Actinomycetes Scale-Up for the Production of the Antibacterial,Nocathiacin

摘要

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 )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.