• Journal of Environmental Health Sciences
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• v.31 no.1
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• pp.15-22
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• 2005

This study was conducted to evaluate air injection mode on stabilization of solid waste in lysimeter. For three lysimeters, one was maintained under anaerobic condition as control, and air was injected into two lysimeters in continuous mode (atmospheric pressure) and intermittent mode (high pressure of 2 bar). Distilled water was sprayed over solid waste in 1.4 l/$m^3$(solid waste)/day, supposing rainfall intensity of 1,200 mm/yr and 30% infiltration. Oxygen in landfill gas was not detected in control lysimeter during operational days. After 30 day-aeration, oxygen concentrations of continuous and intermittent modes were maintained in 14% and 6%, respectively. $COD_{Cr}$ removal efficiencies of continuous and intermittent modes were about 70% and 50%, and BOD5 removal efficiencies were about 80% and 20%, respectively. In view of oxygen supply, and $COD_{Cr}$ and $BOD_5$ removal, continuous air injection mode of atmospheric pressure was more effective than intermittent mode of 2 bar. Settling degree of solid waste in case of two air injection modes was 3 times higher than that of anaerobic condition as control. Considering the above results, it was thought that air injection (especially continuous atmospheric pressure) could improve degradation of solid waste and induce preliminary stabilization in landfill site.

• KSBB Journal
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• v.18 no.2
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• pp.155-160
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• 2003

The effect of dissolved oxygen(DO) on microbial transglutaminase(mTG) production by Streptoverticillium morbaraense was studied in on-line computer controlled fermentation system. In order to control dissolved oxygen during fermentation, the agitation speed and aeration rate of 2.5 L fermenter ranged from 260 to 360 rpm and 0.3 to 3.9 L/min, respectively. The maximum microbial transglutaminase production was obtained at controlled 20% of dissolved oxygen among the various dissolved oxygen controlled batch cultures tested. The production of microbial transglutaminase at controlled 20% of dissolved oxygen was about 2.12 U/mL which was 1.1 times higher than that obtained in batch culture without control of dissolved oxygen. Also, the highest microbial transglutaminase production was obtained in fed-batch cultures in which dissolved oxygen was controlled at 20%, and it was improved almost 1.3 times in comparison with that without control of dissolved oxygen. Maximal dry cell weight and microbial transglutaminase production were 13.2 g/L and 2.6 U/mL, respectively. Finally, it was also found that fed-batch fermentation at controlled 20% of dissolved oxygen showed a good performance for the microbial transglutaminase production by on-line computer controlled fermentation system which may be generally applicable to other microbial cultures.

• Journal of Environmental Health Sciences
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• v.29 no.3
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• pp.28-34
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• 2003

This study was performed to compare the effects of chaff and sawdust as bulking materials on temperature, pH, weight and volume reduction and salinity in aerobic composting of food wastes. Volume ratios of food wastes to chaff in reactor of Control, Ch-l, Ch-2, Ch-3 and Ch-4 were 4:0, 4:1, 4:2, 4:3 and 4:4, respectively. Volume ratios of food wastes to sawdust in reactor of Control, Sd-l, Sd-2, Sd-3 and Sd-4 were 4:0, 4:1, 4:2, 4:3 and 4:4, respectively. Reactors were operated for 24 days with 1 hour stirring by 1 rpm and 2 hours aeration per day. The lowering of the volume ratio of food wastes to chaff and sawdust resulted in the reaction at higher reaction temperature and the elongation of the high temperature reaction period. The lowering of the volume ratio of food wastes to chaff and sawdust resulted in faster pH increase. In the volume ratio of 4:3 and 4:4, pH increased faster in food-chaff mixtures than in food-sawdust mixtures. The lowering of the volume ratio of food wastes to chaff and sawdust resulted in faster steady state in the weight reduction rate and the volume reduction rate. The weight reduction rates of chaff mixtures were higher than those of sawdust mixtures, but the volume reduction rates of sawdust mixtures were more higher than those of chaff mixtures. Salinity increased as composting reaction proceeded, due to reduction in mass weight. The final salinity of Control was 2.79%, and the final range of salinities of chaff and sawdust mixtures were 2.18∼2.37% and 1.86∼2.05%, respectively.

