Metabolic interactions within microbial communities are essential for the efficient degradation of complex organic compounds, and underpin natural phenomena driven by microorganisms, such as the recycling of carbon-, nitrogen-, and sulfur-containing molecules. These metabolic interactions ultimately determine the function, activity and stability of the community, and therefore their understanding would be essential to steer processes where microbial communities are involved. This is exploited in the design of microbial fuel cells (MFCs), bioelectrochemical devices that convert the chemical energy present in substrates into electrical energy through the metabolic activity of microorganisms, either single species or communities. In this work, we analyzed the evolution of the microbial community structure in a cascade of MFCs inoculated with an anaerobic microbial community and continuously fed with a complex medium. The analysis of the composition of the anodic communities revealed the establishment of different communities in the anodes of the hydraulically connected MFCs, with a decrease in the abundance of fermentative taxa and a concurrent increase in respiratory taxa along the cascade. The analysis of the metabolites in the anodic suspension showed a metabolic shift between the first and last MFC, confirming the segregation of the anodic communities. Those results suggest a metabolic interaction mechanism between the predominant fermentative bacteria at the first stages of the cascade and the anaerobic respiratory electrogenic population in the latter stages, which is reflected in the observed increase in power output. We show that our experimental system represents an ideal platform for optimization of processes where the degradation of complex substrates is involved, as well as a potential tool for the study of metabolic interactions in complex microbial communities.

This study investigates the microbial community composition, in the biofilms grown on two different support media in fixed biofilm reactors for aerobic wastewater treatment, using next generation sequencing (NGS) technology.

BACKGROUND This research is focused on the effect of temperature on the growth of active biofilms on polypropylene (PP) filter media in aerobic fixed biofilm reactors (FBR) for wastewater treatment. RESULTS High‐throughput sequencing was used to explore the composition and diversity of the microbial community of 14‐days‐old (starting phase) biofilms grown at 10, 20 and 30°C. Members of the classes Proteobacteria, Bacteroidetes, and Firmicutes were predominant in all the biofilm samples retrieved from PP‐FBRs. A total of 108 genera of bacteria were identified, with some of them present in all three reactors, including Trichococcus, Zoogloea, Aeromonas, Acidovorax, and Malikias, among others. Besides these shared populations, certain genera were abundantly found in individual biofilm samples, like Brevundimonas (17.1%), Chitinimonas (10.3%) and Roseateles (39.3%), at 10, 20, and 30°C, respectively. The metabolic capabilities of active microbial communities in PP‐FBRs were estimated by assessing the changes in different variables (BOD, DO, and pH) in the influent and effluent during operation. A noteworthy BOD removal (66.6%) was shown by PP‐FBRs operating at 30°C, compared with 20°C (28.3%) and 10°C (28.8%),consistent with the DO levels recorded in the effluents, highest at 30°C (70.5%), and decreasing with declining temperatures. Substantial wastewater treatment efficiencies were observed in the reactors at 30°C, attributable to the higher relative abundance and diversity of microbial biofilms. CONCLUSIONS The development of physiologically active biofilms in PP at all prevailing temperatures strongly suggests that the material is suitable to be employed in FBRs for wastewater treatment at different operational temperatures. © 2018 Society of Chemical Industry