Microbubbles for enhancement of oxygen transfer in xanthan gum fermentation

This study investigates the use of microbubble sparging for enhancing oxygen transfer and product yield during xanthan gum fermentation. Fermentation runs with full air sparging and partially substituted microbubble sparging were compared for the parameters biomass, xanthan, oxygen uptake, and energy levels. Microorganisms were found compatible at numerous Tween-20 levels and further showed considerable resistance to shear conditions in the microbubble generator. Microbubbles with a size of about 145 mu m, gas hold up of 65%, and foam stability of about 3 min. resulted at standardized microbubble generator operating conditions (8000 rpm, 2 min., 300 ppm surfactant). A comparison of both methods showed that partially substituted microbubble sparging increased oxygen uptake by 50%, final biomass levels by 17%, and final xanthan gum yield by 30%. Results indicate that X. campestris is amenable to conditions encountered within a microbubble generator and that microbubble sparging improved oxygen transfer and xanthan gum yield without affecting gum quality.