A process and system for cultivating adhesive cells in a packed bed of solid cell matrix is disclosed. Adhesive cells are adhered to a solid cell matrix, preferably ceramic particles, and packed in a cell culture tank to form the packed bed. The culture medium is circulated through the packed bed in a direction. The circulating of the culture medium is then stopped and the direction of the medium being circulated is reversed. This periodic switching of the direction of the culture medium reduces channelling of the culture medium. The bottom or head of the culture tank can also contain a separator to trap any bubble existing in the culture medium or to trap any quantity of cell matrix possibly running out from the culture tank.