Retrofit of CD-6 (Smith) impeller in fermentation vessels

We extended prior studies on the influence of impeller type on fermentation performance to include a novel low-power-number, high-efficiency radial fl ow impeller, the CD-6, possessing six curved blades on a disk turbine. Dual impeller combinations of CD-6/CD-6, CD-6/Maxflo T, and CD-6/HE-3 were comp ared with Rushton/Rushton and Maxflo T/Maxflo T base cases. Qualitative com parisons of unaerated and aerated power draw in both water and glycerol wer e conducted. These suggested minimal power drops with aeration for dual CD- 6 impellers and hybrids containing the CD-6 impeller design. We also examin ed fermentation performance for Streptomyces and Glarea secondary metabolit e fermentations. A qualitative comparison of the data suggested that dual C D-6 impellers and hybrids containing the CD-6 impeller design resulted in r easonable power draws, improved mass transfer rates with airflow increases, and acceptable peak titers. These arrangements may warrant further study u nder a wider range of production conditions.