Hyun Yong Shin

Biodiesel production using a mixture of immobilizedRhizopus oryzae andCandida rugosa lipases

Biodiesel conversion from soybean oil reached a maximum of 70% at 18 h using immobilized 1,3-specificRhizopus oryzae lipase alone. Biodiesel conversion failed to reach 20% after 30 h when immobilized nonspecificCandida rugosa lipase alone was used. To increase the biodiesel production yield, a mixture of immobilized 1,3-specificR. oryzae lipase and nonspecificC. rugosa lipase was used. Using this mixture a conversion of greater than 99% at 21 h was attained. When the stability of the immobilized lipases mixture was tested, biodiesel conversion was maintained at over 80% of its original conversion after 10 cycles.

Improvement of electrical properties via glucose oxidase-immobilization by actively turning over glucose for an enzyme-based biofuel cell modified with DNA-wrapped single walled nanotubes

One of the major areas of study associated with enzyme fuel cells (EFCs) has been identification of redox enzymes with high electron transfer rates that lead to a high power output. The effects of a method of enzyme immobilization by actively turning over glucose on the electrical properties of a fuel cell were evaluated under ambient conditions in attempt to increase the power of an EFC modified with DNA-wrapped single walled carbon nanotubes (SWNTs). The anode cyclic voltammetry (CV cycle) electrical properties increased as a result of glucose oxidase (GOD) immobilization by actively turning over glucose. Furthermore, an EFC that employed DNA-wrapped SWNTs and GOD immobilization in conjunction with protection of the active site increased the stability of the cell, which enabled maintenance of a high level of power production (ca. 730-760 μW cm(-2)) for 1 week.

Quantitative Detection of Glyphosate by Simultaneous Analysis of UV Spectroscopy and Fluorescence Using DNA-Labeled Gold Nanoparticles

A sandwich-type immunosensor composed of antigen-double target/probe DNA-coated gold nanoparticles (NPs) was developed for the measurement of fluorescence intensity and quantitative analysis of single-stranded DNA based on the concentration of free glyphosate. The reaction between the antigen-double DNA-gold NPs and immobilized antibody on the substrate was carried out for 2 h. The results of the antigen-antibody reaction were measured on the basis of the fluorescence intensity obtained from comparison with the free antigens at concentrations of 0.01-100 μg mL(-1) for the detection of immobilized antigen-double DNA-gold NPs. For the quantitative analysis based on the concentration of glyphosate(0.01-100 μg mL(-1)), the immunosensor response also revealed the same detection range of glyphosate using DNA detection.

Application of an enzyme-based biofuel cell containing a bioelectrode modified with deoxyribonucleic acid-wrapped single-walled carbon nanotubes to serum.

Enzyme-based biofuel cells (EFCs) are a form of biofuel cells (BFCs) that can utilize redox enzymes as biocatalysts. Applications of an EFC to an implantable system are evaluated under mild conditions, such as ambient temperature or neutral pH. In the present study, an EFC containing a bioelectrode modified with deoxyribonucleic acid (DNA)-wrapped single-walled carbon nanotubes (SWNTs) was applied to a serum system. The protection of immobilized glucose oxidase (GOD) using DNA-wrapped SWNTs was investigated in a trypsin environment, which can exist in a serum. GOD is immobilized by masking the active site onto the anode electrode. The anode/cathode system in the cell was composed of GOD/laccase as the biocatalysts and glucose/oxygen as the substrates in serum. The electrical properties of the anode in serum according to cyclic voltammetry (CV cycle) were improved using the DNA-wrapped SWNTs. Overall, an EFC that employed DNA-wrapped SWNTs and GOD immobilization in conjunction with protection of the active site increased the stability of GOD in serum, which enabled a high level of power production (ca. 190 μW/cm(2)) for up to 1 week.

Stimulation of cephalosporin C production in Acremonium chrysogenum M35 by glycerol.

In this study, the effects of glycerol on cephalosporin C production by Acremonium chrysogenum M35 were evaluated. The addition of glycerol increased cephalosporin production by up to 12-fold. Glycerol caused the upregulation of the transcription of the isopenicillin synthase (pcbC) and transporter (cefT) genes in early exponential phase, and affected the cell morphology since hyphal fragments differentiated into arthrospores. These results indicate that glycerol effectively enhances cephalosporin C production via stimulation of cell differentiation.