• KSBB Journal
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• v.5 no.3
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• pp.269-277
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• 1990

Methylobacillus sp. SK1, an obligate methylotroph, was cultivated in a fed-batch culture using DO as a methanol feeding indicator with a micro computer-aided control system. While 2.07g/l of cell density was obtained after 13 hr in the batch culture (initial methanol concentration: 1.0%(v/v)),45.3g/l of cell density was obtained after 17 hr by feeding methanol and metal ions in the fed-batch culture with oxygen supply. The high-density biomass was obtained in short cultuivation time by fed-batch culture with feedback control, and consequently the biomass productivity was significantly increased. It was mainly due to extension of logarithmic growth period by methanol feeding without methanol inhibition and intensive aeration without DO limitation with microcomputer-aided control system.

• Journal of Environmental Health Sciences
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• v.31 no.2 s.83
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• pp.160-164
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• 2005

This study was performed to evaluate the effects of washing food wastes before aerobic composting on temperature, pH and salinity, and the effects of washing after composting on salinity of sample mixtures. Weight ratios of food wastes to water in washing were 1:0(Control), 1:1(W-1), 1:2(W-2), 1:3(W-3) and 1:0(N-4), respectively. Ratios of food wastes to wood chips in reactor of Control, W-1, W-2, W-3 and N-1 were $5\;kg:0\iota,\;5\;kg:5\iota,\;5\;kg:5\iota,\;5\;kg:5\iota\;and\;5\;kg:5\iota$, respectively. Reactors were operated for 24 days with 1 hour stirring by 1 rpm and 2 hours of forced aeration per day. The increase in the ratio of water to food wastes resulted in the increase of the maximum reaction temperature and the shortening of the high temperature reaction period. The increase in the ratio of water to food wastes also resulted in faster reaching to the lowest pH and then to the steady state of pH 9.0. The final salinities of Control, N-1, W-1, W-2 and W-3 were $1.04\%,\;0.92\%,\;0.78\%,\;0.64\%\;and\;0.53\%$, respectively. The salinities of the N-l samples which were washed by the weight ratios (water:N-l) of 1:1, 2:1 and 3:1 after composting were $0.72\%,\;0.61\%\;and\;0.51\%$, respectively. Therefore, washing food wastes before aerobic composting is more efficient method than that after aerobic composting.

• Korean Journal of Environmental Agriculture
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• v.30 no.3
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• pp.234-242
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• 2011

BACKGROUND: Cultivation of winter cover crops is strongly recommended to increase land utilization efficiency, animal feeding material self-production, and to improve soil and environmental quality. METHODS AND RESULTS: Four major winter crops (barley, Chinese milk vetch, hairy vetch, and rye) having different C/N ratio were seeded in silt loam paddy soil in the November 2007 and the aboveground biomass was harvested on the late May 2008 to evaluate its effectiveness as green manure, and root biomass distribution was characterized at the different depth (0-60 cm) to study its effect on physical properties and carbon sequestration in soil. During this experiment, the naturally growing weed in the rice paddy soil in Korea, short awn foxtail (Alopecurus aequalis Sobol), was considered as control treatment. Above-ground biomass of all cover crops selected was significantly higher than that of the control treatment (2.8 Mg/ha). Comparatively higher above-ground biomass productivity of rye and barley (15.8 and 13.5 Mg/ha, respectively) suggested that these cover crops possibly had the highest potential as a green manure and animal feeding material. Root biomass production of different cover crops followed the same trend as that for their above ground biomass. Rye (Secale cereal) might have the highest potential for soil C accumulation (7893 C kg/ha) by root biomass development, and then followed by barley (6985 C kg/ha), hairy vetch (6467 C kg/ha), Chinese milk vetch (6671 C kg/ha), and control (5791 C kg/ha). CONCLUSION(s): Cover crops like rye and barley having high biomass productivity might be the most effective winter cover crops to increase organic carbon distribution in different soil aggregates which might be beneficial to improve soil structure, aeration etc. and C sequestration.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.548-555
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• 2007

