title: Engineered biosynthesis of medium-chain esters in Escherichia coli.
abstract: Medium-chain esters such as isobutyl acetate (IBAc) and isoamyl acetate (IAAc) are high-volume solvents, flavors and fragrances. In this work, we engineered synthetic metabolic pathways in Escherichia coli for the total biosynthesis of IBAc and IAAc directly from glucose. Our pathways harnessed the power of natural amino acid biosynthesis. In particular, the native valine and leucine pathways in E. coli were utilized to supply the precursors. Then alcohol acyltransferases from various organisms were investigated on their capability to catalyze esterification reactions. It was discovered that ATF1 from Saccharomyces cerevisiae was the best enzyme for the formation of both IBAc and IAAc in E. coli. In vitro biochemical characterization of ATF1 confirmed the fermentation results and provided rational guidance for future enzyme engineering. We also performed strain improvement by removing byproduct pathways (Δldh, ΔpoxB, Δpta) and increased the production of both target chemicals. Then the best IBAc producing strain was used for scale-up fermentation in a 1.3-L benchtop bioreactor. 36g/L of IBAc was produced after 72h fermentation. This work demonstrates the feasibility of total biosynthesis of medium-chain esters as renewable chemicals.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Yi-Shu
authors.initials: YS
authors.lastname: Tai
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Mingyong
authors.initials: M
authors.lastname: Xiong
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA. Electronic address: kzhang@umn.edu.
authors.forename: Kechun
authors.initials: K
authors.lastname: Zhang
mesh_terms: D000085:Acetates / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D060847:Metabolic Engineering / Q000379:methods*; D000439:Pentanols / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
chemical_list: D000085:Acetates; D000439:Pentanols; D011506:Proteins; C038989:isobutyl acetate; C079238:alcohol O-acetyltransferase; C020377:isoamyl acetate
keywords: E. coli; Ester; Isoamyl acetate; Isobutyl acetate; Metabolic engineering; Pathway manipulation; Renewable chemicals