Fractionation of Escherichia coli on the Rupture of Bubbles at a Liquid Surface

Abstract

In order to investigate the collecting mechanism of E. coli particles in a process where small bubbles produced from a tip of a capillary tube in suspended particle solutions, rise up, float and burst at an air/liquid interface (Fig.1), the present study had developed the jet drop method capable of continuously collecting the innermost surface layer of bubbles. This method gives the top jet drops by collecting a thin layer from the surface of bubble with a high reproducibility not to be expected with any conventional mechanical apparatures. The top jet drop ejected from the unstable jet -which rises out of the collapsing bubble cavity upon bubble rupture has a striking capability to fractionate ions (1,5), microparticles and microorganisms(2-4) which are concentrated on the bubble surface layer. To be collected the particle must cross a potential barrier caused by the interaction of the bubble and particle electrostatic double layer. Their analysis yields the concentration factor, η(=CD/CB), of particles in the top jet drops which can be measured as a function of drop sizes (dD), buble release heights (h) and bulk particle concentrations (CB). The studies on the fractionation of E. coli were performed in the presence of surface active materials such as a slight amount of mixed stock medium including peptone, NaCl and beef extract (pH6.6)