Genetically-modified bacteria for conversion of organic compounds to butanol and methods of use

1. A genetically-modified bacterium of Megasphaera elsdenii , comprising a sole exogenous nucleic acid of a carbon chain elongation pathway encoding a bifunctional aldehyde/alcohol dehydrogenase, wherein the bifunctional aldehyde/alcohol dehydrogenase produces butanol as a final product and comprises an amino acid sequence with at least 90% identity to SEQ ID NO: 1, and wherein the genetically-modified bacterium has increased butanol production using lactate as the carbon source compared to a wild type Megasphaera elsdenii.

2. The genetically-modified bacterium of claim 1 , wherein the bifunctional aldehyde/alcohol dehydrogenase is an enzyme from a bacterial species that belongs to the genus Clostridium.

3. The genetically-modified bacterium of claim 1 , wherein the exogenous nucleic acid sequence is codon optimized for Megasphaera elsdenii.

4. The genetically-modified bacterium of claim 1 , wherein the genetically-modified bacterium is an M. elsdenii strain designated as ATCC 25940.

5. A method for converting an organic compound to butanol, the method comprising inoculating a medium comprising said organic compound with the genetically-modified bacterium of claim 1 , thereby converting said organic compound to butanol, wherein the organic compound is lactate.

6. The method of claim 5 , wherein the bifunctional aldehyde/alcohol dehydrogenase is an enzyme from a bacterial species from the genus Clostridium.

7. The method of claim 5 , wherein the exogenous nucleic acid sequence is codon optimized for Megasphaera elsdenii.

8. The method of claim 3 , wherein the lactate is a product of bacterial fermentation, a product of fungal fermentation, a product of chemical synthesis from acetaldehyde, or a composition comprising purified lactate.

9. The method of claim 5 , wherein the genetically-modified bacterium is an M. elsdenii strain designated as ATCC 25940.