• 한국미생물·생명공학회지
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• 제32권1호
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• pp.52-59
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• 2004

Fructose와 galactose를 배지에 동시에 사용하였을 때 catabolite repression에 의한 PAFS생산성 저해 현상을 극복하기 위해서 본 연구에서는 두 가지 탄소원의 공급량과 유속을 달리하는 유가식 배양으로 PAFS 생산성을 향상시키고자 하였다. 또한 통계적으로 성공률이 매우 높다고 밝혀진 실험방법에 의해 모균주로부터 고생산변이주를 선별하여 생산성이 가장 우수한 것으로 판명된 AP-20 균주를 생물반응기를 이용한 회분식 배양 및 유가식 배양 실험에 이용하였다. 생물반응기에서의 유가식 배양이 회분식 배양에서보다 PAFS생산성이 약 4배 이상 향상되었음을 확인할 수 있었다. 또한 생산균주의 배양생리학적 특성으로서 Pseudomonas aeruginosa는 galactose를 이용해서 세포성장과 이차대사산물 생합성과 관련된 유전자의 발현을 하고 fructose를 이용하여 PAFS를 생합성하는 것으로 추론되며, 너무 느린 탄소원의 공급은 세포성장에 제한요소로 작용하여 이차대사산물의 생합성을 저해하는 것으로 판단되었다. 한편 유가식 배양일지라도 배양 조건에 따라 그 생산성이 뚜렷이 차이가 나는 것으로 관찰되었다 즉 galactos의 초기량이 20g/L이고 fructose 30g/L를 0.032 mL/min의 속도로 공급했을 경우의 PAFS생산량을 100%로 정의했을 때, 초기부터 40 g/L의 galactose가 존재하고 20 g/L의 fructose를 0.032 mL/min의 속도로 공급한 경우에 PAFS생산성이 약 580%향상된 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제22권7호
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• pp.967-974
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• 2012

Cultivation of Spirulina platensis using ammonium salts or wastewater containing ammonium as alternative nitrogen sources is considered as a commercial way to reduce the production cost. In this research, by analyzing the relationship between biomass production and ammonium-N consumption in the fed-batch culture of Spirulina platensis using ammonium bicarbonate as a nitrogen nutrient source, an online adaptive control strategy based on optical density (OD) measurements for controlling ammonium feeding was presented. The ammonium concentration was successfully controlled between the cell growth inhibitory and limiting concentrations using this OD-based feedback feeding method. As a result, the maximum biomass concentration (2.98 g/l), productivity (0.237 g/l d), nitrogen-to-cell conversion factor (7.32 gX/gN), and contents of protein (64.1%) and chlorophyll (13.4mg/g) obtained by using the OD-based feedback feeding method were higher than those using the constant and variable feeding methods. The OD-based feedback feeding method could be recognized as an applicable way to control ammonium feeding and a benefit for Spirulina platensis cultivations.

• 한국약용작물학회지
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• 제8권4호
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• pp.351-361
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• 2000

알콜 발효 증진을 위해 5L 배양조에서 혐기적으로 회분 배양 시 건지황 착즙액을 농도별로 첨가하며 알콜 발효 및 균체 생육을 측정한 결과 균체 생육 및 알콜 생산 수율 모두 착즙액 첨가량이 증가함에 따라 일반 발효에 비해 증가했으며, 30% (v/v) 첨가 시 11.8 (g/L)의 최대 균체양, 0.092 (%/hr)의 최대 알콜 생산성과 같은 최대치를 나타냈다. 하지만 40% 이상 첨가 시는 균체 생육 및 알콜 생산 두 경우 다 감소하는 경향을 보였으며 50% 에서는 심각한 생육 저해 현상이 나타났다. 또한 알콜 생산성 증진을 위해 30% 착즙액을 첨가해 유가식 배양을 실시 한 결과 회분 배양보다 월등히 높은 균체 생육 및 알콜 생산성을 보였다. 이 같은 생산성은 일반 알콜 발효에서 얻을 수 있는 수율보다 약 30-40% 이상 높은 것으로 건지황 착즙액이 알콜 발효에 직접적인 영향을 주는 것이 입증되었다. 이는 알콜 발효 시 건지황의 유용 성분의 활용과 함께 알콜 생산 수율 증진에도 이용이 가능한 지황의 이중적 활용도가 있음을 입증한 것으로 평가된다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제3권2호
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• pp.115-118
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• 1998

