This study will concentrate upon achieving high productivity of .-endotoxin protein by Bacillus Thuringiensis cells by controlled fed- batch operation of stirred bioreactors. The strategy involves growing the cells to high concentrations in vegetative phase during which the fermentation parameters will be controlled to minimize formation of undesirable toxic products. Minimal requirements of nutrients for cell growth to high densities will be established by continuous cultivation techniques. The fed-batch cultivation will be fine tuned so that medium composition at high densities is optimum for subsequent sporulation and endotoxin formation. Biological insecticides are increasingly being viewed as more advantageous than chemical pesticides which are generally energy intensive, have long half lives, and adversely affect many harmless forms of life. .-endotoxin is a commercially produced insecticide that is being studied extensively with major improvements in its potency. In addition, spore-forming bacilli are commonly used to produce many industrially important products; therefore, fundamental studies involving high density cultivation can improve productivity of several processes.