A novel membrane bioreactor, previously assessed for its gas transfer characteristics, was used in various size and membrane configurations for the growth of the strictly aerobic bacterium Pseudomonas aeruginosa. The bioreactor was found to readily support growth, and the initial growth rates showed the previously demonstrated enhanced effect in gas O-2 mass transfer of the dimpled membrane bioreactor over flat membrane bioreactors. The production of a secondary metabolite by a Pseudomonas sp. following growth was demonstrated, as was the biotransformation of a nitrile by nocardia rhodochrous with the removal of the biotransformation products across a membrane. The potential of the bioreactor, in terms of other applications in the field of biotechnology, is discussed.