BelloCell is a novel packed bed bioreactor that allows alternating nutrient and gas transfer to a culture. Spodoptera frugiperda Sf-9 grown in the BelloCell (300 ml culture) reached 1.3-1.5x10(7) cells ml(-1) in 7-8 days and the total baculovirus-expressed protein yield was 2.3-times that in a stirred tank bioreactor (600 ml culture). The superior cell and protein yields underline the potential of BelloCell for cell culture and recombinant protein production.