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Quantitative Methods for Metabolite Analysis in Metabolic Engineering
안치윤,이민경,정철희 한국생물공학회 2023 Biotechnology and Bioprocess Engineering Vol.28 No.6
We present a brief overview of metabolic engineering, depicting the necessity of exploiting microorganisms for obtaining desired metabolites and the difficulty of metabolic pathway optimization under numerous conditions. The advantages, limitations, and examples of conventional quantitative analytical methods that focus on accuracy but have low throughput rates are presented. We have also described in vivo analytical methods with high-throughput rates, which indirectly compare the yield of the reporter protein. Additionally, we have explained a few considerations for engineering in vivo analytical methods. This review also highlights the current challenges faced by the analytical methods in the metabolic engineering.
온도 조건에 따른 폴리머 소재의 트라이볼로지 특성 연구
안치윤,김대은 한국트라이볼로지학회 2023 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.39 No.6
Research to replace metal mechanical elements with polymer materials has recently accelerated. However, polymers exhibit less favorable mechanical properties than metal materials, and are often easily worn-out owing to frictional heat when their mechanical elements contact while in relative motion. Therefore, research on the polymer tribological properties is required to employ polymer materials in mechanical elements operating under harsh conditions. In this study, we examine the effect of mechanical part operating temperatures on the material friction and wear characteristics of polymer materials. We conduct ball-on-disk friction tests under dry conditions at various temperatures, using a metal ball with high hardness and a polymer as the counter surface. Each test is repeated at least three times to ensure the reliability of the test results. Before the friction test, we analyze the surface hardness and roughness of each polymer specimen; after the friction test, we use a three-dimensional confocal microscope to compare and analyze the polymer specimen wear characteristics. Based on this study, we systematically elucidate the polymer material tribological characteristics. This information should be useful for selecting and utilizing polymer materials at various temperatures.
Selection of Escherichia coli Glutamate Decarboxylase Active at Neutral pH from a Focused Library
Chen Yuan Hou,안치윤,조병관,강택진 한국생물공학회 2018 Biotechnology and Bioprocess Engineering Vol.23 No.4
Bacterial glutamate decarboxylase (GAD) converts glutamate (Glu) into γ-aminobutyric acid (GABA) at acidic conditions. Since the reaction consumes a proton per GABA synthesis, cells use this reaction to survive in the acidic environments. Characteristically, the enzyme displays a sigmoidal decrease in its activity as pH rises becoming completely inactive at or above pH 6. This cooperative activity loss is accompanied by several distinct structural changes. Previously, by examining structures at acidic and neutral pH, two key regions had been chosen and mutated to break the cooperativity; Glu89 and C-terminal 15 residues. In this study, we included Asp86 in candidate key residues for mutation to break the cooperativity of GAD. We devised a selection strategy according to which only Escherichia coli cells expressing a variant GAD that was active at neutral pH could survive. In this scheme, an alanine (Ala) auxotroph was rescued by the intracellular synthesis of GABA that was subsequently converted into Ala by heterologously expressed GABA-pyruvate transaminase. New GAD variants were readily selected using this strategy and the most of them indeed had a mutation at residue 86. The results suggest that the role of Asp86 in the wild-type enzyme might be the same as Glu89; to make GAD keep its activity only at acidic environments. Characterization of representative variants are also presented.