Preparative purification of Escherichia coli heat-stable enterotoxin

Heat-stable enterotoxin (STa) isolated from bovine Escherichia coli strains was purified to homogeneity by growing the bacterial strains in a chemically defined medium, desalting, and concentrating the culture filtrate by batch adsorption chromatography on Amberlite XAD-2 resin, batch adsorption chromatography on reversed-phase silica, and preparative reversed-phase high-performance liquid chromatography. This rapid preparative purification scheme gave high recovery yields of pure STa which exhibited biochemical homology to STa purified by more complicated procedures.