Metabolically engineered Saccharomyces cerevisiae for branched-chain ester productions

•Branched-chain esters are produced by the engineered yeast.•Mitochondrial isobutanol biosynthetic pathway is used for ester synthesis.•Alcohol acyltransferase is functional in yeast mitochondria.•Segmentation the pathway into two compartments increased the ester yield.•Subcellular metabolic engineering offers an effective way for ester synthesis.

Medium branched-chain esters can be used not only as a biofuel but are also useful chemicals with various industrial applications. The development of economically feasible and environment friendly bio-based fuels requires efficient cell factories capable of producing desired products in high yield. Herein, we sought to use a number of strategies to engineer Saccharomyces cerevisiae for high-level production of branched-chain esters. Mitochondrion-based expression of ATF1 gene in a base strain with an overexpressed valine biosynthetic pathway together with expression of mitochondrion-relocalized α-ketoacid decarboxylase (encoded by ARO10) and alcohol dehydrogenase (encoded by ADH7) not only produced isobutyl acetate, but also 3-methyl-1-butyl acetate and 2-methyl-1-butyl acetate. Further segmentation of the downstream esterification step into the cytosol to utilize the cytosolic acetyl-CoA pool for acetyltransferase (ATF)-mediated condensation enabled an additional fold improvement of ester productions. The best titre attained in the present study is 260.2 mg/L isobutyl acetate, 296.1 mg/L 3-methyl-1-butyl acetate and 289.6 mg/L 2-methyl-1-butyl acetate.