Metabolic engineering of Saccharomyces cerevisiae for enhanced production of caffeic acid

Abstract Background As a natural phenolic acid product of plant source, caffeic acid displays diverse biological activities and acts as an important precursor for the synthesis of other valuable compounds. Limitations in chemical synthesis or plant extraction of caffeic acid trigger interest in its microbial biosynthesis. Recently, Saccharomyces cerevisiae has been reported sporadically for biosynthesis of caffeic acid via free plasmid‑mediated pathway assembly. However, the production was far from satisfactory and even relied on the addition of precursor. Results In this study, we first established a controllable caffeic acid pathway by employing a modified GAL regulatory system in S. cerevisiae and realized de novo biosynthesis of 313.8 mg/L caffeic acid from glucose. Combinatorial engineering strategies including eliminating the tyrosine-induced feedback inhibition, deleting genes involved in competing pathways and overexpressing rate-limiting enzymes led to about 2.5-fold improvement in the caffeic acid production, reaching up to 769.3 mg/L in shake-flask cultures. To our knowledge, this is the highest ever reported titer of caffeic acid de novo synthesized by engineered yeast. Conclusions Caffeic acid production in S. cerevisiae strain was successfully improved by adopting a glucose-regulated GAL system and comprehensive metabolic engineering strategies. This work showed the prospect for microbial biosynthesis of caffeic acid and laid the foundation for constructing biosynthetic pathways of its derived metabolites.