Optimization of benzylisoquinoline alkaloid synthesis in yeast

Benzylisoquinoline alkaloids (BIAs) are a large family of plant secondary metabolites. Several members of the BIA family are commercially available as probiotics and pharmaceuticals. Still more BIAs have been demonstrated to have pharmaceutically relevant properties. Unfortunately, most BIAs do not accumulate in sufficient quantities in planta to merit further study. Microbial synthesis of BIAs could open the door to further commercial development of BIAs. Both Escherichia coli and Saccharomyces cerevisiae have been developed into microbial platforms for BIA synthesis. Currently, E. coli produces significantly higher de novo titers of BIAs (160 mg/L in E. coli vs. 2 mg/L in yeast). However, yeast remain an attractive target for BIA synthesis, as BIA derivatization often requires endomembrane-associated cytochrome P450s that tend to be more easily expressed in eukaryotic hosts. In this work we demonstrate a general improvement of BIA synthesis in yeast by manipulation of multiple areas of yeast metabolism, including increase of precursor synthesis, reduction of precursor catabolism, and balance of flux through pathway branchpoints. This improvement brings yeast titers in line with E. coli titers, establishing yeast as a competitive platform for BIA synthesis