(66c) Area 15A Plenary Award - Engineering of Aromatic Amino Acid Production in Cyanobacteria

Cyanobacteria are increasingly being developed due to their ability to directly convert CO₂ to biochemicals with energy from sunlight. The essential aromatic amino acids, Phenylalanine (Phe) and Tryptophan (Trp), are valuable products in the food and feed industries. Each of these biochemicals are currently produced from heterotrophs engineered by mutagenesis and rational metabolic engineering approaches. Our research is exploring process intensification by combining the separate processes of producing the carbon source and engineering the microbe into a single process. We selected several cyanobacteria (Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002 and Synechococcus sp. PCC 11801) for comparison of production of Phe and Trp. We applied two methods for strain development: 1) classical random mutagenesis and 2) targeted metabolic engineering of feedback resistant enzymes. Interestingly, the genes identified qualitatively varied by cyanobacterial strain. Notably, for Trp, combining both approaches by inserting key genes in the randomly mutated host strain resulting in superior titers compared to either single approach. Notably, in all the studies, isolated mutants displayed no reduction in biomass accumulation, but fix CO₂ significantly more CO₂. To understand this phenomenon, we measured the efficiencies of key components of the electron transport chain in the wild-type and mutant PCC 11801 strains. Finally, we will present technoeconomic analysis of bioprocesses designed for production and purification of the amino acids.