“Once a fermentation has started it can only get worse, not better.” The quote was attributed to DJ Hockenhull, who used fermentation to produce penicillin in the 1940’s. Today, bootcamp was all about fermentation. To start off we added glucose and ampicillin to prepare the media for fermentation with E. coli. The strain we are using is transformed with a plasmid containing the lac operon and the gene for green fluorescent protein (GFP). One difference from the lab I teach on GFP is that the inducer is IPTG, not arabinose, but otherwise everything is very similar.
Bioreactor bubbles with 20 liters of bacteria.
We inoculated the media with our bacteria through the bioreactor’s feed valve. At that point the fermentation was officially in the lag phase. It is typical to use 3-10% of the final volume for your inoculation volume. We were closer to 10% so we would quickly move out of the lag phase and into the log growth phase. The bioreactor is equipped to control temperature, agitation speed, dissolved oxygen, pH, pressure, and airflow. We could also have added an anti-foaming agent into one of the ports but it was not necessary for this process. In addition, we sampled our batch frequently through the sample valve to monitor the progress of the fermentation. We measured OD 600 using a spectrophotometer and glucose concentration using a bioanalyzer (YSI 2700 Select). The whole run took about six hours and then we harvested our cells and cleaned the bioreactor. All that was needed after that was to wash the cells to prepare them for the next day: cell disruption and centrifugation.
Glowing green fluorescent protein.
If there was one pull quote from today’s class, it would be that “the bioreactor is the queen” of the fermentation process. Everything in upstream processing should ultimately optimize the use of the bioreactor for fermentation — in other words, everything should serve the queen. If the queen isn’t happy, no one should be happy because it means that money is being lost. Oh, and don’t let the smell of fermentation put you off. That’s the smell of money!
