AbstractBatch foam separation has been employed to separate Saccharomyces carlsbergensis cells from their broth without the use of any external surface‐active agent. A model has been developed to predict the foamate cell concentration as well as the variation of cell concentration in the bulk liquid in the foam column as a function of time. The model assumes a linear equilibrium relation between the cell concentrations at the interface and the bulk. The foam has interface as well as interstitial liquid. The interface is assumed to be in equilibrium with the interstitial liquid, which in turn is assumed to have the same concentration as the bulk. The interfacial area is calculated by assuming the foam bubbles to be pentagonal dodecahedral in shape. The model has been found to explain the results of foam separation of cells quite well, particularly with respect to the effect of bubble size and aeration rate.