Biocatalyst application of newly isolated Enterococcus species using microbial fuel cell (MFC) in wastewater treatment

Abstract

Potentially useful species, electrogenicbacteria are used as sustainable anode biocatalysts to produce green energy and in wastewater management. Here, this study aims to identify and characterize electrogenic bacteria from six wastewater and one soil samples. Double chambered microbial fuel cell (MFC) system was designed to develop anode biofilm. Bio-electrochemical property of electrogenic bacteria isolates (EBIs) were characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and observation of biofilm on the anode using scanning electron microscope (SEM). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and 16S rRNA gene sequencing was performed for identification. From a total of 72 biofilm forming EBIs, MALDI-TOF-MS identified 21 selected EBIS, including Aeromons, Bacillus, Citrobacter, Pseudomonas and Raoultella genus. This is the first study to characterize Enterococcus species from real brewery sludge waste, using the 16S rRNA sequencing. Evolutionary history analysis, GC content (53.72 %) and sequence alignment profiles infer this isolate as the first time report with biocatalyst potential. The evolutionary history for EBIs was found to be Enterococcus species and designated as E. faecium strain BSE14. The isolate showed biologically stable for long term operation of MFC (0.46 ± 0.038 V) with chemical oxygen demand (COD) (95.4 ± 0.82 %), biological oxygen demand (BOD) (53.3 ± 0.531 %), total nitrogen (TN) (73.1 ± 0.674) and total phosphorus (TP) (44.8 ± 0.281). Voltage generation among unknown mixed and pure EBIs exhibited significant variation (df=6, p < 0.05 and df=7, p < 0.05, respectively). Finally, the EBIs contribute as a potential biocatalyst in energy generation and wastewater treatment applications.