Production of cephalosporin C using crude glycerol in fed-batch culture of Acremonium chrysogenum M35.

In this study, cephalosporin C production by Acremonium chrysogenum M35 cultured with crude glycerol instead of rice oil and methionine was investigated. The addition of crude glycerol increased cephalosporin C production by 6-fold in shake-flask culture, and also the amount of cysteine. In fed-batch culture without methionine, crude glycerol resulted only in overall improvement in cephalosporin C production (about 700%). In addition, A. chrysogenum M35 became highly differentiated in fed-batch culture with crude glycerol, compared with the differentiation in batch culture. The results presented here suggest that crude glycerol can replace methionine and plant oil as cysteine and carbon sources during cephalosporin C production by A. chrysogenum M35.

Production of cellulases and β-glucosidase in Trichoderma reesei mutated by proton beam irradiation

To obtain mutant strains producing high levels of cellulases (FPase and CMCase) and β-glucosidase, Trichoderma reesei KCTC 6950 was mutated by proton beam irradiation. Five mutants were selected out of 1,000 mutants of T.reesei treated with proton beam irradiation, based on their ability for enzyme production on a plate screening medium. In submerged cultures containing Mandel’s fermentation medium, the mutant strain T-2 (MT-2) demonstrated a 165% increase in the activity of FPase, a 146% increase in the activity of CMCase, and a 313% increase in the activity of β-glucosidase, compared with the wild type strain. Additionally, the properties of high level β-glucosidase produced by MT-2 were the same as those of the wild type strain, e.g., an optimum pH of 4.8, and an optimum temperature of 65 °C. Moreover, the protein concentrations of β-glucosidase produced by the wild type strain and MT-2 were measured by SDS-PAGE, and then β-glucosidase activities were detected by the MUG-zymogram assay.

Utilization of glycerol as cysteine and carbon sources for cephalosporin C production by Acremonium chrysogenum M35 in methionine-unsupplemented culture

In this study, the role of glycerol in cephalosporin C production was evaluated in Acremonium chrysogenum M35. Methionine-unsupplemented culture with glycerol stimulated cephalosporin C production in A. chrysogenum M35 by up to 10-fold while increasing the amount of cysteine. Glycerol caused the upregulation of isopenicillin N-CoA epimerase (cefD2) and δ-(L-α-aminoadipyl)-L-cysteinyl-D-valine synthase (pcbAB) transcription in exponential phase. These results indicate that glycerol without methionine effectively enhanced cephalosporin C production via stimulation of cysteine and valine in A. chrysogemun M35.

Differentiation of Acremonium chrysogenum M35 in submerged culture with glass beads or silicone rubbers

In this study, we investigated the effects of glass beads and silicone rubbers on the differentiation and morphological changes of A. chrysogenum M35 in submerged culture. Differentiation in the center of the cell pellets was improved by the addition of glass beads or silicone rubbers to the primary medium. The fragmentation rate constant (kfrag), which is used to estimate the tensile strength of fungal hyphae, was increased by more than 40% in baffled flasks containing glass beads. The maximum fragmentation rate was also increased by 48% when silicone rubbers were added to a 5 L bioreactor containing the culture. During the cultivation in the main medium with 6 glass beads, the value of the fractal dimension increased by about 8% when it was compared with baffled flasks without glass beads. Additionally, the number of arthrospores and the dry cell weight were increased by more than 10% in baffled flasks containing beads. The degree of roundness, which is the ratio of the object area to the longest Feret diameter, was decreased from 0.85 at day 1 to 0.77 at day 5. The differentiation of A. chrysogenum M35 was also supposedly closely related with the enlargement of the cell surfaces. Taken together, these results indicate that complex changes in morphology resulted in increased cell growth and differentiation in the culture broth containing glass beads and silicone rubbers.

P‐152: Field Emission Properties of t‐RNA Wrapped Carbon Nanotube Emitters

We have developed a method for fabricating a good carbon nanotube (CNT) emitter using electrophoretic deposition (EDP) technique. A film of t-RNA (transfer-ribonucleic acid) wrapped CNTs was deposited on an ITO substrate from an aqueous mixture of single walled CNT (SWCNT), t-RNA, and detergent by electrophoresis. t-RNA wrapped SWCNTs are not only dispersed in de-ionized (DI) water but also deposited on an ITO substrate.