Recombinant microorganisms having modified production of alcohols and acids
View Patent ↗Recombinant acetogenic Clostridia are engineered to modulate production of aliphatic C 2 -C 6 alcohols and aliphatic C 2 -C 6 organic acids from synthetic gases. One aspect of the invention provides a method of producing an aliphatic C 2 -C 6 alcohol using an acetogenic Clostridium micro-organism having at least one genetic modification that reduces or eliminates C 2 -C 6 carboxylic acid production by the modified organism. Another aspect of the invention provides a method of producing an aliphatic C 2 -C 6 alcohol using an acetogenic Clostridium micro-organism having one or more genetic modifications that cause increased enzyme activity of carbon monoxide dehydrogenase, aldehyde ferredoxin oxidoreductase, NADPH-dependent alcohol dehydrogenase, or alcohol dehydrogenase. Yet another aspect of the invention provides a method of producing aliphatic C2-C6 alcohols using acetogenic Clostridium micro-organisms that have been genetically modified to increase C 2 -C 6 aliphatic alcohol formation and decrease the production of the corresponding C 2 -C 6 aliphatic organic acid.
1. A method for producing an aliphatic C 2 , C 4 , or C 6 alcohol comprising:
(a) providing an acetogenic Clostridium micro-organism having a genetic modification within at least one transcriptional unit, wherein the genetic modification substantially increases the expression of an NADPH-dependent secondary alcohol dehydrogenase gene as compared to the acetogenic Clostridium micro-organism without the genetic modification;
(b) supplying a syngas;
(c) culturing the acetogenic Clostridium micro-organism in a growth medium in the presence of the syngas;
(d) producing the aliphatic C 2 , C 4 , or C 6 alcohol by culturing the Clostridium micro-organism; and
(e) recovering the aliphatic C 2 , C 4 , or C 6 alcohol produced in the culture.
2. The method of claim 1 wherein the aliphatic C 2 , C 4 , or C 6 alcohol is selected from the group consisting of ethanol, butanol, and hexanol.
3. The method of claim 1 wherein the acetogenic Clostridium micro-organism is selected from the group consisting of Clostridium ragsdalei, Clostridium ljungdahlii, Clostridium carboxidivorans and Clostridium autoethanogenum.
4. The method of claim 1 wherein the NADPH-dependent secondary alcohol dehydrogenase has the polynucleotide sequence of SEQ ID NO:20.