Plug flow versus stirred tank reactor flow characteristics in two‐compartment scale‐down bioreactor: Setup‐specific influence on the metabolic phenotype and bioprocess performance of Corynebacterium glutamicum

Abstract

In the last two decades, scale‐down studies based on compartmented reactor setups became the standard procedure to mimic inhomogeneous cultivation conditions. In the academic field and with application to industrial‐scale, two basic scale‐down bioreactor configurations both showing a stirred tank reactor (STR) as main compartment predominate this research field. The connection to a plug flow reactor (PFR) generates oscillatory gradients with a distinct residence time of the culture, while the STR provides a broad residence time distribution leading to more heterogeneous oscillations. The influence of these opposed hydrodynamic profiles for their applicability for scale‐down bioreactor setups as well as their specific influence on the metabolic phenotype of l‐lysine producing Corynebacterium glutamicum DM1800 strain was investigated. Batch cultivations under oscillatory oxygen deprivation and substrate excess were carried out in STR–PFR and STR–STR scale‐down devices. In both setups, the induced inhomogeneity resulted in a reduction of growth rate and increased the l‐lactate and l‐glutamate by‐product formation, while biomass and product yields stayed nearly constant. Apart from differing side‐product levels, very similar results were observed when comparing the metabolic phenotype and bioprocess performance of STR–PFR and STR–STR configuration, although opposed back mixing profiles were present.