Separation of the Spores and Crystals of Bacillus thuringiensis

Abstract

THE isolation of the protein crystals of Bacillus thuringiensis, which are toxic to the larvae of certain species of insects, has been described previously^1,2, and involves phase separation in which an aqueous phase consisting of a suspension of spores and crystals is emulsified with a variable volume of an organic solvent such as trifluorotrichloroethane. When the two phases are mixed, most of the spores and some of the crystals are removed from the aqueous phase into the organic phase and crystals are left in the aqueous phase. An ideal method would recover 100 per cent of crystals completely free from spores. This has not yet been achieved; usually the greater the degree of crystal purity required, the lower is the yield of crystals.