Patent ID: 8460906

Claim:
A system for making a solvent or organic acid, comprising a bioreactor that comprises: a) growth medium in contact with a solid or semi-solid support; and b) product tolerant microorganisms of the Clostridium genus on the solid or semi-solid support, wherein said microorganisms produce the solvent or organic acid and have previously been mutagenized and selected for tolerance to the solvent or organic acid on a solid or semi-solid support in the presence of the solvent or organic acid, wherein the tolerance of the selected microorganisms to the solvent or organic acid is greater on a solid or semi-solid support than the tolerance to the solvent or organic acid exhibited when the selected microorganisms are cultured in a liquid media, and wherein the microorganisms have been selected to exhibit at least 125% tolerance to the solvent or organic acid in comparison to the tolerance of corresponding non-mutagenized microorganisms.