Abstract: 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.

Key words: magnetic nanoparticles, immobilized cells, L.reuteri, metabolis

摘要： 利用共沉淀法结合高锰酸钾氧化制备所得表面羧基修饰的超顺磁性纳米粒子吸附于罗伊氏乳酸杆菌表面，在磁场协助下实现细胞的固定化。吸附机理分析表明小尺寸相互作用和静电相互作用是磁性纳米粒子与细胞之间的主要作用。分别考察了菌体/磁性粒子质量比、pH、温度、时间等对固定化罗伊氏乳酸杆菌的影响，确定最佳固定条件为菌体与磁性纳米粒子相对质量比为2.25，在pH=3、温度25℃的条件下固定化0.5 h，可实现91%的细胞固定化。最后，对固定化后的细胞进行再培养，与游离细胞相比，两者表现出类似的代谢特征，证实细胞经固定化后仍具有活性。因此，羧基修饰的超顺磁性纳米粒子可成功用于细胞固定化，在不影响细胞活性的情况下，通过磁分离实现细胞的重复利用。

关键词: 磁性纳米颗粒, 固定化细胞, 罗伊氏乳酸杆菌, 生长代谢