Development of a circulation direct sampling and monitoring system for O2 and CO2 concentrations in the gas–liquid phases of shake-flask systems during microbial cell culture

摘要

Monitoring the environmental factors during shake-flask culture of microorganisms can help to optimise the initialsteps of bioprocess development. Herein, we developed a circulation direct monitoring and sampling system(CDMSS) that can monitor the behaviour of CO2and O2in the gas–liquid phases and obtain a sample without interruptingthe shaking of the culture in Erlenmeyer flasks capped with breathable culture plugs. Shake-flask culturing ofEscherichia coli using this set-up indicated that a high concentration of CO2accumulated not only in the headspace(maximum ~100 mg/L) but also in the culture broth (maximum ~85 mg/L) during the logarithmic phase (4.5–9.0 h).By packing a CO2absorbent in the gas circulation unit of CDMSS, a specialised shake-flask culture was developed toremove CO2from the headspace. It was posited that removing CO2from the headspace would suppress increasesin the dissolved CO2concentration in the culture broth (maximum ~15 mg/L). Furthermore, the logarithmic growthphase (4.5–12.0 h) was extended, the U.O.D.580 and pH value increased, and acetic acid concentration was reduced,compared with the control. To our knowledge, this is the first report of a method aimed at improving the growth of E.coli cells without changing the composition of the medium, temperature, and shaking conditions.