• KSBB Journal
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• 제15권3호
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• pp.274-279
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• 2000

한지자숙폐액을 사료첨가효모의 생산기질로 재이용할 수 있는 가를 검토하기 위하여 사료첨가효모제품으로부터 분리한 Sacch­a aromyces CereVlSlae종을 한지자숙폐액에 배양하였다. 자숙폐액원액에서는 균이 증식하지 못하였으나, 희석액에서는 증식하였으 며, 증류수로 7.5배 희석시 최대증식을 보였다. Jar fennenter배양 에서의 최대총균수는 $1.34{\times}107/mL$이었으며, 최대생균수는 $1.1{\times}107/mL$이었다. 배양액의 균체농도를 증가시키기 위하여 배양중 에 자숙폐액원액을 침가하여 총균수를 최대 $8.2{\times}107/mL$까지 증 가시킬 수 있었다. 지숙폐액원액과 함께 $(NH_4)_2S0_4 및 KH_2P0_4$ 까지 첨가함으로써 최대균체농도에 도달하는 시간을 단축시킬 수 있었다.

• 한국미생물·생명공학회지
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• 제20권2호
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• pp.196-202
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• 1992

Zooloea ramigera 115를 사용하여 생물응집제로서 사용되는 생물고분자생산 실험을 하였다. 생물고분자 생산을 높이기 위하여 회분식, 유가배양, 연속배양방법을 사용하였다. 탄소원으로는 포도당, 유당, 당밀, 유청을 사용하였다. 기질이 포도당의 경우에는 C/N배 98일 때 생물고분자 생산 효과가 좋았으며, 유당의 경우에는 C/N비 30, 당밀과 유청의 경우에는 C/N비 60일 때 생물고분자 생산이 가장 좋았다. 유가배양 방법이 회분식 배양방법 보다 최종 생물고분자 생산이 우수하였다. C/N비를 달리한 2단계 연속 배양방법으로 생산성을 향상시켰다. 당밀의 경우 0.048$hr^{-1}$의 희석속도에서, 유청의 경우 0.096$hr^{-1}$에서 생산성이 가장 좋았다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권2호
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• pp.89-94
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• 2002

The continuous production of citric acid from dairy wastewater was investigated using calcium-alginate immobilized Asrergillus niger ATCC 9142. The citric acid productivity and yield were strongly affected by the culture conditions. The optimal pH, temperature, and dilution rate were 3.0, 30$^{\circ}C$, and 0.025 h$\^$-1/, respectively. Under optimal culture conditions, the maximum productivity, concentration, and yield of citric acid produced by the calcium-alginate immobilized Aspergillus niger were 160 mg L$\^$-1/ h$\^$-1/, 4.5 g/L, and 70.3%, respectively, The culture was continuously perfored for 20 days without any apparent loss in citric acid productivity. Conversely, under the same conditions with a batch shake-flask culture, the maximum productivity, citric acid concentration, and yield were only 63.3 mg L$\^$-1/h$\^$-1/, 4.7 g/L and 51.4%, respectively, Therefore, the results suggest that the bioreactor used in this study could be potentially used for continuous citric acid production from dairy wastewater by applying calcium-alginate immobilized Aspergillus niger.

• Journal of Mechanical Science and Technology
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• 제15권10호
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• pp.1442-1450
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• 2001

The EGR system has been widely used to reduce nitrogen oxides (NO$\_$x/) emission, to improve fuel economy and suppress knock by using the characteristics of charge dilution. However, as the EGR rate at a given engine operating condition increases, the combustion instability increases. The combustion instability increases cyclic variations resulting in the deterioration of engine performance and emissions. Therefore, the optimum EGR rate should be carefully determined in order to obtain the better engine performance and emissions. An experimental study has been performed to investigate the effects of EGR on combustion stability, engine performance,70x and the other exhaust emissions from 1.5 liter gasoline engine. Operating conditions are selected from the test result of the high speed and high acceleration region of SFTP mode which generates more NO$\_$x/ and needs higher engine speed compared to FTP-75 (Federal Test Procedure) mode. Engine power, fuel consumption and exhaust emissions are measured with various EGR rate. Combustion stability is analyzed by examining the variation of indicated mean effective pressure (COV$\_$imep/) and the timings of maximum pressure (P$\_$max/) location using pressure sensor. Engine performance is analyzed by investigating engine power and maximum cylinder pressure and brake specific fuel consumption (BSFC)

