• Journal of Microbiology and Biotechnology
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• v.30 no.6
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• pp.868-877
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• 2020

Bicarbonate has been considered as a better approach for supplying CO₂ to microalgae cells microenvironments than gas bubbling owing to cost-effectiveness and easy operation. However, the β-carotene production was too low in Dunaliella salina cultivated with bicarbonate in previous studies. Also, the difference in photosynthetic efficiency between these two carbon sources (bicarbonate and CO₂) has seldom been discussed. In this study, the culture conditions, including NaHCO₃, Ca²⁺, Mg²⁺ and microelement concentrations, were optimized when bicarbonate was used as carbon source. Under optimized condition, a maximum biomass concentration of 0.71 g/l and corresponding β-carotene content of 4.76% were obtained, with β-carotene yield of 32.0 mg/l, much higher than previous studies with NaHCO₃. Finally, these optimized conditions with bicarbonate were compared with CO₂ bubbling by online monitoring. There was a notable difference in F_v/F_m value between cultivations with bicarbonate and CO₂, but there was no difference in the F_v/F_m periodic changing patterns. This indicates that the high concentration of NaHCO₃ used in this study served as a stress factor for β-carotene accumulation, although high productivity of biomass was still obtained.

• Horticultural Science & Technology
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• v.34 no.6
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• pp.860-870
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• 2016

Continuous monitoring of environmental parameters provides farmers with useful information, which can improve the quality and productivity of crops grown in greenhouses. The objective of this study was to develop a greenhouse environment measurement system using a low-cost microcontroller with open-source software. Greenhouse environment parameters measured were air temperature, relative humidity, and carbon dioxide ($CO_2$) concentration. The ranges of the temperature, relative humidity, and $CO_2$ concentration were -40 to $120^{\circ}C$, 0 to 100%, and 0 to 10,000 ppm, respectively. A $128{\times}64$ graphic LCD display was used for real-time monitoring of the greenhouse environments. An Arduino Uno R3 consisted of a USB interface for communicating with a computer, 6 analog inputs, and 14 digital input/output pins. A temperature/relative humidity sensor was connected to digital pins 2 and 3. A $CO_2$ sensor was connected to digital pins 12 and 13. The LCD was connected to digital pin 1 (TX). The sketches were programmed with the Arduino Software (IDE). A measurement system including the Arduino board, sensors, and accessories was developed (totaling $244). Data for the environmental parameters in a venlo-type greenhouse were obtained using this system without any problems. We expect that the low-cost microcontroller using open-source software can be used for monitoring the environments of plastic greenhouses in Korea.

• Carbon letters
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• v.19
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• pp.40-46
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• 2016

Nitrogen-atom doped graphene oxide was considered to prevent the dissolution of polysulfide and to guarantee the enhanced redox reaction of sulfur for good cycle performance of lithium sulfur cells. In this study, we used urea as a nitrogen source due to its low cost and easy preparation. To find the optimum urea content, we tested three different ratios of urea to graphene oxide. The morphology of the composites was examined by field emission scanning electron microscope. Functional groups and bonding characterization were measured by X-ray photoelectron spectroscopy. Electrochemical properties were characterized by cyclic voltammetry in an organic electrolyte solution. Compared with thermally reduced graphene/sulfur (S) composite, nitrogen-doped graphene/S composites showed higher electroactivity and more stable capacity retention.

• Journal of Power System Engineering
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• v.19 no.2
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• pp.90-95
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• 2015

Recently worldwide concern and research is being actively conducted on green energy which can reduce environmental pollution. A plant such as the natural rapeseed oil, soybean oil, palm, etc. is used as a bio source in home and industry. Biofuels is a sustainable fuel having economically benefits and decreasing environmental pollution problems caused due to fossil fuel, and it can be applied to the conventional diesel engine without changing the existing institutional structure. Waste vegetable oil contains a high cetane number and viscosity component, the low carbon and oxygen content. A lot of research is progressing about the conversion of waste vegetable oil as renewable clean energy. In this study, waste oil was prepared to waste cooking oil generated from the living environment, and applied to diesel engine to confirm the possibility and cost-effectiveness of biodiesel blend waste oil. As a result, brake specific fuel consumption and NOx was increased, carbon monoxide and soot was decreased.

