Oxygen mass transfer enhancement by activated carbon particles in xylose fermentation media.

In this work, the effect of activated carbon particles on the production of xylonic acid from xylose by Gluconobacter oxydans in a stirred tank bioreactor was investigated. The enhancement of the oxygen transfer coefficient by activated carbon particles was experimentally evaluated under different solids volume fractions, agitation and aeration rates conditions. The experimental conditions optimized by response surface methodology (agitation speed 800 rpm, aeration rate 7 L min -1 , and activated carbon 0.002%) showed a maximum oxygen transfer coefficient of 520.7 h -1 , 40.4% higher than the control runs without activated carbon particles. Under the maximum oxygen transfer coefficient condition, the xylonic acid titer reached 108.2 g/L with a volumetric productivity of 13.53 g L -1  h -1 and a specific productivity of 6.52 g/g x /h. In conclusion, the addition of activated carbon particles effectively enhanced the oxygen mass transfer rate. These results demonstrate that activated carbon particles enhanced cultivation for xylonic acid production an inexpensive and attractive alternative.