• KSBB Journal
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• v.17 no.1
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• pp.68-72
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• 2002

Supercritical Carbon Dioxide was evaluated and optimized for the enrichment and fractionation of the essential oil and the bitter principles of hops, both of which contribute to the flavor of beer, Selected conditions of extraction(pressure, temperature and co-solvent) influenced the composition, the olfactory results and the colour of the extract. Optimal extraction conditions were 30 min, 1800 psia and $ >45^{\circ}C $ with co-solvent. Under these conditions, yield was 65% from brewer's yeast. The bittering substances from brewer's yeasts almost were removed.

• Horticultural Science & Technology
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• v.30 no.5
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• pp.501-508
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• 2012

Reducing carbon dioxide ($CO_2$) exhaust has become a major issue for society in the last few years, especially since the initial release of the Kyoto Protocol in 1997 that strictly limited the emissions of greenhouse gas for each country. One of the primary sectors affecting the levels of atmospheric greenhouse gases is agriculture where $CO_2$ is not only consumed by plants but also produced from various types of soil and agricultural ecosystems including greenhouses. In greenhouse cultivation, $CO_2$ concentration plays an essential role in the photosynthesis process of crops. Optimum control of greenhouse $CO_2$ enrichment based on accurate monitoring of the added $CO_2$ can improve profitability through efficient crop production and reduce environmental impact, compared to traditional management practices. In this study, a sensor-based control system that could estimate the required $CO_2$ concentration considering emission from soil for cucumber greenhouses was developed and evaluated. The relative profitability index (RPI) was defined by the ratio of growth rate to supplied $CO_2$. RPI for a greenhouse controlled at lower set point of $CO_2$ concentration (500 ${\mu}mol{\cdot}mol^{-1}$) was greater than that of greenhouse at higher set point (800 ${\mu}mol{\cdot}mol^{-1}$). Evaluation tests to optimize $CO_2$ enrichment concluded that the developed control system would be applicable not only to minimize over-exhaust of $CO_2$ but also to maintain the crop profitability.

• Journal of Microbiology and Biotechnology
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• v.19 no.12
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• pp.1665-1671
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• 2009

Anaerobic digestion sludge was cultivated in an electrochemical bioreactor (ECB) to enrich the hydrogenotrophic methanogens. A modified graphite felt cathode with neutral red (NR-cathode) was charged with electrochemical reducing power generated from a solar cell. The methane and carbon dioxide collected in a Teflon bag from the ECB were more than 80 ml/l of reactant/day and less than 20 ml/l of reactant/day, respectively, whereas the methane and carbon dioxide collected from a conventional bioreactor (CB) was around 40 ml/l of reactant/day, respectively. Moreover, the maximal volume ratios of methane to carbon dioxide (M/C ratio) collected in the Teflon bag from the ECB and CB were 7 and 1, respectively. The most predominant methanogens isolated from the CB on the $20^{th}$, $80^{th}$, and $150^{th}$ days of incubation were hydrogenotrophs. The methanogenic diversity analyzed by temperature gradient gel electrophoresis (TGGE) of the 16S rDNA variable region was higher in the ECB than in the CB. The DNA extracted from the TGGE bands was more than 95% homologous with hydrogenotrophic methanogens in the ECB, but was an aceticlastic methanogen in the CB. In conclusion, the ECB was demonstrated as a useful system for enriching hydrogenotrophic methanogens and increasing the M/C ratio of the gas product.

• KSBB Journal
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• v.23 no.3
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• pp.193-198
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• 2008

In this study, the supercritical $CO_2$ extraction was applied for the enrichment of coffee flavors. The extraction efficiency of coffee flavors was dependent on the pressure and temperature and optimized as 350 bar and 80$^\circ$C. Five flavors of high aroma values were analyzed. The flavors extracted by the supercritical $CO_2$ extraction were 76.6 times higher than those by the traditional method, espresso extraction. The modified headspace system proved the enhanced efficiency of supercritical $CO_2$ extraction. The coffee beverage containing the extract of supercritical $CO_2$ resulted 2.3 times of flavor enrichment when it was compared to that without the supercritical extract.

