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Self-disruptive Escherichia coli that produces foreign target protein was developed. E. coli was co-transformed with two vector plasmids, a target gene expression vector and a lysis gene expression vector. The lytic protein was produced after the expression of the target gene, resulting in simplification of the cell disruption process. In this study, the expression of cloned T4 phage gene e or t was used for the disruption of E. coli that produced β-glucuronidase (GUS) as a model target protein. The expression of gene e did not lead to prompt cell disruption but weakened the cell wall. Resuspension with deionized water facilitated cell lysis, and GUS activity was observed in the resuspended liquid. Expression of gene e at mid logarithmic growth phase was the optimal induction period for GUS production and release. On the other hand, the expression of gene t induced immediate cell lysis, and intracellular GUS was released to the culture medium. Maximum GUS production was obtained when gene t was induced at late logarithmic growth phase.

An index of particle dispersion is used to quantify the degree of particle dispersion inside the horizontally rotating bioreactor. Resin particles were suspended inside a horizontally rotating cylinder. The states of particle dispersion were observed and recorded on video, from which data the index of particle dispersion was calculated. The effect of the operating parameters particle concentration and cylinder rotational speed on the state of particle dispersion were described using the index. By comparing the quantitative and qualitative classifications of particle dispersion it was confirmed that the new index does reflect the degree of particle dispersion. From the comparison it can also be concluded that if the index is greater than 0.96, the particle distribution can be considered uniform.

The motion of microcarriers inside the horizontally rotating bioreactor was simulated in order to obtain some insight as to how particle motion can affect radial mass transfer. Fluid motion was modeled taking into account momentum transfer induced by particle motion. The force balance on the particle included the viscous drag, inertia, gravitational and buoyant forces. The main characteristics of observed particle motion under conditions of low particle concentration were reproduced by the model. Some implications of particle motion to mass transfer are discussed.

The motion and distribution of microcarriers inside a horizontally rotating cylindrical bioreactor were simulated using spherical ion exchange resin particles. Particle motion deviated much from that expected under ideal conditions. The possible mass transfer enhancing effects of particle translation and cluster rotation are discussed.

CHO-K1 cells were cultured by using a porous microcarrier. The effects of microcarrier concentration and agitation rate on cell growth in porous microcarrier cultures were investigated. The specific growth rate of 0.041 h-1 in porous microcarrier cultures was independent of both microcarrier concentration and agitation rate. By estimating the total surface area occupied by cells from the maximum cell number, it was found that not all the surface area of the porous microcarrier was utilizable for cell growth.

Abstract: The present research aimed to establish conditions for synchronized plantlet regeneration from rice callus based on a quantitative analysis of the relationship between intracellular 2,4-dichlorophenoxyacetic acid (2,4-D) concentration and shoot regeneration rate. To prepare the rice calli with different intracellular 2,4-D concentrations prior to regeneration, callus precultures were carried out in medium containing 4 mg/l 2,4-D and in 2,4-D-free medium for predetermined periods. As the critical intracellular 2,4-D concentration of the calli precultured in 2,4-D-free medium was too low to analyze precisely by conventional analytical methods, it was estimated using a kinetic model which described the behavior of 2,4-D by taking its uptake, metabolism and/or inactivation rates during the callus preculture into consideration. An experimental relationship between intracellular 2,4-D concentration and regeneration rate of rice calli revealed that the intracellular 2,4-D concentration should be controlled as low as 2.610–2μg/g fresh weight to reach the same synchronization in shoot regeneration as seen with rice seed germination. This condition was realized by feeding sugar into the 2,4-D-free medium after 4 days preculture when the carbon source was exhausted.

AbstractA forced oscillation method applying reverse-piezo electric effect has been proposed for mass-production of biocatalyst-entrapping polymer gel particles. A jet of aqueous alginate solution flowing out through an orifice was disintegrated into droplets by an oscillating pressure which was exerted by a ceramic plate vibrated by the reverse-piezo electric effect. The droplets formed were immediately solidified into gel particles in calcium chloride solution.The particle production rate by the method was up to 270 particles s−1or 1 × 10−6m3.s−1The size of the particles produced were down to I mm depending on the applied frequency. The smallest matrix size of the gel's polymer network was estimated to be around 5 nm.The method was applied for immobilization of yeast cells. The diameter of immobilized particles was 2.5 mm. The immobilized yeast grew well in the particle. The damage of yeast cells caused by the immobilization was not remarkable

Intracellular 2,4-dichlorophenoxyacetic acid (2,4-D) concentration profiles in rice (Oryza sativa L.) callus were measured for various subculture periods. 2,4-D was taken up into the callus by uphill transportation from the medium. The intracellular 2,4-D taken up was metabolized gradually during cultivation. The intracellular 2,4-D concentration markedly affected the redifferentiation process after subculture in such a way that the higher its concentration was, the more strongly the redifferentiation process was suppressed, and the lesser was the browning of the callus.

The effect of shear stress on the activity of cellular enzyme in an animal cell was discussed by using a flow channel. The activity of lactate dehydrogenase (LDH) in cells exposed to a shear stress of 0.5 Pa for 12 h was about 4-fold greater than in the cells without exposure to shear stress. The relative LDH activity was correlated with the dissipation energy density of the flowing medium. A good correlation was obtained and it was found that the dependency of cellular enzyme activity on the shear stress and the exposure time was related to the transmission of the energy from the flowing medium to attached cells.

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