Actinomycetes scale-up for the production of the antibacterial, nocathiacin.
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 scale-up operating conditions. Inoculum volume (6 vs. 2 vol %) and medium sterilization (R(o) of 68 vs. 92 min(-1)) 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 (40-50% decrease). High off-gas CO2 levels were likely reasons for observed lower productivity. Consequently, air flow rate for this 25-fold scale-up (600-15,000 L) was controlled to match off-gas CO2 profiles of acceptable smaller scale batches to maintain levels below 0.5%. The 15,000 L-scale fermentation achieved an expected nocathiacin I titer of 310 mg/L after 7 days. Other on-line data (i.e., pH, oxygen uptake rate, and CO2 evolution rate) and off-line 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 scale-up.
Junker
Beth
B
Fermentation Development and Operations, Bioprocess Research and Development, Merck Research Laboratories, Rahway, NJ 07065, USA. beth_junker@merck.com
Walker
Andre
A
Hesse
Michelle
M
Lester
Mike
M
Christensen
Jens
J
Connors
Neal
N
D039903:Actinobacteria / Q000254:growth & development* / Q000378:metabolism*; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D005285:Fermentation; D007218:Industrial Microbiology / Q000379:methods*; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D010455:Peptides / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C463319:nocathiacin I