Ethanol production by engineered thermophiles.
We compare a number of different strategies that have been pursued to engineer thermophilic microorganisms for increased ethanol production. Ethanol production from pyruvate can proceed via one of four pathways, which are named by the key pyruvate dissimilating enzyme: pyruvate decarboxylase (PDC), pyruvate dehydrogenase (PDH), pyruvate formate lyase (PFL), and pyruvate ferredoxin oxidoreductase (PFOR). For each of these pathways except PFL, we see examples where ethanol production has been engineered with a yield of >90% of the theoretical maximum. In each of these cases, this engineering was achieved mainly by modulating expression of native genes. We have not found an example where a thermophilic ethanol production pathway has been transferred to a non-ethanol-producing organism to produce ethanol at high yield. A key reason for the lack of transferability of ethanol production pathways is the current lack of understanding of the enzymes involved.
Thayer School of Engineering at Dartmouth College, Hanover, NH 03755, United States; BioEnergy Science Center, Oak Ridge, TN 37830, United States.
Daniel G
DG
Olson
Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada R3T 5V6.
Richard
R
Sparling
Thayer School of Engineering at Dartmouth College, Hanover, NH 03755, United States; BioEnergy Science Center, Oak Ridge, TN 37830, United States. Electronic address: Lee.R.Lynd@Dartmouth.edu.
Lee R
LR
Lynd
D000255:Adenosine Triphosphate / Q000378:metabolism; D000596:Amino Acids / Q000096:biosynthesis; D000431:Ethanol / Q000378:metabolism*; D006358:Hot Temperature; D019289:Pyruvic Acid / Q000378:metabolism
D000596:Amino Acids; D000431:Ethanol; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate