Microbial ElectroSynthesis biofilm communities Raw sequence reads
Biofilm-based microbial electrosynthesis (MES) is a promising technology that converts CO2 into industrially relevant organic compounds using renewable energy sources. The highest performing MES systems are biofilm-driven and rely on mixed microbial communities. However, challenges remain, including the long colonisation time of the biocathode, and the difficulty of controlling the product profile. Understanding the key microbial components responsible for desired metabolic functions has been limited. In this study, we conducted an in-depth characterisation of three high-performing mixed microbial MES communities using metagenomics, -proteomics and advanced metabolic network reconstruction. Our findings identified Eubacterium limosum, Sporomusa sphaeroides and Clostridium aromativorans as key contributors to the production of acetate, butyrate and caproate via the Wood-Ljungdahl pathway and the reverse beta-oxidation pathway. Notably, higher production of butyrate and caproate production was linked to the higher abundance of C. aromativorans, an organism only recently discovered and never reported in gas-fermenting systems before. The recovered genome of C. aromativorans consisted of one circular fragment and provides a more complete and contiguous representation of the genome than the current reference. We found genes encoding the enzymes for lactate and ethanol production from acetyl-CoA in the metagenomes, and evidence of protein expression of lactate production steps in C. aromativorans. This study provides valuable insights into the key microbial players driving product formation in biofilm-based MES, advancing our understanding of microbial community dynamics in CO2 conversion, bringing the technology closer to industrial application.