP) is evaluated to apply as slip casting molds. HIPed porous alumina molds have higher water suction rate than conventionally sintered ones with a same open porosity. The high water suction rate of HIPed molds is due to the low specific surface area of HIPed porous materials. The high water suction rate of HIPed porous alumina molds allows high casting rates.