Optimization of culture conditions for toxin production of type G Clostridium botulinum.

Culture conditions were optimized for toxin production of Clostridium botulinum type G, the last toxigenic serotype described. Six factorial experiments were performed to assess the effect of medium composition (nutrients, metal ions, sterile soil, pH), incubation conditions (time, temperature and anaerobiosis) and associated microorganisms (Bacillus subtilis, Lactobacillus plantarum) on the toxinogenesis of C. botulinum type G. A significant (4 to 10 fold) improvement of toxin production was obtained by using an optimized medium (3% proteose-peptone, 0.5% trypticase, 1.1% glucose, 0.5% yeast extract, adjusted to pH 8.0) and incubation of the culture for 12 days at 26 degrees C in a nitrogen atmosphere.