• Journal of Microbiology and Biotechnology
• /
• v.11 no.6
• /
• pp.973-978
• /
• 2001

The bacterial flagellar motor is a molecular machine that couples proton or sodium influx to force generation, mostly for driving rotation of the helical flagellar filament. In this study, we cloned a gene (motX) encoding a component of the sodium-driven flagellar motor from Vibrio fluvialis. The nucleotide sequence of the motX gene, composed of 633 bp and 211 amino acid residues, was determined. Overexpression of the motX gene in Escherichia coli using a strong promoter induced growth inhibition and cell lysis. The lethal effect of E. coli was suppressed by adding amiloride, as a potent inhibitor for the sodium channel. Electron microscopic observation of the expressed protein indicated that MotX protein induced by isopropyl ${\beta}$-D-thiogalactopyranoside caused the lysis of host cell.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.2
• /
• pp.234-238
• /
• 2005

Glucose oxidase was immobilized on the carboxylated multi-wall carbon nanotubes (MWNT-COOHs) in the presence of a coulping reagent, 1-ethy1-3-(3-dimethylaminopropy1) carbodiimide. Significant amounts of glucose oxidase were also immobilized on MWNT-COOHs without the coupling reagent. Various conditions for the immobilization of glucose oxidase were optimized. Optimal pH for the maximal activity of the immobilized glucose oxidase shifted to 7 from the optimal pH of 6 for the maximal activity of free enzyme due to the carboxy1 groups on the surface of MWNT-COOHs. An electrode of graphite rod with a diameter of 6 mm was fabricated using the immobilized glucose oxidase. The cyclic voltammetry study of the enzyme electrode revealed that the oxidation of glucose and subsequent transfer of electrons from the oxidation of glucose to the electrode were possible by the immobilized glucose oxidase without a mediator, implying that the enzyme electrode can be utilized for the development of biofuel cells.

• Mycobiology
• /
• v.50 no.1
• /
• pp.1-11
• /
• 2022

The ascomycete fungus Cordyceps militaris infects lepidopteran larvae and pupae and forms characteristic fruiting bodies. Owing to its immune-enhancing effects, the fungus has been used as a medicine. For industrial application, this fungus can be grown on geminated soybeans as an alternative protein source. In our study, we performed a comprehensive transcriptomic analysis to identify core gene sets during C. militaris cultivation on germinated soybeans. RNA-Seq technology was applied to the fungal cultures at seven-time points (2, 4, and 7-day and 2, 3, 5, 7-week old cultures) to investigate the global transcriptomic change. We conducted a time-series analysis using a two-step regression strategy and chose 1460 significant genes and assigned them into five clusters. Characterization of each cluster based on Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases revealed that transcription profiles changed after two weeks of incubation. Gene mapping of cordycepin biosynthesis and isoflavone modification pathways also confirmed that gene expression in the early stage of GSC cultivation is important for these metabolic pathways. Our transcriptomic analysis and selected genes provided a comprehensive molecular basis for the cultivation of C. militaris on germinated soybeans.

• International Journal of Fluid Machinery and Systems
• /
• v.4 no.3
• /
• pp.324-333
• /
• 2011

Phase resonance in a centrifugal compressor was experimentally observed and simulated with a commercial CFD code. It was found that pressure fluctuation at the volute outlet becomes the maximum when the rotational speed of the modes caused by the rotor-stator interaction agrees with the sound velocity. A simple one-dimensional theory is presented to explain the phase resonance in turbomachinery.

• Korean Journal of Food Science and Technology
• /
• v.33 no.3
• /
• pp.333-337
• /
• 2001

The effect of roasting of Omija (Schizandra chinensis Baillon) on the physicochemical properties and the sensory quality of the extract was investigated in order to improve the quality of Omija beverage. The response surface methodology was introduced to optimize the roasting condition of Omija based on the sensory quality of the extract. The titratable acidity, the soluble solid content and the reducing sugar content of the extract increased with a mild roasting, but decreased with an excessive roasting. Prolonged roasting at high temperature decomposed red pigment making the color of the extract lighter, less red and less yellow. A mild roasting of Omija improved the sensory quality of the extract, and the highest sensory quality of the extract was provided with the roasting at $180^{\circ}C$ for 10 min, indicating the optimum roasting condition of Omija. The extract of the roasted Omija was superior in sensory properties to that of the unroasted one.

