Fermentative Production of L-Leucine with Auxotrophic Mutants of Corynebacterium glutamicum

An auxotrophic mutant of Corynebacterium glutatmicum was found to accumulate a large amount of L-leucine in the culture medium. The nutritional requirement of the mutant is rather complex but it's growth was most remarkably stimulated by L-phenylalanine. Acetate (1.5_??_3.0%) or pyruvate (3%) stimulated the L-leucine production. By a further mutagenic treatment, 329 mutants carring some defect in addition to phenylalanine auxotrophy were derived from the mutant No. 190. Among them, a histidine auxotrophic derivative produced twice as much L-leucine as the parent strain, i.e., the level of L-leucine production by this derivative reached 16mg/ml in a medium containing 12% glucose, 1% (NH4)2SO4 and 2.5% CH3COONH4 as carbon and nitrogen sources. Some other auxotrophic markers such as isoleucine- (or threonine-), threonine-, purine(s)-, homoserine-, or methionine-auxotrophy also improved the L-leucine production by No. 190.