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Anti-MRSA Properties of Prodigiosin from Serratia sp. PDGS 120915
Keunho Ji(지근호),Tae Hyug Jeong(정태혁),Young Tae Kim(김영태) 한국생명과학회 2015 생명과학회지 Vol.25 No.1
천연의 붉은 색소인 prodigiosin은 Serratia marcescens에 의해서 생산되며 이는 pyrrolylpyrromethane 골격으로 구성되어 있다. 이 색소는 그 분자가 가진 특성 때문에 넓은 범위에서 활용되고 있다. 또한 항암제, 면역억제제, 항진균제, 살조제 등 다양한 분야의 효과가 보고되소 있다. Methicillin-resistant Staphylococcus aureus (MRSA)는 세계적으로 가장 주요한 원내 감염균으로써, 미국에서 해마다 HIV로 사망하는 수보다 더 많은 사망률을 보이고 있다. 그러므로 MRSA에 대한 새로운 치료제의 개발이 매우 중요하며 급박한 문제이다. 본 연구에서는 중증오염도를 가진 하천수로부터 Serratia sp. PDGS 120915를 분리하였으며 항 MRSA 활성을 가진 prodigiosin에 대하여 연구하였다. 본 연구를 위하여 HPLC를 이용하여 물질을 정제하였으며, 분리된 물질의 항 MRSA 활성을 확인하였다. Prodigiosin의 MRSA에 대한 최소억제농도(Minimal inhibitory concentration; MIC)는 32 μg/ml 이었으며, 분할저해농도(Fractional inhibitory concentration; FIC)는 ampicillin과 penicillin에서 상승작용이 있는 것으로 나타났다. Prodigiosin, a member of natural red pigment family, is produced by Serratia marcescens, and characterized by a common pyrrolylpyrromethane skeleton. This pigment has been reported with the effects of anticancer, immunosuppressant, antifungal, and algicidal activities. Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital infections. In this study, anti-MRSA properties of prodigiosin isolated from Serratia sp. PDGS 120915 were investigated. We identified and purified prodigiosin using high performance liquid chromatography (HPLC) and evaluated anti-MRSA activity. Purified prodigiosin inhibited the growth of MRSA. The minimum inhibitory concentrations (MICs) of prodigiosin were determined to 32 μg/ml against the MRSA strains. Fractional inhibitory concentration (FIC) indices of ampicillin and penicillin were indicated synergistic effects of prodigiosin on MRSA.
New Collaborative Filtering Based on Similarity Integration and Temporal Information
Keunho Choi(최근호),Gunwoo Kim(김건우),Donghee Yoo(유동희),Yongmoo Suh(서용무) 한국지능정보시스템학회 2011 한국지능정보시스템학회 학술대회논문집 Vol.2011 No.5
As personalized recommendation of products and services is rapidly growing in importance, a number of studies provided fundamental knowledge and techniques for developing recommendation systems. Among them, the collaborative filtering (CF) technique has been most widely used and has proven to be useful in many practices. However, current CF technique has still considerable rooms for improving the effectiveness of recommendation systems: 1) a similarity function most systems use to find like-minded people is not well defined; and 2) temporal information that contains the changing preference of customers needs to be considered when making recommendations. We hypothesize that integration of multiple aspects of similarity and utilization of temporal information will improve the accuracy of recommendations. The objective of this paper is to test the hypothesis through a series of experiments using MovieLens data. The experimental results show that the proposed recommendation system highly outperforms the conventional CF-based systems, confirming our hypothesis.
A Study on the Tyrosinase Inhibitory and Antioxidant Effect of Microalgae Extracts
( Keunho Ji ),( Yeeun Kim ),( Young Tae Kim ) 한국미생물생명공학회(구 한국산업미생물학회) 2021 한국미생물·생명공학회지 Vol.49 No.2
Reactive oxygen species (ROS) disrupt the cellular redox balance, exert cytotoxic effects, and consequently promote the development of various diseases in humans. Previous studies have reported that antioxidants counteract the adverse effects of ROS. Several studies examine the whitening effects of various agents based on their ability to inhibit tyrosinase activity. Tyrosinase is a critical enzyme involved in the synthesis of melanin, which protects the skin against radiation. Various agents exhibiting antioxidant and tyrosinase inhibitory activities have been synthesized. However, these synthetic drugs are associated with toxicity, decreased safety, and poor skin penetration in vivo, which has limited the clinical application of synthetic drugs. This study examined the antioxidant and tyrosinase inhibitory activities of some microalgae. The methanol, dichloromethane, and ethyl acetate extracts of four microalgal species (Tetraselmis tetrathele, Dunaliella tertiolecta, Platymonas sp., and Chaetoceros simplex) were prepared. The physiological and whitening effects of microalgal extracts were investigated by measuring the antioxidant and tyrosinase inhibitory activities. The ethyl acetate extract of D. tertiolecta exhibited the highest antioxidant and tyrosinase inhibitory activities. Future studies must focus on examining the whitening effects of microalgae on cell lines to facilitate the development of microalga-based therapeutics for skin diseases, functional health foods, and whitening agents. Thus, microalgae have potential applications in the pharmaceutical, food, and cosmetic industries.
How Does Creditor’s Liquidation Decision Affect Debt and Equity Values?
Keunho Hwang,Jangkoo Kang 한국재무학회 2008 한국재무학회 학술대회 Vol.2008 No.05
Bankruptcy and liquidation procedures are important to determine the values of equity, debt and firm. During the liquidation process, the creditors play an important role as well as borrowers. This paper models the creditors’ liquidation decision and examines its effects on the equity and debt values and credit premiums of risky debt. If the liquidation costs are considerable, the debtholders tend to delay liquidation and it provides the equityholders with an opportunity to behave strategically. Without Chapter 11 of the U.S. Bankruptcy Code, the bankruptcy does not lead to immediate liquidation due to the costly liquidation. Additionally, we address that the tax benefit, in addition to liquidation costs, is one of the factors that cause the strategic debt service. Our model incorporates the equityholders’ bankruptcy decision and debtholders’ liquidation decision. We suggest how to determine the equity and debt values numerically using finite difference methods. And we show that Leland (1994) model is a special case of ours. Finally, this paper also examines the determinants of values of equity, debt, firm and risky debt’s credit premium.
( Keunho Ji ),( Young Tae Kim ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 한국미생물·생명공학회지 Vol.47 No.3
This study aimed to identify and characterize the antimicrobial activity of prodigiosin produced by Serratia sp. PDGS<sup>120915</sup> isolated from stream water in Busan, Korea; the identification was performed using phonological, biochemical, and molecular techniques, including 16S rRNA sequence analysis. Prodigiosin from the bacterial culture was purified by high-performance liquid chromatography (HPLC), and its antimicrobial activity and minimum inhibitory concentrations (MICs) were evaluated against 10 intestinal pathogenic gram-positive and negative bacteria. The results revealed that the isolated prodigiosin exhibited high antimicrobial activity against Listeria monocytogenes, Bacillus cereus, Pseudomonas aeruginosa, Salmonella typhimurium, Staphylococcus aureus, and Vibrio parahaemolyticus; further, the isolated prodigiosin showed minimum inhibitory concentrations (MICs) between 3 μg/ml and 30 mg/ml, but they were not active against Bacillus subtilis, Enterococcus faecalis, Klebsiella pneumonia, and Escherichia coli. In conclusion, prodigiosin isolated from Serratia sp. PDGS<sup>120915</sup> showed high antimicrobial activity against intestinal pathogenic bacteria and has potential applications in the development of new antimicrobial agents.