Improvement in microbial production of L-tyrosine by gene dosage effect of aroL gene encoding shikimate kinase.

Genetic breeding of microbial amino acid producers has been done conventionally by acquiring auxotrophic mutants or regulatory mutants based on fundamental knowledge of amino acid biosynthetic pathways and their regulatory mechanisms. The conventional techniques are effective in that a number of amino acids, such as lglutamate, L-lysine, L-phenylalanine, L-threonine, larginine, L-isoleucine, L-leusine, L-valine, are practically