Abstract
A thiaisoleucine-resistant mutant, ASAT-372, derived from a threonine producer of Corynebacterium glutamicum, KY 10501, produced 5mg/ml each of L-isoleucine and L-threonine. L-Isoleucine productivity of ASAT-372 was improved stepwise, with concurrent decrease in threonine production, by successively endowing it with resistivity to such substances as ethionine, 4-azaleucine and α-aminobutyric acid. The mutant strain finally selected, RAM-83, produced 9.7mg/ml of L-isoleucine with a medium containing 10% (as sugar) molasses.
L-Isoleucine production was significantly affected by the concentration of ammonium sulfate in the fermentation medium. At 4% ammonium sulfate L-isoleucine production was enhanced whereas L-threonine production was suppressed. At 2% ammonium sulfate L-threonine production was stimulated while L-isoleucine production decreased.
