Lactate based caproate production with Clostridium drakei and process control of Acetobacterium woodii via lactate dependent in situ electrolysis

Jan Herzog; Alexander Mook; Tyll Utesch; Frank R Bengelsdorf; An-Ping Zeng

doi:10.3389/fbioe.2023.1212044

Lactate based caproate production with Clostridium drakei and process control of Acetobacterium woodii via lactate dependent in situ electrolysis

Front Bioeng Biotechnol. 2023 Jun 23:11:1212044. doi: 10.3389/fbioe.2023.1212044. eCollection 2023.

Authors

Jan Herzog¹, Alexander Mook², Tyll Utesch¹, Frank R Bengelsdorf², An-Ping Zeng^{1

3}

Affiliations

¹ Institute of Bioprocess and Biosystems Engineering, Hamburg University of Technology, Hamburg, Germany.
² Institute of Molecular Biology and Biotechnology of Prokaryotes, Ulm University, Ulm, Germany.
³ Synthetic Biology and Bioengineering Lab, School of Science, Westlake University, Hangzhou, China.

Abstract

Syngas fermentation processes with acetogens represent a promising process for the reduction of CO₂ emissions alongside bulk chemical production. However, to fully realize this potential the thermodynamic limits of acetogens need to be considered when designing a fermentation process. An adjustable supply of H₂ as electron donor plays a key role in autotrophic product formation. In this study an anaerobic laboratory scale continuously stirred tank reactor was equipped with an All-in-One electrode allowing for in-situ H₂ generation via electrolysis. Furthermore, this system was coupled to online lactate measurements to control the co-culture of a recombinant lactate-producing Acetobacterium woodii strain and a lactate-consuming Clostridium drakei strain to produce caproate. When C. drakei was grown in batch cultivations with lactate as substrate, 1.6 g·L^-1 caproate were produced. Furthermore, lactate production of the A. woodii mutant strain could manually be stopped and reinitiated by controlling the electrolysis. Applying this automated process control, lactate production of the A. woodii mutant strain could be halted to achieve a steady lactate concentration. In a co-culture experiment with the A. woodii mutant strain and the C. drakei strain, the automated process control was able to dynamically react to changing lactate concentrations and adjust H₂ formation respectively. This study confirms the potential of C. drakei as medium chain fatty acid producer in a lactate-mediated, autotrophic co-cultivation with an engineered A. woodii strain. Moreover, the monitoring and control strategy presented in this study reinforces the case for autotrophically produced lactate as a transfer metabolite in defined co-cultivations for value-added chemical production.

Keywords: Acetobacterium woodii; Clostridium drakei; bioelectrochemical system; caproate; carbon fixation; in situ electrolysis; lactate; process control.

Grants and funding

This research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) as part of the priority program InterZell (SPP 2170). DFG requests the following statement: “gefördert durch die Deutsche Forschungsgemeinschaft. (DFG—427864786)”. Publishing fees supported by Funding Programme Open Access Publishing of Hamburg University of Technology (TUHH).