Yeon-Ho Jeong

Screening of hexavalent chromium biosorbent from marine algae

Abstract A highly chromate-selective biosorbent with high adsorption capacity was found by examining the chromate adsorption capacities of 48 species of red, brown, or green marine algae sampled from the east coast of Korea. As a result of screening, a red marine alga showed excellent adsorption characteristics. It was identified as Pachymeniopsis sp. The timing of the sampling of Pachymeniopsis sp. did not affect the adsorption capacity of the alga but the optimum period for mass collection was April–May. The alga also showed high selectivity for chromate and its adsorption capacity for other heavy metal ions such as cadmium and manganese was relatively low. An investigation of the adsorption isotherm of Pachymeniopsis sp. as a dried powder for chromate adsorption at 25 °C showed Langmuir-type dependence. The maximum chromate adsorption capacity of the selected alga was about 225 mg/g. The desorption of adsorbed chromate from Pachymeniopsis sp. was done by treating samples with 1 N NaOH. It was confirmed that ion exchange type adsorption was observed with anion exchangers but not with cation exchangers. Therefore it is believed that the chromate adsorption is based on the anionic exchange of Pachymeniopsis sp.

Role of glutamine in hybridoma cell culture: Effects on cell growth, antibody production, and cell metabolism

Abstract The effects of glutamine on cell growth kinetics, monoclonal antibody productivity, and cell metabolism of hybridoma cells were investigated. The mouse-mouse hybridoma cell line V111 H-8, which produces mouse immunoglobulin (IgG 2a ) was used as a model system. Glutamine showed a Monod-type effect on specific cell growth rate with a very small Monod constant of 0.089 (m m ). A reciprocal relationship between initial glutamine concentration and specific cell death rate was observed. Monoclonal antibody (MAb) production was a strong function of glutamine concentration. Glutamine enhanced MAb production not only by stimulation of cell growth, but also by increasing the specific MAb productivity. Increasing glutamine concentration stimulated specific glutamine consumption rate and specific ammonium ion production rate. The specific glucose consumption rate decreased with increasing glutamine concentration up from 0 to 0.1 n m , and then increased. The specific lactate production rate decreased as glutamine concentration decreased.

Continuous Culture of Immobilized Streptomyces Cells for Kasugamycin Production

Continuous cultures of immobilized Streptomyces kasugaensis, a kasugamycin producer, were carried out on Celite beads. When using a prototype separator for immobilized‐cell separation and recycling, the continuous operation could not be sustained for an extended period as a result of an excessive loss of immobilized cells caused by the poor performance of the separator. Accordingly, the immobilized‐cell separator was revised to provide better immobilized‐cell settling and thus recycling into the reactor. In a subsequent culture using the revised separator, a stable operation was maintained for over 820 h with a high kasugamycin productivity. The kasugamycin productivity ranged from 9.8 to 16.1 mg/L/h, which was about 14‐ to 23‐fold higher than that in a batch suspended‐cell culture. When the original feeding medium concentration was doubled at the end of the continuous culture, the productivity became severely impaired for several reasons, which will be discussed. An excessive formation of free cells and loss of immobilized cells through the separator were also observed.

Kinetic study for the optimization of ginsenoside Rg3 production by heat treatment of ginsenoside Rb1

Background Ginsenoside Rg3 is a promising anticancer agent. It is usually produced by heat treatment of ginseng, in which ginsenoside Rb1 is the major ginsenoside. A kinetic study was conducted to optimize ginsenoside Rg3 production by the heat treatment of ginsenoside Rb1. Methods Ginsenoside Rb1 was heated using an isothermal machine at 80°C and 100°C and analyzed using HPLC. The kinetic parameters were calculated from the experimental results. The activation energy was estimated and used to simulate the process. The optimized parameters of ginsenoside Rg3 production are suggested based on the simulation. Results The rate constants were 0.013 h−1 and 0.073 h−1 for the degradation of ginsenosides Rb1 and Rg3 at 80°C, respectively. The corresponding rate constants at 100°C were 0.045 h−1 and 0.155 h−1. The estimated activation energies of degradation of ginsenosides Rb1 and Rg3 were 69.2 kJ/mol and 40.9 kJ/mol, respectively. The rate constants at different temperatures were evaluated using the estimated activation energies, and the kinetic profiles of ginsenosides Rb1 and Rg3 at each temperature were simulated based on the proposed kinetic model of consecutive reaction. The optimum strategies for producing ginsenoside Rg3 from ginsenoside Rb1 are suggested based on the simulation. With increased temperature, a high concentration of ginsenoside Rg3 is formed rapidly. However, the concentration decreases quickly after the reaching the maximal concentration value. Conclusion The optimum temperature for producing ginsenoside Rg3 should be the highest temperature technically feasible below 180°C, in consideration of the cooling time. The optimum reaction time for heat treatment is 30 min.

Processing and Reducing Factors of Difenoconazole during Ginseng Processing

This study was performed to acquire processing and reducing factors of difenoconazole during ginseng processing, and to establish the maximum residue limits of ginseng and its commodities. Difenoconazole was used in two fields (Wonju and Icheon) containing 6 year old ginseng plants. The amount of residue at Wonju and Icheon were

Repeated-batch culture of immobilizedGibberella fujikuroi B9 for gibberellic acid production: An optimization study

The performance of immobilized fungal cells on celite beads for the production of gibberrelic acid was investigated in flasks and 7-L stirred-tank reactor. Repeated incubations of immobilized fungal cells increased cell concentrations and volumetric productivity. The maximum volumetric productivity obtained in the immobilized-cell culture was 3-fold greater than that in suspended-cell culture. The concentration of cotton seed flour (CSF), amont the various nutrients supplied, most significantly influenced productivity and operational stability. Notably, insoluble components in CSF were found to be essential for production. CSF at 6 g/L with 60 g/L glucose was found to be optimal for gibberellic acid production and stable operation by preventing excessive cell growth.

Effects of Aster scaber Seed Oil Containing trans-Δ3 Fatty Acids on Lipid Profiles of Hamsters and Rats

The effects of Aster scaber seed oil (ASO) on lipid profiles were studied in rats and hamsters. ASO contained considerable amounts of Δ3t-16:1 (11.4%), Δ3t, 9c-18:2 (4.6%), and Δ3t, 9c, 12c-18:3 (11.3%). Young rats and hamsters were fed diets containing ASO, soybean oil (SBO), or olive oil (OLO) as fat sources for 4 weeks in separate experiments with or without cholesterol. In the rat study, there were no significant differences in the concentrations of serum total cholesterol, high-density lipoprotein (HDL)-cholesterol, and triacylglycerol among the groups. The serum but not liver malondialdehyde (MDA) level was significantly lower in the ASO-fed group than it was in the other groups. The biochemical and growth parameters revealed no significant biological damages in the ASO-fed animals. In the hamster study, dietary cholesterol-dependent effects were evident in the serum lipids profiles, whereas the fat-induced effect was only observed in the ratio of serum low-density lipoprotein (LDL)-/HDL-cholesterol. Furthermore, fat- and cholesterol-induced effects were evident in the ratio of serum LDL-/HDL-cholesterol. Significant interactions between dietary fat and cholesterol were observed as evident from the concentration of serum cholesterol and triacylglycerol, as well as the activity of serum cholesterol ester transfer protein. These results suggest that dietary ASO containing trans-Δ3 fatty acids appeared to improve the serum LDL-/HDL-cholesterol ratio more than the SBO did, especially when hamsters were simultaneously fed cholesterol-supplemented diet.