In the L-sorbose fermentation by Gluconobacter suboxydans var. α IFO 3254, which was immobilized with Ca-alginate gel, the effect of pure oxygen gas with increased pressure was studied for accelerating the reaction rate. When pure oxygen gas was used, the rate of oxidation increased proportionally to the oxygen pressure at least until 25 kg/ cm² gauge pressure. Beyond this point, it was found that the increasing rate become rather slowly because sorbitol dehydrogenase (SLDH) of cells were injured by high pressure oxygen gas. It was also found that this entrapping method could protect SLDH of cells from oxygen toxicity by 5-times-reusing test under 5 kg/ cm² gauge pressure pure oxygen pressure.
Under pure oxygen and at 15°C, more than 80 % of D-sorbitol solution could be converted constantly through 15-times-reusing test and this conversion rate was about 0.61 mol/ (sec·g dry cells).