For the development of Bacillus subtilis as a host for foreign protein synthesis, three types of sigma factor deleted mutants (spoIIAC, spoIIIG and spoIIIC) were constructed by antibiotic marker insertion using plasmid vector-mediated method or LFH (Long Flanking Homology)-PCR. Mother cell specific sigma factor mutants of B. subtilis (sigma (K)), B. subtilis DB104 Delta spoIIIC (km(r))::pMK101, had two to three times higher subtilisin activity than the wild type DB104::pMK101. Subtilisin expression by the other two mutants, B. subtilis DB104 Delta spoIIAC (km(r))::pMK101 and DB104 Delta spoIIIG (km(r))::pMK101, which are pre-spore specific sigma factor (sigma (F) and sigma (G)) deleted strains, was similar to, or less than that of the wild type.