• Journal of the Korean Wood Science and Technology
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• v.52 no.3
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• pp.289-299
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• 2024

The current study aimed to investigate the impact of CO₂ enrichment on the width of annual tree rings, earlywood and latewood, and the area of annual growth of Pinus densiflora Siebold & Zucc. grown in open-top chamber (OTC). To this end, two CO₂ enrichment cases were considered, namely 1.4 × increment (560 ppm in OTC-II) and 1.8 × (720 ppm in OTC-III) were compared with the current atmosphere (400 ppm in OTC-I). The CO₂ enrichment conditions for a period of 12 years (2010-2021) were considered, and all measurements were done through image analysis. The study showed that the increment in CO₂ concentrations positively affected the tree growth. The measurement data from the trees in OTC-III were considerably higher than those from OTC-I, whereas those from OTC-II were slightly higher than those from OTC-I. Decreasing patterns of the measured widths and area in 6-7 years after the beginning of CO₂ enrichment was found for all the OTCs. These patterns were possibly due to changes in the physiological features, such as aging. The findings of the present study can have potential uses as fundamental data for forest management considering CO₂ concentrations.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05b
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• pp.147-152
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• 2004

Gas separation membrane technology is useful for a variety of applications [1, 2]. such as hydrogen recovery from reactor purge gas, nitrogen and oxygen enrichment, water vapor removal from air, stripping of carbon dioxide from natural gas. etc. Although membrane separations are attractive because of low energy costs and simple operation, low permeabilities and/or selectivity often limit membrane applications [3, 4].(omitted)

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.3
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• pp.242-248
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• 2013

The purpose of this study is to obtain low-emission and high-efficiency by hydrogen enriched LPG fuel in LPG engine and is to clarify the effects of hydrogen enrichment in LPG fuelled engine on exhaust emission and performance. An experimental study was carried out to obtain fundamental data for performance and emission characteristics of hydrogen enrichment in LPG engine. The research was held by changing the hydrogen ratio to 0, 5, 10, 20% in 1500rpm, bmep 2 and 4bar. The result turned out that the combustion duration was shortened due to fast flame propagation of hydrogen. And the amount of Carbon dioxide and Hydrocarbon decreased. However, the amount of NOX increased, which is thought to be the result of high adiabatic flame temperature of hydrogen. It has been confirmed that this phenomenon has changed by the Hydrogen mixing ratio.

• New & Renewable Energy
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• v.16 no.1
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• pp.58-67
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• 2020

Microbial electrosynthesis has recently been considered a potentially sustainable biotechnology for converting carbon dioxide (CO₂) into valuable biochemicals. In this study, bioelectrochemical acetate production from CO₂ was studied in an H-type two-chambered reactor system with an anaerobic microbial consortium. Metal-rich mud flat was used as the inoculum and incubated electrochemically for 90 days under a cathode potential of -1.1 V (vs. Ag/AgCl). Four consecutive batch cultivations resulted in a high acetate concentration and productivity of 93 mmol/L and 7.35 mmol/L/day, respectively. The maximal coulombic efficiency (rate of recovered acetate from supplied electrons) was estimated to be 64%. Cyclic voltammetry showed a characteristic reduction peak at -0.2~-0.4 V, implying reductive acetate generation on the cathode electrode. Furthermore, several electroactive acetate-producing microorganisms were identified based on denaturing- gradient-gel-electrophoresis (DGGE) and 16S rRNA sequence analyses. These results suggest that the mud flat can be used effectively as a microbial source for bioelectrochemical CO₂ conversion.

• Microbiology and Biotechnology Letters
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• v.35 no.1
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• pp.52-57
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• 2007

A gas-circulating bioreactor was used for enrichment of autotrophic methanogens. Mixture of hydrogen and carbon dioxide (5:1) was used as a sole energy and carbon source. Anaerobic digestive sludge isolated from wastewater treatment system was inoculated into the gas-circulating bioreactor. The enrichment of two chemolithotrophic methanogens, Methanobacterium curvum and Methanobacterium oryzae was accomplished in the gas-circulating bioreactor. The enriched bacteria were cultivated in a bioreactor equipped with hollow-fiber hydrogen-supplying system (hollow-fiber bioreactor), and a hybrid-type bioreactor equipped with hollow-fiber hydrogen-supplying system and electrochemical redox control system. The methane productivity was maximally 30% (V/V) in the hollow-fiber bioreactors and 50% (V/V) in the hybrid-type bioreactor.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.76-83
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• 2017

Biogas, combine with ever-increasing natural gas demand, has been on the center stage in South Korea for the early part of twenty first century in an effort to reduce the emission of global warming gases. With the passage of legal system of City Gas Business Law in 2014, the biogas has its place of production and distribution to consumers. However, it has a room for its technological improvements in terms of enrichment, by separating carbon dioxide and removing impurities efficiently. For these improvements, four different methane enrichment processes were tested in this study; membrane separation, water absorption, Chemical Absorption and Adsorption. A variety of operation scenarios were applied to the processes and the best practices were drawn out. The optimum process was selected based on case study results. Methane produced in this study showed 97% purity and 98% recovery rate, which meets the requirements of the City Gas quality standards.