The Study Of Adsorption And Desorption Of Cry1Ac Protein On SiO₂ Surface

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.Cry proteins may have effect on soil biodiversity and ecosystem function.The research of Bt cotton biosafey mainly focus on the source,adsorption and time of retention of Cry proteins in soil,but little is known about translocation,degradation and removal of Cry proteins.Taking into consideration the environmental risk of Cry proteins,biosurfactant—rhamnolipids were applied to desorb Cry proteins from soil environment.Quartz crystal microbalance with dissipation(QCM-D)was used in this article to investigate the adsorption and desorption behaviors of Cry1 Ac on Si O2 surface(model soil).The main results are described below:1)Patch-controlled electrostatic attraction(PCEA)governed Cry1 Ac adsorption to Si O2,and the solution p H or ionic strength can affect PCEA.The isotherm adsorption curves were L-type,and the adsorption data fitted well with both Langmuir and Freundlich isotherm models,but the Langmuir equation was more suitable.The adsorption kinetics could be fitted by the pseudo-second-order model.2)The desorption characteristics of Cry1 Ac from Si O2 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 Cry1 Ac reached when mono-rhamnolipid concentration was up to 50 mg·L-1.3)The desorption of Cry1 Ac proteins by rhamnolipid may be affected by changing the p H of the solution.Changing p H environment to as low as 5-6,rhamnolipids would deposit on the protein layer or Si O2 surface which can not be desorbed.While at alkaline p H range,the high removal efficiency of Cry1 Ac protein was found.4)Cry1Ac proteins can be completely and rapidly desorbed by rhamnolipids from Si O2 at ionic strength of 5 × 10-2M.