Analysis and effect of conventional flasks in shaking culture of Escherichia coli.

The circulation direct monitoring and sampling system (CDMSS) is used as a monitoring device for CO and O concentrations of bypass type in shake-culture flask. The CDMSS could measure ka, an index for evaluating the performance of aerobic culture incubators, and k, an indicator of the degree of CO ventilation in the flask gas phase. We observed that cylindrical flasks provided a different culture environment, yielded a much higher k than the Erlenmeyer and Sakaguchi flasks, and yielded ka equivalent to that by Erlenmeyer flask by setting the ring-type baffle appropriately. Baffled cylindrical flask used for Escherichia coli K12 IFO3301 shake culture maintained lower CO concentrations in the headspace than conventional flasks; therefore, CO accumulation in the culture broth could be suppressed. Cell growth in baffled cylindrical flask (with ka equivalent to that of the Erlenmeyer flask) was about 1.3 and 1.4 times that in the Erlenmeyer and Sakaguchi flasks, respectively. This study focused on the batch culture at the flask scale and designed the headspace environment with low CO accumulation. Therefore, we conclude that redesign of flasks based on ka and k may contribute to a wide range of fields employing microorganism culture.