An automated system and method for cultivating bacteria in a fluid medium and thereafter selectively discharging the fluid medium, wherein an initial supply of the selected strain or strains of bacteria is combined with nutrients and water in a biogenerator in the presence of air to promote mixing and bacterial cultivation. The disclosed system and method utilize a vortex created by recirculation of the fluid medium to achieve aeration and mixing without substantial foaming. The disclosed system and method are particularly useful for supplying bacteria to control grease accumulation in restaurant grease traps.