Parallel use of shake flask and microtiter plate online measuring devices (RAMOS and BioLector) reduces the number of experiments in laboratory-scale stirred tank bioreactors

TLDR

Small‑scale bioprocess studies are typically performed in a black‑box manner, measuring only final product concentrations and lacking online monitoring of key parameters, which forces detailed investigations to rely on large, costly stirred‑tank bioreactors that are impractical for parallel experiments. The study proposes a new experimental approach that uses parallel small‑scale culture systems equipped with online monitoring devices (RAMOS and BioLector) to obtain dense quantitative process information. The same mastermix was distributed to a RAMOS device, a 48‑well microtiter plate for the BioLector, and separate shake flasks or plates for offline sampling, enabling simultaneous monitoring of respiration and fluorescence in parallel. The combined RAMOS and BioLector data complemented each other across multiple microorganisms and conditions, enabling comprehensive quantitative insights and substantially reducing the number of required experiments in laboratory‑scale stirred‑tank bioreactors, thereby accelerating process development.

Abstract

Conventional experiments in small scale are often performed in a 'Black Box' fashion, analyzing only the product concentration in the final sample. Online monitoring of relevant process characteristics and parameters such as substrate limitation, product inhibition and oxygen supply is lacking. Therefore, fully equipped laboratory-scale stirred tank bioreactors are hitherto required for detailed studies of new microbial systems. However, they are too spacious, laborious and expensive to be operated in larger number in parallel. Thus, the aim of this study is to present a new experimental approach to obtain dense quantitative process information by parallel use of two small-scale culture systems with online monitoring capabilities: Respiration Activity MOnitoring System (RAMOS) and the BioLector device. The same 'mastermix' (medium plus microorganisms) was distributed to the different small-scale culture systems: 1) RAMOS device; 2) 48-well microtiter plate for BioLector device; and 3) separate shake flasks or microtiter plates for offline sampling. By adjusting the same maximum oxygen transfer capacity (OTRmax), the results from the RAMOS and BioLector online monitoring systems supplemented each other very well for all studied microbial systems (E. coli, G. oxydans, K. lactis) and culture conditions (oxygen limitation, diauxic growth, auto-induction, buffer effects). The parallel use of RAMOS and BioLector devices is a suitable and fast approach to gain comprehensive quantitative data about growth and production behavior of the evaluated microorganisms. These acquired data largely reduce the necessary number of experiments in laboratory-scale stirred tank bioreactors for basic process development. Thus, much more quantitative information is obtained in parallel in shorter time.