• Microbiology and Biotechnology Letters
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• v.25 no.6
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• pp.598-605
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• 1997

The characteristics of cell growth and cellulose production by Acetobcter xylinum BRC5 were studied in shaking flasks and jar fermentors. Of the substrates tested, the highest cellulose yield was obtained from the fructose medium. Some inductive cultivation was observed and then cellulose was produced with cell growth. When glucose alone or mixture of glucose and fructose was used as the carbon source, cellulose could be biosynthesized under the glucose limitation. Corn steep liquor (CSL), as a low-cost nitrogen source, was a good substitute for yeast extract. In a jar fermentor experiment, 4.14 g/l of disintegrated cellulose was obtained from 8% CSL- medium containing 0.5% glucose and 1.5% fructose.

• Microbiology and Biotechnology Letters
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• v.51 no.3
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• pp.257-267
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• 2023

The potential polyhydroxyalkanoates (PHA)-producing bacteria, Bacillus megaterium PP-10, was successfully isolated and studied its feasibility for utilization of pineapple peel waste (PPW) as a cheap carbon substrate. The PPW was pretreated with 1% (v/v) H₂SO₄ under steam sterilization and about 26.4 g/l of total reducing sugar (TRS) in pineapple peel hydrolysate (PPH) was generated and main fermentable sugars were glucose and fructose. A maximum cell growth and PHA concentration of 3.63 ± 0.07 g/l and 1.98 ± 0.09 g/l (about 54.58 ± 2.39%DCW) were received in only 12 h when grown in PPH. Interestingly, PHA productivity and biomass yield (Y_x/s) in PPH was about 4 times and 1.5 times higher than in glucose. To achieve the highest DCW and PHA production, the optimal culture conditions e.g. carbon to nitrogen ratios of 40 mole/mole, incubation temperature at 35℃ and shaking speed of 200 rpm were performed and a maximum DCW up to 4.24 ± 0.04 g/l and PHA concentration of 2.68 ± 0.02 g/l (61% DCW) were obtained. The produced PHA was further examined its monomer composition and found to contain only 3-hydroxybutyrate (3HB). This finding corresponded with the presence of class IV PHA synthase gene. Finally, certain thermal properties of the produced PHA i.e. the melting temperature (T_m) and the glass transition temperature (T_g) were about 176℃ and -4℃, respectively whereas the M_w was about 1.07 KDa ; therefore, the newly isolated B. megaterium PP-10 is a promising bacterial candidate for the efficient conversion of low-cost PPH to PHA.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.150-150
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• 2016

Mankind is enjoying a great convenience of their life by the rapid growth of secondary industry since the Industrial Revolution and it is possible due to the invention of huge power such as engine. The automobile which plays the important role of industrial development and human movement is powered by the Engine Module, and especially Diesel engine is widely used because of mechanical durability and energy efficiency. The main work mechanism of the Diesel engine is composed of inhalation of the organic material (coal, oil, etc.), combustion, explosion and exhaust Cycle process then the carbon compound emissions during the last exhaust process are essential which is known as the major causes of air pollution issues in recent years. In particular, COx, called carbon oxide compound which is composed of a very small size of the particles from several ten to hundred nano meter and they exist as a suspension in the atmosphere. These Diesel particles can be accumulated at the respiratory organs and cause many serious diseases. In order to compensate for the weak point of such a Diesel Engine, the DPF(Diesel Particulate Filter) post-cleaning equipment has been used and it mainly consists of ceramic materials(SiC, Cordierite etc) because of the necessity for the engine system durability on the exposure of high temperature, high pressure and chemical harsh environmental. Ceramic Material filter, but it remains a lot of problems yet, such as limitations of collecting very small particles below micro size, high cost due to difficulties of manufacturing process and low fuel consumption efficiency due to back pressure increase by the small pore structure. This study is to test the possibility of new structure by direct infiltration of SiC Whisker on Carbon felt as the next generation filter and this new filter is expected to improve the above various problems of the Ceramic DPF currently in use and reduction of the cost simultaneously. In this experiment, non-catalytic VS CVD (Vapor-Solid Chemical Vaporized Deposition) system was adopted to keep high mechanical properties of SiC and MTS (Methyl-Trichloro-Silane) gas used as source and H2 gas used as dilute gas. From this, the suitable whisker growth for high performance filter was observed depending on each deposition conditions change (input gas ratio, temperature, mass flow rate etc.).

