• Microbiology and Biotechnology Letters
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• v.29 no.4
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• pp.240-247
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• 2001

The effect of microsparged aeration in mammalian cell bioreactor on the oxygen transfer rate and cell viability was studied. The microspargers with differ- ent micron-sized pores were used to supply oxygen to the medium. The oxygen transfer coefficients (k$_{L}$a) measured in the bioreactor were markedly increased, which is due to the increase of the contacting area between air bubbles and liquid medium when the pore size of microsparger decreases. When the impellers of two different types (square-pitch marine impeller and $45^{\circ}$ pitched flat blade impeller) were used for agitation, the k$_{L}$a values were slightly higher with the marine impeller than with the blade impeller. The detrimental effect of direct gas sparging with microsparger on mammalian cells was investigated in bubble columns with various air flow rates and different pore sized microspargers. The first-order cell death rate constant ($k_{d}$ /7) was shown to be directly proportional to the air flow rate and inversely proportional to the pore size. During the cultivation of hybridoma cells using microsparger with the pore size of $0.57\mu$m in the mammalian cell culture bioreactor, the continuous sparging caused the cell death and suppressed the cell growth. However, cells grew normally and cell viability was maintained above 90% in the logarithmic phase when the air was intermittently sparked in order to maintain the dissolved oxygen level above 20%.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2175-2185
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• 2000

Respiration rate should be a reasonable state variable for the activated sludge and could be used to simulate the performance of the activated sludge process. Toxic materials are classified into three groups, competitive, noncompetitive and uncompetitive. They increase/decrease the half saturation coefficient or specific growth rate. that means decreasing of the substrate removal capacity. In this research, a pilot-scale activated sludge process was operated under extended aeration method, and a representative noncompetitive inhibitor, acidic wastewater was applied to establish a respirometry-based toxicity model. Using this model. the correlation coefficient between measured and calculated respiration rate was 0.96 when acidic wastewater(pH 3.9~5.5) was introduced continuously to the aeration tank. Even though respiration rate was decreased by toxic effect of acidic wastewater, effluent substrate concentration represented to COD was deteriorated just a little bit. It might be caused by the low ratio of readily biodegradable substrate in the input substrate. Reduction of respiration rate by decreasing of input substrate concentration was much lower than that by acidic wastewater, and hence it was estimated that the possibility of false toxic alarm caused by decreasing of substrate concentration should be low.

• Journal of Microbiology and Biotechnology
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• v.11 no.4
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• pp.607-613
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• 2001

The biodegradation rates of diesel oil by a selected diesel-degrading bacterium, Pseudomonas stutzeri strain Y2G1, and microbial consortia composed of combinations of 5 selected diesel-degrading bacterial were determined in liquid and soil systems. The diesel degradation rate by strain Y2G1 linearly increased $(R^2=0.98)$ as the diesel concentration increased up to 12%, and a degradation rate as high as 5.64 g/l/day was obtained. The diesel degradation by strain Y2G1 was significantly affected by several environmental factors, and the optimal conditions for pH, temperature, and moisture content were at pH8, $25^{\circ}C$, and 10%, respectively. In the batch soil microcosm tests, inoculation, especially in the form of a consortium, and the addition of nutrients both significantly enhanced the diesel degradation by a factor of 1.5 and 4, respectively. Aeration of the soil columns effectively accelerated the diesel degradation, and the initial degradation rate was obviously stimulated with the addition of inorganic nutrients. Based on these results, it was concluded that the major rate-limiting factors in the tested diesel-contaminated soil were the presence of inorganic nutrients, oxygen, and diesel-degrading microorganisms. To resolve these limiting parameters, bioremediation strategies were specifically designed for the tested soil, and the successful mitigation of the limiting parameters resulted in an enhancement of the bioremediation efficiency by a factor of 11.

• Microbiology and Biotechnology Letters
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• v.25 no.4
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• pp.427-433
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• 1997

Sludge Returned CMAS process was applied to treat the wastewater from electric accessory manufacturing company while this type of wastewater was usually treated by chemical process. This result show that the removal rate of TCOD was about 70-80% regardless of hydraulic retention time, On the contrary, the removal rate of BOD was abtained in a range of 77-92% depending on hydraulic retention time. In order to remove more than 80% of organic materials with the proposed process, the F/M ratio should be maintained below 0.17. In this case, the calculated value of organic removal rate, Km, was calculated to be 1.26 hr$^{-1}$, and the ratio of cell synthesis/total energy was 0.32 and 0.26 for COD and BOD base, respectively. The yield coefficient was calculated to be 0.242 and the half velocity coefficient was 0.3 hr$^{-1}$. The value of endogenous respiration coefficient was 0.02 hr$^{-1}$. The measured effluent BOD concentration, MLSS concentration in aeration tank, oxygen uptake rate, and sludge production were matched relatively well with the calculated values using above coefficients, In order to optimize the dewatering of sludge, the hydraulic retention time was recommended to be 15. 6 hrs. These results indicate that the wastewater from an eletric accessory manufacturing company can be treated safely with a biological process.

