Histidine production by a regulatory mutant of Streptomyces coelicolor.

Streptomyces coelicolor mutant RF-59, isolated as a revertant of a histidine auxotroph after mutagenic treatment with N-methylN'-nitro-N-nitrosoguanidine, was found to accumulate L-histidine. The mutant was sensitive to 2-thiazo-lealanine and L-2,4-diaminobutyric acid and partially sensitive to alpha-methylhistidine but resistant to 1,2,4-triazolealanine, indicating that repression of the histidine operon was modified in the mutant. Culture conditions were investigated, and optimal media for L-histidine production were developed, resulting in L-histidine accumulation of 2.1 to 3.5 g/liter.