Oxygen Transfer Mechanisms in the Gluconic

The oxygen uptake rate to suspended cells of Pseudomonas ovalis was measured in two ways using the same cell suspension. Initially the rate was found by measuring the rate of production of gluconic acid by cells suspended in a nitrogenfree, aerated medium. Then, an oxygen electrode was used to measure the rate of transfer of dissolved oxygen to cells suspended in a liquid that was being agitated but not sparged. It was found that agitation affected the oxygen transfer rates in aerated solutions at dissolved oxygen concentrations well above the critical level, but had no affect on the oxygen uptake rates by cells suspended in an unsparged but agitated medium. The data suggested that an additional path existed for oxygen transfer. This alternate route, parallel to the conventional pathway of oxygen transfer, becomes operative when the liquid films surrounding the cells and bubbles merge. The resulting shorter path presents a mechanism for direct transfer of oxygen which increases in importance as the gas-liquid interfacial area increases. These rates were markedly different.