• 한국미생물·생명공학회지
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• 제20권6호
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• pp.707-710
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• 1992

Bacillus stearothermophilus No.239 isolated from soil was mutated with N-methyl-N'nitro-N-nitrosoguanidine (MNNG) to yield a series of mutants with increasing levels of cyclomalto-dextrin glucanotransferase (EC 2.4.1.19` CGTase) production. After five consecutive mautation steps, a mutant MNNG 8 with about 14 times of CGTase activity than the parent strain was obtained.

• 생명과학회지
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• 제22권1호
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• pp.7-15
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• 2012

이전 연구에서 Streptomyces sp. M3 균주로부터 polyguluronate에 기질특이성을 가지는 알긴산분해효소를 cloning하고 활성을 연구하였다. 이번 연구에서는 pColdI vector에 들어있는 M3 알긴산분해효소 유전자를 돌연변이시켜 알긴산분해효소의 활성을 증진시키고자 하였으며, 점-돌연변이 또는 무작위-돌연변이 방법을 사용하여 돌연변이를 실시하였다. Ser25Arg, Phe99Leu, Asp142Asn, Val163Ala, Lys191Glu 및 Gly194Cys 등 6 종류의 돌연변이 단백질을 얻을 수 있었다. Phe99Leu 및 Lys191Glu 돌연변이 단백질은 알긴산을 분해하는 능력을 완전히 잃었으나 Gly194Cys 돌연변이 단백질의 활성은 원래 단백질에 비하여 10배 증가하였다. 또한 돌연변이된 M3 알긴산분해효소 단백질의 3차 구조는 Swiss-Model 자동모델러를 이용하여 생성하였으며 다른 알긴산분해효소의 결정구조와 비교하였다. 194 번째 아미노산인 글리신은 알긴산의 C-말단 보존서열인 YFKAGXYXQ의 Gly193과 Tyr195 사이에 위치한다. 이 연구에서 돌연변이된 글리신과 페닐알라닌 잔기들은 활성자리로부터 많이 떨어져있음에도 불구하고 돌연변이에 의하여 알긴산 분해활성이 강하게 영향을 받는 것으로 나타났다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.299-302
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• 2000

Actinoplanes teichomyceticus ATCC 31121 was mutated with UV to obtain a superior mutant strain with increasing level of teicoplanin production. In this investigation lethal curve was obtained and the optimal condition to induce mutagenesis was determined and to isolate the desirable mutant strain. It was also confirmed that teicoplanin activities by agar diffusion method to be compared to the mother strain. One mutant strain, T991014-1 that had the highest teicoplanin productivity was finally selected for further investigation including fermentation pattern. The mutant was characterized by the various tests such as amylase activity, protease activity, antibiotic resistance, autotoxicity, and productivity.

• KSBB Journal
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• 제17권3호
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• pp.290-294
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• 2002

경제적으로 에리스리톨을 대량 생산하기 위해 Moniliella suaveolens var. nigra의 wild type을 mutation시켜 변이주를 선별하였다. 선별된 변이주는 400 g/L 포도당배지 플라스크 배양에서 에리스리톨 172 g/L, 글리세롤 20 g/L를 생산하였는데 wild-type의 배양결과와 비교하면 에리스리롤의 생산성은 비슷하고 부산물인 글리세롤의 생성은 50% 적다. 변이주는 wild type 배양시 발생하는 다량의 foam을 적게 발생시킴이 관찰되었다. 배양기 5 L 배양에서 변이주는 에리스리톨의 생산과 부산물 글리세롤의 생성이 wild-type의 것들과 비슷하였다. 이의 원인은 아직 규명되지 않았으나 배양 중 부적절한 산소전달이나 배양 중 발생하는 거품에 세포가 응집하였기 때문인 것으로 추측된다. 균주의 대사를 조사한 결과, 글리세롤은 에리스리톨로 변환되나 에리스리톨은 글리세롤로 변환되지 않음이 관찰되었다. 새로운 고생산성 Moniliella 변이주는 분리.정제 비용이 절감된 순도 놀은 에리스리톨 생성을 가능 하게 할 것이다.

• Archives of Pharmacal Research
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• 제16권3호
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• pp.231-236
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• 1993

Gly-224 residue of yeast alcohol dehydrogenase was mutated by site-directed mufagenesis to isoleucine, which is the corresponding amino acid residue of horse liver alcohol dehydrogenase. The mutated gene on M13 vector was subcloned in YEp13 and used to transform Saccharomyces cerevisiae 302-21 #2 strain, and the expressed protein was purified. The tumover numbers of mutant enzyme for ethanol and acetaldehyde were decreased copared to wild-type enzyme. The results of product inhibition studies indicated that the reaction mechanism was changed to Iso Theorell-Chance from Ordered Bi Bi. We supposed that Gly-224 was related to the enzyme reaction mechanism.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVI)
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• pp.82-85
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• 2005

