Improving the Cathodic Biofilm Growth Capabilities of Kyrpidia spormannii EA-1 by Undirected Mutagenesis

Abstract

The biotechnological usage of carbon dioxide has become a relevant aim for future processes. Microbial electrosynthesis is a rather new technique to energize biological CO2 fixation with the advantage to establish a continuous process based on a cathodic biofilm that is supplied with renewable electrical energy as electron and energy source. In this study, the recently characterized cathodic biofilm forming microorganism Kyrpidia spormannii strain EA-1 was used in an adaptive laboratory evolution experiment to enhance its cathodic biofilm growth capabilities. At the end of the experiment, the adapted cathodic population exhibited an up to fourfold higher biofilm accumulation rate, as well as faster substratum coverage and a more uniform biofilm morphology compared to the progenitor strain. Genomic variant analysis revealed a genomically heterogeneous population with genetic variations occurring to various extends throughout the community. Via the conducted analysis we identified possible targets for future genetic engineering with the aim to further optimize cathodic growth. Moreover, the results assist in elucidating the underlying processes that enable cathodic biofilm formation.

A scalable, Rotating Disc Bioelectrochemical Reactor (RDBER) suitable for the cultivation of both cathodic and anodic biofilms

“…Previously it was shown that at the initially uncovered cathode a part of the dissolved oxygen might be abiotically reduced into reactive oxygen species (ROS) (Hackbarth et al, 2020; Jung et al, 2020). As the initial cell number decreases, the cumulative ROS-detoxification capacity of the cells also decreases, possibly preventing a sufficient initial cathode coverage that serves as an insulator to minimize abiotic ROS formation.…”

Sprayable biofilm – Agarose hydrogels as 3D matrix for enhanced productivity in bioelectrochemical systems

“…Furthermore, the utilization of this technique is not only limited to anodic processes but can also improve cathodic processes used for bioelectrosynthesis as well as biofilm-based gas fermentation. Consequently, following experiments will aim for the development of spray biofilms containing methanogens, acetogens or knallgas bacteria as biocatalysts and their application on cathodes in bioelectrochemical systems [ [36] , [37] , [38] ].…”

Electron transfer of extremophiles in bioelectrochemical systems

“…As the most likely mechanism might be the consumption of hydrogen which is produced even at rather high potentials at pH 3, selective evolution experiments also suggested that the ability of the organism to grow also with molecular sulfur as electron donor might have an impact. Jung and colleagues grew the organism for several transfers on cathodes and observed a fourfold increase of the biofilm accumulation rate (Jung et al 2021 ). Bioinformatic analysis revealed that the adapted cells carried three loud mutations compared to the progenitor strain.…”

“…Still, as a genetic system is not available for the organism thus far, direct proof for a potential influence of the electron transport chain from sulfur in electron import from cathodes is still missing. Nevertheless, that the production of reactive oxygen species on the electrodes also hampers the activity of K. spormannii is rather undoubtedly expressed by the mutation within the perR regulator gene which will likely lead to constitutive production of proteins dealing with oxidative stress (Jung et al 2021 ). Moreover, Pillot et al recently modified graphite cathodes by means of electrodeposition with different catalytically active metals such as platinum that enhance abiotic hydrogen evolution.…”