Cell immobilization is the main means to realize cells reutilization in the biotransformation process.Immobilizing cells with superparamagnetic nanoparticles directly is a new method of immobilization.The carboxyl-functioned magnetic nanoparticles prepared by the coprecipitation method with oxidization by KMnO4 solution were directly adsorbed to the surface of Lactobacillus reuteri CG001

and the cells were immobilized in magnetic field.Based on the analysis of adsorption mechanism

it was deduced that the main interactions between superparamagnetic nanoparticles and cells were the small size effect of nanoparticle

and electrostatic.Immobilization conditions

such as temperature

pH

time and cell/particle ratio were investigated in detail.The optimum condition was that the cells were immobilized for 0.5 h at 25℃ with the mass ratio of cell/particle 2.25.Furthermore

the immobilized cells were cultured to compare its growth and metabolism properties with free cells.The similar growth and metabolism properties shown by the immobilized cells and free cells indicated that the superparamagnetic nanoparticles on the surface of cells had little adverse effect on cell activity.So the carboxyl-functioned magnetic nanoparticles could be used to immobilize microbial cells and realize cell reutilization with little impact on cell activity.