Sung Ho Ha - Academia.edu (original) (raw)
Papers by Sung Ho Ha
Science China Chemistry, 2012
The expression of recombinant proteins in microorganism frequently leads to the formation of inso... more The expression of recombinant proteins in microorganism frequently leads to the formation of insoluble aggregates, inclusion bodies (IBs). Thus, the additional in vitro protein refolding process is required to convert inactive IBs into water-soluble active proteins. This study investigated the effect of sulfur residue and hydrophobicity of imidazolium-based room temperature ionic liquids (RTILs) on the refolding of lysozyme as a model protein in the batch dilution method which is the most commonly used refolding method. When lysozyme was refolded in the refolding buffer containing [BF 4 ]-based RTILs with a systematic variety of alkyl chain on cations varying from two to eight, less hydrophobic imidazolium cations having shorter alkyl chains were effective to facilitate lysozyme refolding. Compared to the conventional refolding buffer, 2 times higher lysozyme refolding yield was obtained in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF 4 ]) containing refolding buffer. The refolding yield of lysozyme was even more increased by 2.5 times when 1-butyl-3-methylimidazolium methylsulfate ([BMIM][MS]) containing sulfur residue on anion was used. The sulfur residue in [BMIM][MS] is supposed to improve the refolding yield of lysozyme which has 4 intramolecular disulfide bonds. For dilution-based refolding of lysozyme, the optimum concentrations of RTILs in refolding buffer were found to be 1.0 M [EMIM][BF 4 ] and 0.5 M [BMIM][MS], respectively. The optimum temperate for dilution-based refolding of lysozyme with RTILs was 4 °C.
Soft Materials, 2010
The cellulose was directly dissolved in 1-butyl-3-methylimidazolium chloride at 80°C. The clear a... more The cellulose was directly dissolved in 1-butyl-3-methylimidazolium chloride at 80°C. The clear and transparent cellulose solution was cast on the glass substrate using tape-casting method. The cast films were soaked into various solvents such as methanol, methanol-deionized water, deionized water, and isopropyl alcohol-deionized water. UV-visible transmittances were approximately 74% to 50% depending on the curing solvents. High thermal stability was
Korean Journal of Chemical Engineering, 2010
Nuclear power has once again attracted from all over the world due to many factors including the ... more Nuclear power has once again attracted from all over the world due to many factors including the rise in oil process and environmental concerns on greenhouse gas emission resulting in global warming. However, spent fuel from nuclear power reactors is an enormous problem both from radiation hazard and economical point of view. Therefore, this review presents an overview of application of ionic liquids (ILs) in spent fuel reprocessing, particularly in the extraction of high-level radioactive aqueous waste from the processing of nuclear fuel.
Journal of Molecular Catalysis B: Enzymatic, 2010
The immobilization of lipases within solgel derived silica, using multi-walled carbon nanotubes ... more The immobilization of lipases within solgel derived silica, using multi-walled carbon nanotubes (MWNTs) as additives in order to protect the inactivation of lipase during solgel process and to enhance the stability of lipase, was investigated. Three solgel immobilized lipases ( ...
Journal of Biotechnology, 2008
Journal of Biotechnology, 2008
Bioprocess and Biosystems Engineering, 2011
Although caffeic acid phenethyl ester (CAPE), an active flavonoid, plays an important role in the... more Although caffeic acid phenethyl ester (CAPE), an active flavonoid, plays an important role in the antioxidant activity of honeybee propolis, the isolation of CAPE from honeybee propolis is time-consuming due to wide variety of impurities present. Therefore, biochemical method to synthesize CAPE was investigated in this study. Since ionic liquids (ILs) possess some unique characteristics as appreciated alternatives to conventional solvents for certain biotransformation, the effect of ILs as reaction media for enzymatic synthesis of CAPE was assessed. Several factors including substrate molar ratio, and reaction temperature affecting the conversion yield of lipase-catalyzed CAPE synthesis were also investigated. Reaction yields were significantly higher in hydrophobic ILs than in hydrophilic ILs (almost zero). Among nine hydrophobic ILs tested, the highest conversion of synthetic reaction was obtained in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([Emim][Tf 2 N]). A reaction temperature of 70°C was found to give high conversion. In addition, optimal substrate molar ratio between phenethyl alcohol and caffeic acid (CA) was decreased significantly from 92:1 to 30:1 when ILs were used instead of isooctane.
