• 대한핵의학회지
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• 제27권1호
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• pp.104-111
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• 1993

Trace elements are important components in the biological system, as a structural material and metabolic controller. Neutron activation analysis (NAA) with high neutron flux and high energy resolution Ge (Li) detector coupled to multichannel analyzer (MCA) has been one of the most accurate method for the determination of ultra-trace level components, and is applicable to biological material. In human body, the NAA can be used for quantitation of trace elements in various organs and tissue with endocrinological and metabolic disease and industrial metal poisoning. In this study, Triga Mark III nuclear reactor in Korea Atomic Research Institute was used for quantitation of trace eleement in human lung cancer tissues by neutron activation analysis. In the squamous cell carcinoma tissues, Br, Hg, La, Sb, Sc, Cl, Fe and I content were lower than normal lung tissues, and K, Rb and Se content were higher. In the adenocarcinoma tissues, Fe, Au, La, Sc and Zn content were lower than normal lung tissues, and Rb, Co and Se content were higher. Rb content was higher in the adenocarcinoma tissues than in the squamous cell carcinoma tissues. Fe and Na content were higher in the squamous cell carcinoma tissues than in the adenocarcinoma tissues.

• Journal of Microbiology and Biotechnology
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• 제29권6호
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• pp.923-932
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• 2019

Current strategies of strain improvement processes are mainly focused on enhancing the synthetic pathways of the products. However, excessive metabolic flux often creates metabolic imbalances, which lead to growth retardation and ultimately limit the yield of the product. To solve this problem, we applied a dynamic regulation strategy to produce $\text\tiny{L}$-phenylalanine ($\text\tiny{L}$-Phe) in Escherichia coli. First, we constructed a series of Phe-induced promoters that exhibited different strengths through modification of the promoter region of tyrP. Then, two engineered promoters were separately introduced into a Phe-producing strain xllp1 to dynamically control the expression level of one pathway enzyme AroK. Batch fermentation results of the strain xllp3 showed that the titer of Phe reached 61.3 g/l at 48 h, representing a titer of 1.36-fold of the strain xllp1 (45.0 g/l). Moreover, the $\text\tiny{L}$-Phe yields on glucose of xllp3 (0.22 g/g) were also greatly improved, with an increase of 1.22-fold in comparison with the xllp1 (0.18 g/g). In summary, we successfully improved the titer of Phe by using dynamic regulation of one key enzyme and this strategy can be applied for improving the performance of strains producing other aromatic amino acids and derived compounds.

• Journal of Microbiology and Biotechnology
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• 제16권6호
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• pp.993-998
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• 2006

We earlier suggested a hierarchical regulatory network using defined modeling symbols and weights in order to improve the flux balance analysis (FBA) with regulatory events that were represented by if-then rules and Boolean logic. In the present study, the simulation results of the models, which were developed and improved from the previou model by incorporating a hierarchical regulatory network into the FBA, were compared with the experimental outcome of an aerobic batch growth of E. coli on glucose and tryptophan. From the experimental result, a diauxic growth curve was observed, reflecting growth resumption, when tryptophan was used as an alternativee after the supply of glucose was exhausted. The model parameters, the initial concentration of substrates (0.92 mM glucose and 1 mM tryptophan), cell density (0.0086 g biomass/1), the maximal uptake rates of substrates (5.4 mmol glucose/g DCW h and 1.32 mmol tryptophan/g DCW h), and lag time (0.32 h) were derived from the experimental data for more accurate prediction. The simulation results agreed with the experimental outcome of the temporal profiles of cell density and glucose, and tryptophan concentrations.

• Journal of Microbiology and Biotechnology
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• 제15권3호
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• pp.551-559
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• 2005

