Host cells and methods for production of isobutanol

A recombinant host cell comprising an engineered isobutanol production pathway comprising:

• a. a heterologous polypeptide having ketol-acid reductoisomerase (KARI) activity, wherein said heterologous polypeptide having KARI activity comprises an amino acid sequence that is at least 95% identical to the amino acid sequence set forth in SEQ ID NO:
• 27 with the exception of at least four mutations selected from the group consisting of amino acid residues at positions corresponding to A41, Y53, S56, K57, S58, I86, N87, K90, T93, T131, T191, R227, and Q246 of the amino acid sequence of SEQ ID NO:
• 27;
• and
• b. at least one host cell modification selected from the group consisting of eliminated aldehyde dehydrogenase expression or activity, wherein said host cell modification is a deletion of an endogenous polynucleotide encoding aldehyde dehydrogenase, and eliminated acetolactate reductase expression or activity, wherein said host cell modification is a deletion of an endogenous polynucleotide encoding acetolactate reductase.