Isolation of Bacillus subtilis (chungkookjang), a poly-^γ-glutamate producer with high genetic competence

Abstract.

A bacterium with high poly-γ-glutamate (PGA) productivity was isolated from the traditional Korean seasoning, Chung-Kook-Jang. This bacterium could be classified as a Bacillus subtilis, but sporulation in culture was infrequent in the absence of Mn²⁺. It was judged to be a variety of B. subtilis and designated B. subtilis (chungkookjang). L-Glutamate significantly induced PGA production, and highly elongated PGAs were synthesized. The volumetric yield reached 13.5 mg ml^–1 in the presence of 2% L-glutamate. The D-glutamate content was over 50% in every PGA produced under the conditions used. During PGA production, glutamate racemase activity was found in the cells, suggesting that the enzyme is involved in the D-glutamate supply. Molecular sizes of PGAs were changed by the salt concentration in the medium; PGAs with comparatively low molecular masses were produced in culture media containing high concentrations of NaCl. B. subtilis (chungkookjang) harbors no plasmid and is the first B. subtilis strain reported with both naturally high PGA productivity and high genetic competence.