Electron transport phenomena of electroactive bacteria in microbial fuel cells: a review of Proteus hauseri

Abstract

This review tended to decipher the expression of electron transfer capability (e.g., biofilm formation, electron shuttles, swarming motility, dye decolorization, bioelectricity generation) to microbial fuel cells (MFCs). As mixed culture were known to perform better than pure microbial cultures for optimal expression of electrochemically stable activities to pollutant degradation and bioenergy recycling, Proteus hauseri isolated as a "keystone species" to maintain such ecologically stable potential for power generation in MFCs was characterized. P. hauseri expressed outstanding performance of electron transfer (ET)-associated characteristics [e.g., reductive decolorization (RD) and bioelectricity generation (BG)] for electrochemically steered bioremediation even though it is not a nanowire-generating bacterium. This review tended to uncover taxonomic classification, genetic or genomic characteristics, enzymatic functions, and bioelectricity-generating capabilities of Proteus spp. with perspectives for electrochemical practicability. As a matter of fact, using MFCs as a tool to evaluate ET capabilities, dye decolorizer(s) could clearly express excellent performance of simultaneous bioelectricity generation and reductive decolorization (SBG and RD) due to feedback catalysis of residual decolorized metabolites (DMs) as electron shuttles (ESs). Moreover, the presence of reduced intermediates of nitroaromatics or DMs as ESs could synergistically augment efficiency of reductive decolorization and power generation. With swarming mobility, P. hauseri could own significant biofilm-forming capability to sustain ecologically stable consortia for RD and BG. This mini-review evidently provided lost episodes of great significance about bioenergysteered applications in myriads of fields (e.g., biodegradation, biorefinery, and electro-fermentation). Keywords

Polyphenolic compounds as electron shuttles for sustainable energy utilization

“…Moreover, if hydroxyl-bearing ES compounds are obtained from natural polyphenols (or polyhydroxyphenols), the ESs could be less toxic and more biocompatible than compounds containing amino groups, making them green and sustainable compounds for practical uses. For example, 4-AP is toxic to electroactive bacteria, and the bioelectricity-generating capability of an MFC inoculated with Proteus hauseri ZMd44 was significantly repressed by this compound [8, 30]; thus, the biotoxicities of the compounds must be assessed before use for biotechnological applications. That is, as hydroxyl groups are more electrochemically stable and reversible, and less toxic than amino groups, polyhydroxy derivatives of benzenes/polybenzenes (e.g., benzoquinone, naphthoquinones, anthraquinones, and other polyphenolic compounds) are good candidate ESs for sustainable applications [23].…”

“…Moreover, electron transfer between microbes and from microbes to electron-accepting compounds can be facilitated using ESs. This is a promising way to decline the activation energy and increase efficient electron between the intracellular compartment and extracellular medium during microbial energy metabolism [7, 8]. That is, ESs are “electrochemical catalysts” that increase the reaction rate under appropriate environmental conditions.…”

Comparative static and shaking culture of metabolite derived from methyl red degradation byLysinibacillus fusiformisstrain W1B6

“…There is no report on MR degradation in both aerobic and anerobic cultures by an organism excepting the report on suspended cells of A. jandaei , which found the same decolorization rate with DMPD as the only main product of MR degradation under both conditions [19]. However, some reports recorded that anaerobic conditions give a higher efficiency in dye decolorization with the hazardous metabolite product, while aerobic conditions inhibit the reduction of dye [2,18,23,24].…”

Turn on the Mtr pathway genes under pLacI promoter in Shewanella oneidensis MR-1

“…In recent years, energy conservation, environmental protection, and circular economics are of great importance in a highly resource-limiting world. As a matter of fact, bioremediation, bioeconomic, and generating energy by waste to electricity are becoming increasingly important (Chen et al 2013;Chaturvedi and Verma 2016;Ng et al 2017;Takahashi et al 2016). Among most of microorganisms used in bioenergies and bioresources, Shewanella genus is the most important dissimilatory metal reducing bacteria (DMRB) which have been widely studied for biodecolorization, bioremediation, microbe fuel cell, and biofabrication (Bretschger et al 2007;Jayasinghe et al 2014;Nealson and Scott 2006;Ng et al 2014a, b;Wu and Ng 2017).…”