Bioaugmentation of microbial electrolysis cells with Geobacter sulfurreducens YM18 for enhanced hydrogen production from starch

Bioaugmentation of microbial fuel cells with Geobacter sulfurreducens strain 60473 for boosting power outputs from food wastes

Microbial fuel cells are expected to be applied to sustainable power generation, while substantial increases in process performances, including power output, are necessary for practical application. Here we examined the utility of bioaugmentation with electro-active bacteria for boosting power outputs from microbial fuel cell reactors. Single-chamber reactors were operated using digester effluent as an inoculum and food wastes as organic substrates, and effects of bioaugmentation with Geobacter sulfurreducens strain 60473 were examined. It has been shown that bioaugmentation with strain 60473 substantially improves organics removal and power output, and the maximum power density (per anode projection area) reaches over 1700 mW m-2, a value tenfold larger than that without bioaugmentation. Metabarcoding analyses showed that Geobacter shared more than 40% of anode bacteria in 60473-augmented reactors. These results suggest the utility of bioaugmentation with strain 60473 for improving the performance of microbial fuel cells treating food wastes.

Zero-discharge, self-sustained 3D-printed microbial electrolysis cell for biohydrogen production: a review

Microbial fuel cell (MFC) and microbial electrolysis cell (MEC) technologies have been used recently in bench-scale bioenergy (electricity) generation, biohydrogen (H2) production, biosensing, and wastewater treatment. There are still a lot of obstacles to overcome in terms of commercialization and industrial settling. These difficulties include lengthy start-up times, intricate reactor designs for managing large reaction volumes, and expensive and time-consuming large-scale system fabrication procedures. Interestingly, combining three-dimensional (3D) printing with MFC and MEC technology appears to be a workable and promising way to get past these obstacles. Moreover, a rapid start-up with no delays in the current generation using MFC and MEC is possible with 3D printed bio-anodes. Furthermore, H2 can be generated from wastewater by powering a stacked MFC and MEC-coupled with electrochemical capacitor (ECC) system using 3D printing technology. To the best of the author's knowledge, this review paper is the first to explicitly highlight the use of 3D printing in creating a stacked MFC-ECC-MEC system in conjunction with a photobioreactor (PBR) to produce significant quantities of H2 and carbon dioxide (CO2) can be utilized for algae production. A notable feature of 3D printing technology is its reliable production capabilities, enabling MFC-ECC-MEC-PBR systems to be expanded by setting up numerous stacks of MFC-ECC-MEC-PBR units devoid of material waste and human error. The present review attempts to provide an update on the current status of the 3D printing application, that is meant to propel the MFC-ECC-MEC-PBR system forward.

Geobacter sulfurreducens strain 60473, a potent bioaugmentation agent for improving the performances of bioelectrochemical systems

Bioaugmentation with electrochemically active bacteria (EAB) has been suggested useful for improving the performance of bioelectrochemical systems (BESs) for sustainable energy generation, while its success is dependent on EAB introduced into the systems. Here we report on the isolation of a novel EAB, Geobacter sulfurreducens strain 60473, from microbes that colonized on an anode of a sediment microbial fuel cell. This strain is highly adhesive to graphite electrodes, forms dense biofilms on electrode surfaces, and generates high current densities in BESs. When microbial electrolysis cells (MECs) inoculated with paddy-field soil and fed starch as the major organic substrate were augmented with strain 60473, Geobacter bacteria predominantly colonized on anodes, and MEC performances, including current generation, hydrogen production and organics removal, were substantially improved compared to non-bioaugmented controls. Results suggest that bioaugmentation with electrode-adhesive EAB, such as strain 60473, is a promising approach for improving the performance of BESs, including MECs treating fermentable organics and biomass wastes.

Hydrogen Production in Microbial Electrolysis Cells Using an Alginate Hydrogel Bioanode Encapsulated with a Filter Bag

The bacterial anode of microbial electrolysis cells (MECs) is the limiting factor in a high hydrogen evolution reaction (HER). This study focused on improving biofilm attachment to a carbon-cloth anode using an alginate hydrogel. In addition, the modified bioanode was encapsulated by a filter bag that served as a physical barrier, to overcome its low mechanical strength and alginate degradation by certain bacterial species in wastewater. The MEC based on an encapsulated alginate bioanode (alginate bioanode encapsulated by a filter bag) was compared with three controls: an MEC based on a bare bioanode (non-immobilized bioanode), an alginate bioanode, and an encapsulated bioanode (bioanode encapsulated by a filter bag). At the beginning of the operation, the Rct value for the encapsulated alginate bioanode was 240.2 Ω, which decreased over time and dropped to 9.8 Ω after three weeks of operation when the Geobacter medium was used as the carbon source. When the MECs were fed with wastewater, the encapsulated alginate bioanode led to the highest current density of 9.21 ± 0.16 A·m-2 (at 0.4 V), which was 20%, 95%, and 180% higher, compared to the alginate bioanode, bare bioanode, and encapsulated bioanode, respectively. In addition, the encapsulated alginate bioanode led to the highest reduction currents of (4.14 A·m-2) and HER of 0.39 m3·m-3·d-1. The relative bacterial distribution of Geobacter was 79%. The COD removal by all the bioanodes was between 62% and 88%. The findings of this study demonstrate that the MEC based on the encapsulated alginate bioanode exhibited notably higher bio-electroactivity compared to both bare, alginate bioanode, and an encapsulated bioanode. We hypothesize that this improvement in electron transfer rate is attributed to the preservation and the biofilm on the anode material using alginate hydrogel which was inserted into a filter bag.

Degradation of sulfamethazine by microbial electrolysis cell with nickel-cobalt co-modified biocathode

In this study, nickel-cobalt co-modified stainless steel mesh (Ni-Co@SSM) was prepared and used as the biocathode in microbial electrolysis cell (MEC) for sulfamethazine (SMT) degradation. The optimal electrochemical performance of the Ni-Co@SSM was obtained at the electrodeposition time of 600 s, electrodeposition current density of 20 mA cm-2, and nickel-cobalt molar ratio of 1:2. The removal of SMT in MEC with the Ni-Co@SSM biocathode (MEC-Ni-Co@SSM) was 82%, which increased by 30% compared with the conventional anaerobic reactor. Thirteen intermediates were identified and the potential degradation pathways of SMT were proposed. Proteobacteria, Firmicutes, Patescibacteria, Chloroflexi, Bacteroidetes, and Euryarchaeota are the dominant bacteria at the phylum level in the MEC-Ni-Co@SSM, which are responsible for SMT metabolism. Due to the electrical stimulation, there was an increase in the abundance of the metabolic function and the genetic information processing. This work provides valuable insight into utilizing MECs for effective treatment of antibiotic-containing wastewater.