• Culinary science and hospitality research
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• v.9 no.3
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• pp.114-129
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• 2003

This study aimed at drawing a scheme for more developmental and rational improvement of the screening examination system to cope with the rapidly changing industrial environment positively, enhance the food service industry qualitatively, and reinforce engaged specialty of those engaged in the industry. To set a rational improvement scheme for a cook screening system, the study conducted a prior study on job analysis of those engaged in cooking, a review on relevant laws, and a theoretical research on those problems in the current cook screening examination system. On this basis, it understood the actual condition of the current cook screening system and implemented a demonstrative analysis through a survey to draw a section on a future improvement scheme. The results were analyzed largely from two viewpoints: the general condition of the cook screening system and the future improvement scheme for the system.

• Korean Journal of Weed Science
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• v.13 no.2
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• pp.81-88
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• 1993

For searching the photosynthetic electron transport(PET) inhibitors, bio-rational screening system using thylakoid membranes extracted from wild and mutant cyanobacteria(Anacystis nidulans $R_2$) was developed. Generally, thylakoid membrane was more sensitive to the tested herbicides than the chloroplast from spinach in the Hill reaction. Higher resistant characteristics appeared in mutant D-5, Di-22 to diuron and mutant G-264 to atrazine as compared to wild type. To test the reaction of thylakoid membrane to herbicides, diuron and atrazine were applied simultaneously. Diuron and atrazine competed each other for binding with substituted amino acids, while diuron and dinoseb were non-competitive, and inhibiting activity was increased. Conclusively, bio-rational screening system using cyanobacteria was proved to be fast and efficient screening method for the development of PET inhibitors.

• KSBB Journal
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• v.20 no.5 s.94
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• pp.376-382
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• 2005

Avermectin (AVM) $B_{1a}$ produced by Streptomyces avermitilis via polyketide pathway is a secondary metabolite with powerful anthelmintic and insecticidal activities, thus being used as an efficient agent in the field of agriculture and animal health. It has been reported that a precursor for AVM $B_{1a}$ biosynthesis was isoleucine and the biosynthetic pathway of AVM $B_{1a}$ was closely similar to that of fatty acid. Based on understanding of the biosynthetic pathway of AVM $B_{1a}$, we intended to screen various mutants resistant against O-methyl threonine (OMT), an isoleucine-anti metabolite, and/or mutants resistant against p-fluoro phenoxy acetic acid (pFAC), an inhibitor of fatty acid biosynthesis. It was inferred that these mutants could produce AVM $B_{1a}$ more efficiently, due to the acquired capability of not only overproducing isoleucine intracellularly but also channelling metabolized carbon-sources into the polyketide pathway, thus leading to enhanced biosynthesis of AVM $B_{1a}$. The resulting mutant (PFA-1 strain) resistant against 100 ppm of pFAC was able to produce approximately 42 fold higher amount of AVM $B_{1a}$ compared to the parallel mother strain (4,200 vs. 100 units/l). In addition, through the process of continuous strain improvement program carried out by gradually increasing the OMT concentration, it was possible to obtain a more attractive mutant with greater AVM $B_{1a}$ production capacity (9,000 units/l). Notable was that significantly higher producer (12,000 units/l) could be selected through further screening of the resistant mutants, this time, to even higher concentration of PFAC. Meanwhile, through the analysis of AVM Bla production histograms (i.e., number of strains according to their AVM $B_{1a}$ biosynthetic ability) for the earlier strains in comparison with the high producers having the characteristics of resistance to OMT and pFAC, it was found that production stability of the high-yielding producers were remarkably improved, as demonstrated by the fact that larger proportion of the mutated strains had greater capability of AVM $B_{1a}$ biosynthesis ($71\%$ in the range between 5,000 and 7,000 units/L; $47\%$ in the range between 6,000 and 7,000 units/l). Based on these consequences, it was concluded that the rational screening strategy based on the understanding of the biosynthetic pathway of AVM $B_{1a}$ was very effective in obtaining high-yielding mutants with the features of enhanced production stability.

• Proceedings of the PSK Conference
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• 2001.10a
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• pp.244.3-245
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• 2001

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.228-232
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• 2003

Lovastatin produced by Aspergillus terreus via polyketide pathway is a secondary metabolite with high anti-hypercholesterolemic activity. In this paper we are going to present effective strain development strategies for lovastatin production by comparing the productivity of the mutants obtained through traditional rational screening process and protoplast fusion method. Mutants resistant against various antibiotics and/or antimetabolites showed significantly higher lovastatin productivity than the corresponding mother strains, demonstrating that rational screening method was very efficient in selecting high yielding producers. Recombinant fusants obtained using protoplast fusion between high producers were observed to have very different morphology and physiology as represented by the production and secretion of lovastatin, as well as cell growth pattern. In parallel with the strain development, optimization process for the production medium was carried out in order to find optimal concentrations of the medium components using such a powerful statistical method as response surface method (RSM). It was concluded that not only the optimum production medium but also good morphological characteristics of the high-yielding producers led to higher lovastatin production.

