Evolutionary engineering improves tolerance for medium-chain alcohols in .

Background: Yeast-based chemical production is an environmentally friendly alternative to petroleum-based production or processes that involve harsh chemicals. However, many potential alcohol biofuels, such as -butanol, isobutanol and -hexanol, are toxic to production organisms, lowering the efficiency and cost-effectiveness of these processes. We set out to improve the tolerance of toward these alcohols.

Results: We evolved the laboratory strain of BY4741 to be more tolerant toward -hexanol and show that the mutations which confer tolerance occur in proteins of the translation initiation complex. We found that -hexanol inhibits initiation of translation and evolved mutations in the α subunit of eIF2 and the γ subunit of its guanine exchange factor eIF2B rescue this inhibition. We further demonstrate that translation initiation is affected by other alcohols such as -pentanol and -heptanol, and that mutations in the eIF2 and eIF2B complexes greatly improve tolerance to these medium-chain alcohols.

Conclusions: We successfully generated strains that have improved tolerance toward medium-chain alcohols and have demonstrated that the causative mutations overcome inhibition of translation initiation by these alcohols.