• 한국작물학회:학술대회논문집
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• 한국작물학회 1987년도 추계 학술대회지
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• pp.14-15
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• 1987

• 전기학회논문지
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• 제67권12호
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• pp.1641-1647
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• 2018

In this paper, we describe a portable potentiostat which is capable of cyclic voltammetry(CV) and amperometry for electrochemical dissolved oxygen sensor. In addition, this portable potentiostat can also transmit the measured data wirelessly to android devices such as smart phone, tablet, etc. through Bluetooth. The potentiostat system consists of three parts; a voltage generator circuit which is controlled by Arduino nano and 12-bit DAC(digital to analog converter) to generate necessary electric potential for operating the electrochemical sensor, an oxidation/reduction current measurement circuit, and a Bluetooth module to transmit data wirelessly to an android device. Once measurements are carried out with the android application, the measured data is transmitted to the android device via Bluetooth and displayed using the android app. in real time. In this paper, we report the measured reduction current with a fabricated dissolved oxygen sensor in both saturated-oxygen state and zero-oxygen states. The results of the developed portable potentiostat system are in good agreement with those of the commercial portable potentiostat (${\mu}stat200$, Dropsens inc.). The measured peak reduction currents using the developed potentiostat and the commercial ${\mu}stat200$ potentiostat were $-0.755{\mu}A$ and $-0.724{\mu}A$, respectively. The reduction currents measured at zero-oxygen state were $-0.005{\mu}A$ and $-0.004{\mu}A$. The discrepancy between those two systems seems very small, which implies successful development of a portable and wireless potentionstat.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.53-56
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• 2000

효모를 이용하여 높은 생산성으로 고농도의 erythritol을 생산하기 위하여 ‘세포 성장단계’와 ‘erythritol 생성단계’로 나누어 2 단계 유가식 배양을 수행하였다. 세포 성장 단계에서는 pH-stat 유가식 배양을 수행하여 3.62 g/L-H의 생산성으로 76 g/L의 균체 농도를 얻을 수 있었다. pH-stat 유가식 배양을 수행하여 고농도의 균체 농도를 얻은 후에 멸균되지 않은 분말형태의 glucose를 발효조에 400 g/L가 되도록 공급하여 세포에 osmotic stress를 가해준 결과 41%의 수율로 187 g/L의 erythritol을 생산할 수 있었으며, 이때의 생산성은 2.79 g/L-h로서 기존에 보고된 어느 결과보다도 높은 값을 얻을 수 있었다. Production phase에서 erythritol 생산에 대한 삼투압의 영향을 알아 본 결과 glucose의 농도가 증가할 수록 생성되는 erythritol 농도가 증가하였으며 세포 농도에 따른 erythritol 생산 수율은 큰 차이는 없었으나 세포 농도가 증가할수록 이에 비례하여 erythritol 생산성이 크게 증가하였다. Erythritol 생산에서 용존 산소량에 관계없이 butyric acid가 생성되었으며 40%의 DO 미만에서는 citric acid가 생성되고, 40% 이상의 DO에서는 gluconic acid가 생성되어 용존 산소량에 의하여 metabolic shift가 유도되었다. 고 농도의 glucose 첨가 후 용존 산소량을 20%로 조절하면서 pH를 3.0으로 낮춘 결과 citrate synthetase의 활성이 억제되어 citric acid가 생성되지 않았으며 gluconic acid 농도는 $KH_2PO_4$에 의하여 증가하고 $MgSO_4{\cdot}7H_2O$ 또는 $(NH_4)_2SO_4$에 의하여 감소되었다. Butyric acid 농도는 $KH_2PO_4$ 또는 $(NH_4)_2SO_4$에 의하여 감소되었으며 synergic effect에 의하여 억제되었다

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2001년도 추계학술발표대회
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• pp.333-335
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• 2001

A simple control strategy of DO-stat was introduced to the recombinant rGuamerin production process in Pichia pastoris. This induction strategy consisted of two interrelated control loops ‘by which oxygen ratio of inlet gas and methanol feeding rate was controlled. Using this control strategy, over-feeding or under-feeding of methanol could be avoided in concomitance with the efficient control of dissolved oxygen level. As a result, the cell concentration reached 130 g/L and rGuamerin expression level was 450 iu/L, which was more than 40% increased result comparing with the fed-batch process using manual control of methanol feeding rate.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권6호
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• pp.571-575
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• 2005

A simple, but effective on-line method for estimating the mycelial cell mass concentration from agitation speed data, a most readily-available process variable, has been developed for DO-stat cultures of Agaricus blazei. The dynamic change of dissolved oxygen concentration (DOC) in the initial transient period and the change in yield were considered in the development of the estimation algorithm or estimator. Parameters in the estimation algorithm were calculated from the agitation speed data at 20% of DOC. The proposed estimator could accurately predict the cell mass concentration regardless of DOC levels in the tested range of $10{\sim}40%$, showing a good extrapolation capability.

