Integrating Electrochemistry Into Bioreactors: Effect of the Upgrade Kit on Mass Transfer, Mixing Time and Sterilizability

Abstract

Microbial electrosynthesis (MES) is an exciting and dynamic research area at the nexus of microbiology and electrochemistry. To pave the way of MES to application, reactor infrastructure is needed that meets the requirements of both biological, and electrochemical engineering. Recently we presented an upgrade kit facilitating turning commercial bioreactors based on batch stirred tank reactors (BSTR) into electrobioreactors that can be scaled and benchmarked. The upgrade kit comprises electrodes and an inlay with membrane, separating the BSTR chamber into anode and cathode compartments. The obtained electrobioreactors enable seizing the existing infrastructure for monitoring and controlling the bioprocess while being complemented by electrochemical control and measurement. Here the effect of the upgrade kit on mass transfer was investigated in a 1 L electrobioreactor using experimental approaches and modeling of fluid dynamics. It is shown that the fluid dynamics in the BSTR are changed dramatically, impacting the integral parameters volumetric mass transfer coefficient, k L a, and mixing time, θ. The influences of the inlay chamber and electrodes as well as stirrer position and geometry are described. Additionally, the sterilizability of the inlay, housing the polymer-based membrane of the electrobioreactor, which is needed for operating two-chamber MES based on microbial pure cultures, are demonstrated.

Response‐Surface‐Optimized and Scaled‐Up Microbial Electrosynthesis of Chiral Alcohols

“…For H‐cell reactors, scale‐up is limited, but for transfer of MES to industrial production processes a scalable reaction system is necessary that fits into a biotechnological process environment. To this end, we recently introduced an upgrade kit to turn conventional bioreactors into electrobioreactors, which enable standard process engineering and can be scaled systematically . Utilizing the 1 L electrobioreactors as a platform, combined with the results and information derived from the DoE optimization, MES of ( R )‐1‐phenylethanol was performed.…”

“…Experiments were conducted in 1 L electrobioreactors based on bioreactor vessels (Infors Multifors, Infors AG, Bottmingen, Switzerland) equipped with the upgrade kit (Figure S3) . The upgrade kit comprises a custom‐made lid and an inlay, which together create two chambers inside the glass bioreactor vessel, all parts made of polyetheretherketone (PEEK).…”

Bioelectrochemical engineering analysis of formate-mediated microbial electrosynthesis

“…In our model, we assume a value of 300 hr -1 , which corresponds to a power demand of 4000 W m -3 with a superficial gas velocity of ~0.11 m s -1 . We note that the actual value in a given reactor is highly dependent on the gas feeding mechanism, [40] the reactor geometry and gas contacting strategies, [41] and components integrated into bioreactors, [27] so any model of experimental results must rely on carefully measured values before valid comparisons can be made.…”

“…[3,5] Formate/ic acid stands out as an especially promising redox mediator because it is readily and specifically produced from CO2 [18][19][20] and multiple natural and engineered formatotrophic growth mechanisms exist in workhorse bacteria. [21][22][23][24][25] Initial scale-up, [26] component integration, [27] and media optimization [28] studies have been performed for MES systems, demonstrating the need for careful attention to process parameters including the gas/liquid mass transfer coefficient (kLa). However, progress towards scaled, optimized systems has been limited, in part due to the complex nature of coupled bioelectrochemical systems.…”

A Comprehensive Modeling Analysis of Formate‐Mediated Microbial Electrosynthesis**

“…Initial scaleup, [26] component integration, [27] and media optimization [28] studies have been performed for MES systems, demonstrating the need for careful attention to process parameters including the gas/liquid mass transfer coefficient (k L a). However, progress towards scaled, optimized systems has been limited, in part due to the complex nature of coupled bio‐electrochemical systems.…”