Fermentive production of four carbon alcohols

A method for the production of 2-butanone comprising:

• a) providing a recombinant microbial host cell comprising at least one DNA molecule encoding a B12-independent butanediol dehydratase that catalyzes the substrate to product conversion of 2,3-butanediol to 2-butanone and a source of 2,3-butanediol;
• wherein the at least one DNA molecule is heterologous to said microbial host cell;
• and
• b) growing the microbial host cell of (a) under conditions whereby the isolated nucleic acid molecule is expressed and the 2,3-butanediol is converted to 2-butanone;
• and
• c) optionally recovering the 2-butanone.

A method for the production of 2-butanol comprising:

• a) providing a recombinant microbial host cell comprising at least one DNA molecule encoding a B12-independent butanediol dehydratase that catalyzes the substrate to product conversion of 2,3-butanediol to 2-butanone, butanol dehydrogenase activity and a source of 2,3-butanediol;
• wherein the at least one DNA molecule is heterologous to said microbial host cell;
• and
• b) growing the microbial host cell of (a) under conditions whereby the isolated nucleic acid molecule is expressed and the 2,3-butanediol is converted to 2-butanone, and the 2-butanone is converted to 2-butanol;
• and
• c) optionally recovering the 2-butanol.

A recombinant microbial host cell comprising at least one DNA molecule encoding a polypeptide that catalyzes a substrate to product conversion selected from the group consisting of:

• i) pyruvate to alpha-acetolactate;
• ii) alpha-acetolactate to acetol;
• iii) acetoin to 2,3-butanediol;
• iv) 2,3-butanediol to 2-butanone;
• and
• v) 2-butanone to 2-butanol;
• wherein the at least one DNA molecule is heterologous to said microbial host cell and wherein said microbial host cell produces 2-butanol.