The enhancement of microbial fuel cell performance by anodic bacterial community adaptation and cathodic mixed nickel-copper oxides on a graphene electrocatalyst.

BACKGROUND: Although microbial fuel cells (MFCs) represent a promising technology for capturing renewable energy from wastewater, their scaling-up is significantly limited by a slow-rate cathodic oxygen reduction reaction (ORR) and the development of a resilient anodic microbial community. In this study, mixed transition metal oxides of nickel and copper (Ni and Cu), supported on a graphene (G) (NiO-CuO/G) electrocatalyst, were synthesized and tested as a cost-effective cathode for ORR in MFCs. Electrochemical measurements of electrocatalyst were conducted using a rotating disk electrode (RDE) and linear sweep voltammetry (LSV) in a neutral electrolyte, and compared with a benchmark Pt/C catalyst. Furthermore, the long-term performance of the as-synthesized electrocatalyst was evaluated in a single-chamber MFC by measuring organic matter removal and polarization behavior. The successful enrichment of electroactive biofilm was also monitored using transmission electron microscopy and the Vitek2 compact system technique. RESULTS: When compared with the benchmark platinum cathode, the NiO-CuO/G electrocatalyst exhibited high selectivity toward ORR. The rotating disk electrode (RDE) experiments reveal that ORR proceeds via a 4-electron ORR mechanism. Furthermore, the NiO-CuO/G electrocatalyst also exhibited a high power density of 21.25 mW m-2 in an air-cathode MFC, which was slightly lower than that of Pt/C-based MFC (i.e., 50.4 mW m-2). Biochemical characterization of the most abundant bacteria on anodic biofilms identified four genera (i.e., Escherichia coli, Shewanella putrefaciens, Bacillus cereus, and Bacillus Thuringiensis/mycoides) that belonged to Gammaproteobacteria, and Firmicutesphyla. CONCLUSIONS: This study demonstrates that the NiO-CuO/G cathode had an enhanced electrocatalytic activity toward ORR in a pH-neutral solution. This novel mixed transition metal oxide electrocatalyst could replace expensive Pt-based catalysts for MFC applications.

Microbial diversity structure in acetate single chamber microbial fuel cell for electricity generation.

This study investigates the performance of acetate feed membrane less single chamber microbial fuel cell and physical characterization of the bio film present on the anode surface using Scanning Electron Microscope (SEM) and 16S rRNA analyzer. The performance has been investigated using Teflon treated carbon paper with 0.3 mg/cm2 Pt/C loaded as a cathode and carbon paper as an anode. The maximum open circuit potential is noticed as 791 mV, the system successfully revealed a maximum power density of 86.1 mW m-2 at stable current density of 354 mA m-2 with high coulombic efficiency of 65% at maximum degradation rate of 96%. SEM showed the dense adherence of microorganisms on the anode. 16S rRNA sequencing results indicates phylogenetic mixture in the communities of anodic biofilm and there is no single dominant bacterial species. The dominant phyla are Firmicutes, Gamma Proteobacteria, Alpha Proteobacteria, Actinobacteria, with ten dominant microbial strains: Bacillus firmus, Shewanella profunda, Bacillus isronensis, Brevundimonas bullata, Pseudomonas putida, Planococcus citreus, Micrococcus endophyticus, Acinetobacter tandoii, Bacillus safensis and Shewanella xiamenensis.

Partial purification and characterization of extracellular protease from a halophilic and thermotolerant strain Streptomyces pseudogrisiolus NRC-15.

An alkaline protease was purified from a halophilic and thermotolerant potent alkaline protease-producing strain Streptomyces pseudogrisiolus NRC-15 using ammonium sulphate precipitation and Sephadex G-100 column chromatography. The enzyme was purified to 77.24-folds with a yield of 91.8% and the specific activity was 112 U/mg of protein. The protease showed a single band on SDS-PAGE with its molecular mass at 20 kDa and exhibited a maximum relative activity of 100% using casein as a substrate and. The enzyme had an optimum pH of 9.5 and displayed optimum activity at 50 degrees C. The enzyme activity was completely inhibited by the serine protease inhibitor PMSF, suggesting the presence of serine residue in the active site. The enzyme activity was increased by the metal ions Ca2+, Co2+, K+ and Mg2+. The enzyme significantly enhanced the removal of stains when used with wheel detergent, indicating the potential of the enzyme for using as a laundry detergent additive to improve the performance of heavy-duty laundry detergent.