• KSBB Journal
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• 제13권1호
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• pp.6-12
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• 1998

In order to produce xylitol from hemicellulose hydrolysate which is widely used as a substrate, the development of strain such as catabolite derepressed mutant is required. After treatment of Candida sp. with EMS, GM-17 and PM-34 as catabolite derepressed mutant were isolated from Candida guilliermondii and Candida parapsilosis, respectively. Mutant GM-17 and PM-34 simultaneously assimilated xylose and glucose during the fermentation. The specific xylose reductase and xylitol dehydrogenase activities of mutant strains were also higher than those of wild strains in glucose medium and mixed medium of glucose and xylose. The xylitol productivity and yield of mutant GM-17 and PM-34 were improved as compared to the wild types in the mixed medium. The xylitol productivity and yield of mutant GM-17 were 0.09 g/L·hr and 0.56 g-xylitol/g-xylose, and those of mutant PM-34 were 0.21 g/L·hr and 0.52 g-xylitol/g-xylose in the mixed medium, respectively.

• 한국미생물·생명공학회지
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• 제19권5호
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• pp.464-469
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• 1991

$\alpha$-Amylase를 생산하는 Bacillus sp. 2B를 토양에서 분리하였으며 이 균주에 반복적으로 돌연변이원인 NTG를 처리하여 효소생산성이 증대된 변이주를 유도하였다. $\alpha$-Amylase 고 생산성 균주의 효율적인 획득방법으로 glucose에 의한 $\alpha$-amylase의 생성억제를 받지않는 변이주를 분리한 결과, 효소생산성이 약 30배 향상된 변이주 Bacillus sp. HG4를 획득하였다. 이 균주는 lactose를 탄소원으로 하여 최대 효소생성능을 나타내었으며 빠른 균체성장 및 최대 효소생성시기에 균체 lysis가 적은 점 등 산업적으로 사용하기에 유리한 특성을 가진 것으로 판단된다.

• 미생물과산업
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• 제19권2호
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• pp.34-41
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• 1993

Industrial strain improvement is concerned with developing or modifying microorganisms used in production of commercially important fermentation products. The aim is to reduce the production cost by improving productivity of a strain and manipulating specific characteristics such as the ability to utilize cheaper raw materials or resist bacteriophages. The traditional empirical approach to strain improvement is mutation combined with selection and breeding techniques. It is still used by us to improve the productivity of organisms in amino acids, organic acids and enzymes production. The breeding of high L-lysine-producing strain Au112 is one of the outstanding examples of this approach. It is a homoserine auxotroph with AEC, TA double metabolic analogue resistant markers. The yield reaches 100 g/l. Besides, the citric acid-producing organism Aspergillus niger, Co827, its productivity reaches the advanced level in the world, is also the result of a series mutations especially with $^60Co{\gamma}$-radiation. The thermostable .alpha.-amylase producing strain A 4041 is the third example. By combining physical and chemical mutations, the strain A 4041 becomes an asporogenous, catabolite derepressed mutant with rifamycin resistant and methionine, arginine auxotroph markers. The .alpha.-amylase activity reaches 200 units/ml. The fourth successful example of mutation in strain improvement is the glucoamylase-producing strain Aspergillus niger SP56, its enzyme activity is 20,000 units/ml, 4 times of that of the parental strain UV-11. Recently, recombinant DNA approach provides a worthwhile alternative strategy to industrial strain improvement. This technique had been used by us to increase the thermostable .alpha.-amylase production and on some genetic researches.

• 미생물과산업
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• 제15권1호
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• pp.38-42
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• 1989

Industrial strain Improvement is concerned with developing or modifying microorga-nisms used In production of commercially important fermentation products. The aim is to reduce the production cost by improving productivity of a strain and manipulating specific cilarafteristic such as the ability to utilize cheaper raw materials or resist bacteriophages. The traditional empiri-cal approach to strain improvement is mutation combined with selection and breeding techniques. It is still used by us to improve the productivity of organisms in amino acids. organic acids andenzymes production. The breeding of high L-lysine-producing strain Au112 is one of the outstanding examples of this approach. It is it homoserine auxotroph with AEC, TA double metabolicanalogue resistant markers. The yield reaches 100g/1. Resides, the citric acid-producing organism Aspergillus nuger, Co827, its productivity reches the advanced level in the world, is also the result of a series mutations expecially with Co Y-radiation. The thermostable a-amylaseroducing strain A 4041 is the third example. By combining physical and chemical multations. the strain ,A 4041becomes an asporogenous, catabolite derepressed mutant with rifamycin resistant and methionine, arginine auxotroph markers. The a-amylase activity reaches 200 units/ml. The fourth successful example of mutation in strain improvement is the glucoamylase-producing strain Aspergillus nigerSP56 its enzyme activity is 20,000 units/ml, 4 times of that of the parental strain UV_11. Recently recombinant DNA approach Provides a worth while alternative strategy to Industrial strain improve-ment. This technique had been used by us to increase the thermostable a-amylase production and on some genetic researches.

• Applied Biological Chemistry
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• 제39권6호
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• pp.430-436
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• 1996

대장균에서 xylose isomerase(XI) 생산의 조절양상을 밝히기 위한 연구의 일환으로 유도물질인 xylose에 의한 XI 생산유도 및 glucose에 의한 이화물 억제 양상을 조사하였다. XI 생산 유전자인 xylA 유전자의 발현을 조절하는 xylR 유전자가 염색체에 존재하는 상태에서 xylA 유전자가 고복제수 유래의 플라스미드에 존재하는 경우 (pEX202/DH77)와 저복제수 유래의 플라스미드에 존재하는 경우(pEX102/DH77)에는 염색체에 존재하는 경우 (JM109)보다 0.4% xylose 첨가에 의한 XI의 유도생산이 각각 1.9 및 1.7배 정도 증가하였다. 염색체에 존재하는 xylR 유전자에 의해 생산된 xylR유전자 산물이 xylA 유전자가 플라스미드에 존재할 경우에도 염색체에 존재할때와 마찬가지로 작용하는 것으로 나타났다. 형질전환주 pEX202/DH77과 pEX102/DH77 및 친주 JM109에서 다 같이 0.2% glucose 첨가에 의해 완전히 XI 유도생산이 억제되었으며 이와같은 glucose에 의한 이화물 억제는 1 mM cAMP의 첨가로 해제되었다. DM 최소배지에서 xylose에 의한 XI 유도시 1 mM CAMP를 첨가하면 0.4% xylose만 첨가했을때 보다 XI 생산이 1.7 내지 2배 정도 증가하었다. Xylose isomerase와 cAMP 생산 변이주(xyl, cya ; TP2010)에 xylA 유전자를 형질전환시킨 pEX13/TP2010은 xylose 첨가로 Xl가 유도생산되지 않았고 cAMP를 함께 첨가해야만 XI가 유도되었다. 이와같이 대장균의 xylA 유전자에서 XI의 생산조절에는 xylose이외에 cAMP도 필수적인 효과물질임을 알 수 있었다.