• Journal of Microbiology and Biotechnology
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• 제24권1호
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• pp.59-69
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• 2014

One of the major challenges in metabolic engineering for enhanced synthesis of value-added chemicals is to design and develop new strains that can be translated into well-controlled fermentation processes using bioreactors. The aim of this study was to assess the influence of various fed-batch strategies in the performance of metabolically engineered Pseudomonas putida strains, ${\Delta}gcd$ and ${\Delta}gcd-pgl$, for improving production of medium-chain-length polyhydroxyalkanoates (mcl-PHAs) using glucose as the only carbon source. First we developed a fed-batch process that comprised an initial phase of biomass accumulation based on an exponential feeding carbon-limited strategy. For the mcl-PHA accumulation stage, three induction techniques were tested under nitrogen limitation. The substrate-pulse feeding was more efficient than the constant-feeding approach to promote the accumulation of the desirable product. Nonetheless, the most efficient approach for maximum PHA synthesis was the application of a dissolved-oxygen-stat feeding strategy (DO-stat), where P. putida ${\Delta}gcd$ mutant strain showed a final PHA content and specific PHA productivity of 67% and $0.83g{\cdot}l^{-1}{\cdot}h^{-1}$, respectively. To our knowledge, this mcl-PHA titer is the highest value that has been ever reported using glucose as the sole carbon and energy source. Our results also highlighted the effect of different fed-batch strategies upon the extent of realization of the intended metabolic modification of the mutant strains.

• Journal of Microbiology and Biotechnology
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• 제6권3호
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• pp.221-224
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• 1996

Pseudomonas putida BM01 was grown efficiently on glucose as the sole carbon source with a supply of a nitrogen source in pH-stat mode using a low setpoint limit. A final cell concentration of 100 g/l was obtained in 30 h of fed-batch cultivation by controlling glucose concentration within the range of 5-20 g/l and maintaining dissolved oxygen tension above 10$%$ saturation using pure oxygen. This high cell density culture technique is believed highly useful for the production of poly(3-hydroxyalkanoates) by this strain.

• KSBB Journal
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• 제15권3호
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• pp.219-225
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• 2000

Bacillus thuringiensis를 생물농약으로 이용하기 위해서는 고농도의 포자형성에 의한 높은 살충성의 8 -endotoxin를 생산하는 것이 중요하다. 따라서 본 연구에서는 B. thuringiensis의 고농도 배양에 의한 높은 포자형성 수율을 얻기 위하여 40%의 용존산 소량과 $28^{\circ}C$에서 여랴 가지 방법의 유가식 배양법을 검토하였다. 최종 배양액의 glucose 농도가 50 g/L가 되도록 하는 경우의 유가식 배양에서는 continuos fed-batch culture의 linear gradient f feeding 법에 의하여 $9.37{\times}109$ cell/mL의 최대 생존 세포 수와 8 8.33 X 109 spore/mL의 최대 포자 수를 얻었으며, 이때의 포자 형 성율은 88.9% 이었다 최종 배양액의 glucose 농도가 100 m/L가 되도록 하는 경우의 유가식 배양에서는 intermittent fed-batch culture의 pH-stat 법에 의하여 $1.35{\times}1010$cell/mL의 최대 생존 세포 수와 $1.35{\times}1010$ spore/mL의 최대 포자 수를얻었으며, 이 때의 포자 형성율은 97.8% 이엇다.

• KSBB Journal
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• 제18권3호
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• pp.197-201
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• 2003

알콜증류 폐액에 빵효모를 배양하는 중에 포도당, 암모늄 및 인산을 자동 첨가하여 균체량을 효율적으로 증가시킴으로써 폐액의 재이용성을 향상시키고자 하였다. 포도당은 DO를 제어파라미터로 하는 제어방법을 사용하여 자동 첨가함으로서 그 농도를 300 mg/L 이하로 유지하였다. 암모늄은 pH-stat 방법을 사용하여 N $H_4$OH로서 자동 첨가함으로서 12.6~17.4mM의 낮은 농도범위로 유지하였다. 인산의 경우에는 분석방법으로써 ascorbic acid법을 채택한 자동화 FIA sysetm을 제작하여 사용하였다. 이 system으로 배양 19.4 시간 후부터 배양액을 자동분석하고 제어한 결과 배양액의 P $O_4$-P 농도를 23.3~43.4 mg/L 의 낮은 농도범위로 유지할 수 있었다. 세가지 영양성분을 자동첨가하면서 배양한 결과 증식의 정체없이 균체량을 33.0배 더 증가시킬 수 있었다. 비증식속도는 0.19 $hr^{－l}$였다.

• Journal of Microbiology and Biotechnology
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• 제12권2호
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• pp.273-278
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• 2002

Two-step fed-batch fermentations were carried out to overproduce Bacillus licheniformis maltogenic amylase (BLMA) in recombinant Escherichia coli. The first step was to increase the cell mass by controlling the feeding of a glucose solution, while the second step was designed to improve the amylase expression efficiency by supplementing organic nitrogen sources. The linear gradient feeding method was successfully adopted to maintain the glucose concentration below 0.2 g/l during the fed-batch mode, as effectively minimizing acetic acid formation. When the dissolved oxygen (DO) level became limiting, an accumulation of acetic acid and drastic decrease in specific BLMA productivity were observed. Glucose and organic nitrogen sources consisting of yeast extract and casein hydrolysate were simultaneously supplied in the pH-stat mode to further increase the specific BLMA expression efficiency. An organic nitrogen source consisting of 200 g/1 yeast extract and 100 g/1 casein hydrolysate was found to be the best among the various combinations tested. The feeding of an organic nitrogen source in the second-step fed-batch period was highly beneficial in enhancing the BLMA production. The optimized two-step fed-batch culture resulted in 78 g/l maximum dry cell mass and 443 U/ml maximum BLMA activity, corresponding to 1.5-fold increase in the dry cell mass and 3.7-fold enhancement in BLMA production, compared with the simple fed-batch fermentation.