• Polymer(Korea)
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• v.34 no.2
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• pp.150-153
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• 2010

In this research, biomolecule-immobilized multi-walled carbon nanotubes (MWCNTs) were prepared by using radiation-induced graft polymerization. For the immobilization of biomolecules, the surface of MWNCTs was functionalized by radiation-induced graft polymerization of acrylic acid. Based on the results of TGA and Raman spectroscopy it was found that acrylic acid was effectively graft-polymerized on the MWCNTs. Biomolecules such as DNA and proteins were immobilized onto the resultant poly(acrylic acid)-grafted MWCNTs. The results of the X-ray photoelectron spectroscopy and fluorescence microscopy confirmed that the biomoelcules were successfully immobilized on the poly(acrylic acid)-grafted MWCNTs.

• Journal of Electrochemical Science and Technology
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• v.8 no.2
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• pp.87-95
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• 2017

Enzymatic fuel cells are promising low cost, compact and flexible energy resources. The basis of enzymatic fuel cells is transfer of electron from enzyme to the electrode surface and vice versa. Electron transfer is done either by direct or mediated electron transfer (DET/MET), each one having its own advantages and disadvantages. In this study, the DET and MET of laccase-based biocathodes are compared with each other. The DET of laccase enzyme has been studied using two methods; assemble of needle-like carbon nanotubes (CNTs) on the electrode, and CNTs/Nafion polymer. MET of laccase enzyme also is done by use of ceramic electrode containing, ABTS (2,2'-azino-bis [3-ethylbenzthiazoline-6-sulphonic acid]) /sol-gel. Cyclic voltammetric results of DET showed a pair of well-defined redox peaks at $200{\mu}A$ and $170{\mu}A$ in a solution containing 5and $10{\mu}M$ o-dianisidine as a substrate for needle-like assembled CNTs and CNTs-Nafion composite respectively. In MET method using sol-gel/ABTS, the maximum redox peak was $14{\mu}A$ in the presence of 15 M solution o-dianisidine as substrate. The cyclic voltammetric results showed that laccase immobilization on needle-like assembled CNTs or CNTs-Nafion is more efficient than the sol-gel/ABTS electrode. Therefore, the expressed methods can be used to fabricate biocathode of biofuel cells or laccase based biosensors.

• Journal of Microbiology and Biotechnology
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• v.23 no.4
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• pp.511-517
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• 2013

In this work, a fibrous bed bioreactor with high specific surface area and good adsorption efficacy for S. cerevisiae cells was used as the immobilization matrix in the production of ethanol. In batch fermentation, an optimal ethanol concentration of 91.36 g/l and productivity of 4.57 g $l^{-1}\;h^{-1}$ were obtained at an initial sugar concentration of 200 g/l. The ethanol productivity achieved by the immobilized cells was 41.93% higher than that obtained from free cells. Ethanol production in a 22-cycle repeated batch fermentation demonstrated the enhanced stability of the immobilized yeast cells. Under continuous fermentation in packed-bed reactors, a maximum ethanol concentration of 108.14 g/l and a productivity of 14.71 g $l^{-1}\;h^{-1}$ were attained at $35^{\circ}C$, and a dilution rate of 0.136 $h^{-1}$ with 250 g/l glucose.

• KSBB Journal
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• v.21 no.4
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• pp.279-285
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• 2006

We investigated the effects of immobilization chemistry on the yield of immobilization and the bioactivity of the immobilized enzymes. Trypsin as a model protein and macroporous polymer beads(Toyopearl AF 650M, Tosho Co., Japan) was used as a model matrix. Four methods were used to immobilize trypsin; covalent conjugation by reductive amination(at pH 10.0 and pH 4.0) and affinity interaction via streptavidin-biotin, and double-affinity interaction via biotin-streptavidin-biotin system. The covalent conjugation immobilized $3{\sim}4$ mg/ml-gel, ca. 3-fold higher than the affinity method. However, the specific activity of the covalently(pH 10.0) and affinity-immobilized trypsin(via streptavidin-biotin) are ca. 37% and 50%, respectively, of that of the soluble enzyme(on the low-molecular-weight BAPNA substrate). When the molecular size of a substrate increased, the affinity-immobilized trypsin showed higher clavage activity on insulin and BSA. This result seemed to indicate the streptavidin-biotin system allowed more steric flexibility of the immobilized trypsin in its interaction with a substrate molecule. To confirm this, we studied the molecular flexibility of immobilized trypsin using quartz crystal microbalance-dissipation. Self-assembled monolayers were formed on the Q-sensor surface by aminoalkanethiols, and gultaraldehyde was attached to the SAMs. Trypsin was immobilized in two ways: reductive amination(at pH 10.0) and the streptavidin-biotin system. The dissipation shift of the affinity-immobilized trypsin was $0.8{\times}10^{-6}$, whereas that of the covalently attached enzyme was almost zero. This result confirmed that the streptavidin-biotin system allowed higher molecular flexibility. These results suggested that the bioactivity of the immobilized enzyme be strongly dependent on its molecular flexibility.

