Engineering a Carotenoid-Overproducing Strain of Azospirillum brasilense for Heterologous Production of Geraniol and Amorphadiene

To date, the major host organisms used for the heterologous production of terpenoids, i.e., E. coli and S. cerevisiae , do not have high-flux isoprenoid pathways and involve tedious metabolic engineering to increase the precursor pool. Since carotenoid-producing bacteria carry endogenous high-flux isoprenoid pathways, we used a carotenoid-producing mutant of A. brasilense as a host to show its suitability for the heterologous production of geraniol and amorphadiene as a proof-of-concept. The advantages of using A. brasilense as a model system include (i) dispensability of carotenoids and (ii) the possibility of overproducing carotenoids through a single mutation to exploit high carbon flux for terpenoid production.