De Novo Synthesis of Dihydro-ß-ionone through Metabolic Engineering and Bacterium-Yeast Coculture.

ABSTRACT

Dihydro-ß-ionone is a common type of ionone used in the flavor and fragrance industries because of its characteristic scent. The production of flavors in microbial cell factories offers a sustainable and environmentally friendly approach to accessing them, independent of extraction from natural sources. However, the native pathway of dihydro-ß-ionone remains unclear, hindering heterologous biosynthesis in microbial hosts. Herein, we devised a microbial platform for de novo syntheses of dihydro-ß-ionone from a simple carbon source with glycerol. The complete dihydro-ß-ionone pathway was reconstructed in Escherichia coli with multiple metabolic engineering strategies to generate a strain capable of producing 8 mg/L of dihydro-ß-ionone, although this was accompanied by a surplus precursor ß-ionone in culture. To overcome this issue, Saccharomyces cerevisiae was identified as having a conversion rate for transforming ß-ionone to dihydro-ß-ionone that was higher than that of E. coli via whole-cell catalysis. Consequently, the titer of dihydro-ß-ionone was increased using the E. coli-S. cerevisiae coculture to 27 mg/L. Our study offers an efficient platform for biobased dihydro-ß-ionone production and extends coculture engineering to overproducing target molecules in extended metabolic pathways.