• BMB Reports
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• 제45권2호
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• pp.59-70
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• 2012

Carbon catabolite repression (CCR) is a key regulatory system found in most microorganisms that ensures preferential utilization of energy-efficient carbon sources. CCR helps microorganisms obtain a proper balance between their metabolic capacity and the maximum sugar uptake capability. It also constrains the deregulated utilization of a preferred cognate substrate, enabling microorganisms to survive and dominate in natural environments. On the other side of the same coin lies the tenacious bottleneck in microbial production of bioproducts that employs a combination of carbon sources in varied proportion, such as lignocellulose-derived sugar mixtures. Preferential sugar uptake combined with the transcriptional and/or enzymatic exclusion of less preferred sugars turns out one of the major barriers in increasing the yield and productivity of fermentation process. Accumulation of the unused substrate also complicates the downstream processes used to extract the desired product. To overcome this difficulty and to develop tailor-made strains for specific metabolic engineering goals, quantitative and systemic understanding of the molecular interaction map behind CCR is a prerequisite. Here we comparatively review the universal and strain-specific features of CCR circuitry and discuss the recent efforts in developing synthetic cell factories devoid of CCR particularly for lignocellulose-based biorefinery.

• Journal of Microbiology and Biotechnology
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• 제15권4호
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• pp.800-808
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• 2005

Leuconostoc mesenteroides SY1, an isolate from kimchi, was able to ferment $\alpha$-galactosides, such as melibiose and raffinose. $\alpha$-Galactosidase ($\alpha$-Gal) activity was higher in cells grown on melibiose and raffinose than cells grown on galactose, sucrose, and fructose. $\alpha$-Gal activity was not detected in cells grown on glucose, indicating the operation of carbon catabolite repression (CCR). A 6 kb DNA fragment was PCR amplified using a primer set based on the nucleotide sequence of a putative $\alpha$-galactosidase gene (aga) from L. mesenteroides ATCC 8293. Nucleotide sequencing of the 6 kb fragment confirmed the presence of aga and other genes involved in the galactosides utilization, and the gene order was galR (transcriptional regulator)-aga-gaIK (galactokinase)-gaIT (galactose-1-phosphate uridylyltransferase). Northern blotting experiment showed that aga, gaIK, and gaIT constituted the same operon, that the transcription was induced by galactosides, such as melibiose and raffinose, whereas gaIR was independently transcribed as a monocistronic gene, and that the level of transcription was fairly constant. The aga was overexpressed in E. coli BL21 (DE3) using pET26b(+) vector, and $\alpha$-Gal was accumulated in E. coli as an inclusion body.

• 농업과학연구
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• 제3권2호
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• pp.235-243
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• 1976

Cellulomonas sp. CS1-1의 셀룰라아제 생산에 있어서 분해생성물에 의한 저해 기구를 연구하고 아울러 효소 작용시 생성물의 저해 작용 여부를 구명하기 위하여 각종 함량의 셀로비오스를 함유한 아비셀 중층 한천배지시험, 셀로비오스의 공급을 극소화함으로써 세포외 셀룰라아제의 증산을 목적으로 한 연속배양 시험, 그리고 효소기질에 각기 다른 농도의 셀로비오스가 존재할 때의 활성도에 대한 저해 시험을 시도한 결과 i) 효소반응 혼액중 셀로바오스의 농도가 10mM 이하에서는 셀룰라아제의 작용이 저해되지 않았으나 20mM에서 30%, 50mM에서 약 55% 저해됨이 인정되었다 ii) 아비셀 중층 배지 시험에서 셀룰라아제의 분해 작용은 글루코오스및 셀로비오스에 의해 크게 저해되었다 iii ) 연속 배양에 의하여 배지중의 셀로비오스의 잔존량을 극히 적게 한 경우(희석율 0.05 및 $0.1hr^{-1}$)에도 세포내외 효소가 증산되지 않았다.

• 한국미생물·생명공학회지
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• 제28권6호
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• pp.341-348
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• 2000

Selection of high producer strain, optimization of production medium and cultivation in bioreactor system were carried out in order to produce an antifungal substance, PAFS in large amounts which sources and 41 kinds of nitrogen sources, a synthetic medium consisting of fructose(70 g/1) and ammonium sulfate (10g/l) and a complex medium including galactose(30g/l), fructose(20g/l) and cottonseed flour(35g/l) were determined as opti-mized media for PAFS production. In bioreactor studies examining physiological characteristics of the pro- ducer microorganism with the complex medium, typical pattern of diauxic growth was observed as demonstrated by the result that fructose was not used before almost exhaustion on readily utilizable carbon source, galactose. When galactose was supplemented additionally during the fermentation period. PAFS pro-ductivity did no increases any more, indicating that large portion of the added galactose was used for cell growth instead of biosynthesis of the secondary metabolite. It was deduced that PAFS production could be enhananced by employing fed-batch operation in order to overcome the apparent phenomenon of catabolite repression and /or inhibition.