Bioprocess and Biosystems Engineering, 2009
Lipase-catalyzed esterification of glucose with fatty acids in ionic liquids (ILs) mixture was in... more Lipase-catalyzed esterification of glucose with fatty acids in ionic liquids (ILs) mixture was investigated by using supersaturated glucose solution. The effect of ILs mixture ratio, substrate ratio, lipase content, and temperature on the activity and stability of lipase was also studied. The highest yield of sugar ester was obtained in a mixture of 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim][TfO]) and 1-methyl-3-octylimidazolium bis[(trifluoromethyl)-sulfonyl]amide ([Omim][Tf(2)N]) with a volume ratio of 9:1, while Novozym 435 (Candida antarctica type B lipase immobilized on acrylic resin) showed the optimal stability and activity in a mixture of [Bmim][TfO] and [Omim][Tf(2)N] with a 1:1 volume ratio. Reuse of lipase and ILs was successfully carried out at the optimized reaction conditions. After 5 times reuse of Novozym 435 and ILs, 78% of initial activity was remained.
Applied Biochemistry and Biotechnology, 2013
Ionic liquids (ILs) are molten salts which do not crystallize at room temperature. Tunable physic... more Ionic liquids (ILs) are molten salts which do not crystallize at room temperature. Tunable physicochemical properties of ILs including hydrophobicity and polarity facilitate their applications in many biological processes. In this study, a copper-based IL was employed in order to enhance the refolding efficiency of laccase from Trametes versicolor which requires copper as a cofactor. When 1-ethyl-3-methylimidazolium trichlorocuprate ([EMIM][CuCl₃]) was added to refolding buffer instead of urea, the laccase refolding yield was improved more than 2.7 times compared to the conventional refolding buffer which contains urea. When the refolding of laccase was carried out at different temperatures (4, 25, and 37 °C), the highest refolding yield was obtained at 25 °C. At low temperature, two conflicting effects, i.e., suppression of the aggregate formation and decrease of folding rate, influence the protein refolding. In contrast, a copper-based IL did not enhance the refolding of lysozyme, a non-copper-containing protein. From these results, we can conclude that this copper-based IL, [EMIM][CuCl₃], was exclusively effective on the refolding process of a copper-containing protein.
Biotechnology Techniques, 1996
The effectiveness of silkworm hemolymph was investigated as a substitute for fetal bovine serum (... more The effectiveness of silkworm hemolymph was investigated as a substitute for fetal bovine serum (FBS) in insect cell culture. Cells were adapted to grow in reduced FBS medium supplemented with silkworm hemolymph through a gradual adaptation process. FBS concentration in the medium could be reduced to 1% without decrease in cell growth rate and maximum cell concentration by adding 5% silkworm hemolymph. IXTRODUCTION In the early stages of insect tissue culture development, silkworm hemolymph was used as a culture medium. Wyatt et al. (1956) chemically analyzed the hemolymph and Wyatt (1956) formulated a synthetic medium, which was fortified by Grace (1962). Grace's medium still had to be supplemented with silkworm hemolymph. Ever since FBS was proven to be beneficial for the growth of insect cells (Martignoni and Scallion, 1961; Mitsuhashi and Maramorosch, 1964) insect cell medium has been supplemented with FBS instead of insect hemolymph FBS has been used as a supplement since it contains a large number of different growth-promoting activities in a physiologically balanced blend (Ham and McKeehan, 1979). However, the FBS presents some problems including high cost, nonreproducibility due to lot-to-lot variation, undefined composition, increased contamination risk from mycoplasma, and the complication of downstream processing due to a high protein concentration (Zhang et al., 1992). Many attempts have been made to develop serum-free medium. There have been several reports of insect cell cultures in serum-free media; however, in most cases, the medium is supplemented with 10% FBS.
