XANTHAN GUM PRODUCTION IN A FERMENTER WITH TWIN IMPELLERS

The production of xanthan gum by Xanthomonas campestris ATCC 13951 in a fermentor using twin turbine-type impellers with 6 flat blades was studied to determine the effects of impeller spacing on the specific production rate, the volume of high shear stress region around the impellers, and the agitation power requirements, and a comparison was made with the use of a single impeller. The following results were obtained. (i) The specific rate of xanthan gum production was dependant on the volume of the high shear region in the fermentor, even in the twin-impeller system. (ii) The greater was the space between the two impellers, the larger was the volume of the high shear region. (iii) The volume of the high shear region and the specific rate of xanthan gum production were greater with two impellers than with a single impeller, even if the agitation rate was adjusted to consume the same power. These results strongly indicate that the production of xanthan gum depends on the overall volume of the high shear region, which is enhanced by duplication of impellers, and that a twin-impeller system is also economically advantageous in terms of the power consumption required for agitation.