• 한국미생물·생명공학회지
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• 제2권1호
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• pp.29-35
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• 1974

We have studied the applicability of the principles and inherent advantages of the two-stage dontinuous uclture technique to an enzyme process for the purpose of improving and optimizing the productivity of 3-ketosteroid-delta-1-dehydrogenase. By using a two-stage continuous culture system, the growth st ageand enzyme produdtion stage are separated. In each stage an optimal set of toperaing conditions was determined, and this was tested for feasibility for the period of 10 days. During this period, at least 70％ of the maximum enzyme productivity could be maintained. The important design parameters studied are: (1) optimal specific growth rate in the first stage which corresponds to the maximal cell productivity, (2) the optimal dilution rate in the second stage which in turn determines the size of second stage fermentor and the mean residence time of cells in the second stage, (3) cell concentration in both stages, add (4) the specific enzyme productivity and enzyme productivity of the second stage. In addition, by using two-stage continuous culture system we have been able to reduce or eliminate the effect of catabolite repression due to high medium concentration and the adverse effect of the solvent used to dissolve the inducer. We have found the balance between the opposing effects of induction and repression in the second stage judging from the observation that the enzyme productivity goes through a maximum.

• Journal of Microbiology and Biotechnology
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• 제17권5호
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• pp.712-720
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• 2007

To investigate clonal variations of recombinant Chinese hamster ovary(rCHO) clones in response to culture pH and temperature, serum-free suspension cultures of two antibody-producing CHO clones(clones A and B), which were isolated from the same parental clone by the limiting dilution method, were performed in a bioreactor at pH values in the range of 6.8-7.6, and two different temperatures, $33^{\circ}C\;and\;37^{\circ}C$. In regard to cell growth, clone A and clone B displayed similar responses to temperature, although their degree of response differed. In contrast, clones A and B displayed different responses to temperature in regard to antibody production. In the case of clone A, no significant increase in maximum antibody concentration was achieved by lowering the culture temperature. The maximum antibody concentration obtained at $33^{\circ}C$(pH 7.4) and $37^{\circ}C$(pH 7.0) were $82.0{\pm}2.6$ and $73.2{\pm}4.1{\mu}g/ml$, respectively. On the other hand, in the case of clone B, an approximately 2.5-fold increase in maximum antibody concentration was achieved by lowering the culture temperature. The enhanced maximum antibody concentration of clone B at $33^{\circ}C$($132.6{\pm}14.9{\mu}g/ml$ at pH 7.2) was due to not only enhanced specific antibody productivity but also to prolonged culture longevity. At $33^{\circ}C$, the culture longevity of clone A also improved, but not as much as that of clone B. Taken together, CHO clones derived from the same parental clone displayed quite different responses to culture temperature and pH with regards antibody production, suggesting that environmental parameters such as temperature and pH should be optimized for each CHO clone.

• 웰빙융합연구
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• 제4권2호
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• pp.19-25
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• 2021

Purpose: The purpose of this study is to reduce odor complaints by identifying problems with odor management at the site of the water regeneration center and researching odor management methods. Due to the high population density of Korea, sewage treatment facilities are adjacent to residential and industrial areas. According to previous studies, the main malodor-emitting facilities of sewage treatment facilities were preliminary treatment facilities (2,220 times), sedimentation basins (4,628 times), and sludge treatment facilities (9,616 times). Research design, data and methodology: Compound malodors and designated malodor-producing substances were collected from five site boundaries of the water regeneration center and analyzed according to the official methods to test malodor, and a total of two times (August and September 2020) were conducted. Results: As a result of the measurement, in the green area in front of the center office, compound malodors were detected at a maximum of 8 times and at least 3 times during the dawn time. As for the designated malodor-producing substances, 0.1ppm of ammonia was detected in the green area in front of the center office and the park golf course. This is within 15 times the maximum allowable emission level of compound malodors and within 1ppm of the maximum allowable emission level of ammonia. Conclusions: Even if the dilution rate of the compound malodors did not exceed the maximum allowable emission level, the odor could be recognized, and more research is needed in the future to establish effective reduction measures according to the subjective and individual and seasonal odor characteristics.

