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Metabolic pathway analysis of Scheffersomyces (Pichia) stipitis: effect of oxygen availability on ethanol synthesis and flux distributions.
MedLine Citation:
PMID:  22526806     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Elementary mode analysis (EMA) identifies all possible metabolic states of the cell metabolic network. Investigation of these states can provide a detailed insight into the underlying metabolism in the cell. In this study, the flux states of Scheffersomyces (Pichia) stipitis metabolism were examined. It was shown that increasing oxygen levels led to a decrease of ethanol synthesis. This trend was confirmed by experimental evaluation of S. stipitis in glucose-xylose fermentation. The oxygen transfer rate for an optimal ethanol production was 1.8 mmol/l/h, which gave the ethanol yield of 0.40 g/g and the ethanol productivity of 0.25 g/l/h. For a better understanding of the cell's regulatory mechanism in response to oxygenation levels, EMA was used to examine metabolic flux patterns under different oxygen levels. Up- and downregulation of enzymes in the network during the change of culturing condition from oxygen limitation to oxygen sufficiency were identified. The results indicated the flexibility of S. stipitis metabolism to cope with oxygen availability. In addition, relevant genetic targets towards improved ethanol-producing strains under all oxygenation levels were identified. These targeted genes limited the metabolic functionality of the cell to function according to the most efficient ethanol synthesis pathways. The presented approach is promising and can contribute to the development of culture optimization and strain engineers for improved lignocellulosic ethanol production by S. stipitis.
Authors:
Pornkamol Unrean; Nhung H A Nguyen
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-4-25
Journal Detail:
Title:  Applied microbiology and biotechnology     Volume:  -     ISSN:  1432-0614     ISO Abbreviation:  -     Publication Date:  2012 Apr 
Date Detail:
Created Date:  2012-4-24     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8406612     Medline TA:  Appl Microbiol Biotechnol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Biochemical Engineering and Pilot Plant Research and Development Unit, King Mongkut's University of Technology Thonburi, 49 Soi Tientalay 25, Bangkhuntien-Chaytalay Rd., Thakhum, Bangkhuntien, Bangkok, 10150, Thailand, pornkamol.unr@biotec.or.th.
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