Celite R‐630, a commercially available catalyst support, was used successfully in the batch and continuous production of Penicillin‐G by mycelial cells of Penicillium chrysogenum. As an extension of previous work, the productivity of a 1.2 L three phase fluidized bed bioreactor using the Celite support was compared directly with the same reactor in which cells had been immobilized inside a larger carrageenan support matrix. With Celite particles, maximum yields and specific reaction rates for continuous reactor runs were 0.11 g Pen‐G (K+)/g lactose and 0.05 mmol Pen‐G/h/g protein respectively. These results were similar to those obtained with carrageenan beads. However, on a reactor volume basis, Celite was five times more productive than carrageenan. Results are discussed in terms of the potential for using Celite in industrial bioreactor systems.