Electrochemical communication in anaerobic digestion

Abstract

Anaerobic microbial consortia in AD or fermentation oxidise or reduce a target organics (including nutrients) in order to share (i.e. extract and utilise) thermodynamic enthalpy energy (i.e. ATP with thermal energy). Herein, the oxidation and reduction (i.e. electrochemical reaction) is a type of biochemical reaction that involves a transfer of electrons or hydrogens between two species and or taxa. The review discusses an electrochemical communication in the bacterial communal society leading to a 'bacterial cartel' which can be a type of struggling for life (to obtain the biochemical energy constantly). Interestingly, syntrophic bacteria (mostly acetogenic bacteria) bind or flocculate the AD bacterial consortia and build two-layer biofilms or bioflocs to obtain the energy while producing a peculiar profile of fatty acids. The hydrolytic fermentative bacteria also dissociate with acidogenic bacteria for an association with the syntrophic bacteria when ∆ψ approaches at between-200 and-250 mV. Three examples (singlemethanogenesis, long-chain fatty acid (LCFA) degradation and acid-fermentation process) explain in the electrochemical origin. This concept remains quite controversial, but if true, may have major implications in broad areas of environmental and biological processes.

Integrating microbial electrochemical technologies with anaerobic digestion to accelerate propionate degradation

“…A recent work by [37] confirms the existence of a syntrophic relationship between these two genera, with direct interspecies electron transfer (DIET) as the most probable interaction mechanism, which in our case could lead to a more versatile metabolism that favors propionate conversion to CO 2 and electrons. In addition, the occurrence of DIET could explain the absence of H 2 in the biogas composition, although a fast consumption kinetics by microorganisms present in the planktonic phase (Pseudomonas and Syntrophomonas, Broths R4 and R5) would also be consistent with these results [38], as discussed in Section 3.1 (performance).…”

Biological Treatment of Organic Waste in Wastewater—towards a Circular and Bio-Based Economy

“…In this respect, the role of perceived self-efficacy is key to understanding the behavioral intention of NCS producers to use LCB (supporting H6). This finding could be explained by the fact that people with high self-efficacy believe they can perform well using technology [58]. As a result, they are more likely to try the technology and continue to evaluate its benefits.…”

“…Observations support the hypothesis that enhanced EPS excretion may have played an essential adhesive role in the formation of aggregates and the maintenance of their integrity. Accordingly, considering the EPS sorptive capacities and their possible role in immobilizing the extracellular enzymes, the observed accelerated hydrolysis and acidification process can be explained by (i) the physical trapping of particulate and colloidal organics by means of the EPS, which leads to enhanced hydrolysis; (ii) immobilization and localization of extracellular enzymes by EPS; (iii) the minimization of hydrolysis and acidification product diffusion distances as a result of aggregation [58]. The enhanced aggregation of biomass and solid substrates implies that both enzymes and hydrolysis/acidification products remain relatively close to microbial thus reducing the need for maintaining high levels of extracellular enzymes in the bulk solution reducing the diffusive losses of products away from cells [59].…”

Impact of Nanoscale Magnetite and Zero Valent Iron on the Batch-Wise Anaerobic Co-Digestion of Food Waste and Waste-Activated Sludge

“…Observations support the hypothesis that enhanced EPS excretion may have played an essential adhesive role in the formation of aggregates and the maintenance of their integrity. Accordingly, considering the EPS sorptive capacities and their possible role in immobilizing the extracellular enzymes, the observed accelerated hydrolysis and acidification process can be explained by (i) the physical trapping of particulate and colloidal organics by means of the EPS, which leads to enhanced hydrolysis; (ii) immobilization and localization of extracellular enzymes by EPS; (iii) the minimization of hydrolysis and acidification product diffusion distances as a result of aggregation [58]. The enhanced aggregation of biomass and solid substrates implies that both enzymes and hydrolysis/acidification products remain relatively close to microbial cells, thus reducing the need for maintaining high levels of extracellular enzymes in the bulk solution and reducing the diffusive losses of products away from cells [59].…”