Coordinated synthesis of aromatic amino acid derivatives via local and global transcriptional engineering

Rational metabolic pathway engineering is capable of boosting upstream flux towards downstream synthesis of target products, such as aromatic amino acid derivatives. However, biosynthesis of complex compounds requires multiple precursors of aromatic amino acids as phenylalanine, tyrosine and tryptophane, facing difficulty of metabolic pathway optimization. Here, we develop a strategy to optimize synthesis of aromatic amino acid derivatives in yeast by combing both the local transcriptional engineering of particular upstream pathway genes and the global transcriptional engineering of the transcriptional factors SPT15 and GCN4. It is verified the special mutants of SPT15p and GCN4p can respectively improve the biosynthesis of betaxanthin, a tyrosine derived edible pigment. Comparative transcriptome analysis explored similar transcriptional tuning in glycolysis, pentosephosphate, and aromatic amino acid synthesis pathways, and some other indirectly related pathways. In addition, combinatorial local and global transcriptional engineering is proved to enhance the biosynthesis of both tyrosine and tryptophan derivatives, betaxanthin and violacein. Finally, we obtain a 10-fold optimized production of 150 mg/L betaxanthin in yeast cells by basic flask fermentation. Our strategy supplies a promising way to optimize the complex pathway product synthesis relying on multiple precursors.