Patent ID: 8735114

Claim:
A method comprising: (a) providing a recombinant yeast host cell that expresses an engineered biosynthetic isobutanol pathway, wherein the engineered biosynthetic isobutanol pathway comprises an acetolactate synthase (ALS) enzyme, a ketol-acid reductoisomerase (KARI) enzyme, a dihydroxy-acid dehydratase (DHAD) enzyme, a branched chain keto acid decarboxylase enzyme, and an alcohol dehydrogenase (ADH) enzyme, each of which is encoded by a heterologous gene that lacks a mitochondrial targeting sequence, and wherein said yeast host cell is provided in a growth phase; (b) growing the yeast host cells in fermentation medium comprising suitable carbon substrates from renewable feedstocks, whereby isobutanol is bioproduced and wherein said cells grow during fermentation; (c) recovering the bioproduced isobutanol; and (d) blending the bioproduced isobutanol with a fossil fuel to make a fuel or fuel additive.