Enhancing electrical outputs of the fuel cells with Geobacter sulferreducens by overexpressing nanowire proteins

Abstract

Protein nanowires are critical electroactive components for electron transfer of Geobacter sulfurreducens biofilm. To determine the applicability of the nanowire proteins in improving bioelectricity production, their genes including pilA, omcZ, omcS and omcT were overexpressed in G. sulfurreducens.The voltage outputs of the constructed strains were higher than that of the control strain with the empty vector (0.470-0.578 vs. 0.355 V) in microbial fuel cells (MFCs). As a result, the power density of the constructed strains (i.e. 1.39-1.58 W m −2 ) also increased by 2.62-to 2.97-fold as compared to that of the control strain. Overexpression of nanowire proteins also improved biofilm formation on electrodes with increased protein amount and thickness of biofilms. The normalized power outputs of the constructed strains were 0.18-0.20 W g −1 that increased by 74% to 93% from that of the control strain.Bioelectrochemical analyses further revealed that the biofilms and MFCs with the constructed strains had stronger electroactivity and smaller internal resistance, respectively. Collectively, these results demonstrate for the first time that overexpression of nanowire proteins increases the biomass and electroactivity of anode-attached microbial biofilms. Moreover, this study provides a new way for enhancing the electrical outputs of MFCs. TA B L E 1 Bacterial strains and plasmids used in this study Strains or plasmids Relevant genotype or uses Source or reference Bacterial strains G. sulferreducens PCA Wild-type G. sulferreducens Liu et al. (2015) Control strain G. sulferreducens PCA containing empty pAWP78 vector This study GNW1 G. sulferreducens PCA containing pOEpilA This study GNW2 G. sulferreducens PCA containing pOEomcZ This study GNW3 G. sulferreducens PCA containing pOEomcS This study GNW4 G. sulferreducens PCA containing pOEomcT This study

Microfluidic membraneless microbial fuel cells: new protocols for record power densities

“…Thus, a focus on current density should be the priority for future microfluidic MFC improvements, for example, by using other bacterial strains, including mixed-culture and genetically engineered EABs. 33,50 Other iterative improvements on the base-model MFC presented here can enable continuous advances by exploiting recent innovations including structured anodes, 4 3D scaffolded anodes, 49 use of biopolymer membranes and their functionalization, 51 carefully chosen metal electrodes, 52 ionomer electrode coatings, 53 and doping of anodic EABs with metals and other materials. 54,55 In addition, more standard methods can also be considered, such as the use of higher buffer concentrations and solution conductivity and cathodes with a higher reduction potential.…”

Microbe–Anode Interactions: Comparing the impact of genetic and material engineering approaches to improve the performance of microbial electrochemical systems (MES)

“…Nevertheless, it was also elucidated that the c ‐type cytochrome OmcS forms long‐protein filaments that can extend several micrometres away from the cell. In fact, there is evidence that these OmcS filaments are the nanowires that were previously thought to be formed by type IV pilus subunits and that were hypothesized to be conductive via overlapping π‐orbitals (Filman et al, 2019 ; Lovley and Walker, 2019 ; Wang et al, 2019 ; Wang, Hu, Dong, Shi, & Jiang, 2022 ). The export of these conductive structures is based on the type IV pilus production machinery, which might be the reason why they have been thought to be pilus subunits instead of cytochromes (Gu et al, 2021 ).…”

“…In a very recent study Wang et al ( 2022 ) also followed a classical genetic engineering approach. The authors aimed to determine the applicability of nanowire proteins in improving bioelectricity production by overexpressing them.…”

Exploiting synergies between microbial electrochemical technologies and synthetic biology

“…One key problem is decreasing biofilm activity with increasing biofilm thickness, mainly due to the mass and electron transfer limits within the biofilm. In this special issue, (Wang, et al, 2022b ) reported on their efforts to tackle this issue (at least to a certain degree) by using a synthetic biology approach. The authors overexpressed several nanowire subunits of Geobacter sulfurreducens and they found that the mutants could form 45% to 70% thicker biofilms.…”