Abstract: A recombinant microorganism expressing at least a heterologous enzyme of an NADH-dependent pathway for conversion of a carbon source to n-butanol, metabolic intermediate and/or a derivative thereof and capable of producing n-butanol, a metabolic intermediate and/or a derivative thereof at a high yield and related methods. The recombinant microorganism engineered to inactivate a native enzyme of one or more pathways that compete with NADH-dependent heterologous pathway, and/or to balance the NADH-dependent heterologous pathway with respect to NADH production and consumption.

Abstract: In an embodiment, there is disclosed a recombinant microbial host cell having each of the DNA molecules encoding a polypeptide or group of polypeptides that catalyze the conversion: (i) Acetyl-CoA to Acetate and CoA ??(conversion 1) (ii) Acetyl-CoA to Acetoacetyl-CoA and CoA ??(conversion 2) (iii) Acetoacetyl-CoA and Acetate to Acetoacetate and Acetyl-CoA ??(conversion 3.1) (iv) Acetoacetate to Acetone and CO2 ??(conversion 4) (v) Acetone and NAD(P)H and H+ to Isopropanol and NAD(P)+ ??(conversion 5) wherein at least one DNA molecule is heterologous to the microbial host cell and wherein the microbial host cell produces isopropanol. In another embodiment, a method is disclosed for the production of isopropanol including providing a recombinant microbial host cell, the host cell of (i) with a fermentable carbon substrate in a fermentation medium under conditions whereby isopropanol is produced, and recovering the isopropanol.