For years, organic farmers have been using sprays containing Bacillus thuringiensis, or Bt, a naturally occurring bacteria, different strains of which are toxic to certain insects.

The two varieties that passed safety inspection express a gene for a protein from the bacterium Bacillus thuringiensis (Bt) that's toxic to insects.

The techniques for seperation, dissolution and purification of the toxic protein crystal from Bacillus thuringiensis are reviewed in this paper.