Effects of an Escherichia coli ilvA mutant gene encoding feedback-resistant threonine deaminase on L-isoleucine production by Brevibacterium flavum.

A mutated ilvA gene of Escherichia coli encoding a threonine deaminase that is resistant to feedback inhibition by L-isoleucine was obtained. It was functional in Brevibacterium flavum, and a wild strain of B. flavum into which it was introduced became able to convert exogeneous L-homoserine and L-threonine to L-isoleucine. When it was introduced into a L-threonine-producing B. flavum strain, the transformant accumulated 20 g/liter L-isoleucine from 100 g/liter glucose.