The recent rapid increase in genomic data related to many microorganisms and the development of computational tools to accurately analyze large amounts of data have enabled us to design several kinds of simulation approaches for the complex behaviors of cells. Among these approaches, dFBA (dynamic flux balance analysis), which utilizes FBA, differential equations, and regulatory events, has correctly predicted cellular behaviors under given environmental conditions. However, until now, dFBA has centered on substrate concentration, cell growth, and gene on/off, but a detailed hierarchical structure of a regulatory network has not been taken into account. The use of Boolean rules for regulatory events in dFBA has limited the representation of interactions between specific regulatory proteins and genes and the whole transcriptional regulation mechanism with environmental change. In this paper, we adopted the operon as the basic structure, constructed a hierarchical structure for a regulatory network with defined fundamental symbols, and introduced a weight between symbols in order to solve the above problems. Finally, the total control mechanism of regulatory elements (operons, genes, effectors, etc.) with time was simulated through the linkage of dFBA with regulatory network modeling. The lac operon, trp operon, and tna operon in the central metabolic network of E. coli were chosen as the basic models for control patterns. The suggested modeling method in this study can be adopted as a basic framework to describe other transcriptional regulations, and provide biologists and engineers with useful information on transcriptional regulation mechanisms under extracellular environmental change.

• Journal of Plant Biotechnology
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• 제41권3호
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• pp.107-115
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• 2014

식물지방은 주로 종자에서 생산되는데 인류에게 필수 지방산을 공급하는 식품 뿐 아니라 바이오디젤 등 산업원료로 그 이용가치가 크다. 식물지방의 수요 증가에 따른 식물지방의 생산증대가 필요하다. 식물지방을 종자 이외의 바이오매스가 큰 식물의 잎에서 생산한다면 식물지방 생산 증진이 가능할 것이다. 잎은 지방을 생산하는 기관이 아니며 주로 광합성을 통해 탄소를 고정하여 다른 기관으로 탄소를 공급하는 기능을 하고 있어 지방을 생산 축적하는 기관으로 전환하는 데는 많은 고려가 필요하다. 그럼에도 불구하고 최근 지방합성 조절인자인 WRI 유전자, 지방을 생성하는 acyltransferase인 DGAT 유전자의 발현에 의해 잎에서 지방을 합성할 수 있었다. 또한 지방의 분해를 안정화하는 올레오신 단백질의 추가 도입으로 잎에서 건조중량당 15%의 중성지방 생산을 보여 잎에서 지방생산 가능성을 보여주었다(Vanhercke et al. 2014). 앞으로 바이오매스에서 지방을 생산하는 연구가 활발할 것으로 예측되며 이 기술을 식용작물이 아닌 비식용이며 바이오매스가 큰 거대억새 등에 도입하여 농지로 적합하지 않은 열악한 토지 및 간척지 등에 재배하여 실용화한다면 미래 지속 생산 가능 친환경 바이오 원료 생산 자원으로 사용 가능하리라 사료된다.

• Journal of Ginseng Research
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• 제38권2호
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• pp.97-105
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• 2014

Background: Understanding what causes changes in the flux of free fatty acids (FFA) is important to elucidate the etiology of metabolic syndrome. The first aim of this study was to test whether or not hormones and the autonomic nervous system influence blood FFA levels. A secondary aim was to test by means of a multiple group path analysis whether the consumption of fermented red ginseng (FRG; Panax ginseng) would influence those causal relationships. Methods: Ninety-three postmenopausal women (age 50e73 yr) were randomly divided into two groups. One group (44 women; age, $58.4{\pm}5.9yr$; body mass index, $3.6{\pm}2.5kg/m^2$) was supplied place capsules and the other group (49 women, age $58.4{\pm}5.5yr$; body mass index, $22.9{\pm}2.4kg/m^2$) was supplied FRG capsules. Both prior to and after the study (2 wk), blood samples were collected from the participants and several blood variables were measured and analyzed. Results: Squared multiple correlations of FFA were 0.699 in the placebo group and 0.707 in the FRG group. The unstandardized estimate of estradiol (E2) for FFA was 0.824 in both groups. Conclusion: The path coefficients of cortisol and the branchial pulse for FFA were significantly different between the FRG group and the placebo group.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2001년도 추계학술발표대회
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• pp.70-73
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• 2001

