Pathway and organelle engineering for production of useful chemicals in yeast

Researchers in the field of metabolic engineering aim to develop processes to produceuseful chemicals, sustainably and responsibly, using biotechnology. These processes areoften designed to replace products derived from fossil fuels, which are unsustainable andcontribute to climate change, or plant-based products, which compete with foodproduction for scarce land and are subject to supply uncertainty due to weather, cropdisease, and climate change. Here, we present two research projects in metabolicengineering. First, we demonstrate microbial production of the red food dye betanin byengineering the betalain biosynthesis pathway into yeast. Betanin is currentlymanufactured through extraction from red beets specifically grown for dye production.We achieved betanin production levels of 17 mg/L, which is equivalent to the amount ofbetanin found in 10 g/L of beet extract. With further production improvements, thisbioprocess may become cost-competitive with agricultural production and is likely tolead to a purer product. We also demonstrate the synthesis of a suite of non-naturalbetalain dyes achieved through feeding of diverse amines to a yeast production host,including several which have never been reported. In the second research project, wediscover that an enzyme that limits production levels of a drug family is toxic to the yeastproduction host. This enzyme, norcoclaurine synthase, is critical to the production ofbenzylisoquinoline alkaloids, an important family of medicines that are extracted fromplants like the opium poppy. We devised a novel subcellular compartmentalizationstrategy, sequestering norcoclaurine synthase in the peroxisome to alleviate cytotoxicitywhile maintaining access to the enzyme’s substrates. By targeting norcoclaurine synthasefor organellar compartmentalization, we achieved improved cell growth, final titer, andculture productivity. These projects highlight the potential of engineering complex plantpathways into microbial hosts for economical and sustainable chemical production