20-L Scale-Up Fermentation and Biotransformation of Gaseous Propane to Propanol

摘要

Two E. coli BW28357 hosts (one with pyk A mutation and one without) harboring the same PMO plasmid were used in a 20-L scale-up fermentation process to compare the effect of pyk A mutation in propane to propanol biotransformation yield. Also, one additional 20-L fermentation run with E. coli BW28357 without pyk A mutation was conducted without IPTG induction to serve as a baseline in terms of cell yield and dissolved oxygen profile. The same media and operating conditions were used for each three runs. For the two IPTG induced runs, the same timing (around 4.5 hr into fermentation w/optical density of approximately 0.8) was used. No significant differences in dissolved oxygen profiles and final optical density in each fermentation run (approximately 10) were observed. The levels of expressed PM-450 were significant and similar at approximately 30% of the total cellular proteins. However, low propanol yields of approximately 2 mM for both fermentation runs, which represented only 0.0017% of the total gaseous propane fed during the course of each fermentation run, indicated a low catalytic turnover rate of the expressed P450 BM-3 enzymes.