Production of extracellular bifidogenic growth stimulator (BGS) from Propionibacterium shermanii using a bioreactor system with a microfiltration module and an on-line controller for lactic acid concentration

Production of a bifidogenic growth stimulator (BGS) by Propionibacterium freudenreichii subsp. shermanii (Propionibacterium shermanii) using lactic acid as a carbon source was investigated using different cultivation methods. When a continuous bioreactor system with a filtration device was used at a dilution rate of 0.075 h(-1), the average BGS concentration was 2.4 mg/l, which corresponds to a BGS productivity per cultivation time of 1.8 x 10(-1) mg x l(-1) x h(-1). The BGS productivity per cultivation time in continuous cultivation with filtration was 1.9-fold that (9.4 x 10(-2) mg x l(-1).h(-1)) in a conventional batch cultivation. In fed-batch cultivation with feed-back control using an on-line lactic acid controller with a lactic acid biosensor, it was possible to prevent substrate inhibition by maintaining the lactic acid concentration in culture broth low at 3.3 g/l, and an enhanced BGS production (31 mg/l) was successfully attained. The BGS productivity per cultivation time (2.1x10(-1) mg x l(-1) x h(-1)) in the fed-batch cultivation with feed-back control was 2.2-fold that in the conventional batch cultivation. A new bioreactor system was developed by coupling a continuous bioreactor system with a filtration device to an on-line lactic acid controller. Using the new bioreactor system, we produced BGS continuously at a high level of 47 mg/l. The BGS productivities per cultivation time (3.5 mg.l(-1) x h(-1)) and the total volume of medium used (1.7 x 10(-1) mg x l(-1) x h(-1)) obtained in the new bioreactor system were 37-fold and 2.1-fold those in the conventional batch cultivation, respectively. These results described above clearly demonstrate the positive effects of both the continuous filtration for removal of metabolites (propionic and acetic acids) inhibitory to cell growth and feed-back control of lactic acid concentration in the culture broth on BGS production by P. shermanii. This paper is the first report on BGS production by the propionic acid bacterium using lactic acid as a carbon source.     

Effect of Milling Treatment on the Particle Size in the Preparation of AIN Powder from Aluminum Polynuclear Complexes

Aluminum nitride powder was synthesized from aluminum polynuclear complexes. Basic aluminum chloride (BAC) provided the aluminum polynuclear complexes. The effect of the milling treatment for the precursor made from basic aluminum chloride and glucose on the particle size was investigated. BAC and glucose were dissolved in water and mixed homogeneously. AIN powder was obtained by calcining under a nitrogen gas flow after drying, milling by vibration mill, and precalcining at 800°C. Then excess carbon was removed by firing in air. It was found that the milling treatment affected the particle size of AIN powder and nitridation mechanism. Without the milling treatment, AIN powder was synthesized directly from the γ-alumina of an intermediate product. In using a milled precursor, however, α-alumina was formed during the calcining, and the particle size of the AIN powder obtained was about five times larger than that of AIN powder synthesized from a raw precursor. The formation of α-alumina phase began at the rather low temperature of 800°C. These results suggest that the mechanochemical effects added by the milling promotes the formation of α-alumina during calcining, and the α-alumina phase formed accelerates the particle growth. AIN powders obtained were very uniform. The oxygen content and the surface area of AIN powders synthesized from the raw and milled precursors were 2.9 wt% and 17.5 m²/g, and 1.1 wt% and 3.6 m²/g, respectively.     

Preparation and cured properties of novel cycloaliphatic epoxy resins

Preparation and characterization of novel cycloaliphatic epoxy resins, which are derived from octadienyl compounds, were studied. From a model peracetic acid epoxidation reaction using 2,7-octadienyl acetate-1, the structure of the liquid resins is estimated to be mainly terminal epoxides and some amount of inner epoxide depending on the epoxide content. The epoxy resins offer lower toxicity and lower vapor pressure. The reactivity of the resin with acid anhydrides is moderate but faster than that of traditional cyclohexane epoxide-type resins and slower than that of the glycidyl ester-type resins. This reactivity was also examined using model compounds. The heat deflection temperature of the hexahydro-phthalic anhydride-cured resins is shown to be directly proportional to the number of epoxy groups in the molecules. The flexural strength of the cured resins is nearly equivalent to that of the commercial resins, although the flexural elongation of the resins is larger than that of the rigid cyclohexane epoxide-type resins. The thermal stability of the cured resins is comparable to typical rigid cycloaliphatic resins; furthermore, high water resistance of the cured resins is suggested to be attributed to the hydrophobic character of the C₈ chain by cross-linking. © 1993 John Wiley & Sons, Inc.     