Science China Chemistry, 2012
The expression of recombinant proteins in microorganism frequently leads to the formation of inso... more The expression of recombinant proteins in microorganism frequently leads to the formation of insoluble aggregates, inclusion bodies (IBs). Thus, the additional in vitro protein refolding process is required to convert inactive IBs into water-soluble active proteins. This study investigated the effect of sulfur residue and hydrophobicity of imidazolium-based room temperature ionic liquids (RTILs) on the refolding of lysozyme as a model protein in the batch dilution method which is the most commonly used refolding method. When lysozyme was refolded in the refolding buffer containing [BF 4 ]-based RTILs with a systematic variety of alkyl chain on cations varying from two to eight, less hydrophobic imidazolium cations having shorter alkyl chains were effective to facilitate lysozyme refolding. Compared to the conventional refolding buffer, 2 times higher lysozyme refolding yield was obtained in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF 4 ]) containing refolding buffer. The refolding yield of lysozyme was even more increased by 2.5 times when 1-butyl-3-methylimidazolium methylsulfate ([BMIM][MS]) containing sulfur residue on anion was used. The sulfur residue in [BMIM][MS] is supposed to improve the refolding yield of lysozyme which has 4 intramolecular disulfide bonds. For dilution-based refolding of lysozyme, the optimum concentrations of RTILs in refolding buffer were found to be 1.0 M [EMIM][BF 4 ] and 0.5 M [BMIM][MS], respectively. The optimum temperate for dilution-based refolding of lysozyme with RTILs was 4 °C.
Soft Materials, 2010
The cellulose was directly dissolved in 1-butyl-3-methylimidazolium chloride at 80°C. The clear a... more The cellulose was directly dissolved in 1-butyl-3-methylimidazolium chloride at 80°C. The clear and transparent cellulose solution was cast on the glass substrate using tape-casting method. The cast films were soaked into various solvents such as methanol, methanol-deionized water, deionized water, and isopropyl alcohol-deionized water. UV-visible transmittances were approximately 74% to 50% depending on the curing solvents. High thermal stability was
Korean Journal of Chemical Engineering, 2010
Nuclear power has once again attracted from all over the world due to many factors including the ... more Nuclear power has once again attracted from all over the world due to many factors including the rise in oil process and environmental concerns on greenhouse gas emission resulting in global warming. However, spent fuel from nuclear power reactors is an enormous problem both from radiation hazard and economical point of view. Therefore, this review presents an overview of application of ionic liquids (ILs) in spent fuel reprocessing, particularly in the extraction of high-level radioactive aqueous waste from the processing of nuclear fuel.
Journal of Molecular Catalysis B: Enzymatic, 2010
The immobilization of lipases within solgel derived silica, using multi-walled carbon nanotubes ... more The immobilization of lipases within solgel derived silica, using multi-walled carbon nanotubes (MWNTs) as additives in order to protect the inactivation of lipase during solgel process and to enhance the stability of lipase, was investigated. Three solgel immobilized lipases ( ...
Journal of Biotechnology, 2008
Journal of Biotechnology, 2008
Bioprocess and Biosystems Engineering, 2011
Although caffeic acid phenethyl ester (CAPE), an active flavonoid, plays an important role in the... more Although caffeic acid phenethyl ester (CAPE), an active flavonoid, plays an important role in the antioxidant activity of honeybee propolis, the isolation of CAPE from honeybee propolis is time-consuming due to wide variety of impurities present. Therefore, biochemical method to synthesize CAPE was investigated in this study. Since ionic liquids (ILs) possess some unique characteristics as appreciated alternatives to conventional solvents for certain biotransformation, the effect of ILs as reaction media for enzymatic synthesis of CAPE was assessed. Several factors including substrate molar ratio, and reaction temperature affecting the conversion yield of lipase-catalyzed CAPE synthesis were also investigated. Reaction yields were significantly higher in hydrophobic ILs than in hydrophilic ILs (almost zero). Among nine hydrophobic ILs tested, the highest conversion of synthetic reaction was obtained in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([Emim][Tf 2 N]). A reaction temperature of 70°C was found to give high conversion. In addition, optimal substrate molar ratio between phenethyl alcohol and caffeic acid (CA) was decreased significantly from 92:1 to 30:1 when ILs were used instead of isooctane.