• KSBB Journal
• /
• v.26 no.4
• /
• pp.357-364
• /
• 2011

This study was carried out to investigate the effects of agitation, aeration and scale-up on the mycelial growth, exo-polysaccharide (EPS) production, and mycelial morphology in the liquid culture of Ganoderma lucidum. A correlation between roughness and operating variables was also studied to scale-up the liquid culture of G. lucidum in a jar fermenter. When the agitation speed or aeration rate increased, the morphological form was changed from rough pellet to smooth pellet form. Increase of the agitation and aeration reduced the mycelial roughness. On the other hand, in the case of pellet size, it was not affected by aeration. The higher EPS production was obtained at approximately 17% of roughness and mycelial pellet size of 3~5 mm. The morphology at each fermenter was closely correlated with kLa value, and it was found that similarity of morphology would be used as a criteria of scale-up for liquid culture of G. lucidum.

• KSBB Journal
• /
• v.25 no.2
• /
• pp.109-115
• /
• 2010

The demand of biodiesel that is a renewable, alternative fuel for fossil-based petrodiesel seems to keep increasing. Exploiting lipids of microalgae as a raw material for biodiesel is already technically feasible. To realize economical production of microalgal biodiesel, several factors or strategies should be addressed and improved. Especially, researches on improvement of lipid synthesis by genetic or metabolic engineering are now in early stage, and prospects of this field are bright, requiring concerns and interests of many researchers to put practical use of microalgal biodiesel forward.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.10 no.2
• /
• pp.115-121
• /
• 2005

Using a general Saccharomyces cerevisiae as a model strain, continuous ethanol fermentation was carried out in a stirred tank bioreactor with a working volume of 1,500 mL. Three different gravity media containing glucose of 120, 200 and 280 g/L, respectively, supplemented with 5 g/L yeast extract and 3 g/L peptone, were fed into the fermentor at different dilution rates. Although complete steady states developed for low gravity medium containing 120 g/L glucose, quasi-steady states and oscillations of the fermented parameters, including residual glucose, ethanol and biomass were observed when high gravity medium containing 200 g/L glucose and very high gravity medium containing 280 g/L glucose were fed at the designated dilution rate of $0.027\;h^{-1}$. The observed quasi-steady states that incorporated these steady states, quasi-steady states and oscillations were proposed as these oscillations were of relatively short periods of time and their averages fluctuated up and down almost symmetrically. The continuous kinetic models that combined both the substrate and product inhibitions were developed and correlated for these observed quasi-steady states.

• Korean Journal of Food Science and Technology
• /
• v.32 no.2
• /
• pp.444-447
• /
• 2000

The microbial changes during the fermentation of salted and fermented shrimp at different salt levels $(3{\sim}30%)$ were investigated to elucidate the effect of salt on the microflora of the fermented shrimp. During 22 weeks of fermentation, the numbers of total bacteria and yeasts of the fermented shrimp with 3, 8, 30% salt generally decreased with fermentation time, while those in the fermented shrimp of 18% salt increased. Halophilic bacteria were found only in the late stage of the fermentation at 18% salt. The greatest number of the halophilic yeasts was observed also at 18% salt level. The results indicated that 18% salt provided the most favorable environment for the microorganisms related to the shrimp fermentation.

• Journal of Industrial Technology
• /
• v.43 no.1
• /
• pp.25-31
• /
• 2023

Stretchable and flexible electronics that comply with dynamic movements and micromotion of the human tissues can enable real-time monitoring of physiologic signals onto the human skin and in the brain, respectively. Especially, gallium based liquid metal stretchable electronics can offer human-interactive biosensors to monitor various physiologic parameters. However, the liquid-like nature, surface oxidation and contamination by organic materials, and low biostability of the liquid metals have still limited the long-term use as bioelectronics. Here we introduced electrochemical deposition without oxidation pathways to overcome these practical challenges in liquid metal bioelectronics. CNT/PDDA composite with reduction way and PEDOT:BF₄ with oxidation way under organic solvent are suggested as rationally designed material engineering approaches. We confirmed that the structures with the soft, flexible, and stretchable liquid metal platform can successfully detect dopamine with a high sensitivity and selectivity, record neural signals including action potentials without scar formation, and monitor physiologic signals such as EMG and ECG.