Abstract
Genetically modified Bacillus thuringiensis (Bt) crops, which have been widely used in agricultural trans genic plants, express insecticidal Cry proteins and release the toxin into soils. Taking into consideration the environmental risk of Cry proteins, biosurfactant rhamnolipids were applied to desorb Cry proteins from soil environment, which has not been elucidated before. Quartz crystal microbalance with dissipation (QCM-D) was used in this article to investigate the adsorption and desorption behaviors of Cryl Ac on SiO2 surface (model soil). Results showed that patch-controlled electrostatic attraction (PCEA) governed Cry1Ac adsorption to SiO2, and the solution pH or ionic strength can affect PCEA. The adsorption kinetics could be fitted by the pseudo-second-order model, and the adsorption isotherm was fitted to Langmuir model with correlation coefficients higher than 0.999. The desorption characteristics of Cryl Ac from SiO2 were assessed in the presence of mono-rhamnolipid, di-rhamnolipid or complex-rhamnolipid. Monorhamnolipid exhibited the most significant positive effect on desorption performance. With a complete removal of CrylAc reached when mono-rhamnolipid concentration was up to 50 mg L-1. Additionally, the desorption was enhanced at alkaline pH range, and CrylAc can be completely and rapidly desorbed by rhamnolipids from SiO2 at ionic strength of 5 x 10(-2) M. (C) 2017 Elsevier B.V. All rights reserved.