• 한국미생물·생명공학회지
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• 제31권2호
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• pp.157-164
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• 2003

알칼리성 xylanase를 생산하는 균주를 토양으로부터 분리한 후 동정을 실시한 결과 Bacillus alcaiophilus으로 판명되었다. B. alcalophilus AX2000으로 명명한 본 균주는 pH 10.5에서 생육이 가장 좋았으며 효소활성도 가장 높았고 배지 중에 탄소원과 질소원으로서 0.5%(w/v) birchwood xylan과 0.5%(w/v) polypeptone/yeast extract를 각각 사용하였을 경우에 최대의 xylanase생산성을 나타내었다. Xylanase의 생합성근 glucose에 의한 catabolite repression을 받았으며 고농도의 xylose에 의해 효소의 생합성이 저해되었다. 조효소의 최적활성은 pH 10과 $50^{\circ}C$에서 나타났으며, pH 5에서 11까지의 넓은 pH범위에서 활성이 안정하게 유지되었고 효소의 열 안정성은 20~$60^{\circ}C$에서 30분간 처리시 90%이상의 잔존활성을 나타내었다.

• 한국미생물·생명공학회지
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• 제24권4호
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• pp.404-407
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• 1996

The effects of carbon sources on vancomycin production were investigated using Nocardia orientalis CSVC 3300. Among carbon sources tested, glucose, maltose and fructose were effective for the production of vancomycin. Glucose was favored for growth, but decrease the production of vancomycin at the concentration above 7.5%. In comparison, maltose did not decrease the production of vancomycin up to the concentration of 20%. When the mixture of glucose and maltose was used in the ratio 1:3 to 1:4, the highest production of vancomycin was achieved. When glucose concentration was set at 3.0%, catabolite repression could not be observed up to total sugar concentration of 16.0%. Fermentation was carried out using commercial hydrolyzed starch composed of glucose, maltose, maltotriose and maltotetraose, The initial glucose concentration was set at 3.0% and subsequent oligosaccharide consumption was monitored by checking their supernatant with HPLC. During initial cultivation for 38 hour, glucose was the sole carbon source leading to rapid growth. After cell growth stopped, the maltose and glucose concentrations increased due to degradation of maltotriose and maltotetraose, but glucose level was maintained at around 3.0%. After 70 hour fermentation, maltose slowly converted to glucose, and vancomycin production continued during the period.

• 한국식품영양학회지
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• 제15권2호
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• pp.126-130
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• 2002

고온성이며 호알칼리성인 Bacillus sp. TA-11이 생성하는 Invertase의 생합성 조절 기작을 규명하고자 먼저 이들의 유도와 억제에 관하여 검토하였다. Invertase는 10mM sucrose을 함유한 생합성 조절배지에서 3시간에 효율적으로 유도되었고 glucose는 sucrose에 의한 invertase 유도를 inducer exclusion 방식으로 억제시켰다. CAMP의 첨가로 glucose에 의한 catabolic repression이 다소 줄어들었다.

• Journal of Microbiology and Biotechnology
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• 제9권2호
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• pp.201-205
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• 1999

The effects of growth temperature and a carbon source on the expression of $\beta$-galactosidase gene of Lactococcus lactis ssp. lactis ATCC 7962 (L. lactis 7962) were investigated. At $25^{\circ}C$, L. lactis 7962 had a higher $\beta$-galactosidase activity than cells grown at $30^{\circ}C$ or $37^{\circ}C$, although cells grew most quickly at $37^{\circ}C$ The highest $\beta$-galactosidase activity was observed in cells grown in M17 with lactose (l %) followed by cells grown in a galactose (1 %) medium. L. lactis 7962 exhibited the minimum $\beta$-galactosidase activity in glucose media, indicating catabolite repression. When the cellular levels of $\beta$-galactosidase mRNA were examined using slot blot hybridization, no significant differences were observed between cells grown at $25^{\circ}C$ and cells at $30^{\circ}C$ or $37^{\circ}C$ in the same media. This suggests that the quantity of $\beta$-galactosidase mRNA may not be the reason for the higher $\beta$-galactosidase activities of L. lactis 7962 at $25^{\circ}C$ The level of ccpA (Catabolite Control Protein) transcript remained almost constant during the exponential growth phase irrespective of a carbon sourse.

• Journal of Microbiology and Biotechnology
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• 제26권7호
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• pp.1182-1189
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• 2016

Lactobacillus brevis ATCC 14869 exhibited a carbon catabolite derepressed phenotype that has ability to consume fermentable sugars simultaneously with glucose. To evaluate this unusual phenotype under harsh conditions during fermentation, the effects of lactic acid and hydrogen ion concentrations on L. brevis ATCC 14869 were examined. Kinetic equations describing the relationship between specific cell growth rate and lactic acid or hydrogen ion concentration were deduced empirically. The change of substrate utilization and product formation according to lactic acid and hydrogen ion concentration in the media were quantitatively described. Although the simultaneous utilization has been observed regardless of hydrogen ion or lactic acid concentration, the preference of substrates and the formation of two-carbon products were changed significantly. In particular, acetic acid present in the medium as sodium acetate was consumed by L. brevis ATCC 14869 under extreme pH of both acid and alkaline conditions.

• 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.