• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.253-259
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• 2013

In the present study, the characteristics of combustion phenomena and NOx emission in the OFA-type tangentially injected coal-fired boiler have been investigated numerically in order to find the effect of geometrical variation on the performance of the boiler. For these, numerical analyses of turbulent flow, chemical reaction, and radiation heat transfer are performed by using the computational fluid dynamics method. The predicted results clearly show that NOx formation highly depends on the combustion processes, the temperature and species concentrations. In addition, the optimum conditions for both the maximum NOx reduction and highest boiler efficiency can be obtained by considering the amount of supplied air and the injection angle at OFA, and modifying the boiler configuration. It is also found that the variation of supplied air at OFA is more effective than that of the injection angle for reducing the NOx emission, within the present operating conditions.

• Proceedings of the Korean Society for Bioinformatics Conference
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• 2000.11a
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• pp.13-16
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• 2000

Microorganisms have been widely employed for the production of useful bioproducts including primary metabolites such as ethanol, succinic acid, acetone and butanol, secondary metabolites represented by antibiotics, proteins, polysaccharides, lipids and many others. Since these products can be obtained in small quantities under natural condition, mutation and selection processes have been employed for the improvement of strains. Recently, metabolic engineering strategies have been employed for more efficient production of these bioproducts. Metabolic engineering can be defined as purposeful modification of cellular metabolic pathways by introducing new pathways, deleting or modifying the existing pathways for the enhanced production of a desired product or modified/new product, degradation of xenobiotics, and utilization of inexpensive raw materials. Metabolic flux analysis and metabolic control analysis along with recombinant DNA techniques are three important components in designing optimized metabolic pathways, This powerful technology is being further improved by the genomics, proteomics, metabolomics and bioinformatics. Complete genome sequences are providing us with the possibility of addressing complex biological questions including metabolic control, regulation and flux. In silico analysis of microbial metabolic pathways is possible from the completed genome sequences. Transcriptome analysis by employing ONA chip allows us to examine the global pattern of gene expression at mRNA level. Two dimensional gel electrophoresis of cellular proteins can be used to examine the global proteome content, which provides us with the information on gene expression at protein level. Bioinformatics can help us to understand the results obtained with these new techniques, and further provides us with a wide range of information contained in the genome sequences. The strategies taken in our lab for the production of pharmaceutical proteins, polyhydroxyalkanoate (a family of completely biodegradable polymer), succinic acid and me chemicals by employing metabolic engineering powered by genomics, proteomics, metabolomics and bioinformatics will be presented.

• BMB Reports
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• v.36 no.4
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• pp.409-416
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• 2003

The isoform 1 of cyclodextrin glycosyltransferase (CGTase, EC 2.4.1.19) from Paenibacillus sp. A11 was purified by a preparative gel electrophoresis. The importance of histidine, tryptophan, tyrosine, and carboxylic amino acids for isoform 1 activity is suggested by the modification of the isoform 1 with various group-specific reagents. Activity loss, when incubated with diethylpyrocarbonate (DEP), a histidine modifying reagent, could be protected by adding 25 mM methyl-$\beta$-cyclodextrin substrate prior to the modification. Inactivation kinetics of isoform 1 with DEP resulted in second-order rate constants ($k_{inactivation}$) of $29.5\;M^{-1}s^{-1}$. The specificity of the DEP-modified reaction for the histidine residue was shown by the correlation between the loss of isoform activity and the increase in the absorbance at 246 nm of N-carbethoxyhistidine. The number of histidines that were modified by DEP in the absence and presence of a protective substrate was estimated from the increase in the absorbance using a specific extinction coefficient of N-carbethoxyhistidine of $3,200\;M^{-1}cm^{-1}$. It was discovered that methyl-$\beta$-CD protected per mole of isoform 1, two histidine residues from the modification by DEP. To localize essential histidines, the native, the DEP-modified, and the protected forms of isoform 1 were digested by trypsin. The resulting peptides were separated by HPLC. The peptides of interest were those with $R_t$ 11.34 and 40.93 min. The molecular masses of the two peptides were 5,732 and 2,540 daltons, respectively. When the data from the peptide analysis were checked with the sequence of CGTase, then His-140 and His-327 were identified as essential histidines in the active site of isoform 1.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.1
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• pp.137-145
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• 2004

