Optimizing Culturing Conditions for Bacillus Subtilis

Optimization of Bacillus subtilis (isolate B246) growth conditions for mass cell production under laboratory conditions was investigated as part of a biological control programme. Aspects such as increasing yield using various starter culture volumes, various media and incubation time and temperatures, were studied. No significant differences between starter culture volumes were found. Potato media gave the highest yield and was the most economical. A significant drop in viable and in total cell counts was found when B. subtilis was harvested through centrifugation. Freezing B. subtilis at -78 °C as well as using Ringer-Glycerol as preservation medium was more effective than freezing at -20 °C, or skim-milk medium. Conversion of fresh cultures to dry forms resulted in a 60 % reduction in c.f.u. The lyophilized antagonist remained viable for up to seven months storage at room temperature, although a significant drop in viable cells was observed after the first month's storage.