• Environmental Engineering Research
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• v.15 no.2
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• pp.79-84
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• 2010

Three biological aerated filters (BAFs) composed of a PVC pipe with a diameter of 75 mm were constructed and operated at a waste-water temperature at $13^{\circ}C$. The media used for each BAF were: 5-mm gravel; 5-mm lava rock; 12.5-mm diameter by 15-mm long plastic rings, all with a media depth of 1.7 m. The feedwater, which simulated the effluent of aerated lagoons, had influent soluble chemical oxygen demand (sCOD) and ammonia concentrations of approximately 50 and 25 mg/L, respectively. For a hydraulic retention time (HRT) of two hours without recirculation, ammonia percent removals were 98.5, 98.9, and 97.8%, for the gravel, lava rock, and plastic rings, respectively. By increasing the effluent recirculation from 100 to 200% for an HRT of one hour, respective ammonia removals improved from 90.1 to 96, 76.5 to 90, and 65.3 to 79.5% for gravel, lava rock, and plastic rings. Based on the ammonia and sCOD loadings for different HRTs, the estimated maximum ammonia loading was approximately 0.6 kg $NH_3-N/m^3$-day for the three BAFs of different media types. The zero-order biotransformation rates for the BAF with gravel were found to be higher than the lava rock and plastic ring media. The results ultimately showed that BAF can be used as an add-on system to aerated lagoons or as a secondary treatment unit to meet ammonia discharge limits.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.350-354
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• 2010

In natural world various inorganic crystals are grown with controlled shape and size in hybrid forms with organics. Such natural processes have been attempted much to mimick artificially. One of the example is calcium carbonate which has been examined a lot in the field of biomineralization. In this study, we utilize well-organized surface of polydiacetylene(PDA) films as the crystal-growing template. We devised a novel mini-arrayer device that transfers PDA films at air/water interfaces of each array well and deposit them to hydrophobized glass substrates. This technical improvement will contribute to facilitate better understandings of biomineralization mechanism.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.206-210
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• 2011

We fabricated rod-like poly(lactic acid)(PLA) specimens through applying various methods of equal-channel angular extrusion(ECAE) process and investigated the change of thermal and mechanical properties of specimens before and after each ECAE process. Combining three re-injection routes(A, BC, and C) and three pass counts(1, 2 and 4) allowed us to fabricate 7 different PLA specimens. Thermal properties of each specimen were measured by both differential scanning calorimeter and thermo-gravimetric analyzer. Shear strains of each specimen with respect to applied loads were measured by indentation hardness tester. Field emmision scanning electron microscopy was used to observe internal microstructure of cross-section of each specimen. The observed microstructures qualitatively supported the explanation of hardness test results. Among 7 specimens, PLA-P2A showed the biggest shear strain probably due to its dense microstructure.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.87-92
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• 2013

Microalgae have been suggested as a promising feedstock for producing biofuel because of their potential of lipid production. In this study, a first principles ODE model for microalgae growth and neutral lipid synthesis proposed by Surisetty et al. (2010) is investigated for the purpose of maximizing the rate of microalgae growth and the amount of neutral lipid. The model has 6 states and 12 parameters and follows the assumption of Droop model which explains the growth as a two-step phenomenon; the uptake of nutrients is first occurred in the cell, and then use of intra-cellular nutrient to support cells growth. In this study, optimal input design using D-optimality criterion is performed to compute the system input profile and sensitivity analysis is also performed to determine which parameters have a negligible effect on the model predictions. Furthermore, model predictive control based on successive linearization is implemented to maximize the amount of neutral lipid contents.

• KSBB Journal
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• v.32 no.3
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• pp.193-198
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• 2017

Sialylation is important in producing therapeutic proteins such as antibody, cytokine and fusion protein. Thus, enhancement of sialylation is usually performed in CHO cell cultures. ${\alpha}2,6$-Sialyltransferase (ST), which plays a key role in the attachment of ${\alpha}2,6-sialic$ acid, is present in human cells but not in Chinese hamster ovary (CHO) cells. Overexpression of ${\alpha}2,6-ST$ can be used for enhancing the degree of sialylation and achieving human-like glycosylation. In this study, we constructed CHO cells producing human cytotoxic T-lymphocyte antigen4-immunoglobulin (hCTLA4-Ig) as well as ${\alpha}2,6-ST$. Transfected CHO cells were selected using G418 and stable cell line was established. Profiles of viable cell density and hCTLA4-Ig titer in an overexpressed cell line were similar to those of a wild-type cell line. It was confirmed that the total amount of sialic acid was increased and ${\alpha}2,6-sialic$ acid was attached to the terminal residues of N-glycan of hCTLA4-Ig by ESI-LC-MS. Compared to 100% of ${\alpha}2,3-sialic$ acid in wild type cells, 70.9% of total sialylated N-glycans were composed of ${\alpha}2,6-sialic$ acid in transfected cells. In conclusion, overexpression of ${\alpha}2,6-ST$ in CHO cells led to the increase of both the amount of total sialylated N-glycan and the content of ${\alpha}2,6-sialic$ acid, which is more resemble to human-like structure of glycosylation.

