To increase the butanol titers and selectivity in <em>Clostridium acetobutylicum</em> we replaced the promoter of the alcohol/aldehyde dehydrogenase (<em>aad</em>) gene with the phosphotranbutyrylase (<em>ptb</em>) promoter and combined this with CoAT downregulation to minimize acetone production. This led to early production of high alcohol (butanol plus ethanol) titers and overall solvent...