• Journal of Microbiology and Biotechnology
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• v.29 no.3
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• pp.419-428
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• 2019

Phytases are enzymes that can hydrolyze phytate and its salts into inositol and phosphoric acid, and have been utilized to increase the availability of nutrients in animal feed and mitigate environmental pollution. However, the enzymes' low thermostability has limited their application during the feed palletization process. In this study, a combination of B-value calculation and protein surface engineering was applied to rationally evolve the heat stability of Escherichia coli phytase. After systematic alignment and mining for homologs of the original phytase from the histidine acid phosphatase family, the two models 1DKL and 1DKQ were chosen and used to identify the B-values and spatial distribution of key amino acid residues. Consequently, thirteen potential amino acid mutation sites were obtained and categorized into six domains to construct mutant libraries. After five rounds of iterative mutation screening, the thermophilic phytase mutant P56214 was finally yielded. Compared with the wild-type, the residual enzyme activity of the mutant increased from 20% to 75% after incubation at $90^{\circ}C$ for 5 min. Compared with traditional methods, the rational engineering approach used in this study reduces the screening workload and provides a reference for future applications of phytases as green catalysts.

• Journal of Microbiology and Biotechnology
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• v.33 no.10
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• pp.1257-1267
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• 2023

Although rational genetic engineering is nowadays the favored method for microbial strain improvement, building up mutant libraries based on directed evolution for improvement is still in many cases the better option. In this regard, the demand for precise and efficient screening methods for mutants with high performance has stimulated the development of biosensor-based high-throughput screening strategies. Genetically encoded biosensors provide powerful tools to couple the desired phenotype to a detectable signal, such as fluorescence and growth rate. Herein, we review recent advances in engineering several classes of biosensors and their applications in directed evolution. Furthermore, we compare and discuss the screening advantages and limitations of two-component biosensors, transcription-factor-based biosensors, and RNA-based biosensors. Engineering these biosensors has focused mainly on modifying the expression level or structure of the biosensor components to optimize the dynamic range, specificity, and detection range. Finally, the applications of biosensors in the evolution of proteins, metabolic pathways, and genome-scale metabolic networks are described. This review provides potential guidance in the design of biosensors and their applications in improving the bioproduction of microbial cell factories through directed evolution.

• Journal of Preventive Medicine and Public Health
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• v.24 no.1 s.33
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• pp.16-28
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• 1991

Service diversification is recognized as an important strategy against turbulent environmental change. This study is designed to find out the trend of service diversification in Korean health care organizations and also to identify factors associated with the degree of service diversification. Data were collected from 69 hospitals out of 71 hospitals with over 300 beds. Important findings are summarized below. 1. Types of diversification are closely related to hospital size. Large hospitals have a tendency to provide sophisticated services requiring specialized skills and equipment, while small hospital have concentrated their efforts on health screening programs. 2. The more competitive and bigger hospitals are, the greater number of services that provide. Also, hospitals operating rational management information systems provide more services. Contrary to the expectation hospitals with a low performance during last 3 years showed more service diversification. 3. A trend of more diversification was observed in hospitals whose chief executive officer used a prospector strategy. 4. A multiple regression analysis revealed that bed size, competitive environment, degree of rational management, and the growth pattern were significantly associated with the service diversification.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.92-93
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• 2002

With the recent development of combinatorial chemistry, recombinant biotechnology and rational drug design, millions of compounds are being produced in the laboratories of pharmaceutical companies. These new drug candidates are evaluated their efficacy and toxicity through in vivo animal model studies which is very important in drug development. From these studies, very successful drug candidates are selected. (omitted)

• Journal of Pharmaceutical Investigation
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• v.33 no.3
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• pp.157-162
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• 2003

The feasibility of [P(AA-co-PEGMM)] film as a buccal mucoadhesive patch was previously reported by estimating mucoadhesiveness and release characteristics. To find a rational penetration enhancer of [P(AA-co-PEGMM)] film containing butorphanol tartrate (Bt), penetration of Bt from [P(AA-co-PEGMM)] film which contained various additives was estimated by measuring its flux, Papp and lag tme in in vitro buccal membrane of porcine. EDTA showed almost no increase of Bt permeability, wherease SGC, STDHF and SLS increased the permeability of Bt with the order of SGC > STDHF > SLS. The rational additive concentration of SGC was 4% and its Papp and lag time were $1.93{\times}10^{-4}{\pm}4.21{\times}10^{-6},\;126.60{\pm}21.88min\;(control\;:\;Papp\;0.45{\times}10^{-4};\;lag\;time\;211.01{\pm}16.77\;min)$, respectively.