Introduction of two mutations into AroG increases phenylalanine production in Escherichia coli

l-Phenylalanine is an important amino acid commercially, and therefore optimization of its manufacture is of interest. We constructed a range of mutant alleles of AroG, the enzyme involved in the first step of phenylalanine biosynthesis. Three single-site mutant alleles were constructed (aroG8, aroG15, and aroG29), which were then combined to generate three double-site aroG (fbr) mutant alleles (aroG8/15, aroG8/29, and aroG15/29). Enzymatic activity, feedback inhibition, and fermentation were analyzed in all of the mutants. All double-site mutants, except AroG15/29, showed higher enzymatic activity and greater resistance to feedback inhibition than their respective single-site mutants. The E. coli strain carrying the aroG8/15 allele produced a phenylalanine titer of 26.78 g/l, a 116 % improvement over the control phenylalanine overproducing strain (12.41 g/l). Our findings provide an effective method for modifying phenylalanine biosynthetic genes, which may be applied to optimize the commercial manufacture of phenylalanine.