Transient hopping transport in percolation clusters

Monte Carlo simulation for percolative hopping transport has been carried out to explain the increase in transit‐time dispersion and decrease in drift mobility with increasing applied electric field, found in molecularly doped polymers with low concentrations of charge transporting molecules. These two phenomena cannot be understood in terms of the Gaussian disorder model (GDM), which has been widely accepted for the analysis of the transport data of molecularly doped polymers. It is found that the two phenomena are successfully explained by the present computer simulation. The GDM analysis is applied to the analysis of the simulation data, and it is shown that energetic disorder can be estimated from the GDM analysis even in the case of percolative hopping transport and that the percolative motion of hopping carriers is one of the origins of geometrical disorder. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 1–9, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10014     

Self-assembly of size- and position-controlled ultralong nanodot chains using near-field optical desorption

We report the self-assembly of a size- and position-controlled ultralong nanodot chain using a novel effect of near-field optical desorption. A sub-100-nm dot chain with a deviation of 5 nm forms at a size based on plasmon resonance, depending on the photon energy; the resulting structure forms a high-transmission-efficiency nanoscale waveguide. Using this method with simple lithographically patterned substrates allows one to increase the throughput of the production of nanoscale structures dramatically at all scales.     

FM noise reduction and subkilohertz linewidth of an AlGaAs laser bynegative electrical feedback

Negative electrical feedback was applied to a CSP-type AlGaAs laser, reducing its FM noise at the Fourier frequency range of f⩽40 MHz. The magnitude of the FM noise was far lower than the quantum noise level of the free-running laser at 100 Hz⩽f ⩽4.4 MHz. It was as low as 1×10^-7~1×10 ^-6 that of the free-running laser at 100 Hz⩽f⩽1 kHz. The full width at half maximum of the field spectrum was reduced to 560 Hz. The major factors necessary for realizing the very low FM noise level were: (1) the laser had almost constant FM response characteristics for a wide Fourier frequency range; (2) a high-finesse Fabry-Perot interferometer was employed for highly-sensitive FM noise detection and to get higher feedback gain; (3) the reflection mode of the Fabry-Perot interferometer was employed to increase the bandwidth and efficiency of the FM noise detection; and (4) a computer simulation was utilized for optimum design of the feedback loop     

Flame retardancy effects of halogenated phosphates on poly(ethylene terephthalate) fabric

A Chemical research on the flame retardancy effect of halogenated phosphates on poly(ethylene terephathalate) fabric was carried out by thermogravimetry, infrared spectral analysis, and mass spectrometry. The following conclusions were drawn: (1) The flame retardancy effect of halogenated phosphates such as tris(2,3-dibromopropyl) phosphate is due to altering the pyrolysis reaction of polyester by aldol condensation. (2) The probability that liberated halogen compounds from the phosphates act as radical acceptors in a flame zone may be low. (3) Incorporation of halogen elements into phosphates appear to depress evaporation of phosphates, which act as acidic catalysts in aldol condensation from the condensed phase.     

Dielectric properties of anodic oxide film on Nb solid solution/Nb2N two phase alloys

The structure and dielectric properties of an anodic oxide on Nb solid solution (Nb_ss)/Nb₂N two phase alloys were investigated. The anodized specimens were covered with two types of anodic oxides on the Nb_ss and Nb₂N phases, respectively. The relative permittivity and leakage current density of the anodized specimens can be explained by the combination of the two oxides; the relative permittivity of the specimens increased with the volume fraction of the oxide on the Nb_ss phase, because the relative permittivity of the oxide on the Nb_ss phase is higher than that on the Nb₂N phase. The leakage current was suppressed irrespective of the constitute phases as compared with the anodized pure Nb, because it was reduced in both the oxides on the Nb_ss and Nb₂N phases.     

Quantum fidelity and dynamical scar states on chaotic billiard system

It is found that the decay rate of the quantum fidelity is suppressed, when the periodic orbit scars in the accumulation of the time-evolving wavefunction become obvious in two-dimensional (2D) nanostructure. The fidelity is numerically evaluated by the time-evolution of the wavepacket inside a 2D chaotic nanostructure: the stadium, which is the typical chaotic system. The suppression is apparent in the Lyapunov regime, where the decay rate does not depend on the strength of the perturbation.