• Environmental Engineering Research
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• v.15 no.3
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• pp.149-156
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• 2010

The objective of this study was to investigate microbial removal using layered double hydroxides (LDHs) and iron (hydr)oxides (IHs) immobilized onto granular media. Column experiments were performed using calcium alginate beads (CA beads), LDHs entrapped in CA beads (LDH beads), quartz sand (QS), iron hydroxide-coated sand (IHCS) and hematite-coated sand (HCS). Microbial breakthrough curves were obtained by monitoring the effluent, with the percentage of microbial removal and collector efficiency then quantified from these curves. The results showed that the LDH beads were ineffective for the removal of the negatively-charged microbes (27.7% at 1 mM solution), even though the positively-charged LDHs were contained on the beads. The above could be related to the immobilization method, where LDH powders were immobilized inside CA beads with nano-sized pores (about 10 nm); therefore, micro-sized microbes (E. coli = 1.21 ${\mu}m$) could not diffuse through the pores to come into contact with the LDHs in the beads, but adhere only to the exterior surface of the beads via polymeric interaction. IHCS was the most effective in the microbial removal (86.0% at 1 mM solution), which could be attributed to the iron hydroxide coated onto the exterior surface of QS had a positive surface charge and, therefore, effectively attracted the negatively-charged microbes via electrostatic interactions. Meanwhile, HCS was far less effective (35.6% at 1 mM solution) than IHCS because the hematite coated onto the external surface of QS is a crystallized iron oxide with a negative surface charge. This study has helped to improve our knowledge on the potential application of functional granular media for microbial removal.

• KSBB Journal
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• v.22 no.4
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• pp.260-264
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• 2007

Peptides are frequently studied as candidates for new drug development. Recently, synthesized peptide library is screened for a certain functionality on a microarray biochip format. In this study, in order to replace the conventional cellulose membrane with glass for a microarray chip substrate for peptide library screening, we modified the glass surface from amines to thiols and covalently immobilized the peptides. Using trypsin-FITC (fluorescein isothiocyanate) conjugate that could specifically bind to a trypsin binding domain consisting of a 7-amino acid peptide, we checked the degree of surface modification. Because of the relatively lower hydrophilicity and reduced surface roughness, the conjugation reaction to the glass required a longer reaction time and a higher temperature. It took approximately 12 hr for the reaction to be completed. From the fluorescence signal intensity, we could differentiate between the target and the control peptides. This difference was confirmed by a separate experiment using QCM. Furthermore, a smaller volume and higher concentration of a spot showed a higher fluorescence intensity. These data would provide the basic conditions for the development of microarray peptide biochips.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.1038-1046
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• 2008

This study was carried out to develop a small-sized biosensor based on surface plasmon resonance (SPR) for the rapid identification of insecticide residues for food safety. The SPR biosensor module consists of a single 770 nm-light emitting diodes (LED) light source, several optical lenses for transferring light, a hemisphere sensor chip, photo detector, A/D converter, power source, and software for signal processing using a computer. Except for the computer, the size and weight of the sensor module are 150 (L)$\times$70 (W)$\times$120 (H) mm and 828 g, respectively. Validation and application procedures were designed to assess refractive index analysis, affinity properties, sensitivity, linearity, limits of detection, and robustness which includes an analysis of baseline stability and reproducibility of ligand immobilization using carbamate (carbofuran and carbaryl) and organophosphate (cadusafos, ethoprofos, and chlorpyrifos) insecticide residues. With direct binding analysis, insecticide residues were detected at less than the minimum 0.01 ppm and analyzed in less than 100 sec with a good linear relationship. Based on these results, we find that the binding interaction with active target groups in enzymes using the miniaturized SPR biosensor could detect low concentrations which satisfy the maximum residue limits for pesticide tolerance in Korea, Japan, and the USA.

• Bulletin of the Korean Chemical Society
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• v.23 no.3
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• pp.385-390
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• 2002

Laccase could be successfully assembled on an amine-derivatized platinum electrode by glutaraldehyde coupling. The enzyme layer formed on the surface does not communicate electron directly with the electrode, but the enzymatic activity of the surf ace could be followed by electrochemical detection of enzymatically oxidized products. The well-known laccase substrates, ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) and PPD (p-phenylenediamine) were used. ABTS can be detected down to 0.5 ${\mu}M$ with linear response up to 15 ${\mu}M$ and current sensitivity of 75 nA/ ${\mu}M.$ PPD showed better response with detection limit of 0.05 ${\mu}M$, linear response up to 20 ${\mu}M$, and current sensitivity of 340 nA/ ${\mu}M$ with the same electrode. The sensor responses fit well to the Michaelis-Menten equation and apparent $K_M$ values are 0.16 mM for ABTS and 0.055 mM for PPD, which show the enzymatic reaction is the rate-determining step. The laccase electrode we developed is very stable and more than 80% of initial activity was still maintained after 2 months of uses.

• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.25-34
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• 2017

Concurrent electrocatalysis and sensing of hydrazine, sulfite ions, and nitrite ions in a mixture were studied using electrodes modified by electrodeposited Au nanostructures (NSs). The ${\beta}$-cyclodextrin-mixed silicate sol-gel composite was drop-casted on the electrode surface and nucleation guided by ${\beta}$-cyclodextrin occurred, followed by the electrodeposition of Au NSs. The additive, ${\beta}$-cyclodextrin, played an evident role as a structure-directing agent; thus, small raspberry-like Au NSs were obtained. The modified electrodes were characterized by surface characterization techniques and electrochemical methods. The Au NSs-modified electrodes effciently electrocatalyzed the oxidation of toxic molecules such as hydrazine and sulfite and nitrite ions even in the absence of any other electron transfer mediator or enzyme immobilization. Well-resolved oxidation peaks along with decreased overpotentials were noticed during the electrooxidation process. The fabricated Au nanostructured electrode clearly distinguished the electrooxidation peaks of each of the three analytes from their mixture.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.546-549
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• 2000

Liposomes and proteoliposomes, artificial membranes, can interact with many solutes, such as drugs, peptides and proteins. Immobilization of (proteo)liposomes as supramolecular aggregates on gold surfaces have potential applications in nanotechnology and biosensors. We demonstrate a quartz crystal analyzer (QCA) method to monitor the construction of multi layers of unilamellar liposomes based on avidin-biotin binding on gold surface using quartz crystal microbalance(QCM). Thus, QCA provides an on line and efficient method to detect the protein membranes construction and have applications to biosensing system.