Influence of mechanical properties of pectin films on charge density and charge density distribution in pectin macromolecule

The hydration and mechanical properties of citrus pectin films were examined in conditions relevant to those in the plant cell wall. The pectins used for this study varied in the degree of esterification (DE) (high or low) and charge distribution on the backbone (random or block). The hydration of the films was controlled in an osmotic pressure experiment using polyethylene glycol solutions (PEG 20000). Hysteresis tests at constant deformation rate (stress vs deformation) were used for investigating the mechanical behaviour of films. Mechanical and hydration properties of pectin films were examined as a function of charge density, charge density distribution and counterion environment—K⁺, Ca²⁺, Mg²⁺. Swelling decreased with increasing counterion concentration. The effect is stronger in the case of Ca²⁺ and Mg²⁺ for low esterified pectins and therefore crosslinks from divalent ions could be assumed. The crosslink effect is confirmed in mechanical experiments where an increase in the film tensile modulus is observed with increasing counterion concentration. It is shown for the first time that in case of highly concentrated pectin solutions Mg²⁺ cations also act as a crosslinker for pectin macromolecules.     

Concavine, an unusual diterpenic alkaloid produced by the fungus Clitocybe concava

A novel alkaloid with an unprecedented ring system consisting of a dodecahydro-7-oxa-9a-aza-benzo[a]azulene ring (1), has been isolated from cultures of Clitocybe concava (Basidiomycetae). Its structure and relative stereochemistry were elucidated on the basis of spectroscopic data. Concavine presents a weak antibacterial activity.     

Succession of stacking disorder in hard-sphere crystal under gravity by Monte Carlo simulation

We have performed Monte Carlo simulations of hard spheres under gravity. Vertical boundaries are hard walls, which are well separated with each other. On the other hand, the periodic boundary condition is imposed in the horizontal direction. While we previously reported enhancement of crystallinity as well as crystallization due to gravity, we present here the results that demonstrate the succession of a defect. In case that the crystal formed at the bottom of the system includes kinds of stacking disorders for the (0 0 1) growth, twin band structure develops as mediated by a stacking disorder succeeded in the crystal formed in the fluid region which lies on the bottom crystal. In case that the stacking structure along horizontal direction changes from the (1 1 1) stacking to the (0 0 1) stacking, twin band structure in the (0 0 1) stacking region develops as succeeded in the crystal transformed. The twin band structure also becomes large with its upward growth.     

Acid Pullulanase from Bacillus polymyxa MIR-23

Within the frame of a screening program aimed at the isolation of amylolytic sporeformers, one strain with high amylolytic activity designated MIR-23 was selected. The microbial characterization was carried out by morphological and biochemical tests and, by means of statistical treatment, was identified asBacillus polymyxa. The organism could grow in acidic conditions (pH 5.0) on a starch medium and produce α-amylase, pullulanase, and α-glucosidase. Batch cultures showed the highest enzyme activities in the stationary phase. Pullulanase activity exhibited an optimal temperature of 52–57°C at pH 4.5–5.5. These properties would allow its use in the saccharification processes in the starch industries.     

1H-NMR Relaxation of Water Molecules in the Aqueous Microcrystalline Cellulose Suspension Systems and Their Viscosity

An intensive study for aqueous microcrystalline cellulose (MCC) suspensions was carried out in view of the relationship between a viscosity and a 1H spin-spin relaxation time (T2) of water. An investigation was carried out for four suspension systems with the different particle size distributions. The proton mole ratio () of bound water against MCC particles and T2 of bound water (T2,b) were evaluated from the T2 values obtained by Carr-Purcell- Meiboom-Gill (C.P.M.G) method and those by solid echo method, respectively. As a result of these analyses, the T2,b value for the aqueous MCC suspension was evaluated as 5 × 10–3 s and it was found that the system having a larger tended to show a higher viscosity. By relating the above results to the observation of the suspensions by an optical microscope, it was concluded that a network formed by MCC particles plays an important role in generating a high viscosity of MCC suspension, and that an averaged mobility of water molecules is sensitively affected by the network structure.     

The photosensitizing effect of the photoproduct of protoporphyrin IX

The photodynamic effect of a photoproduct of protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (ALA) was investigated in WiDr cells, a human adenocarcinoma cell line. The fluorescence excitation and emission spectra of PpIX and the photoproduct were measured. After 1, 3 or 5 min exposure of the ALA-incubated cells to 140 mW/cm² light at 635 nm, the photoproduct — the chlorin photoprotoporphyrin (Ppp), had an emission band around 670 nm. The Ppp excitation peak at 670 nm is well separated from the PpIX peak at 635 nm. The outcome of photodynamic therapy (PDT) was determined by measuring intracellular fluorescence intensity of propidium iodide (PI) 2 h following PDT and methylene blue (MB) staining 24 h following PDT. A significant increase in the fluorescence intensity of PI was noted when the ALA-loaded cells were exposed to 670 nm light after exposure to 635 nm, indicating enhanced cell membrane inactivation induced by the photodynamic action of the photoproduct. However, the fraction of the cells that survived following the same treatment as measured by MB staining was not significantly affected based on an analysis of variance. The fluorescence of PpIX decayed significantly during 635 nm light exposure. Exposure to light at 670 nm does not lead to any photodegradation of PpIX. The fluorescence of Ppp was bleached during 670 nm light exposure. Exposure of Ppp at 670 nm gives no PpIX back. Thus, the phototransformation of PpIX to Ppp is probably not a reversible process.     

