Bacillus thuringiensis subsp. medellin was grown until sporulation in a 1.1 l fermenter in batch and intermittent fed-batch culture. At optimum conditions 25 g dry cells l− 1 and 9× 108 spores ml− 1 were produced. Toxicity of the final biomass showed a half lethal concentration on third instar Culex quinquefasciatus larvae of 295 ng ml− 1.