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.685-690
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• 2017

Ammonia is a useful substance which is widely used in various industries. It is generally released by the decomposition of agricultural wastes and known to have toxic effects on human beings. Due to the common usage, it is possible to cause water pollution through either direct or indirect leakage. Such cases, it is preferable to use the adsorption capacity of zeolite to rapidly remove ammonium ions, but it is not sufficiently removed by the adsorption only. In this paper, the removal efficiency of ammonium ion through both the adsorption capacities of commercial synthetic zeolites and the biological mechanism of microorganisms were compared. In addition, microorganisms were immobilized on the zeolite in order to enhance the removal efficiency by applying a chemo-biological process. As a result, the standard commercial zeolite showed 67~81% of the removal efficiency in 2~4 hours at a 100 ppm concentration of ammonium, whereas the selected microorganism Klebsiella pneumoniae subsp. Pneumoniae showed up to 97% within 8 hours. When the microorganism was immobilized on the zeolite, the highest removal efficiency of approximately 98.5% were observed within 8 hours.

• Journal of Korean Society on Water Environment
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• v.22 no.6
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• pp.996-1003
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• 2006

The absorption characteristics of powdered activated carbon doped by transition-metal nanoparticles were investigated to enhance the remove efficiencies of $TCOD_{Mn}$ and Color from the flexo-inks wastewater. According to the adsorption dynamics of PAC and MPAC, the optimal dosage of activated-carbon adsorbents was 3 g/L under the reaction conditions of pH6.0, 30 mill of reaction time, 240 rpm of mixing intensity. The removal efficiencies by the optimal dosages were maximized as 19% $TCOD_{Mn}$, 57% Color for PAC and 88% $TCOD_{Mn}$, 95% Color for MPAC. Freundlich indexes of isotherm absorption were estimated as follows: i) For PAC, k=-8.11, 1/n=2.98, r=0.91 in the raw water, and k=0.14, b/n=0.75, r=0.96 in the biological treatment water, ii) For MPAC, k=2.69, 1/n=0.21, r=0.80 in the raw water, and k=0.74, 1/n=1.17, r=0.95 in the biological treatment water. MPAC (Powdered activated carbon doped by transition-metal nanoaprticles) was very effective in the removal of organics from the raw water and biological treatment water, as Freundlich indexes of 1/n for both types of water were estimated less than 2.0.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.1
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• pp.99-102
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• 2005

Organic solvents are widely used in biotransformation systems. There are many efforts to reduce the consumption of organic solvents because of their toxicity to the environment and human health. In recent years, several groups have started to explore novel organic solvents called room temperature ionic liquids in order to substitute conventional organic solvents. In this work, lipase-catalyzed transesterification in several uni- and bi-phasic systems was studied. Two representative hydrophobic ionic liquids based on 1-butyl-3-methylimidazolum coupled with hexafluorophosphate ([BMIM][$PF_6$]) and bis[{trifluoromethylsulfonyl} imide] ([BMIM] [$Tf_{2}N$]) were employed as reaction media for the transesterification of n-butanol. The commercial lipase, Novozym 435, was used for the transesterification reaction with vinyl acetate as an acyl donor. The conversion yield was increased around $10\%$ in a water/[BMIM][$Tf_{2}N$] bi-phasic system compared with that in a water/hexane system. A higher distribution of substrates into the water phase is believed to enhance the conversion yield in a water/[BMIM][$Tf_{2}N$] system. Partition coefficients of the substrates in the water/[BMIM][$Tf_{2}N$] bi-phasic system were higher than three times that found in the water/hexane system, while n-butyl acetate showed a similar distribution in both systems. Thus, RTILs appear to be a promising substitute of organic solvents in some biotransformation systems.

• Journal of Korean Society on Water Environment
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• v.31 no.6
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• pp.693-699
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• 2015

It has been known that torrential rainfall events have been occurring worldwide due to climate change. The accelerated soil erosion has caused negative impacts on water quality and ecosystem of receiving waterbodies. Since soil security issues have been arising in various areas of the world, intensive interests have been given to topsoil management in Korea. Thus in this study, Web GIS-based computing system of physical, chemical, and biological topsoil quality indices were developed. In this study, five soil quality maps at national scale and top soil erosion potential were prepared for evaluation of soil quality based on soil erosion potential. For this system, the open source Web GIS engine, OpenGeo, was used as core engine of the system. With this system, decision makers or related personnel in areas of soil erosion Best Management Practices (BMPs) would be able to find the most appropriate soil erosion BMPs based on soil erosion potential and soil quality at the area of interest. The Web GIS system would be efficiently used in decision making processes because of ease-of-use interface and scientific data used in this system. This Web GIS system would be efficiently used because this system could provide scientific knowledge to decision makers or stakeholders. Currently various BMP database are being built to be used as a decision support system in topsoil management and topsoil quality areas.

• KSBB Journal
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• v.22 no.4
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• pp.179-184
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• 2007

This study introduces the characteristics and some applications of repetitive polypeptides, especially to the biomaterial, tissue engineering scaffolds, drug delivery system, and DNA separation systems. Since some fibrous proteins, which consist of repeating peptide monomers, have been reported that their physical properties are changed dramatically by means of temperature alteration or pH shifting. For that reason, fibrous protein-mimetic polypeptides, which are produced by the recombinant technology, can be applied to the diverse biological fields. Repetitive polypeptides can also be used in the bioseparation area such as DNA sequencing, because they make DNA separation possible in free-solution electrophoresis by conjugating DNA fragments to them. Moreover, artificial synthesis of repetitive polypeptides helps to demonstrate the correlations between mechanical properties and structures of natural protein polymer, which have been proven that repetitive domains are affected by the sequence of the repeating domains and the number of repeating subunits. Repetitive polypeptides can be biologically synthesized using some special cloning methods, which are represented here. Recursive directional ligation (RDL) and controlled cloning method (CCM) have been proposed as excellent cloning methods in that we can control the number of repetition in the multimerization of polypeptides and the components of repetitive polypeptides by either method.