In situ surface transfer process of Cry1Ac protein on SiO2： The effect of biosurfactants for desorption

•QCM-D for real-time monitoring of Cry1Ac adsorption and desorption kinetic.•PCEA govern the adsorption of Cry1Ac to SiO2 surface is demonstrated.•Comparing mono-, di- and complex-rhamnolipid on the application of removing Cry1Ac.•Rhamnolipids can rinse Cry1Ac rapidly and completely at ionic strength up to 50 mM.•Cry1Ac can be desorbed during rhamnolipid solutions alkaline pH.

Genetically modified Bacillus thuringiensis (Bt) crops, which have been widely used in agricultural transgenic 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 Cry1Ac 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 Cry1Ac from SiO2 were assessed in the presence of mono-rhamnolipid, di-rhamnolipid or complex-rhamnolipid. Mono-rhamnolipid exhibited the most significant positive effect on desorption performance. With a complete removal of Cry1Ac reached when mono-rhamnolipid concentration was up to 50 mg L−1. Additionally, the desorption was enhanced at alkaline pH range, and Cry1Ac can be completely and rapidly desorbed by rhamnolipids from SiO2 at ionic strength of 5 × 10−2 M.

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