Paving the way for bioelectrotechnology: Integrating electrochemistry into bioreactors

Abstract

The reactor systems used for microbial electrosynthesis, i.e. bioelectrochemical systems for achieving bioproduction so far reported in literature are relatively small in scale and highly diverse in their architecture and modes of operation. The often diverging requirements of the electrochemical and the biological processes and the interdisciplinarity of the field make the engineering of these systems a special challenge. This has led to multiple, differently optimized approaches of reactor vessels, designs and operating conditions making standardization and normalization or even a systematic engineering almost impossible. Overcoming this lack of standardization, scalability and knowledge‐driven engineering is the driving force for this work introducing an upgrade kit for bioreactors transforming these reversibly to bioelectroreactors. The prototypes of the bioreactor upgrade kit were integrated with commercial bioreactor (fermentor) systems and performances compared to a classic, small‐scale bioelectrochemical glass cell system. The use of the upgrade kit allowed interfacing with the existing infrastructure of the conventional bioreactors for growing electroactive microorganisms in pure culture conditions, with the added electrochemical control and further process monitoring. The results of growing Shewanella oneidensis MR‐1 clearly show that these systems can be used to control, monitor, and scale microbial bioelectrochemical processes, providing better resolution of the data for the tested experimental conditions.

Characterization of a membrane‐separated and a membrane‐less electrobioreactor for bioelectrochemical syntheses

“…Higher internal resistances were not responsible for the difference between the separated and non‐separated electrobioreactor, as the electrochemical characterization showed only low electrochemical losses due to the membrane (Figure ). The highest current densities in electrobioreactors with S. oneidensis previously reported were 55 μA/cm 2 (Rosa et al, ). Cells were first cultivated aerobically and gassing with nitrogen started after 24 hr of cultivation, which may have led to rather small current efficiencies due to oxygen in the system in the reported electrobioreactor.…”

“…Current densities reported for unbalanced fermentations are in the range of 55 μA/cm 2 for a S. oneidensis based microbial fuel cell in a modified bioreactor (Rosa et al, ). For cathodic processes where current is consumed and acetate or butyrate is produced using pure or mixed cultures, current densities range from several μA/cm 2 up to 3.7 mA/cm 2 (de Campos‐Rodrigues & Rosenbaum, ; Ganigué, Puig, Batlle‐Vilanova, Dolors Balaguer, & Colprim, ; Giddings, Nevin, Woodward, Lovley, & Butler, ; Jourdin et al, ).…”

A novel All‐in‐One electrolysis electrode and bioreactor enable better study of electrochemical effects and electricity‐aided bioprocesses

“…c H2assumed = (c ethanol + c acetate + 2 c butyrate + 2 c butanol ) (11) c H2electrode was calculated from the operation parameters and time of the electrolysis electrode according to experimental characterization (see Results below).…”

Same but different–Scale up and numbering up in electrobiotechnology and photobiotechnology

“…A suitable BES design for scale up might be a stirred tank reactor with an “upgrade kit” to allow bioelectrochemical processes within the reactor. This has been shown for the production of para‐hydroxybenzoate in a single chamber reactor with up to 2.5 L working volume , for current production in a single chamber system with 2.5 L , for current production in a two chamber electro‐stirred tank reactor with up to two liter and for the production of organic acids in a two chamber reactor with up to 2 l . It has also been shown that CFD (Computational Fluid Dynamics) studies for the “upgraded” bioreactors reveal the mixing conditions within the reactor, so it might be possible to use the knowledge gained from CFD simulations for the scale up of the systems .…”