Refactoring β‐amyrin synthesis in S accharomyces cerevisiae

Triterpenoids are a highly diverse group of natural products and used particularly as medicine. Here, a strategy combining stepwise metabolic engineering and transcriptional control was developed to strengthen triterpenoid biosynthesis in Saccharomyces cerevisiae . Consequently, an efficient biosynthetic pathway for producing β‐amyrin, a commercially valuable compound and precursor of triterpenoids, was constructed through expressing a plant‐derived β‐amyrin synthase. Introducing a heterologous squalene monooxygenase greatly dragged intermediate metabolite squalene toward β‐amyrin. Increasing squalene pool by overexpressing IPP isomerase, FPP, and squalene synthase further enhanced β‐amyrin synthesis of 49‐folds. Through reconstructing the promoters with the binding site of transcription factor UPC2, directed transcriptional regulation on engineered pathway was availably achieved, resulting in β‐amyrin titer increased by 65‐folds. Using ethanol fed‐batch fermentation, β‐amyrin titer was finally improved up to 138.80 mg/L with a yield of 16.30 mg/g dry cell, almost 185 and 232 and folds of the initially engineered strain, respectively. © 2015 American Institute of Chemical Engineers AIChE J , 61: 3172–3179, 2015