Bacillus subtilis strain whose extracellular protease activities are reduced, method for obtaining the strain and method for secreting proteins by using the strain

摘要

Residual extracellular protease activities of a Bacillus subtilis strain can be further reduced by introducing a gene for the stimulation of extracellular protease levels into the genomic DNA of the strain. PPThe resultant strain whose extracellular protease activities are further reduced is transformed with a recombinant plasmid for secretion of a desired protein and the desired protein can be efficiently produced and accumulated in the culture medium in a large amount. The accumulated desired protein can be easily recovered from the culture medium.PPFor example, the accumulation level of human growth hormone secreted by a B. subtilis MT-430 strain carrying recombinant DNA phGH427 for the expression and secretion of human growth hormone can be increased five to tenfold as a result of the above treatment for reduction of the residual extracellular protease activities of the extracellular protease-activity-deficient strain.