ABSTRACT
Isolation of suppressive bacteria was tried from each compost that showed a significant suppressive effect on the agar plates against any of the phytopathogenic fungi. The bacteria isolated from different sources that showed a broader suppressive spectrum were B. subtilis. The suppressive substance, iturin, purified from the culture broth of B. subtilis NB22, is heat resistant and pH stable in a wide range. It was newly found that this substance is effective not only to phytopathogenic fungi but also to bacteria. The application of B. subtilis NB22 as an agent for the biological control of plant diseases will be either by direct inoculation to the raw material used for composting or mixing with compost products. Dewatered sewage sludge cake from the Minamitama Wastewater Treatment Plant was used as the composting material. A compost product was put into a plastic bag such that a thin layer of compost was formed inside the bag.