Bioprocess and Biosystems Engineering, 2009
Lipase-catalyzed esterification of glucose with fatty acids in ionic liquids (ILs) mixture was in... more Lipase-catalyzed esterification of glucose with fatty acids in ionic liquids (ILs) mixture was investigated by using supersaturated glucose solution. The effect of ILs mixture ratio, substrate ratio, lipase content, and temperature on the activity and stability of lipase was also studied. The highest yield of sugar ester was obtained in a mixture of 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim][TfO]) and 1-methyl-3-octylimidazolium bis[(trifluoromethyl)-sulfonyl]amide ([Omim][Tf(2)N]) with a volume ratio of 9:1, while Novozym 435 (Candida antarctica type B lipase immobilized on acrylic resin) showed the optimal stability and activity in a mixture of [Bmim][TfO] and [Omim][Tf(2)N] with a 1:1 volume ratio. Reuse of lipase and ILs was successfully carried out at the optimized reaction conditions. After 5 times reuse of Novozym 435 and ILs, 78% of initial activity was remained.
Applied Biochemistry and Biotechnology, 2013
Ionic liquids (ILs) are molten salts which do not crystallize at room temperature. Tunable physic... more Ionic liquids (ILs) are molten salts which do not crystallize at room temperature. Tunable physicochemical properties of ILs including hydrophobicity and polarity facilitate their applications in many biological processes. In this study, a copper-based IL was employed in order to enhance the refolding efficiency of laccase from Trametes versicolor which requires copper as a cofactor. When 1-ethyl-3-methylimidazolium trichlorocuprate ([EMIM][CuCl₃]) was added to refolding buffer instead of urea, the laccase refolding yield was improved more than 2.7 times compared to the conventional refolding buffer which contains urea. When the refolding of laccase was carried out at different temperatures (4, 25, and 37 °C), the highest refolding yield was obtained at 25 °C. At low temperature, two conflicting effects, i.e., suppression of the aggregate formation and decrease of folding rate, influence the protein refolding. In contrast, a copper-based IL did not enhance the refolding of lysozyme, a non-copper-containing protein. From these results, we can conclude that this copper-based IL, [EMIM][CuCl₃], was exclusively effective on the refolding process of a copper-containing protein.
Biotechnology Techniques, 1996
The effectiveness of silkworm hemolymph was investigated as a substitute for fetal bovine serum (... more The effectiveness of silkworm hemolymph was investigated as a substitute for fetal bovine serum (FBS) in insect cell culture. Cells were adapted to grow in reduced FBS medium supplemented with silkworm hemolymph through a gradual adaptation process. FBS concentration in the medium could be reduced to 1% without decrease in cell growth rate and maximum cell concentration by adding 5% silkworm hemolymph. IXTRODUCTION In the early stages of insect tissue culture development, silkworm hemolymph was used as a culture medium. Wyatt et al. (1956) chemically analyzed the hemolymph and Wyatt (1956) formulated a synthetic medium, which was fortified by Grace (1962). Grace's medium still had to be supplemented with silkworm hemolymph. Ever since FBS was proven to be beneficial for the growth of insect cells (Martignoni and Scallion, 1961; Mitsuhashi and Maramorosch, 1964) insect cell medium has been supplemented with FBS instead of insect hemolymph FBS has been used as a supplement since it contains a large number of different growth-promoting activities in a physiologically balanced blend (Ham and McKeehan, 1979). However, the FBS presents some problems including high cost, nonreproducibility due to lot-to-lot variation, undefined composition, increased contamination risk from mycoplasma, and the complication of downstream processing due to a high protein concentration (Zhang et al., 1992). Many attempts have been made to develop serum-free medium. There have been several reports of insect cell cultures in serum-free media; however, in most cases, the medium is supplemented with 10% FBS.