Engineering the Hydrocarbon Biosynthetic Pathway from the Green Microalga Botryococcus braunii into the Faster Growing Heterologous Host Chlamydomonas reinhardtii
Botryococcus braunii is a green microalga that is capable of producing large amounts of liquid hydrocarbons that can be processed into liquid fuels such as gasoline, kerosene and diesel. Lycopaoctaene is a C40 hydrocarbon produced by race L of B. braunii using the enzyme lycopaoctaene synthase (LOS). LOS catalyzes the head-to-head linkage between two geranylgeranyl diphosphate (GGPP) molecules to yield lycopaoctaene, which is then further reduced to lycopadiene. Lycopadiene is the hydrocarbon that accumulates within the colony extracellular matrix and usually constitutes 8-12% of algal dry weight. The slow growing nature of B. braunii is one of the main factors limiting the use of this alga as a viable host for biofuel production. Because B. braunii has not been able to be transformed, it would be advantageous to transform a faster growing model alga with hydrocarbon biosynthetic genes. Chlamydomonas reinhardtii is a faster growing model green microalga with many genetic tools developed for it, and is being used in our study to express the LOS gene for lycopaoctaene production. In order to increase lycopaoctaene production in C. reinhardtii, GGPP synthase (GGPPS) will be expressed constitutively along with LOS. In order to do this, transformant lines of C. reinhardtii will be generated and compared. The four C. reinhardtii transformant lines being compared include one overexpressing GGPPS, one overexpressing LOS, the LOS tranformant further transformed with C. reinhardtii derived GGPPS, and the LOS line further transformed with A. thaliana derived GGPPS11. Using two different sources of GGPPS genes will allow us to compare levels of expression and lycopaoctaene production.
Yell, Victoria (2017). Engineering the Hydrocarbon Biosynthetic Pathway from the Green Microalga Botryococcus braunii into the Faster Growing Heterologous Host Chlamydomonas reinhardtii. Undergraduate Research Scholars Program. Available electronically from