Disclosed is a process for producing L-isoleucine which comprises culturing in a medium a microorganism obtained by transforming a host microorganism belonging to the genus Corynebacterium or Brevibacterium with a recombinant DNA wherein a DNA fragment containing a threonine operon of Escherichia coli is inserted into a vector DNA, accumulating L-isoleucine in the culture and recovering L-isoleucine therefrom. Furthermore, recombinant DNA molecules and the corresponding transformants which can be used in the aforementioned process are described.
