Abstract
An Amycolatopsis fastidiosa culture, which produces the nocathiacin class of antibacterial compounds, was scaled up to the 15,000 L working volume. Lower volume pilot fermentations (600, 900, and 1,500 L scale) were conducted to determine process feasibility at the 15,000 L scale. The effects of inoculum volume, impeller tip speed, volumetric gas flow rate, superficial gas velocity, backpressure, and sterilization heat stress were examined to determine optimal scaleβup operating conditions. Inoculum volume (6 vs. 2 vol %) and medium sterilization (R~o~ of 68 vs. 92 min^β1^) had no effect on productivity or titer, and higher impeller tip speeds (2.1 vs. 2.9 m/s) had a slight effect (20% decrease). In contrast, higher backpressure, incorporating increased head pressure at the 15,000 L scale (1.2 vs. 0.7 kg/cm^2^) and low gas flow rates (0.25 vs. 0.8 vvm), appeared to be problematic (40β50% decrease). High offβgas CO~2~ levels were likely reasons for observed lower productivity. Consequently, air flow rate for this 25βfold scaleβup (600β15,000 L) was controlled to match offβgas CO~2~ profiles of acceptable smaller scale batches to maintain levels below 0.5%. The 15,000 Lβscale fermentation achieved an expected nocathiacin I titer of 310 mg/L after 7 days. Other onβline data (i.e., pH, oxygen uptake rate, and CO~2~ evolution rate) and offβline data (i.e., analog production, glucose utilization, ammonium production, and dry cell weight) at the 15,000 L scale also tracked similarly to the smaller scale, demonstrating successful fermentation scaleβup. Β© 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009