A forced aeration system for microbial culture of multiple shaken vessels suppresses volatilization.

Shake-flask culture, an aerobic submerged culture, has been used in various applications involving cell cultivation. However, it is not designed for forced aeration. Hence, this study aimed to develop a small-scale submerged shaking culture system enabling forced aeration into the medium. A forced aeration control system for multiple vessels allows shaking, suppresses volatilization, and is attachable externally to existing shaking tables. Using a specially developed plug, medium volatilization was reduced to less than 10%, even after 45 h of continuous aeration (~ 60 mL/min of dry air) in a 50 mL working volume. Escherichia coli IFO3301 cultivation with aeration was completed within a shorter period than that without aeration, with a 35% reduction in the time-to-reach maximum bacterial concentration (26.5 g-dry cell/L) and a 1.25-fold increase in maximum concentration. The maximum bacterial concentration achieved with aeration was identical to that obtained using the Erlenmeyer flask, with a 65% reduction in the time required to reach it.

Erratum to: Development of a circulation direct sampling and monitoring system for O2 and CO2 concentrations in the gas-liquid phases of shake­flask systems during microbial cell culture.

Following publication of the original article (Takahashi et al. 2017), the authors reported that there was a mistake in the legend of Figure 2.

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.

Monitoring the environmental factors during shake-flask culture of microorganisms can help to optimise the initial steps of bioprocess development. Herein, we developed a circulation direct monitoring and sampling system (CDMSS) that can monitor the behaviour of CO2 and O2 in the gas-liquid phases and obtain a sample without interrupting the shaking of the culture in Erlenmeyer flasks capped with breathable culture plugs. Shake-flask culturing of Escherichia coli using this set-up indicated that a high concentration of CO2 accumulated 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 CO2 absorbent in the gas circulation unit of CDMSS, a specialised shake-flask culture was developed to remove CO2 from the headspace. It was posited that removing CO2 from the headspace would suppress increases in the dissolved CO2 concentration in the culture broth (maximum ~15 mg/L). Furthermore, the logarithmic growth phase (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.