The immobilization of living Acetobacter cells by adsorption onto a large-surface-area ceramic support was studied in a pulsed flow reactor. The high oxygen transfer capability of the reactor enabled acetic acid production rates up to 10.4 g L(-1) h(-1) to be achieved. Using a simple mathematical model incorporating both internal and external mass transfer coefficients, it was shown that oxygen transfer in the microbial film controls the reactor productivity.