• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.732-738
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• 2008

Simulated moving bed (SMB) process is a continuous chromatographic technology used to separate a large amount of petrochemicals, fine chemicals, pharmaceuticals, and so on, drawing a great attraction of related industries. With the recent development of biotechnology, the SMB process has been adopted for the separation of various useful bio-products. Attempts to understand the separation mechanism of the SMB process in many aspects are reported in many publications. These researches have dealt with the improvement of SMB for easier operation and solving problem in process. The feed mixture fed into the SMB process may be of different concentration batch by batch rather than in uniform concentration. Retention behaviors of feed (psicose (A) and fructose (B) mixture) existing in the SMB unit in dynamic steady-state and feed (psicose (C) and fructose (D) mixture) newly injected into the SMB were analyzed. It was observed that the existing components, (A) and (B), were eluted relatively faster as the injection time of new feed was earlier during the port-switching period. In addition, the components (C) and (D) were eluted earlier as fresh feed was injected earlier in a port-switching time.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.451-455
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• 2006

Heterotrophic biomass yield coefficients, $Y_H$, for aerobic, anoxic and anaerobic reactors were successfully estimated for the two wastewater treatment plants, where one plant was operating in the $A^2/O$ process and the other was operating in the 4-stage BNR process. The estimation of $Y_H$ was undertaken by plotting the biomass COD concentrations versus the soluble COD concentrations in order to calculate the ${\Delta}biomass$ COD/ ${\Delta}soluble$ COD in each batch reactor. The batch reactors employed in this study were fed by filtered influent and mixed liquors in the ratio of 10:1, and operated in the aerobic, anoxic and anaerobic conditions, which represented the actual operating conditions for the $A^2/O$ and 4-stage BNR process. The average $Y_H$ values of the aerobic, anoxic and anaerobic reactor for the $A^2/O$ process were 0.52, 0.41 and 0.18 mg COD/mg COD, respectively, and those for the 4-stage BNR process were 0.58, 0.40 and 0.20 mg COD/mg COD, respectively. The average ratio of the $Y_H$ for aerobic reactors to those for the anoxic reactors were about 1:0.79 for the $A^2/O$ process, and about 1:0.69 for the 4-stage BNR process. The experimental method for anoxic and anaerobic $Y_H$ estimation shown in this study has turned out to be simple and efficient in its practical application.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.2
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• pp.165-172
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• 2006

In order to analyze the bacterial community structure including P-removal related organisms, PAOs(polyphosphate accumulating organisms) and GAOs(glycogen-accumulating non-poly-P organisms) occurred in biological phosphate removing process, 2 reactors(SBR; sequencing batch reactor) were operated on different carbon sources(sodium acetate, glucose). For the analysis of bacterial community structure, molecular methods(FISH: fluorescent in situ hybridization and DGGE; denaturing gel gradient electrophoresis) were employed. After 100 days reaction, $PO_4-P$ in effluent dropped to 3.92 mg/L in SBR #1(60.8% removal) fed by sodium acetate, and at the same time FISH results showed that ${\beta}$-subclass proteobacteria(39.67%) and PAOs(45.10%) were dominantly present whereas those value in SBR #2 fed by glucose was 8.30 mg/L(17% removal), and ${\gamma}$-subclass proteobacteria were considerably observed(23.89%) and PAOs was 21.42%. Also the result of DGGE indicated that ${\beta}$-subclass proteobacteria was dominantly observed in SBR #1. However as the temperature increased, the proportion of ${\beta}$-subclass proteobacteria and PAOs decreased, but phosphorus removing inhibitors(GAOs) increased. It suggests that the environmental factor like as temperature and types of carbon source had influence on the prevalence of phosphorus removing organism(PAOs) and phosphorus removing inhibitors(GAOs) in biological phosphate removing process.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.775-780
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• 2009