Intensive animal industries create large volumes of nutrient rich effluent which, if untreated, has the potential for substantial environmental degradationand to recover valuable nutrients that would otherwise be lost. Members of the family Lemnaceae are widely used in lagoon systems, to achieve inexpensive and efficient remediation of effluent. Only limited research has been conducted into their growth in highly eutrophic media and there has been little done to systematically distinguish between different types of media. This study examined the growth characteristics of duckweed in abattoir effluent and explored possible ways of ameliorating the inhibitory factors to growth on this medium. A series of pot trials was conducted to test the tolerance of duckweed to abattoir effluent partially remediated by a sojourn in anaerobic fermentation ponds, both in its unmodified form and after the addition of acid to manipulate pH, and the addition of bentonite. Unmodified abattoir effluent was highly toxic to duckweed, even at dilutions of 3:1. Duckweed remained viable and grew sub-optimally in simplified media with total ammonia nitrogen (TAN) concentrations of up to 100 mg/L. Duckweed grew vigorously in effluent diluted 1:4 v/v, containing 56 mg TAN/L when modified by addition of acid (to decrease pH to 7) and bentonite at 0.5%. The results of this study suggest that bentonite plays an important role in modifying the toxicity of abattoir effluent to duckweed.

• Journal of Nutrition and Health
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• v.26 no.7
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• pp.829-838
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• 1993

This study was designed to compare the effect of different dietary fats on the incidence of colorectal tumor, the level of plasma thromboxane B2(TXB2) and fatty acid profiles of platelet and colonic mucosal lipids in N - methyl - N - nitro - N - nitrosoguanidine(MNNG) - treated rats. Male Sprague Dawley rats, at 8 weeks old, were divided into 2 groups and infused intrarectally with saline(control group) or with 2mg MNNG(carcinogen-treated group) twice a week for 3 weeks. Each group was again divided into 4 groups and fed one of four diets(BT, CO, PO, FO) containing dietary fat at 9%(w/w) level for 37 weeks, Dietary fats were beef tallow(7.2%)+corn oil(1.8%) for BT, corn oil(9.0%) for CO, perilla oil(9.0%) for PO, fish oil (6.5%)+corn oil (2.5%) for FO diets. MNNG-treated rats had colonic tumor, while no tumors(adenocarcinoma and adenoma) than others. Tumor sizes in BT-MNNG rats ranged from 2mm papillary form to 15mm of polypoid. However, the size of tumors in PO-MNNG or FO-MNNG rats could not be measured by gross examination. BT-MNNG and CO-MNNG groups were higher in the level of plasma TXB2 and the ratio of c20 : 4/c20 :5 platelet. PO-MNNG groups were lower in the ratio of c20 : 4/c20 : 5(p<0.05) in fatty acid of colonic mucosal lipids suggesting that perilla oil and fish oil could reduce the level of PGE2 and TXB2 by modifying its precursor content and restrain tumor promotion in colon. Effect of perilla oil rich in $\alpha$-linolenic acid on colon carcinogenesis was similar to that of fish oil and thus perilla oil could have a protective effect against colon cancer possibly by inhibiting the production of arachidonic acid metabolite.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.505-505
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• 2011

The control of wettability of thin films is of great importance and its success surely brings us huge applications such as self-cleaning, antifogging and bio-passive treatments. Usually, the control is accomplished by modifying either surface energy or surface topography of films. In general, hydrophobic surface can be produced by coating low surface energy materials such as fluoropolymer or by increasing surface roughness. In contrast, to enhance the hydrophillicity of solid surfaces, high surface energy and smoothness are required. Silica (SiO2) is environmentally safe, harmless to human body and excellently inert to most chemicals. Also its chemical composition is made up of the most abundant elements on the earth's crest, which means that SiO2 is inherently economical in synthesis. Moreover, modification in chemistry of SiO2 into various inorganic-organic hybrid materials and synthesis of films are easily undertaken with the sol-gel process. The contact angle of water on a flat silica surface on which the Young's equation operates shows ~50o. This is a slightly hydrophilic surface. Many attempts have been made to enhance hydrophilicity of silica surfaces. In recent years, superhydrophilic and antireflective coatings of silica were fabricated from silica nanoparticles and polyelectrolytes via a layer-by-layer assembly and postcalcination treatment. This coating layer has a high transmittance value of 97.1% and a short water spread time to flat of <0.5 s, indicating that both antireflective and superhydrophilic functions were realized on the silica surfaces. In this study, we assessed hydrophillicity and hydrophobicity of silica coating layers that were synthesized using the sol-gel process. Systematic changes of processing parameters greatly influence their surface properties.

