Famílies bacterianes comunes en els biofilms catòdics de quatre diferents sistemes bioelectroquímics

Abstract

Bioelectrochemical systems (BES) are a wide range of unique reactors. They are able to utilize the reduction-oxidation metabolism of microorganisms for the synthesis or degradation of compounds at an experimental, pilot or industrial scales. In that way BESs hold as many different processes as bioremediation, desalination, sustainable energy production, organic synthesis or biofuel synthesis among others. BES’s potential of action has awaken, especially in the last decade, much interest among the scientific community specialized in the fields mentioned above. Recently, there has been a boom in the varieties of BES capable of synthesizing highvalue compounds in a process named Microbial Electrosynthesis (MES). Inside MES reactors, biofilms catalysing the reduction of the produced compounds are an essential requisite. This reduction takes place on the cathode. In MES specifically this cathode is biological so it is referred as biocathode. Biofilms inhabiting the biocathodes are key to the efficiency and productivity of MES systems. Ideally, these bacterial populations should be able to transfer the electrons coming from the cathode directly to the compounds being produced, hence, the biofilms should manifest electrotrophic activity. The actual situation is that the bacterial ecosystem on the cathode is unstable and susceptible to changes in its environment, and in addition not all species inhabiting this cathode are electrotrophs. Therefore, these changes in the biofilm composition can dramatically damage the efficiency of the system. In search of solutions to this problem, the present work intends to find potentially electrotrophic microorganisms with high adaptability to different cathode treatments, in order to determine which bacteria are more resistant to changes in the cathode environment. Sequencing data of the 16S rRNA gene have been extracted from four different articles. Each article applied a different treatment on the biocathode: active energy harvesting, addition of ferric iron, reduction of p-nitrophenol and dechlorination of tetrachlorethylene. After the processing and the taxonomic analysis with Rstudio, three bacterial families have been determined (Pseudomonedaceae, Porphyromonadaceae and Microbacteriaceae), all of them abundant and present in at least one sample of the four experiments, which denotes their adaptability to different cathode environments. Moreover, there are known species such as P. aeruginosa in the Pseudomonedaceae family that manifest electrotrophic activity, which makes them good candidates to be introduced into MES systems. However, it has not been possible to determine more candidates because of the depth of the taxonomic analysis carried out. In addition, complementary studies are needed to confirm the electrotrophy of the bacteria within the two remaining selected families (Porphyromonadaceae and Microbacteriaceae)