Assessment of various carbon sources and nutrient feeding strategies for Panax ginseng cell culture

Ginseng (root of Panax ginseng C. A. Meyer) cells were cultivated on medium supplemented with various carbohydrates including sucrose, glucose, and fructose, at initial concentrations ranging from 10 to 110 g/L. Sucrose was shown to be the superior carbon source to the monosaccharides for ginseng cell growth and the optimal concentration was between 30 and 50 g/L. An increase in the initial concentration within this range increased the maximum cell density and growth index significantly, whereas much higher concentrations inhibited cell growth. Feeding of sucrose and some other medium components during the growth (fed-batch mode) was more effective in enhancing the cell growth and biomass productivity, increasing the growth index by more than 60–70% and biomass productivity by more than 50%.     

反相悬浮聚合法合成超强吸水剂

以两性高分子作悬浮稳定剂，用反相悬浮聚合法合成了聚（丙烯酸盐－丙烯酰胺）类超强吸水剂．研究了交联剂、稳定剂、引发剂等用量、中和程度、单体组成及链转移剂等聚合条件对吸水剂吸水性能的影响．得到了吸蒸馏水１０５０ｍＬ／ｇ及吸０．９％ＮａＣｌ溶液８６ｍＬ／ｇ的超强吸水剂．此外，还比较了含不同反离子的聚丙烯酸类吸水剂的吸水性能     

Methane production from synthesis gas using a mixed culture ofR. rubrum M. barkeri,and M. formicicum

The components of synthesis gas, CO, H₂, and CO₂, may be converted into CH₄ biologically through either acetate or H₂/CO₂ as intermediates. Of these two routes, conversion through H₂/CO₂ is preferred. This paper presents results of mixed-culture studies employing the photosynthetic bacteriumR. rubrum for converting CO to CO₂ and H₂ by the water gas shift reaction and two methanogens,M. formicicum andM. barkeri, for converting CO₂ and H₂ into CH₄. Results are presented for triculture operation in two types of reactors, the packed bubble column and the trickle-bed reactor.     

Effects of glucose,glutamine, and malate on the metabolism of spodoptera frugiperda clone 9 (sf9) cells

Optimal design and operation of bioreactors for insect cell culture is facilitated by functional relations providing quantitative information on cellular metabolite consumption kinetics, as well as on the specific cell growth rates (μ_G). Initial specific consumption rates of glucose, malate, and oxygen, and associated changes in μ_G, were measured forSpodoptera frugiperda clone 9 (Sf9) cells grown in batch suspension culture in medium containing 7–35 mM glucose, 0–16 mM malate, and 4–16 mM glutamine. The initial specific glucose consumption rate (q _G ) could be described by a modified Michaelis-Menten equation treating malate as a “competitive” inhibitorK ₁ = 6.5 mM) and glutamine as a “noncompetitive” inhibitorK _I = 14 mM) ofq _G , with aK _m of 7.1 mM for glucose. All three carbon sources were found to increase μ_G in a saturable manner, and a modified Monod equation was employed to describe this relationship (μ_Gmax = 0.047 h^-1). The initial specific oxygen consumption rate (q_O2) in Sf9 cells could be related to μ_G by the maintenance energy model, and it was calculated that, under typical culture conditions, about 15–20% of the cellular energy demand comes from functions not related to growth. Fitted parameters in mathematical expression for μg: K₄, Monod constant for glucose (mM); K₅, modified Monod constant for malate (mM); K₆, Monod constant for glutamine (mM); m_o2, specific consumption rate of oxygen by the cells under zero-growth conditions (nmol/cell/h); q_F, initial specific fumarate production rate (nmol/cell/ h);q _G , initial specific glucose consumption rate (nmol/cell/h); q_Gmax, maximum initial specific glucose consumption rate (nmol/cell/h);q _M , initial specific malate consumption rate (nmol/cell/h); q_o2, initial specific oxygen consumption rate (nmol/cell/h); Y_o2, cell yield on oxygen (cells/nmol); μ, initial specific cell growth rate (h^-1); μ_g, initial specific cell growth rate (h^-1); μG_max, maximum initial specific cell growth rate (h^-1).