Optimization of a hybrid bacterial/ fatty acid synthase system II in .

Fatty acids are produced by eukaryotes like baker's yeast mainly using a large multifunctional type I fatty acid synthase (FASI) where seven catalytic steps and a carrier domain are shared between one or two protein subunits. While this system may offer efficiency in catalysis, only a narrow range of fatty acids are produced. Prokaryotes, chloroplasts and mitochondria rely instead on a FAS type II (FASII) where each catalytic step is carried out by a monofunctional enzyme encoded by a separate gene. FASII is more flexible and capable of producing a wider range of fatty acid structures, such as the direct production of unsaturated fatty acids. An efficient FASII in the preferred industrial organism could provide a platform for developing sustainable production of specialized fatty acids. We functionally replaced either yeast FASI genes ( or ) with a FASII consisting of nine genes from (, and -, -, -, -, -, -, -) as well as three from (, and ). The genes were expressed from an autonomously replicating multicopy vector assembled using the Yeast Pathway Kit for assembly in yeast. Two rounds of adaptation led to a strain with a maximum growth rate (μmax) of 0.19 h without exogenous fatty acids, twice the growth rate previously reported for a comparable strain. Additional copies of the or genes resulted in cultures with higher final cell densities and three times higher lipid content compared to the control.