• Journal of Microbiology and Biotechnology
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• 제10권4호
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• pp.455-461
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• 2000

Abstract Spirulina platensis was grown in SWlUe waste to reduce inorganic compowlds and simultaneously produce feed resources. Spirulina platensis prefers nitrogenous compounds in Ibe order: $NH_4^{+}-N>NO_3^{-}-N>simple-N$ such as urea and simple amino acids. It even consumes $NH_4^{+}-N$ first when urea or nitrate are present. Therefore, the content of residual $NH_4^{+}-N$ in Spimlina platensis cultures can be determined by the relative extent of the following processes: (i) algal uptake and assimilation; (ii) ammonia stripping; and (iii) decomposition of urea to NH;-N by urease-positive bacteria. The removal rates of total nitrogen ffild total phosphorus were estimated as an indicator of the treatment effIciency. It was found that Spirulina platensis was able to reduce 70-93% of $P_4^{3-}-P$, 67-93% of inorganic nitrogen, 80-90% of COD, and 37-56% of organic nitrogen in various concentrations of swine waste over 12 days of batch cultivation. The removal of inorganic compounds from swine waste was mainly used for cell growth, however, the organic nitrogen removal was not related to cell growlb. A maximum cell density of 1.52 dry-g/l was maintained with a dilution rate of 0.2l/day in continuous cultivation by adding 30% swine waste. The nitrogen and phosphorus removal rates were correlated to the dilution rates. Based on the amino acid profile, the quality of the proteins in the Spirulina platensis grown in the waste was the same as that in a clean culture.ulture.

• Journal of Microbiology and Biotechnology
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• 제2권4호
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• pp.278-283
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• 1992

Aldehyde production by cells of a methanol utilizing yeast, Hansenula nonfermentans KYP-1 was improved when they were grown in a methanol-limited continuous culture, in comparison with cells grown in a batch culture. A higher cell yield was also obtained in continuous culture than in batch culture. This could be due to the fact that a lower methanol concentration was maintained in the jar fermentor to minimize growth inhibition by methanol. A maximum cell productivity of 0.219 g.$liter^{-1}.hr^{-l}$ and a cell yield of 47% were obtained at dilution rates of 0.1 $hr{-1}$ and 0.06 hr{-1}, respectively. The greatest amount of aldehyde was measured at a dilution rate of 0.08 $hr{-1}$. Under optimum reaction conditions, 915.7 mM of acetaldehyde was produced from 1.5 M ethanol after 21 hours reaction, with a conversion rate of 61%. Propionaldehyde and acrolein were produced with conversion rates of 32.7% and 44%, respectively.

• Applied Biological Chemistry
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• 제39권6호
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• pp.488-493
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• 1996

농약의 토양 표면유출에 관한 연구의 일차단계로 사과 과수원에서 자연강우를 이용한 captafol의 토양 표면 유출 실험을 수행하였다. Captafol 유출농도는 약제를 살포한 직후 강우가 있었던 5차시기에 가장 높은 180 ppb의 수준을 보였으며, 그 이외의 시기에는 대부분 20 ppb 이하였고, 전체 유출된 양은 처리한 유효성분량에 대하여 0.1% 이하 수준이었다. 지천과 합류되는 지점에서 captafol의 희석배율은 과수원의 배출구와 바로 인접한 지천에서는 약 10배, 좀 더 이동되어 큰 지천과 합류되는 지점에서는 약 50배의 수준이었다. 따라서 captafol이 유출로 인하여 인접 하천으로 유입되는 경우는 희석요인(약 $10{\sim}50$배로 희석)과 빠른 가수분해성을 고려할 때 환경생물에 대한 급성적인 독성은 문제가 되지 않을 것으로 판단되었다.