Evolution for exogenous octanoic acid tolerance improves carboxylic acid production and membrane integrity.

Carboxylic acids are an attractive biorenewable chemical, but as with many biorenewables, their toxicity to microbial biocatalysts limits their fermentative production. While it is generally accepted that membrane damage is the main mechanism of fatty acid toxicity, previous metabolic engineering efforts that increased membrane integrity did not enable increased carboxylic acid production. Here we used an evolutionary approach to improve tolerance to exogenous octanoic acid, with the goal of learning design strategies from this evolved strain.