Expression Mutant Screening for Improved Benzylisoquinoline Production in Yeast 

Benzylisoquinoline alkaloids (BIAs) comprise a pharmaceutically valuable class of natural molecules. To relieve issues with chemical and plant-based production of BIAs, several metabolic engineering efforts have reconstituted natural BIA pathways in Saccharomyces cerevisiae. Our lab has previously used a fluorescent biosensor to identify an enzyme necessary to complete the pathway from glucose to reticuline, a key intermediate in the production of a variety of BIAs. Current yields of reticuline are approximately 5 orders of magnitude below theoretical yields, one of the main bottlenecks being the low and tightly regulated supply of free tyrosine, which is required for BIA synthesis. Using the same fluorescent biosensor, we screened collections of expression mutants to enhance our strain background for the increased production of reticuline.