Improvement of isobutanol production in Saccharomyces cerevisiae by increasing mitochondrial import of pyruvate through mitochondrial pyruvate carrier

Subcellular compartmentalization of the biosynthetic enzymes is one of the limiting factors for isobutanol production in Saccharomyces cerevisiae. Previously, it has been shown that mitochondrial compartmentalization of the biosynthetic pathway through re-locating cytosolic Ehrlich pathway enzymes into the mitochondria can increase isobutanol production. In this study, we improved mitochondrial isobutanol production by increasing mitochondrial pool of pyruvate, a key substrate for isobutanol production. Mitochondrial isobutanol biosynthetic pathway was introduced into bat1 Delta ald6 Delta lpd1 Delta strain, where genes involved in competing pathways were deleted, and MPC1, MPC2, and MPC3 genes encoding the subunits of mitochondrial pyruvate carrier (MPC) hetero-oligomeric complex were overexpressed with different combinations. Overexpression of Mpc1 and Mpc3 forming high-affinity MPCOX was more effective in improving isobutanol production than overexpression of Mpc1 and Mpc2 forming low-affinity MPCFERM. The final engineered strain overexpressing MPCOX produced 330.9 mg/L isobutanol from 20 g/L glucose, exhibiting about 22-fold increase in production compared to wild type.