Impact of the start-up process on the microbial communities in biocathodes for electrosynthesis

• Published in: Bioelectrochemistry (Amsterdam, Netherlands) Vol. 121; pp. 27 - 37
• Main Authors: Mateos, Raúl, Sotres, Ana, Alonso, Raúl M., Escapa, Adrián, Morán, Antonio
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-06-2018; Elsevier BV
• Subjects: Anaerobic digestion; Antimicrobial agents; Archaea; Bacteria; Biocathode; Bioelectrochemical systems; Biofilms; CO2 reduction; High throughput sequencing; Impact analysis; Inoculum; Microbial activity; Microbial electrosynthesis; Microorganisms; Mud; Next-generation sequencing; Rivers; Silver chloride; Start-up; Studies; Start-up; Microbial electrosynthesis; Biocathode; High throughput sequencing; CO2 reduction; Bioelectrochemical systems; CO reduction
• ISSN: 1567-5394; 1878-562X
• DOI: 10.1016/j.bioelechem.2018.01.002

This study seeks to understand how the bacterial communities that develop on biocathodes are influenced by inocula diversity and electrode potential during start-up. Two different inocula are used: one from a highly diverse environment (river mud) and the other from a low diverse milieu (anaerobic digestion). In addition, both inocula were subjected to two different polarising voltages: oxidative (+0.2 V vs. Ag/AgCl) and reductive (−0.8 V vs. Ag/AgCl).
Bacterial communities were analysed by means of high throughput sequencing. Possible syntrophic interactions and competitions between archaea and eubacteria were described together with a discussion of their potential role in product formation and current production. The results confirmed that reductive potentials lead to an inconsistent start-up procedure regardless of the inoculum used. However, imposing oxidative potentials help to quickly develop an electroactive biofilm ready to withstand reductive potentials (i.e. biocathodic operation). The microbial structure that finally developed on them was highly dependent on the raw community present in the inoculum. Using a non-specialised inoculum resulted in a highly specialised biofilm, which was accompanied by an improved performance in terms of consumed current and product generation. Interestingly, a much more specialised inoculum promoted a rediversification in the biofilm, with a lower general cell performance.
•Some electrogenic bacteria grown on anodes resist inversion to cathode.•A specialised biofilm improves bioelectrosynthesis performance.•Direct cathode start-up promotes H2 producing communities.•Slow biofilm evolution on direct cathodes is improved following oxidative start-up.