Photoactive Manganese Ferrite-Modified Bacterial Anode to Simultaneously Boost Both Mediated and Direct Electron Transfer Processes in Microbial Fuel Cells

Abstract

Photomicrobial fuel cells can efficiently improve the power density of microbial fuel cells (MFCs), but bimetallic spinel ferrite photoactive material-based microbial devices have not been investigated yet. Herein, a dissimilatory iron-reducing bacterium, Shewanella putrefaciens CN32 (S. putrefaciens CN32), is selected as a model bacterium due to its possible enhanced affinity with iron-containing photoactive materials. Three bimetallic spinel ferrite nanoparticles, cobalt ferrite (CoFe2O4), nickel ferrite (NiFe2O4), and manganese ferrite (MnFe2O4), were used to modify the surface of S. putrefaciens CN32 for photo-MFCs, showing that MnFe2O4 has the best catalytic effect. Results reveal that these nanoparticle coatings on bacteria not only enhance direct electron transfer mediated by outer membrane c-type cytochromes (OMCs) while serving as conductive paths for charge transport between bacteria and the electrode surface but also significantly promote bacterial growth for increased flavin production from S. putrefaciens CN32. In addition, the extracellular electron transfer can be greatly accelerated with the assistance of photosensitive MnFe2O4 nanoparticles under visible light. This work demonstrates that the photomicrobial anode can simultaneously enhance both mediated and direct electron transfer processes and offers universal significance for photo-bio-electrocatalysis.

Enhanced detoxification of Cr6+ by Shewanella oneidensis via adsorption on spherical and flower-like manganese ferrite nanostructures

“…The affinity of MnFe 2 O 4 NPs to bind proteins on the bacterial outer membrane can improve the contact area between a single bacterium cell and an external electron acceptor. 37 There are some explanations for NP-enhanced bio-reduction of Cr 6+ to Cr 3+ by S. oneidensis MR-1; however, the exact mechanism is not fully unravelled. 102 NPs can act as a bridge between the bacterial cell and Cr 6+ to promote electron transfer.…”

“…36 The adsorption of Cr 6+ on the surface of NPs and its reduction to Cr 3+ decreases the availability and toxicity of Cr 6+ , which improves the efficiency of microbial respiration. 90,104 Since MnFe 2 O 4 NPs have electrochemical properties, 37,38 they can link S. oneidensis MR-1 with Cr 6+ as an electron mediator from the cell to Cr 6+ , a terminal electron acceptor. In MnFe 2 O 4 , the existence of Mn and Fe in different oxidation states facilitates the redox processes on the NP surface.…”

“…34,35 A biocompatible material such as manganese ferrite (MnFe 2 O 4 ) 36 was considered for enhancing microbial respiration of Cr 6+ . This ferrite was used to accelerate extracellular electron transfer in the microbial fuel cell, 37,38 and it showed the highest adsorption capacity among other ferrites for Cr 6+ . 39 The maximum adsorption capacity of MnFe 2 O 4 NPs for Cr 6+ was reported to be ranging from 31 to 35 mg g −1 .…”

Interface Visualization of Bio-material Interaction Via Cryo-AEM Using the Biosynthesis of Iron-Based Nanoparticles as a Model

“…This is mutually confirmed with EELS results that M-nFe can facilitate electron shuttling. 31,32 M-nFe facilitates the entire MR-1 extracellular electron transfer process as electrons shuttle. Its oxidation state mediator obtains electrons from the terminal end of the cell's respiratory chain, and the reduced state mediator transfers the electrons to the Fe(III) and itself is oxidized again.…”

Electromagnetic Field Drives the Bioelectrocatalysis of γ-Fe2O3-Coated Shewanella putrefaciens CN32 to Boost Extracellular Electron Transfer

“…However, the establishment of a tightly coupled and efficient pathway for electron transfer between EAMs and conductive non-biological surfaces continues to be elusive. To exploit the active sites on the bacterial outer membrane, researchers have proposed the use of nanomaterials to modify the surface or interior of bacteria [24][25][26][27]. The efficient construction of the microbial-nanomaterial interface can optimize the EET efficiency and enhance the power generation performance of MFC.…”