Utilization of yeast extract and formation of byproduct metabolite were investigated for hyperthermophilic archaeon Sulfolobus solfataricus (DSH 1617). In both batch and fed-batch cultivations of S. solfataricus, maximal cell density, {{{{ { NH}`_{4 } ^{ +} }}} ion production and pH change were highly dependent on the ratio of yeast extract to glucose in the medium. Variation of {{{{ { NH}`_{4 } ^{ +} }}}} ion level was identified as a major cause of pH change during cultivation, and acidification of culture broth was attributed to consumption of {{{{ { NH}`_{4 } ^{ +} }}}} ions rather than formation of acid byproducts. It was also observed that increase of {{{{ { NH}`_{4 } ^{ +} }}}} ion concentrations in the medium resulted in greater degree of growth inhibition.

• Biotechnology and Bioprocess Engineering:BBE
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• 제1권1호
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• pp.51-53
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• 1996

Fed-batch culture of Pseudomonas oleovorans was carried out for the production of medium-chain-length polyhydroxyalkanoates (MCL-PHAs) using octanoate as a carbon source. Octanoate and the salt solution containing ammounium sulfate and magnesium sulfate were intermittently fed in the course of fermentation. Cell mass and PHA concentrations of 42.8 and 16.8g/L, respectively, could be obtained in 40 h. The PHA content and the PHA productivity were 39.2% and 0.42 g PHA/L-h, respectively. The yields of cell mass and PHA were 0.71 g dry cell mass/g octanoate and 0.28g PHA/g octanoate, respectively. Therefore, octanoate can be used for the production of MCL-PHAs to a high concentration with high productivity.

• KSBB Journal
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• 제5권3호
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• pp.269-277
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• 1990

메탄올이용균인 Methylobacillus sp. SKI의 균체생산효율을 증대시킬 목적으로 마이크로컴퓨터 제어 배양기를 이용해 고농도 유가배양을 수행하였다. 배양액의 초기 메탄올농도를 1.0%(v/v)로 하여 회분배양할 경우 배양 13시간만에 2.07g/l의 균체농도에 도달하였다. 공기 공급에 의한 유가배양에서 최대교반속도 1200rpm, 최대 공기유량 5.0$\ell$/min의 조건으로 배양시 약 15시간만에 13.7$\ell$/ldml 균체농도에 도달하였다. 산소공급에 의한 유가배양에서 최대교반속도 1200rpm, 공기유량 1.0$\ell$min, 최대산소유량 5.0$\ell$/min의 조건으로 배양시 17시간만에 45.3g/l의 균체농도에 도달하였다. 균의 대수 증식기를 공기공급에 의한 유가 배양으로 회분배양에 비해 약 3시간, 산소공급에 의한 유가배양으로 회분배야에비해 약 3시간, 산소공급에 의한 유가배양으로 회분배양에 비해 약 4시간 더 연장할 수 있었다. 즉, 유가배양로 단시간에 높은 농도의 균체를 얻은 것은 feedback제어에 의해 메탄올을 저해농도 이하로 유지시키면서 용존산소를 한계농도 이상으로 제어함으로써 균의 대수적 증식으로 연장시킨 결과이다. 산소공급에 의한 유가배양중 균체농도 27.6g/l에서 미량원소성분이 결핍되었고, 42.8g/l에서 $Mg^2^+$성분이 결핍되었으므로 배양중에 추가공급되었다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권2호
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• pp.149-154
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• 2005

