Efficient production of acetic acid from glucose was investigated in a mixed culture of Zymomonas mobilis ATCC10988 and Acetobacter sp. TC-1. The culture was initially incubated under low aeration and low agitation conditions to allow ethanol fermentation. A shift from ethanol fermentation to acetic acid fermentation was achieved by enhancing the aerobic conditions when the glucose, whose concentration was monitored using an on-line glucose sensor, dropped below a certain level. Ethanol production decreased when a higher aeration rate and agitation speed were used during the early stage of the cultivation. Acetic acid production was also markedly dependent on agitation and aeration during the early stage. The acetic acid yield from glucose was 0.64 g/g (95.5% of the theoretical value) under the optimum conditions.