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

Tobias Jung,Max Hackbarth,Johannes Gescher,Harald Horn

doi:10.3390/microorganisms9010077

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.

Highlights

IntroductionProcesses that are conducted by autotrophic microorganisms interacting with cathodes are subsumed under the term microbial electrosynthesis [1,2,3]
The adaptation of Kyrpidia spormannii EA-1 to electroautotrophic growth conditions was evident in an approximately fourfold higher biofilm accumulation rate, a faster complete cathode coverage and the formation of a more homogeneous biofilm. These improvements are key for the envisioned industrial application of the strain as the desired end product PHB will be purified from harvested biomass
We will have to define in future studies the trigger for PHB production in K. spormannii but could already provide evidence that cathodic growth itself can trigger to some extend the production of this biopolymer

Summary

Introduction

Processes that are conducted by autotrophic microorganisms interacting with cathodes are subsumed under the term microbial electrosynthesis [1,2,3]. In theory this technology could provide a way for the sustainable storage of renewable energies in the form of organic carbon molecules. The number of applicable electroautotrophic biocatalysts is so far rather small and most of them belong to the group of methanogens or acetogens [4,5] These organisms are often strictly anaerobic and genetic engineering is either not possible or very laborious. Some progress has been made concerning different side-products like butyrate, isopropanol, and acetone produced by homoacetogens like Sporomusa sp

Methods

Discussion

Conclusion