Hydrophobicity and an electric charge are thought to be key factors that influence demulsification performance of demulsifying bacteria. Nonetheless, the exact mechanism of action of these two factors are not clear. Two series of functional magnetic nanoparticles with gradually varied hydrophobicity or surface charge were synthesized and combined with demulsifying bacteria, for manipulation of surface hydrophobicity or a charge of these bacteria. Demulsification results indicated that stronger cell surface hydrophobicity resulted in better demulsification performance of magnetically responsive bacterial demulsifiers (MRBDs), whereas a higher or lower su be useful for broader applications of bacterial demulsifiers in the future.rface charge (in the range from 30 mV to -20 mV) can inhibit it. Hydrophobicity accelerated droplet coalescence by 1.0 h in relation to its stimulatory effect on cell translocation to the interface. A proper surface charge made sure that bacteria aggregate to a certain extent at the interface. These results should