The efficacy of nitrifying sludge existed in biological nutrient removal process was examined for possible removal of endocrine disrupting chemical(EDC) in the effluent of wastewater treatment plant. Some of ammonia oxidizing bacteria causes ammonia oxidation mediated by ammonia monooxygenase(AMO) activity, which has low substrate specificity resulting in cometablic degradation of several chemicals. In this study, the removal of three model EDCs such as bisphenol A(BPA), nonylphenol(NP) and dibutyl phthalate(DBP) was studied in batch cultures using nitrifying sludge, BOD-oxidizing sludge with low nitrifying activity, and sterilized sludge. Nitrifying sludge showed higher initial removal rates in all batches of three EDCs when it was fed with ammonium as an energy source. The acclimation time was required for the removal of EDCs in batches using BOD-oxidizing sludge or nitritefed nitrifying sludge. That retardation seemed to attribute to the slow growth of cells using the EDCs while ammonium-fed nitrifying sludge could degrade EDCs through simultaneous cooxidation with ammonia oxidation. Sterilized sludge was also tested under the same conditions in order to find the contribution of physical adsorption to the removal of EDCs. About 10~20% of initial EDCs dose was removed when using sterilized sludge. Thus the biological activity is likely to play major role for the degradation of BPA, NP, and DBP rather than the physical adsorption from wastewater.

• Applied Biological Chemistry
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• v.40 no.2
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• pp.89-94
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• 1997

In order to reduce energy input in direct ethanol production from raw starch by co-immobilized Aspergillus awamori(A) and Zymomonas mobilis(Z), A-Z 36 culture system which was changed to anaerobic after 36 h of aerobic fermentation without sterilization was investigated. This immobilized cell system can not be carried out under unsterile conditions because of growth of microbial contaminants from original medium. Among some food additives such as sorbic acid, benzoic acid, dehydroacetic acid, p-hydroxybenzoic acid, Vantocil IB and Neupectin-L, Vantocil IB and Neupectin-L were a potent antibacterial agent in A-Z 36 culture cell system and were not affected in hydrolysis of substrate as compared with the case of control. Ethanol yield(6.9 g/l) in system of addition of 0.1% Neupectin-L was slightly higher than that in control(6.4 g/l). When 2% starch was fed five times in fed-batch culture with 0.1% Neupectin-L, ethanol yield and productivity were 34 g/l and 2.0 g/l/day, respectively.

• ALGAE
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• v.20 no.2
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• pp.121-125
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• 2005

The modern integrated fish-seaweed mariculture has been tested to reduce the environmental impacts of an intensive fed culture. To obtain the best seaweed bioremediation performance, the effects of therapeutants used for fish disease control on the selected seaweed species should be considered. As a selected seaweed, Porphyra yezoensis was tested with six commercial antibiotics including erythromycin thiocyanate_A, erythromycin thiocyanate_B, oxytetracycline, doxycycline, pefloxacin, and amoxicillin trihydrate under the batch incubation at a photon flux density of 10 $\mu$mol ${\cdot}m^{-2}\;{\cdot}\;s^{-1}$ at 15$^{\circ}C$. Among the tested commercial antibiotics, erythromycin thiocyanate_A, erythromycin thiocyanate_B, oxytetracycline, and doxycycline showed decreases in Fv/Fm, the photochemical efficiency of photosystem II, with a dose-dependant and time-dependant manner. From the quenching analysis of chlorophyll fluorescence, three differential patterns were observed in the antibiotics-treated Porphyra: (1) high nonphotochemical quenching (NPQ) and low photochemical quenching (qP) in the cases of Erythromycin thiocyanate_B and amoxicillin trihydrate, (2) high NPQ and high qP in the case of pefloxacin and (3) low NPQ and low qP in the case of oxytetracycline. These results indicated that antibiotics affected in various ways on the photosynthetic apparatus, reflecting differential lesion sites of antibiotics. In addition, the rates of ammonium uptake also decreased with a decrease of Fv/Fm in P. yezoensis thalli treated with erythromycin thiocyanate_B and oxytetracycline. Therefore, the four antibiotics mentioned could affect the bioremediation capacity of the selected seaweed species in the integrated fish-seaweed mariculture system due to the decrease of photosynthetic activity and the simultaneous decrease of ammonium uptake.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.681-686
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• 2010

Two different MFC designs were evaluated in batch mode: single compartment combined membrane-electrodes (SCME) design and twin-compartment brush-type anode electrodes (TBE) design (single chamber with two air cathodes and brush anodes at each side of the reactor). In SCME MFC, carbon anode and cathode electrodes were assembled with a proton exchange membrane (PEM). TBE MFC was consisted of brush-type anode and carbon cloth cathode electrodes without the PEM. A brush-type anode was fabricated with carbon fibers and was placed close to the cathode electrode to reduce the internal resistance. Substrates used in this study were glucose, leachate from cattle manure, or sucrose at different concentrations with phosphate buffer solution (PBS) of 200 mM to increase the conductivity thereby reduce the internal resistance. Hydrogen generating bacteria (HGB) were only inoculated in TBE MFC. The peak power densities ($P_{peak}$) produced from the SCME systems fed with glucose and leachate were 18.8 and $28.7mW/m^2$ at external loads of 1000 ohms, respectively. And the $P_{peak}$ produced from TBE MFC were 40.1 and $18.3mW/m^2$ at sucrose concentration of 5 g/L and external loads of 470 ohms, with a mediator (2-hydroxy-1, 4-naphthoquinone) and without the mediator, respectively. The maximum power density ($P_{max}$) produced from mediator present TBE MFC was $115.3mW/m^2$ at 47 ohms of an external resistor.