Doxorubicin is a highly-valuable anthracycline-family polyketide drug with a very potent anticancer activity, typically produced by a Gram-positive soil bacterium called Streptomyces peucetius. Thanks to the recent development of Streptomyces genomics-based technologies, the random mutagenesis approach for Streptomyces strain improvement has been switched toward the genomics-based technologies including the application of DNA microarray systems. In order to identify and characterize the genomics-driven potential target genes critical for doxorubincin overproduction, three different types of doxorubicin overproducing strains, a dnrI(doxorubicin-specific positive regulatory gene)-overexpressor, a doxA (gene involved in the conversion from daunorubicin to doxorubicin)-overexpressor, and a recursively-mutated industrial strain, were generated and examined their genomic transcription profiles using Streptomyces DNA microarray systems. The DNA microarray results revealed several potential target genes in S. peucetius genome, whose expressions were significantly either up- or down-regulated comparing with the wild-type strain. A systematic understanding of doxorubicin overproduction at the genomic level presented in this research should lead us a rational design of molecular genetic strain improvement strategy.

• 한국육종학회지
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• 제40권2호
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• pp.106-112
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• 2008

International conferences to block the spread of Avian bird flu occurred in Beijing, 2006 and others warned of the seriousness of the H5N1 strain. The meetings succeeded in generating billions of dollars from USA, EU and World Bank. Migratory birds seem to play a major role in the spread of the aggressive strain globally from Asia to Europe and Africa. Experiences of tolerance breeding of maize (Zea mays L.) for four decades against 20 biotic stresses suggest that the prime cause of the occurrence of H5N1 strain was due to the human beings' counter-efforts against nature. Excessive use of chemicals (spray and injection) in the commercial poultry farms had created high selection pressure on virus. The new strain had mutated for survival. Attempting to eliminate the virus by chemicals for 100% control is a dangerous way to control biotic stresses. This can create more aggressive strains. A solution would be to build up tolerability of the commercial animals against the virus. Improvement of poultry cage environments and respect for nature must be integrated. Potential foes must be watched.

• Journal of Microbiology
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• 제44권1호
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• pp.113-120
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• 2006

Candida tropicalis was treated with ultraviolet (UV) rays, and the mutants obtained were screened for xylitol production. One of the mutants, the UV1 produced 0.81g of xylitol per gram of xylose. This was further mutated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and the mutants obtained were screened for xylitol production. One of the mutants (CT-OMV5) produced 0.85g/g of xylitol from xylose. Xylitol production improved to 0.87 g/g of xylose with this strain when the production medium was supplemented with urea. The CT-OMV5 mutant strain differs by 12 tests when compared to the wild-type Candida tropicalis strain. The XR activity was higher in mutant CT-OMV5. The distinct difference between the mutant and wild-type strain is the presence of numerous chlamvdospores in the mutant. In this investigation, we have demonstrated that mutagenesis was successful in generating a superior xylitol-producing strain, CT-OMV5, and uncovered distinctive biochemical and physiological characteristics of the wild-type and mutant strain, CT-OMV5.

• 미생물학회지
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• 제37권4호
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• pp.299-304
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• 2001

Teicoplanin은 Actinoplanes teichomyceticus가 생산하는 밴코마이신과 유사한 글리코펩티드계 항생제의 일종으로 메티실린 내성 황색포도상구균에 대해서도 효과가 우수한 치료제이다. 공시균주인 Actinoplanes teichomyceticus ATCC31121에 자외선을 조사하여 teicoplanin 생산성이 우수한 균주를 얻었다. 본 연구에서 우수 변이주 획득을 위한 UV 조사에 대한 균주의 치사곡선을 구하고 변이 유도 최적 조건을 확립하였다. 또한 한천 확산법을 사용하여 모균주와 변이주들의 teicoplanin 생산성 분포를 비교하였다. 변이주 가운데 가장 생산성이 높은 T1014-1를 최종적으로 획득하였으며 효소 활성도, 항생제 내성, 자가내성 및 teicoplanin 생산성을 조사하였으며 발효조에서 발효특성을 조사하였다.

• KSBB Journal
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• 제26권3호
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• pp.229-236
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• 2011

An efficient screening method was developed for rapid selection of a few overproducers of itaconic acid (IA) among the great many mutants derived from mother strains of Aspergillus terreus. For this purpose, an attempt was made to reveal the relationships of the growth rate and sporulation of each mutant on PDA solid medium with its IA productivity in the final liquid production-culture. As a result, it was possible to classify the mutated strains into 5 groups (from [A] to [E] group) according to theirmorphologies (i.e., growth rate and sporulation extent) on the PDA slants. Notably, most of the high-yielding mutants of IA were observed to belong to [A]group which had the properties of the highest growth rate and sporulation among the 5 groups, whereas the mutant groups of [C], [D] and [E] with the contrasting morphological features showed significant reductions in their IA productivities. From these results, it was concluded that the probability of selecting IA overproducing mutants could be remarkably enhanced when the mutated colonies showing faster growth rates are firstly selected on the PDA plate, and then further screening process is performed on the basis of the sporulation extents of the mutants selected. Consequently, through the application of the strategy developed in this study, costs and time involvedin the labor-intensive task of strain improvement could be reduced to a great extent, because the time-consuming liquid culture processes did not need to performed for the unfavorable mutants belonging to the groups other than group [A].