High gradient magnetic separation of yeast

High gradient magnetic separation (HGMS) is used to separate nonmagnetic microorganisms from solution by a technique known as seeding. Fine magnetic particles are adhered to the cells' surfaces, making them magnetic and amenable to magnetic separation. Attachment of the sub-micron, acicular gamma-Fe(2)O(3) seed to the yeast surface occurs irrespective of the solution pH and surface charge and is essentially irreversible. A model is developed to predict the separation of yeast in a high gradient magnetic separator. The effective capture radius is assumed to be proportional to the derived magnetic parameter gamma for the case where the dominant competing force to magnetic attraction is the magnetic floc's inertia. Using this parameter, yeast separation in an HGMS unit is predicted. The measured separation of Saccharomyces cerevisiae at differing magnetic seed concentrations and two flow rates supports the above model.