• YAKHAK HOEJI
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• v.55 no.1
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• pp.69-74
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• 2011

Hyaluronic acid (HA) is a natural polymer consisting of disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine. It has a great potential and success in cosmetic and biomedical applications. However, native HA is highly soluble and easily metabolized by enzymes such as hyaluronidase. Thus, various studies have been reported on modifying the physicochemical properties of HA, while maintaining its biocompatibility. For controlled drug delivery, many trials for fabricating HA microspheres were achieved under chemical reaction. The HA microspheres fabricated to improve the physical stability of HA using adipic acid dihydrazide (ADH) by cross-linking reaction has been reported earlier, however it lacks the desired physical stability and rapidly decomposes by swelling or enzymes. Therefore, we prepared double cross-linked HA microspheres (DC-HA microspheres) and alginate containing HA microspheres (AC-HA microspheres) to enhance its physicochemical properties. DC-HA microspheres were prepared using trisodium trimetaphosphate (STMP) under crosslinking reaction after ADH cross-linking reaction. AC-HA microspheres were prepared by adding alginate as a networking polymer. These microspheres were characterized by morphology, particle size, zeta potential, stability against hyaluronidase. Results showed that the DC-HA and AC-HA microspheres are more stable than that of HA microspheres.

• Journal of Surface Science and Engineering
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• v.44 no.3
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• pp.117-123
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• 2011

We investigated the spectroscopic and electrochemical properties of the citrate-based CuNi solution at different solution pH and analyzed various surface properties of CuNi codeposition layer. By combining UV-Visible spectroscopic data with potentiodynamic polarization curves, it could be found that the complexation of $Ni^{2+}$-citrate pair was completed at lower solution pH than $Cu^{2+}$-citrate pair and was affected by the coexistent $Cu^{2+}$ ions, while the complexation between $Cu^{2+}$ ions and citrate was not sensitive to the presence of $Ni^{2+}$ ions. Also, the electron transfer from cathode to $Cu^{2+}$-citrate and$Ni^{2+}$-citrate was hindered by strong complexation between $Cu^{2+}/Ni^{2+}$ ions and citrate and so apparent codeposition current densities were reduced as the solution pH increases. CuNi codeposited layers had a higher Cu content when they were prepared at high pH solution due to the suppression of Ni deposition, and when codeposition was executed in an agitated condition due to the acceleration of mass transfer of $Cu^{2+}$ ions in the solution. Actually, solution pH had little effect on the surface morphology and deposits orientation, but greatly influenced the corrosion resistance in 3.5% NaCl solution by modifying the chemical composition of CuNi layers and so pH 3 was expected as the most suitable solution pH in the viewpoint of corrosion coatings.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.6
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• pp.479-485
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• 2018

Large amounts of oily wastewater discharged from various industrial operations (petroleum refining, machinery industries and chemical industries) cause serious pollution in the aquatic environment. Although dissolved air flotation (DAF) separating oil pollutants using microbubbles represents current practice, bubble size cannot be selectively controlled, and lots of power is required to generate microbubbles. Therefore, to investigate performance of the DAF process, this study examined the distribution of different sizes of microbubbles resulting from changes in physical shear force via modifying shapes of a slit-nozzle without an additional power supply. Three types of slit-nozzles (different angle, shape and length of the slit-nozzle) were used to analyze the distribution of bubble size. At a slit angle of $60^{\circ}$, shear force was 4.29 times higher than a conventional slit, and particle size distribution (PSD) in the range between 2 and $20{\mu}m$ more than doubled. Treatment efficiency of synthetic oily wastewater through the coagulation-DAF process achieved 90% removal of COD by injecting $FeCl_3$ and PACl of 250 mg/L and 100 mg/L, respectively, and the same performance resulted using $FeCl_3$ of 200 mg/L and PACl of 80 mg/L employing a slit-nozzle angle of $60^{\circ}$. This study shows that a coagulation-DAF process using a modified slit-nozzle can improve the pre-treatment of oily wastewater.

• Mycobiology
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• v.49 no.1
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• pp.1-14
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• 2021

Pleurotus species are commercially essential mushrooms and widely cultivated throughout the world. The production of Pleurotus mushrooms alone accounts for around 25% of that total cultivated mushrooms globally. In America and Europe, Pleurotus species are considered specialty mushrooms, whereas, in Korea, their cultivation is economically profitable, and it is one of the highly consumed species. Pleurotus species are predominantly found in tropical forests and often grow on fallen branches, dead and decaying tree stumps, and wet logs. Biographical studies have shown that the Pleurotus genus is among the more conspicuous fungi that induce wood decay in terrestrial ecosystems worldwide due to its formidable lignin-modifying enzymes, including laccase and versatile peroxidases. Pleurotus species can be grown easily due to their fast colonization nature on diversified agro-substrates and their biological efficiency 100%. Pleurotus mushrooms are rich in proteins, dietary fiber, essential amino acids, carbohydrates, water-soluble vitamins, and minerals. These mushrooms are abundant in functional bioactive molecules, though to influence health. Pleurotus mushrooms are finding unique applications as flavoring, aroma, and excellent preservation quality. Apart from its unique applications, Pleurotus mushrooms have a unique status delicacy with high nutritional and medicinal values. The present review provides an insight into the cultivation of Pleurotus spp. using different agro-waste as growth substances paying attention to their effects on the growth and chemical composition.