Isopentenyl diphosphate (IPP) is the common, five-carbon building block in the biosynthesis of all isoprenoids. IPP in Escherichia coli is synthesized through the non-mevalonate pathway. The first reaction of IPP biosynthesis in E. coli is the formation of 1-deoxy-D-xylulose-5-phosphate(DXP), catalyzed by DXP synthase and encoded by dxs. The second reaction in the pathway is the reduction of DXP to 2-C-methyl-D-erythritol-4-phosphate, catalyzed by DXP reductoismerase and encoded by dxr. To determine if one of more of the reactions in the non-mevalonate pathway controlled flux to IPP, dxs and dxr were placed on several expression vectors under the control of three different promoters and transformed into three E. coli strains ($DH5{\alpha}$, XL1-Blue, and JM101) that had been engineered to produce lycopene, a kind of isoprenoids. Lycopene production was improved significantly in strains transformed with the dex expression vectors. At arabinose concentrations between 0 and 1.33 mM, cells expressiong both dxs and from $P_{BAD}$ on a midium-copy plasmid produced 1.4 -2.0 times more lycopene than cells expressing dxs only. However, at higher arabinose concentrations lycopene production in cell expressing both dxs and dxr was lower than in cells expression dxs only. A comparison of the three E. coli strains trasfomed with the arabinose-inducible dxs on a medium-copy plasmid revealed that lycopene production was highest in XL1-Blue.

• Journal of Microbiology and Biotechnology
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• 제19권10호
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• pp.1127-1134
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• 2009

Escherichia coli excretes acetate during aerobic growth on glycolytic carbon sources, which has been explained as an overflow metabolism when the carbon flux into the cell exceeds the capacity of central metabolic pathways. Nonacetogenic growth of E. coli on gluconeogenic carbon sources like succinate or in carbon-limited slow growth conditions is believed an evidence for the explanation. However, we found that a strain defected in the acs (acetyl Co-A synthetase) gene, the product of which is involved in scavenging acetate, accumulated acetate even in succinate medium and in carbon-limited low growth rate condition, where as its isogenic parental strain did not. The acs promoter was inducible in noncatabolite repression condition, whereas the expression of the ackA-pta operon encoding acetate kinase and phosphotransacetylase for acetate synthesis was constitutive. Results in this study suggest that E. coli excretes and scavenges acetate simultaneously in the carbon-limited low growth condition and in nonacetogenic carbon source, and the activity of the acetate consumption pathway directly affects the accumulation level of acetate in the culture broth.

• 한국미생물·생명공학회지
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• 제26권5호
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• pp.387-392
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• 1998

B. lactofermentum의 lysine 생합성에 있어서 DDH경로 및 ddh gene이 지닌 중요성을 조사하기 위하여, site-specific mutagenesis technique를 통하여 B. lactofermentum의 ddh gene을 disruption함으로서 DDH 경로를 차단시켰다. B. lactofermentum ddh mutant는 wild type 및 AEC내성 균주보다 성장이 매우 저조하였으며 lysine 생산량에서도 급격한 저하를 가져왔다. 이와 같이 B. lactofermentum이 DAP 경로만을 가졌을 때 세포의 성장 및 lysine 생산량에 있어서 극적인 저하를 가져왔기 때문에 B. lactofermentum에서의 DDH 경로는 meso-DAP 및 lysine 생합성에 있어 필수적인 경로로 작용한다는 것을 확인하였다. 그러므로 C. glutamicum과 B. lactofermentum과 같은 corynebacteria가 lysine을 많이 생산하는 것은 DDH 경로가 부가적으로 존재하기 때문이며, 이러한 DDH 경로는 metabolic flux가 증가되면 중간 대사물을 lysine으로 변화시키는 중요한 경로로 작용할 것이라 사료된다.

• Journal of Microbiology and Biotechnology
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• 제23권5호
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• pp.719-723
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• 2013

Nitrification in wastewater treatment emits a significant amount of nitrous oxide ($N_2O$), which is one of the major greenhouse gases. However, the actual mechanism or metabolic pathway is still largely unknown. Selective nitrification inhibitors were used to determine the nitrification steps responsible for $N_2O$ emission with activated sludge and enriched nitrifiers. Allylthiourea (86 ${\mu}M$) completely inhibited ammonia oxidation and $N_2O$ emission both in activated sludge and enriched nitrifiers. Sodium azide (24 ${\mu}M$) selectively inhibited nitrite oxidation and it led to more $N_2O$ emission than the control experiment both in activated sludge and enriched nitrifiers. The inhibition tests showed that $N_2O$ emission was mainly related to the activity of ammonia oxidizers in aerobic condition, and the inhibition of ammonia monooxygenase completely blocked $N_2O$ emission. On the other hand, $N_2O$ emission increased significantly as the nitrogen flux from nitrite to nitrate was blocked by the selective inhibition of nitrite oxidation.