Abstract
SummaryThe formation of combined electrogenic/electrotrophic biofilms from marine sediments for the development of microbial energy storage systems was studied. Sediment samples from the German coasts of the Baltic and the North Sea were used as inocula for biofilm formation. Anodic biofilm cultivation was applied for a fast and reproducible biofilm formation. North-Sea- and Baltic-Sea-derived biofilms yielded comparable anodic current densities of about 7.2 A m−2. The anodic cultivation was followed by a potential reversal regime, transitioning the electrode potential from 0.2 V to −0.8 V every 2 h to switch between anodic and cathodic conditions. The charge-discharge behavior was studied, revealing an electrochemical conversion of biogenic elemental sulfur as major charge-discharge mechanism. The microbial sequencing revealed strong differences between North- and Baltic-Sea-derived biofilms; however with a large number of known sulfur-converting and electrochemically active bacteria in both biofilms.
Highlights
In the search for sustainable methods for electricity generation and CO2 reduction, microbial electrochemical technologies (METs) have attracted significant attention
Biocatalysts in anodic compartments are known for catalyzing organic degradation and electricity generation, while reductive reactions such as CO2 reduction can be catalyzed by cathodic biocatalysts
Regardless of the platforms, the basis for the above technologies lies in the interaction of microorganisms and electrodes, known as extracellular electron transfer (EET) (Ter Heijne et al, 2020)
Summary
In the search for sustainable methods for electricity generation and CO2 reduction, microbial electrochemical technologies (METs) have attracted significant attention. A single electrochemically active biofilm can switch between energy storage and energy release, which advances the bioelectrochemical systems’ applications This application can be in particular applied for locations with harsh conditions of high salinity or alkalinity for instance, such as lakes and marine sediments (Yates et al, 2017). Despite the recent studies on microbial EET, information on the mechanisms involved in bidirectional EET is still scarce – owing to the limited knowledge on the identity of the microorganisms with bidirectional EET capability. This is more particular for inward EET, as the interaction mechanisms involved between cathodes and microorganisms have not been fully understood yet (Jiang et al, 2019). Further studies are required to identify more microorganisms able to perform as both anodic and cathodic biocatalysts and to clarify the mechanisms involved
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