Metabolic engineering of Clostridium acetobutylicum ATCC 824 for isopropanol-butanol-ethanol fermentation.
Clostridium acetobutylicum naturally produces acetone as well as butanol and ethanol. Since acetone cannot be used as a biofuel, its production needs to be minimized or suppressed by cell or bioreactor engineering. Thus, there have been attempts to disrupt or inactivate the acetone formation pathway. Here we present another approach, namely, converting acetone to isopropanol by metabolic engineering. Since isopropanol can be used as a fuel additive, the mixture of isopropanol, butanol, and ethanol (IBE) produced by engineered C. acetobutylicum can be directly used as a biofuel. IBE production is achieved by the expression of a primary/secondary alcohol dehydrogenase gene from Clostridium beijerinckii NRRL B-593 (i.e., adh(B-593)) in C. acetobutylicum ATCC 824. To increase the total alcohol titer, a synthetic acetone operon (act operon; adc-ctfA-ctfB) was constructed and expressed to increase the flux toward isopropanol formation. When this engineering strategy was applied to the PJC4BK strain lacking in the buk gene (encoding butyrate kinase), a significantly higher titer and yield of IBE could be achieved. The resulting PJC4BK(pIPA3-Cm2) strain produced 20.4 g/liter of total alcohol. Fermentation could be prolonged by in situ removal of solvents by gas stripping, and 35.6 g/liter of the IBE mixture could be produced in 45 h.
Department of Chemical and Biomolecular Engineering, Institute for the BioCentury, KAIST, Daejeon, Republic of Korea.
Joungmin
J
Lee
Yu-Sin
YS
Jang
Sung Jun
SJ
Choi
Jung Ae
JA
Im
Hyohak
H
Song
Jung Hee
JH
Cho
Do Young
do Y
Seung
E Terry
ET
Papoutsakis
George N
GN
Bennett
Sang Yup
SY
Lee
D019840:2-Propanol / Q000378:metabolism*; D000096:Acetone / Q000378:metabolism; D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D056804:Biofuels; D000440:Butanols / Q000378:metabolism*; D046969:Clostridium acetobutylicum / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D046970:Clostridium beijerinckii / Q000201:enzymology / Q000235:genetics; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D060847:Metabolic Engineering; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
D056804:Biofuels; D000440:Butanols; D011994:Recombinant Proteins; D000096:Acetone; D000431:Ethanol; D000426:Alcohol Dehydrogenase; D019840:2-Propanol