Enhancement of abscisic acid biosynthesis in Saccharomyces cerevisiae via multidimensional engineering

Abstract

Abscisic acid (ABA), a type of sesquiterpenoid plant hormone, has high application value in agriculture, nutrition and medicine. Herein, we constructed an efficient ABA-producing yeast cell factory by combining multidimensional engineering strategies. Starting from a suitable strain, YS010 was selected from 11 varieties of S. cerevisiae strains by evaluating ergosterol content and growth ability, then the biosynthetic pathway of ABA derived from Botris cinerea was constructed, resulting in 1.93 mg L⁻¹ ABA. Next, the metabolic flux of the mevalonic acid (MVA) pathway was increased to enhance the synthesis of the precursor farnesyl pyrophosphate (FPP). To further increase the FPP competitiveness of the ABA synthesis pathway, we attempted to enhance the catalytic performance of BcABA3 through enzyme engineering, and the ABA yield of the mutant strain YS036-ABAP^A206D reached 2.64 mg L⁻¹ in SC-ura medium. In addition, we developed a multi-copy integration strategy, TPI1-delta driven CRISPR-Cas9 (TDI-CRISPR) integration system, to realize the high copy and stable expression of bcaba1, bcaba2 and bcaba3, which enabled the titer of ABA to reach 17.47 mg L⁻¹. Finally, by optimising the fermentation medium, the ABA titer reached 30.30 mg L⁻¹, which was the highest level ever reported for de novo ABA biosynthesis in S. cerevisiae.