High-yield conversion of cellulose into α-ketoglutaric acid by Yarrowia lipolytica via a simultaneous saccharification and fermentation in ionic liquid process

Ionic liquids (ILs) are benign solvents that are highly effective for biomass pretreatment. However, their application for scale-up biorefinery is hampered by toxicity of ILs on enzymes and microorganisms. Multiple washing steps for IL separation and recovery are typically required before saccharification and fermentation. To overcome this limitation, it is very critical to develop IL-compatible enzymatic and microbial biocatalyst systems to perform the simultaneous saccharification and fermentation in IL, named SSF-IL. While enzyme mixtures were developed to remain reasonably active in up to 10% (v/v) 1-ethyl-3-methylimidazolium acetate [EMIM][OAc] for biomass saccharification, most microbes reported to date could not thrive and perform efficient fermentation at high IL concentrations, >5% ILs. Here, we harnessed the robust metabolism of a Yarrowia sp.that can thrive in at least 10% IL. We demonstrated that this Yarrowia sp. could be used a microbial platform to produce high-value chemicals, such as alpha-ketoglutaric acid, up to ~92% of the maximum theoretical yield from cellulose in SSF-IL containing 10% [EMIM][OAc].