Sesquiterpenoids are a diverse group of compounds with vast uses in medicine, pharmacology, food, fragrance, and fuel industries. However, their chemical production is often complicated, pollutes the environment, or is sometimes unfeasible. The natural host organisms only contain small amounts. Because of this, this project engineered the production of sesquiterpenoids valencene, nootkatone, β-caryophyllene, and parthenolide in a yeast Yarrowia lipolytica. The production of nootkatone (90 mg/l) has been increased 100-fold over the previous reports and β-caryophyllene (390 mg/l) and parthenolide have been produced fully heterologously in Y. lipolytica for the first time.
Modular co-cultures of yeast and cyanobacteria were constructed to further aid inexpensive bioproduction of valuable compounds that does not compete for organic carbon sources or land use with sources of food and feed. A cyanobacterium Synechococcus sp. PCC 7002 was engineered for the production and secretion of up to 4.6 g/l sucrose for the first time in a marine species. This opens avenues for sugar production in remote places from seawater or wastewater. After engineering Y. lipolytica for sucrose consumption and optimising the media composition and salinity, it was shown that the growth of Y. lipolytica can be supported by the sucrose produced by Synechococcus sp. PCC 7002 as the sole carbon source.
Finally, to further assist with the metabolic engineering of any compound, I worked on a CRISPRai system in S. cerevisiae. An assembly method has been improved to dramatically increase its efficiency, the number of gRNAs to be assembled to 24, and to allow for gene activation as well as repression simultaneously. An increase in succinic acid production up to 38-fold or 45-fold over the WT strain was demonstrated using the constitutive and inducible systems, respectively.