Refolding the sweet-tasting protein thaumatin II from insoluble inclusion bodies synthesised in Escherichia coli

A synthetic gene encoding the amino acid sequence of the strongly sweet-tasting protein thaumatin II has been expressed in Escherichia coli. The recombinant protein has been renatured from inclusion bodies using a reduced/oxidized glutathione system to yield a purified protein preparation that is indistinguishable from native thaumatin with respect to its biochemical, spectroscopic and organoleptic properties.