Combining Random Mutagenesis and Metabolic Engineering for Enhanced Tryptophan Production in Synechocystis sp. Strain PCC 6803

Abstract

Aromatic amino acids such as tryptophan are primarily used as additives in the animal feed industry and are typically produced using genetically engineered heterotrophic organisms such as Escherichia coli . This involves a two-step process, where the substrate such as molasses is first obtained from plants followed by fermentation by heterotrophic organisms. We have engineered photoautotrophic cyanobacterial strains by a combination of random mutagenesis and metabolic engineering. These strains grow on CO 2 as the sole carbon source and utilize light as the sole energy source to produce tryptophan, thus converting the two-step process into a single step. Our results show that combining random mutagenesis and metabolic engineering was superior to either approach alone. This study also builds a foundation for further engineering of cyanobacteria for industrial tryptophan production.