Recovery of solubilized delta-endotoxin from Bacillus thuringiensis subsp kurstaki fermentation broth

Insecticidal delta-endotoxin proteins, degraded from parasporal crystals by protease, were recovered by a simple procedure using heat treatment, solub ilization, and ultrafiltration of a fermentation broth of Bacillus thuringi ensis subsp kurstaki HD-1. A 68 kDa insecticidal protein was obtained and c haracterized by SDS-PAGE. The procedure described gave a nearly quantitativ e recovery of toxicity. Furthermore, bioassay results on larvae of the diam ondback moth (Plutella xylostella) showed that the 68 kDa delta-endotoxin f raction (P1) was the principal insecticidal component to this target insect . A similar molecular mass polypeptide P2 (65 kDa) which was solubilized to gether with P1 from the parasporal crystals, gave relatively low mortality. (C) 2000 Society of Chemical Industry.