Secretion of the expressed heterologous proteins can reduce the stress to the host cells and is beneficial to their recovery and purification. In this study, fed-batch cultures of Escherichia coli YK537 (pAET-8) were conducted in a 5-L fermentor for the secretory production of human epidermal growth factor (hEGF) whose expression was under the control of alkaline phosphatase promoter. The effects of feeding of glucose and complex nitrogen sources on hEGF production were investigated. When the fed-batch culture was conducted in a chemically de-fined medium, the cell density was 9.68 g/L and the secreted hEGF was 44.7 mg/L in a period of 60 h. When a complex medium was used and glucose was added in pH-stat mode, the secreted hEGF was improved to 345 mg/L. When the culture was fed with glucose at a constant specific rate of $0.25\;gg^{-1}h^{-1}$, hEGF reached 514 mg/L. The effects of adding a solution containing yeast extract and tryptone were further studied. Different rate of the nitrogen source feeding resulted in different levels of phosphate and acetic acid formation, thus affected hEGF expression. At the optimal feeding rate, hEGF production achieved 686 mg/L.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.600-603
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• 2000

DNA chip containing 207 E. coli genes related to important metabolisms such as (TCA cycle, glycolysis, fermentation and etc) were used to carry out a comprehensive investigation of the change in metabolism and physiology during high cell density culture of E. coli by fed-batch cultivation.

• Journal of Microbiology and Biotechnology
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• 제25권3호
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• pp.358-365
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• 2015

ε-Poly-L-lysine (ε-PL) is a homopolymer of L-lysine molecules connected between the epsilon amino and alpha carboxyl groups. This polymer is currently used as a natural preservative in food. Insufficient biomass is a major problem in ε-PL fermentation. Here, to improve cell growth and ε-PL productivity, various nitrogen-rich nutrients were supplemented into flask cultures after 16 h cultivation, marking the onset of ε-PL biosynthesis. Yeast extract, soybean powder, corn powder, and beef extract significantly improved cell growth. In terms of ε-PL productivity, yeast extract at 0.5% (w/v) gave the maximum yield (2.24 g/l), 115.4% higher than the control (1.04 g/l), followed by soybean powder (1.86 g/l) at 1% (w/v) and corn powder (1.72 g/l) at 1% (w/v). However, supplementation with beef extract inhibited ε-PL production. The optimal time for supplementation for all nutrients examined was at 16 h cultivation. The kinetics of yeast-extract-supplemented cultures showed enhanced cell growth and production duration. Thus, the most commonly used two-stage pH control fed-batch fermentation method was modified by omitting the pH 5.0-controlled period, and coupling the procedure with nutrient feeding in the pH 3.9-controlled phase. Using this process, by continuously feeding 0.5 g/h of yeast extract, soybean powder, or corn powder into cultures in a 30 L fermenter, the final ε-PL titer reached 28.2 g/l, 23.7 g/l, and 21.4 g/l, respectively, 91.8%, 61.2%, and 45.6% higher than that of the control (14.7 g/l). This describes a promising option for the mass production of ε-PL.

• Journal of Microbiology and Biotechnology
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• 제12권5호
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• pp.753-759
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• 2002

$\beta$-Cyclodextrin glucanotransferase ($\beta$-CGTase) was overproduced extracellularly using recombinant E. coli by transforming the plasmid pECGT harboring a secretive signal peptide. The $\beta$-CGTase gene of alkalophilic Bacillus firmus var alkalophilus was inserted into the high expression vector pET20b(+) containing a secretive pelB signal peptide, and then transformed into E. coli BL2l(DE3)pLysS. The optimum culture conditions fer the overproduction of $\beta$-CGTase were determined to be TB medium containing 0.5% (w/v) soluble starch at post-induction temperature of $25^{\circ}C$. A significant amount of $\beta$-CGTase, up to 5.83 U/ml, which was nine times higher than that in the parent strain B. firmus var. alkalophilus, was overproduced in the extracellular compartment. A pH-stat fed-batch cultivation of the recombinant E. coli was also performed to achieve the secretive overproduction of $\beta$-CGTase at a high cell density, resulting in production of up to 21.6 U/ml of $\beta$-CGTase.