Enabling Heterologous Synthesis of Lupulones in the Yeast Saccharomyces cerevisiae

Lupulones, naturally produced by glandular trichomes of hop (Humulus lupulus), are prenylated phloroglucinol derivatives that contribute the bitter flavor of beer and demonstrate antimicrobial and anticancer activities. It is appealing to develop microbial cell factories such that lupulones may be produced via fermentation technology in lieu of extraction from limited plant resources. In this study, the yeast Saccharomyces cerevisiae transformants harboring a synthetic lupulone pathway that consisted of five genes from hop were constructed. The transformants accumulated several precursors but failed to accumulate lupulones. Overexpression of 3-hydroxy-3-methyl glutaryl co-enzyme A reductase, the key enzyme in precursor formation in the mevalonate pathway, also failed to achieve a detectable level of lupulones. To decrease the consumption of the precursors, the ergosterol biosynthesis pathway was chemically downregulated by a small molecule ketoconazole, leading to successful production of lupulones. Our study demonstrated a combination of molecular biology and chemical biology to regulate the metabolism for heterologous production of lupulones. The strategy may be valuable for future engineering microbial process for other prenylated natural products.