• Journal of Microbiology and Biotechnology
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• v.20 no.5
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• pp.853-861
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• 2010

High substrate costs decrease the profitability of polyhydroxyalkanoates (PHAs) production, and thus low-cost carbon substrates coming from agricultural and industrial residuals are tested for the production of these biopolymers. Among them, crude glycerol, formed as a by-product during biodiesel production, seems to be the most promising source of carbon. The object of this study was to characterize the mixed population responsible for the conversion of crude glycerol into PHAs by cultivation-dependent and -independent methods. Enrichment of the microbial community was monitored by applying the Ribosomal Intergenic Spacer Analysis (RISA), and the identification of community members was based on 16S rRNA gene sequencing of cultivable species. Molecular analysis revealed that mixed populations consisted of microorganisms affiliated with four bacterial lineages: ${\alpha}$, ${\gamma}$-Proteobacteria, Actinobacteria, and Bacteroides. Among these, three Pseudomonas strains and Rhodobacter sp. possessed genes coding for polyhydroxyalkanoates synthase. Comparative analysis revealed that most of the microorganisms detected by direct molecular analysis were obtained by the traditional culturing method.

• Journal of Microbiology and Biotechnology
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• v.31 no.2
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• pp.338-347
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• 2021

Polyhydroxyalkanoates (PHA) are a family of microbial polyesters that are used as biodegradable plastics in replacement of conventional plastics for various applications. However, the high production cost is the barrier for PHA market expansion. This study aimed to utilize food waste as low-cost feedstock to produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by Haloferax mediterranei. The effects of acetate (Ac), propionate (Pr), butyrate (Bu), and the short-chain carboxylates derived from food waste were examined on the microbial growth and PHBV production. Results showed that a mixture of carboxylates provided a 55% higher PHBV yield than glucose. The food-waste-derived nutrients achieved the yields of 0.41 to 0.54 g PHBV/g Ac from initial loadings of 450 mg/l to 1,800 mg/l Ac of total carboxylates. And the consumption of individual carboxylate varied between different compositions of the carbon source. The present study demonstrates the potential of using food waste as feedstock to produce PHBV by Haloferax mediterranei, which can provide economic benefits to the current PHA industry. Meanwhile, it will also help promote organic waste reduction in landfills and waste management in general.

• Journal of Sensor Science and Technology
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• v.16 no.5
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• pp.331-336
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• 2007

In this study, we have fabricated an infrared optical fiber based sensor which can monitor the respiration of a patient. The design of a chalcogenide optical fiber based sensor is suitable for insertion into a high electro-magnetic field environment because the sensor consists of low cost and compact mid-infrared components such as an infrared light source, a chalcogenide optical fiber and a thermopile sensor. A fiber-optic respiration sensor is capable of detecting carbon dioxide ($CO_{2}$) in exhalation of a patient using the infrared absorption characteristics of carbon gases. The modulated infrared radiation due to the presence of carbon dioxide is guided to the thermopile sensor via a chalcogenide receiving fiber. It is expected that a mid-infrared fiber-optic respiration sensor which can be developed based on the results of this study would be highly suitable for respiration measurements of a patient during the procedure of an MRI.