The present invention relates, in general, to the over-production of L-isoleucine by nonhuman organisms. More specifically, the present invention relates to methods for producing L-isoleucine comprising: (a) growing a transformed nonhuman organism under conditions that provide for synthesis of L-isoleucine, wherein the nonhuman organism comprises one or more copies of a transgene comprising at least one nucleotide sequence encoding catabolic threonine dehydratase; wherein the L-isoleucine is synthesized by the transformed nonhuman organism, the synthesis being greater than that of the corresponding non-transformed nonhuman organism; and (b) recovering the L-isoleucine from the culture medium in which the transformed nonhuman organism was cultured.