Exploring natural vs. synthetic minimal media to boost current generation with electrochemically-active marine bioanodes

Abstract

One of the greatest challenges in the development of Microbial Electrochemical Technologies (METs) is the achievement of efficient bioanodes, which not only can operate for long term but which can also be effectively and promptly regenerated for the sustained and successive production of electricity out of waste organics contained in aqueous streams. Simple strategies that facilitate the engineering of these systems are then pursued. Sustainable electricity generation was here achieved using electrochemically-active marine biofilms, which reached up to 6.8Am−2 in the best case. These biofilms showed deteriorated current generation after successive transfers in fresh natural media. The electricity-generation functionality of these marine biofilms was recuperated after their relocation into synthetic minimal media (i.e. up to about 3.8Am−2 after a decay down to about 1–2Am−2). Upon this relocation, the overall electrochemical mechanisms were preserved. Fluctuating nutrient stress intensified the effect of minimal media on current generation. The change from natural to minimal media showed an important impact on the selection and adaptation of microbial communities, characterized by CE-SSCP profiles; yet, robust bioanodes in which some microbial species were preserved were obtained in synthetic minimal media, these being sufficient for a reproducible electrochemical functionality. The systematic cycling between natural media and minimal media, regarded as periodic stress conditioning, is therefore proposed as a convenient strategy to boost current generation in robust electrochemically-active marine bioanodes.