Real-time monitoring method of microbial growth using a simple pressure-based respiration detection system

Abstract

Dry cell weight (DCW) and optical density (OD) measurement methods provide useful data for assessing microbial growth. However, their sampling process is labor-intensive and time-consuming. Therefore, we aimed to evaluate a method for measuring microbial growth through continuous CO2 measurement under aerobic conditions using a pressure-based respiration detection system, which is traditionally used in anaerobic environments and applies measurement of reduced pressure by capturing CO2 with KOH. The pressure reduction rate, OD, and DCW values were compared during Ralstonia eutropha H16 culture, which revealed a correlation of R2 of 0.99 between the pressure reduction and DCW and a change of DCW (g/L) per pressure (1 mbar) of -0.02 g/L. It showed theoretical limit of detection at 14.67 mbar corresponding to 0.0428 g/L of DCW and theoretical limit of quantification at 48.9 mbar as lower limits. When the pressure-based method was applied to compare carbon source utilization and growth of different strains, such as E. coli sp., Pseudomonas sp., Burkholderia sp., and Bacillus sp., it showed a high correlation with DCW. Overall, these results demonstrate that the pressure-based respiration detection system is a reliable tool for microbial growth monitoring and offers significant advantages by providing real-time data with less labor.