Hypersaline microbial self-powered biosensor with increased sensitivity

The on-line, self-powered monitoring of the organic carbon content in hypersaline solutions (e.g. chemical oxygen demand, COD) based on a microbial biosensor would avoid the generation of toxic waste, originated by common COD analytical methods, and reduce the release of pollutants into the environment. Herein, a disposable cathode was applied to microbial fuel cells (MFCs) for the environmental friendly monitoring of the COD reaching a sensitivity one order of magnitude higher compared to the MFC with an air breathing cathode. Additionally, the entrapment of bacterial cells in alginate-capsules ensured a considerable linear range (up to approximately 10,000 mg COD L−1), providing opportunities for the wide application of the device to hypersaline solutions characterized by different origins and contamination levels

Alginate-Encapsulated Bacteria for the Treatment of Hypersaline Solutions in Microbial Fuel Cells

A microbial fuel cell (MFC) based on a new wild-type strain of Salinivibrio sp. allowed the self-sustained treatment of hypersaline solutions (100gL-1, 1.71m NaCl), reaching a removal of (87±11)% of the initial chemical oxygen demand after five days of operation, being the highest value achieved for hypersaline MFC. The degradation process and the evolution of the open circuit potential of the MFCs were correlated, opening the possibility for online monitoring of the treatment. The use of alginate capsules to trap bacterial cells, increasing cell density and stability, resulted in an eightfold higher power output, together with a more stable system, allowing operation up to five months with no maintenance required. The reported results are of critical importance to efforts to develop a sustainable and cost-effective system that treats hypersaline waste streams and reduces the quantity of polluting compounds released

Investigating extracellular electron transfer of Rikenella microfusus: a recurring bacterium in mixed-species biofilms

The optimization of bioelectrochemical systems operating with microorganisms requires a deep understanding of the extracellular electron transfer (EET) processes, however, EET studies have been reported for few bacterial species. Herein, the bioelectrocatalytic properties of Rikenella microfusus, an anaerobic bacterium commonly found in electrode-colonizing biofilms, have been investigated for the first time

Sustainable Bioelectrosynthesis of the Bioplastic Polyhydroxybutyrate: Overcoming Substrate Requirement for NADH Regeneration

One of the main limitations to achieve sustainable synthesis of polyhydroxybutyrate (PHB) is the cost of NADH regeneration, as it requires a side enzymatic reaction usually including a NAD-dependent dehydrogenase enzyme with its substrate or other photo- and electrochemical approaches that create unwanted byproducts and the enzymatically inactive dimer NAD2. Herein, a bioelectrocatalytic method combining both enzymatic and electrochemical approaches was used to regenerate enzymatically active NADH. The method employed a modified glassy carbon electrode that possesses both NADH regeneration and acetoacetyl-CoA (AcAcCoA) reduction features. The modified electrode exhibited an apparent Michaelis constant (KM) value of 814 ± 11 μM and a maximum current density (jmax) of 27.9 ± 1.3 μA cm-2 for NAD+ reduction and a KM value of 47 ± 2 μM and jmax of 0.97 ± 0.03 μA cm-2 for AcAcCoA reduction. The modified electrode was subsequently employed in the bioelectrosynthesis of the bioplastic PHB and yielded 1.6 mg in a 5 mL reaction mixture, indicating that the NADH was regenerated at least 8 times during the 16 h reaction