Growth rate of Alcaligenes eutrophus under non-explosive gas mixture of low oxygen partial pressure, where oxygen transfer was rate determining process, was enhanced by adding perfluorocarbon as an oxygen carrier. The trend of enhancement with increase of PFC addition was different across the phase inversion region where continuous phase changes from aqueous medium to PFC. The enhancement was analyzed quantitatively using a mass transfer model, which took into account two cases where either the medium or the PFC was continuous phase. An enhancement factor for the oxygen transfer rate, defined as the ratio of oxygen transfer rate in a medium mixed with PFC to that in a PFC-free medium, was used in evaluating the effect of PFC addition. The factor was a function of the oxygen transfer coefficient and the interfacial area between gas bubble and the medium, and the volume fraction of PFC when the medium was in continuous phase. Also the factor varied with the interfacial area and the oxygen transfer coefficient between the PFC and the medium, the volume fraction of PFC and the dissolved oxygen concentration when the PFC phase became continuous. The model revealed the factors affecting on the observed cell growth rate of A. eutrophus, such that the primary factor contributing to the enhancement of the cell growth in the latter case was the increase of the interfacial area between the PFC and the medium.