• Korean Journal of Microbiology
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• v.35 no.4
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• pp.302-306
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• 1999

Production of biomass by fed-batch culture of Saccharomyces cerevisiae Hansen CBS5926, which is used to treat intestinal disorders, was investigated using ethanol as the sole carbon source. Ethanol was a better carbon source than glucose for high cell density culture of the st-rain since it could decrease the frequency of contamination while increasing the efficiency and final productivity of the fermentation process. Under optimal conditions, 38 g/ℓ of dry cell weight with $2.2{\times}10^{9}$ cfu/㎖ of maximum viable cell count was achieved after 72h cultivation. Freeze-drying of the cultured yeast cells resulted in severe reduction of viability. Of the freeze-drying protectants tested, 20% sucrose and 30% lactose were most effective for the preservation of yeast cells with a viability level of 16.3%. A combination of skim milk and lactose with 20% sucrose(w/v) exerted no synergistic influence upo the viability of the cells during cryopreservation by freeze-drying.

• Microbiology and Biotechnology Letters
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• v.20 no.1
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• pp.73-78
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• 1992

- Enzymatic synthesis of L-tryptophan(Trp) using E. coli tryptophanase has been investigated. In order to reduce the substrate inhibition by indole and to increase the product yield of L-tryptophan three different approaches have been made in this work. First, indole was intermittently fed to the reaction mixture in order to control the indole concentration at lower level. When 15 mM of indole was used as a total amount of substrate, conversion yield of 80% has been obtained with intermittent feeding while only 20% of indole was converted into L-tryptophan by conventional batch operation, The second method employed in this work was the use of cyclohexane-phosphate buffer organic two-phase system. In this system, indole was mainly partitioned into the organic-solvent phase and therefore substrate inhibition was expected to be reduced. L-Tryptophan production in organic two-phase system was, however, unexpectedly lower than that obtained in aqueous buffer solution. As a third method cyclodextrins have been added to the aqueous reaction mixture. It was found that the addition of $\beta$-cyclodextrin enhanced the tryptophan synthesis noticeably while $\alpha$-cycfodextrin showed little effect on tryptophan production.

• Journal of Microbiology and Biotechnology
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• v.15 no.4
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• pp.772-779
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• 2005

Ammonia-oxidizing bacteria (AOB) were enriched by repeating fed-batch cultivations in an AOB-selective medium of activated sludges from a domestic wastewater treatment plant. Enriched culture showed strong capabilities of ammonia oxidation [0.810 mg $NH_4^+$-N/mg mixed liquor suspended solids (MLSS)$\cdot$day] as well as $NO_x^-$-N production (0.617 mg $NO_x^-$-N/ mg MLSS$\cdot$day). Degree of enrichment was examined through fluorescent in situ hybridization (FISH) analyses using an AOB-specific Cy3-labeled oligonucleotide probe (NSOl90) and terminal-restriction fragment length polymorphism (T-RFLP) analyses. FISH analyses confirmed that the fraction of AOB among 4',6-diamidino-2-phenylindole (DAPI)-stained cells increased from about less than $0.001\%$ to approximately $42\%$ after enrichment of AOB, and T-RFLP analyses showed that bacterial community became simpler as enrichment was continued. When the enriched culture of AOB was added (150 mg/l as dry suspended solid) to the normal activated sludge (3,000 mg/l as dry suspended solid), nitrification efficiencies were improved from 0.020 mg $NO_x^-$-N/mg MLSS$\cdot$day to 0.041 mg $NO_x^-$-N/mg MLSS$\cdot$day in a synthetic wastewater and also from 0.0007 mg $NO_x^-$-N/mg MLSS$\cdot$day to 0.0918 mg $NO_x^-$-N/mg MLSS$\cdot$day in a real domestic wastewater. Therefore, it is expected that this enrichment method could be used for improving efficiency of nitrification in wastewater treatment plants.