Location and limitation of cellulose production by Acetobacter xylinum established from oxygen profiles

The static fermentation of coconut water sucrose by Acetobacter xylinum was tarried out at initial pH's of 3.0, 4.0, 5.0 or 6.0. Cellulose was produce d at the surface, and its production was most favourable at pH's 4.0 and 5. 0. These pH values also allowed for optimal bacterial growth. Oxygen concen tration profiles were measured with microelectrodes at different cultivatio n stages, and steep profiles were obtained with penetration depths between 50 and 100 mu m. A substrate penetration depth analysis confirmed the hypot hesis that the first stage of the fermentation is entirely oxygen controlle d. Diffusion calculations showed, however, that at a later stage sucrose be comes a limiting substrate also, which was confirmed by the decrease in cel lulose production rate over time. The effective diffusion coefficient of ox ygen in deactivated cellulose pellicles was measured with microelectrodes, and a value of 1.4 x 10(-9) m(2)/s was obtained under all investigated cond itions. The oxygen flux was 5.9 x 10(-6) mol/m(2).s, while a significantly higher value of 9.1 x 10(-6) mol/m(2).s was obtained at pH 4.0.