Dihydroxyacetone was produced by the strain Gluconobacter oxydans CCM 1783 (= ATCC 621), which is the most frequently cited strain for this conversion. The influence of the oxygen concentration and pH of the fermentation medium on product yield was evaluated using resting cells. A decrease of product yield at acidic pH was observed, but a more significant decrease occurred at oxygen concentrations under 4 x 10(-4) mol l(-1) Batch cultures were run with gassing by air and/or oxygen and yields of 87 and/or 94% were obtained. When using air, a 7% decrease in yield was accompanied by by-product formation, and glycerate was identified in fermentation medium.