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류화원,위영중,김진남,Jong-Sun Yun 한국생물공학회 2005 Biotechnology and Bioprocess Engineering Vol.10 No.1
Lactic acid is a green chemical that can be used as a raw material for biodegradable polymer. To produce lactic acid through microbial fermentation, we previously screened a novel lactic acid bacterium. In this work, we optimized lactic acid fermentation using a newly isolated and homofermentative lactic acid bacterium. The optimum medium components were found to be glucose, yeast extract, (NH4)2HPO4, and MnSO4. The optimum pH and temperature for a batch culture of Lactobacillus sp. RKY2 was found to be 6.0 and 36oC, respectively. Under the optimized culture conditions, the maximum lactic acid concentration (153.9 g/L) was obtained from 200 g/L of glucose and 15 g/L of yeast extract, and maximum lactic acid productivity (6.21 gL-1h-1) was obtained from 100 g/L of glucose and 20 g/L of yeast extract. In all cases, the lactic acid yields were found to be above 0.91 g/g. This article provides the optimized conditions for a batch culture of Lactobacillus sp. RKY2, which resulted in highest productivity of lactic acid.
Method for Evaluating Metabolic Functions of Drugs in Bioartificial Liver
류화원,Yueng Guen Park,Hiroo Iwata,Seiji Satoh,Takehiko Uesugi 한국생물공학회 2003 Biotechnology and Bioprocess Engineering Vol.8 No.5
Lidocaine and galactose loading tests were performed on a bioartificial liver (BAL), an extracorporeal medical device incorporating living hepatocytes in a cartridge without a transport barrier across the membranes. The concentration changes were analyzed using pharmacokinetic equations to evaluate the efficacy and limitation of the proposed method. Lidocaine and galactose were found to be suitable drugs for a quantitative evaluation of the BAL functions, as they did not interact with the plasma proteins or blood vessels, making their concentrations easy to determine. The drug concentration changes after drug loading were easily analyzed using pharmacokinetic equations, and the BAL functions quantitatively expressed by pharmacokinetic parameters, such as the clearance (CL) and galactose elimination capacity (GEC). In addition, these two drugs have already been used in clinical tests to evaluate human liver functions over long periods, and lidocaine CL values and GEC values reported for a normal human liver. Thus, a comparison of the CL and GEC values for the BAL and a natural liver revealed what proportion of normal liver functions could be replaced by the BAL.
류화원,위영중,김진남,윤종선,김선호,Jun-Seok Hwang,Hong-Gi Jang 한국생물공학회 2006 Biotechnology and Bioprocess Engineering Vol.11 No.4
In this study, melamine-formaldehyde microcapsules were prepared via in situ polymerization using peppermint oil as a core material, melamine-formaldehyde as the wall material, Tween 20 as the emulsifier, and poly (vinyl alcohol) as a protective colloid. The melamine-formaldehyde microcapsules prepared in this study were then evaluated with regard to their structures, thermal properties, particle size distributions, morphologies, and release behaviors.
Factors Affecting the Characteristics of Melamine Resin Microcapsules Containing Fragrant Oils
류화원,위영중,김진남,김선호,Jun-Seok Hwang,Hong-Gi Jang 한국생물공학회 2006 Biotechnology and Bioprocess Engineering Vol.11 No.5
Microcapsules containing fragrant oils as a core material were prepared by in situ polymerization, using melamine-formaldehyde prepolymer as the wall material. The several parameters, such as stirring times, stirring rates, emulsifier types, emulsifier concentrations, and the viscosity of the core materials, affect the characteristics of the microcapsules. These parameters were investigated by the analyses of microcapsule size, particle size distribution, and morphology. The average microcapsule size decreased with an increase in stirring time, stirring rate, emulsifier concentration, and viscosity of the core material. It was also found that poly(vinyl alcohol) as a protective colloid could enhance the stability of the melamine-formaldehyde microcapsules.
류화원,Yueng Guen Park,Takehiko Tosha,Satoshi Fujita,Boru Zhu,Hiroo Iwata 한국생물공학회 2003 Biotechnology and Bioprocess Engineering Vol.8 No.1
Difficulties associated with bioartificial liver (BAL) preservation limit not only the commercialization of BAL, but also its clinical trials. In this study, the possibility of cold preservation of BAL cartridges containing porcine hepatocytes was examined at 4 oC. In an in vitro perfusion culture system, BAL cartridges maintained cytochrome P450 metabolic function for at least 50 days. However, all BAL cartridges completely lost their ammonia eliminating ability when stored at 4oC. We also studied the effect of cell density on the maintenance of BAL liver function in a highly differentiated and healthy state. As expected, BALs containing a larger number of hepatocytes demonstrated higher metabolic functions. When metabolic functions were compared per gram of hepatocytes, no large differences were observed between devices containing different densities of hepatocytes. Decreased cell density did not successfully prolong BAL function. The viability and function of isolated hepatocytes highly depend on the culture conditions, such as cell density, substrata, culture media, and additives to the culture media. Perfusion culture of BAL cartridges at 4oC gave a promosing result with respect to the maintenance of P450 activity. However, as indicated by the rapid loss of ammonia metabolic activity, many factors still remain to be optimized for preservation of BAL keeping high metabolic functions for a longer time.
Plackett-Burman 설계, 최대경사법 및 중심합성설계를 이용한 키토산 분해효소 생산 향상
류화원 ( Hwa Won Ryu ),김희강 ( Hee Kang Kim ),위영중 ( Young Jung Wee ) 조선대학교 공학기술연구원 2009 공학기술논문지 Vol.2 No.4
Three parameters affecting chitosanase production, including beef extract, corn steep liquor, and incubation period, were screened as the significant factors through Plackett-Burman design. The optimum levels of the screened parameters determined by the steepest ascent method and central composite design experiments were 9.0 g/l of beef extract, 3.2 g/l of corn steep liquor, and 43.2 h of incubation period. Under the optimized culture conditions, chitosanase activity was peaked to 77.476 ± 2.570 U/ml after 43.2 h of incubation. The statistically predicted chitosanase activity (77.365 U/ml) was nearly similar to the observed chitosanase activity, which indicated that the statistical model established in this study could be considered to have relatively high significance for chitosanase production by Bacillus sp. RKY3.