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Development of a recombinant Corynebacterium glutamicum-based biocatalyst for the production of xylitol from xylose

Title
Development of a recombinant Corynebacterium glutamicum-based biocatalyst for the production of xylitol from xylose
Authors
김소현
Issue Date
2008
Department/Major
대학원 식품공학과
Publisher
이화여자대학교 대학원
Degree
Master
Abstract
Cofactor-dependent biotransformation을 위한 안정한 biocatalyst를 구축하기 위해 Corynebacterium glutamicum에 Pichia stipitis 유래의 xylose reductase gene (xyl1)을 도입하였다. Expression vector와 induction condition을 최적화 시킨 recombinant Corynebacterium glutamicum은 xylose reductase를 충분히 발현시켰고, specific xylose reductase activity는 0.62 U/ mg protein였다. 이것은 발효 중 비교적 안정하게 유지되었고, biotransformation process의 기본이 되는 유가식 배양에 적용해 보았다. 에너지원인 포도당과 용존 산소량을 제한적으로 조절한 recombinant Corynebacterium glutamicum의 유가식 배양을 통해, xylitol은 약 34 g/L 농도로 생산되었다. 이 때, Xylitol의 시간당 생산량은 0.8 g/L/h 이었고, xylitol 수율은 94%를 나타냈으며, 이 수율는 xylitol 생산의 최적의 균주로 알려진 Candida tropicalis의 80%보다 더 높은 결과이다. 마지막으로, Recombinant Corynebacterium glutamicum에 에너지원인 포도당에 의해 저해되는 xylose uptake rate를 향상시킬 수 있는 대사 공학적 연구가 추가된다면, 더 나은 xylitol 수율 기대할 수 있을 것이다.;With an aim to develop a solid biocatalyst for the cofactor-dependent biotransformations, we constructed and investigated a recombinant Corynebacterium glutamicum that expresses the xylose reductase gene (xyl1) of Pichia stipitis. Optimization of expression vector and induction conditions enabled the recombinant biocatalyst to produce xylose reductase to a specific activity of ca. 0.6 U/ mg protein. The enzyme activity was stably maintained during fermentations. We have also developed a fed-batch based biotransformation process. Tight control of feeding of energy source (i.e., glucose) and DOT allowed to produce xylitol to a concentration of 34 g/L. The productivity and product yield reached 0.8 g/L/h and 94%, respectively. The product yield was 80% higher than that of Candida tropicalis, which is one of the best xylitol producer reported. Metabolic engineering of the recombinant C. glutamicum to enhance uptake rate of xylose would increase the productivity further.
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일반대학원 > 식품공학과 > Theses_Master
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