The control of wastewater treatment has two merits; one is to regulate water quality of effluent and the other is to reduce the cost of wastewater treatment. The purpose of this study was to control the ammonium nitrogen in effluent that is known to cause eutrophication. The control was based on simplified ASM No. 1 which had 3 component materials and 8 coefficients, and the control method was as following. Firstly the ammonium concentration of inflow was measured and the optimal aeration time in effluent was determined according to simplified ASM No. 1 to be 1.0 mg/L. If ammonium concentration of effluent was not equal to 1.0 mg/L, the influent ammonium was corrected by adaptive control. These processes above were repeatedly performed. The SBR running aerobic-anoxic phase had been controlled for 1 month with this method. As a result, the ammonium concentration of the effluent showed in the range of $0.22\sim3.1$ mg/L with an average concentration of 1.1 mg/L. The adaptive control method used in this study was found very useful to control and predict the effluent concentration of ammonium.

• Journal of Korean Society on Water Environment
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• v.29 no.3
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• pp.329-336
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• 2013

This study was conducted to reduce excess sludge generation by recycling of return sludge to the aeration tank after solubilization by electric field charger and ultrasonifier. The return sludge was purposely broken-up to the ratio of $SCOD_{Cr}/TCOD_{Cr}$ at 0.1, 0.2, and 0.3, which was tested along with control (i.e., untreated). Solubilized sludge was subsequently treated in a bench-scaled conventional activated sludge reactor. According to varying $SCOD_{Cr}/TCOD_{Cr}$ ratios, TSS in the reactor was correspondingly increased from 129 to 219 mg/L and $TCOD_{Cr}$ was also from 257 to 335 mg/L. However, TSS in the effluent was nevertheless kept lower at below 30 mg/L and $TCOD_{Cr}$ was also unvaryingly below 40 mg/L. For $SCOD_{Cr}/TCOD_{Cr}$ = 0.3, the amount of excess sludge produced was at the highest decreased up to as high as 78%.

• Microbiology and Biotechnology Letters
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• v.28 no.6
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• pp.349-354
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• 2000

Culture conditions and nitrogen sources were optimized for production of erythritol, a natural sweetener, by Candida magnoliae M26. The optimal culture conditions were found to be culture temperature of $28^{\circ}C$, initial pH of 7, aeration of 1 vvm and agitation speed of 500 rpm in a 2.5 1 jar-fermentor. Glucose was chosen as the best carbon cource bsed on cell growth and erythritol productivity. Kight steep water(LSW) and corn steep liquor (CSL) which are by-products in starch processing from corn were tested as a nitrogen source substitute for yeast extract. The use of either LSW or CSL did not change the fermentation performance. The experimental results using LSW and CSL showed 1.5 times higher in cell growth and almost the same value in erythritol productivity com-pared with the control fermentation using yeast extract as a nitrogen source. These results suggested that either LSW of CSL could be used as a nitrogen source in a large-scale fermentation for erythritol production.

• Journal of Microbiology and Biotechnology
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• v.19 no.9
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• pp.982-986
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• 2009

For the production of ghost bacteria vaccine to prevent the streptococcal disease in aquaculture fish species, a double cassettes vector was constructed and cloned in Escherichia coli DH5${\alpha}$. Ghost bacteria vaccine production from Escherichia coli DH5${\alpha}$/pHCE-InaN-GAPDH-Ghost 37 SDM (SIG) was maximized at a glucose concentration of 1 g/l, agitation of 300 rpm, and aeration of 1 vvm. The maximal efficiency of ghost bacteria formation was obtained at the mid-exponential phase ($OD_{600}=2.0$) with the concentration of 0.77 g/l for SIG. The molecular mass of GAPDH was detected at 67 kDa with the insoluble fraction, by SDS-PAGE and Western blot. The protective efficacy of ghost bacteria vaccine was evaluated by challenge test using olive flounder. The cumulative mortalities of the positive control, formalin-killed cell (FKC) vaccine, and SIG vaccine immunized groups were 91%, 74%, and 57%, respectively. These results suggest that SIG vaccine showed efficacy as a vaccine and had a higher potential to induce protective antibodies than did FKC vaccine.