Isobutanol Production from Xylose in Saccaromyces cerevisiae

Abstract

Production of advanced biofuels is essential as the need for sustainable fuel increases.The branched chain alcohols, such as isobutanol, have a similar energy density togasoline and are compatible with current vehicle engine infrastructure. The isobutanolproduction pathway was introduced and modified in a Saccharomyces cerevisiae strainthat was genetically modified to metabolize xylose. Xylose is the second most abundantproduct of breaking down plant biomass and these modified strains allow the use of lessused biomass. A record breaking titer of 534 mg/L was achieved through isobutanolpathway engineering and modification including upregulating the isobutanol pathwaythrough ∂-integration, deletion of the key genes (e. g. BAT1, ALD6, and PHO13) of thecompeting pathways. This isobutanol titer is almost 400 times greater than the previousrecord titer (1.36 mg/L). The effects of xylose consumption, isobutanol production andethanol production were also studied in strains with BAT1, ALD6, and PHO13 single,double and triple deletions. Different small-scale fermentation methods including tubefermentations, 24-well plate fermentation and flask fermentations were compared forhigh cell density fermentation. Tube fermentations are better for isobutanol productionthan plate fermentations and flask fermentations. Two different fermentation media,synthetic complete media and synthetic minimal media were also compared forisobutanol production.