Abstract: Microorganisms or animal cells are cultured in a fluidized or fixed bed bioreactor on porous inorganic sintered support spheres containing inwardly continuous and outwardly open pores. The spheres have a density and diameter such that shear forces created under fluidized bed conditions shear off microorganisms or animal cells grown out of the pores and on the surface of the spheres. Culturing may be carried out in a fixed bed continuous reactor and the bed subjected to intermittent fluidized bed conditions to shear microorganisms or animal cells off the sphere surfaces. The spheres may be coated with a thin plastic layer to increase resistance to abrasion. Also, the spheres may be provided with a surface layer of inorganic and/or organic material for improving immobilization of microorganisms or animal cells.