Loading and Light Degradation Characteristics of Bt Toxin on Nanogoethite: A Potential Material for Controlling the Environmental Risk of Bt Toxin

Abstract

Transgenic Bt-modified crops release toxins into soil through root exudates and upon decomposition of residues. The fate of these toxins in soil has not been yet clearly elucidated. Nanogoethite was found to have a different influence on the lifetime and insecticidal activity of Bt toxin. The aim of this study was to elucidate the adsorption characteristics of Bt toxin on nanogoethite and its activity changes before and after adsorption. The adsorption of toxin on nanogoethite reached equilibrium within 5 h, and the adsorption isotherm of Bt toxin on nanogoethite conformed to the Langmuir equation (R2>0.9690). In the range of pH from 6.0 to 8.0, larger adsorption occurred at lower pH value. The toxin adsorption decreased with the temperature between 10 and 50°C. The results of FTIR, XRD, and SEM indicated that toxin did not influence the structure of nanogoethite and the adsorption of toxin only on the surface of nanogoethite. The LC50value for bound toxin was higher than that of free toxin, and the nanogoethite greatly accelerated the degradation of toxin by ultraviolet irradiation. The above results suggested that nanogoethite is a potential material for controlling the environmental risk of toxin released by Bt transgenic plants.