• Journal of environmental and Sanitary engineering
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• v.24 no.1
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• pp.40-46
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• 2009

The enzyme expressed from strain L-49 was 2.01 times higher than that of original strain. Strain L-49 can grow on culture plate with $50{\mu}g/mL$ ampicillin. The synthesis of $\alpha$-amylase was greatly suppressed when strain L-49 was grown on monosaccharide such as glucose and polysaccharide at the same time cell concentration was low. Amylase production was enhanced when the bacterium was grown on starch and dextrin. Among different nitrogen sources tried, yeast extract was found to be the best followed by panpeptone, peptone, meat extract, bean meal, and corn steep liquor. The average rate of enzyme production was enhanced for 3~4 times in fermentation time from 24h to 44h. The sugar uptake rate has also increased. Low oxygen supply rate enhanced the rate of strain propagation but depressed the enzyme production. Hence it is benefit to obtain high enzyme activity that agitation speed maintained not lower than 400r/min and aeration rate maintained greater than 1:1vvm.

• Journal of Environmental Health Sciences
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• v.23 no.4
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• pp.127-132
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• 1997

The characteristics of the ozone treatments of phenol were studied in a laboratory scale wastewater treatment system. The ozone treatment of wastewater was carried out in a batch-type reactor. The initial pH of wastewater(7-10), volumetric flow rate(1-2l/min) and ozone concentration(20~30 mg/l) of aerating gas were considereal as experimental variables in the ozone treatment. Phenol was decomposed easily by the ozone in a batch treatment, where the rate determining step was the COD removal that is decomposition of intermediates formed by the ozonation of phenol. Phenol decomposition and COD removal could be expressed by the first order reaction for the phenol concentration and COD, respectively. Rate constants of phenol decomposition and COD removal increased with the initial pH, volumetric flow rate and ozone concentration of aeration gas. Under the present experimental condition, their relationships could be given by for the phenol decomposition $k'=4.46\times 10^{-9}[pH]_o ^{3.94}[O_3]^{1.42}Q_{O3}^{1.57}$ for the COD removal $k=2.46\times 10^{-10}[pH]_o ^{5.19}[O_3]^{1.15}Q_{O3}^{1.19}$

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.315-316
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• 2001

In this study various nutritional and environmental parameters such as, initial moisture content, pH. inoculum size, air rate, sample size and nutrient supplement that influence pigment production were evaluated in solid-state cultures. optimum initial moisture content and pH were determined to be 50% and 6.0, respectively. The supplement of the substrate with different carbon, nitrogen, and mineral source reveals a more inhibitive effect as the substrate concentration increase. optimum aeration rate was determined to be 2vvm in flask culture. The maximum amount of red pigment, 3500 OD/g dried fermented rice, was obtained in optimum conditions which is obtained in solid flask culture.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.394-397
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• 2001

In order to maximize the cell growth and the biosurfactant production by the Pseudomonas aeruginosa BYK-2(KCTC 18012P), in the fed-batch fermentation processes were performed varying the feeding medium concentrations and the feeding rate. Feel-batch culture was performed with the optimal agitation speed of 200rpm and the aeration rate of 0.67vvm in a 7L Jar fermentor containing 3L of modified medium and 2.0-2.5%(v/v) fish oil as a carbon source. Addition of fish oil(2.5mL/l00mL modified medium), when fish oil was depleted, the cell and biosurfactant concentration were 6.1g/L and 22.7g/L, respectively.

• Microbiology and Biotechnology Letters
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• v.25 no.1
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• pp.68-74
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• 1997

The conversion of D-sorbitol to L-sorbose by Gluconobater suboxydans was analyzed, and continuous production of L-sorbose was carried out in immobilized cell reactors. L-Sorbose production by high densities of resting cells was more effective than by conventional batch fermentations. Sorbitol dehydrogenase, an enzyme converting D-sorbitol to L-sorbose, did not suffer from substrate inhibition, but from product inhibition. When L-sorbose production was carried out with Ca-alginate-immobilized cells, about 60 g/l of L-sorbose was obtained. On the other hand, when the corn steep liquor (CSL) concentration of medium was reduced to 0.08%, 80 g/l of L-sorbose was obtained. Outgrowth inside the immobilized carriers was thought to block the pores of the carriers so that substrate could not easily diffuse through the carriers. Continuous production of L-sorbose was well accomplished in a bubble column reactor, and 6. 5 g/l.h of productivity and 81.2% of yield were obtained at a substrate feeding rate of 0.08h$^{-1}$ under the optimum conditions with carrier volume of 55% and aeration rate of 3 vvm.

• Journal of Environmental Health Sciences
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• v.21 no.2
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• pp.36-41
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• 1995

In order to treat effectively various type of wastewater discharged from the manufacture factory of organic phosphorous agricultural pesticides by the activated sludge process. The acclimation test of sludge was carried out by the dilution of completely mixed raw wastewater. The results of experiment were obstained as follows. 1. The moderate dilution rate of mixed raw wastewater was founded to about 30 times. 2. The available range of BOD-SS loading was 0.1~0.15 $kg\cdot BOD/kg\cdot SS\cdot day$ and it was similar to the case of extended aeration activated sludge process. 3. After the acclimation of activated sludge, the concentration of MLSS was 2000 mg/L, removal efficiency of BOD more than 90%, and SVI 100, respectively. 4. The oxygen respiratory rate of acclimated sludge was $47 mg\cdot O_2/g\cdot hr$ and this was increased about 5 times than $10 mg\cdot O_2/g\cdot hr$ of ordinary sludge.