Use of sea water as salts source in starch- and soya bean-based media, for the production of Bacillus thuringiensis bioinsecticides

In order to reduce the cost of Bacillus thuringiensis bioinsecticide-process production, a new medium only composed of starch, soya bean and diluted sea water, providing particularly 7.5 g/l NaCl, was optimized. The results obtained with cultures carried out into 1000 ml shake flasks showed 7% improvement of delta-endotoxin production in such cheap medium compared to that containing a mixture of pure minerals instead of sea water. Interestingly, this new formulated medium was shown to be efficient for delta-endotoxin production by several B. thuringiensis strains exhibiting various larvicidal activities towards either Diptera or Lepidoptera. Moreover, the use of such medium for large scale production of bioinsecticides was also evidenced in an automated full controlled 3 l fermenter. So that it was shown that sea water did not affect such requirements and have positive effect on growth, sporulation and delta-endotoxin synthesis. This should contribute to a significant reduction of the cost of B. thuringiensis bioinsecticide production and utilisation.