期刊
METABOLIC ENGINEERING
卷 13, 期 3, 页码 345-352出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ymben.2011.02.004
关键词
Metabolic engineering; Cofactor imbalance; Isobutanol; Ketol-acid reductoisomerase; Biofuels
资金
- U.S. Army Research Laboratory [W911NF-09-2-0022]
- Department of Defense through the National Defense Science Engineering
- National Science Foundation
- China Scholarship Council (CSC)
2-methylpropan-1-ol (isobutanol) is a leading candidate biofuel for the replacement or supplementation of current fossil fuels. Recent work has demonstrated glucose to isobutanol conversion through a modified amino acid pathway in a recombinant organism. Although anaerobic conditions are required for an economically competitive process, only aerobic isobutanol production has been feasible due to an imbalance in cofactor utilization. Two of the pathway enzymes, ketol-acid reductoisomerase and alcohol dehydrogenase, require nicotinamide dinucleotide phosphate (NADPH); glycolysis, however, produces only nicotinamide dinucleotide (NADH). Here, we compare two solutions to this imbalance problem: (1) over-expression of pyridine nucleotide transhydrogenase PntAB and (2) construction of an NADH-dependent pathway, using engineered enzymes. We demonstrate that an NADH-dependent pathway enables anaerobic isobutanol production at 100% theoretical yield and at higher titer and productivity than both the NADPH-dependent pathway and transhydrogenase over-expressing strain. Our results show how engineering cofactor dependence can overcome a critical obstacle to next-generation biofuel commercialization. (C) 2011 Elsevier Inc. All rights reserved.
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