Lipid production from biofilms of Marinobacter atlanticus in a fixed bed bioreactor.

Background: Biotechnologies that utilize microorganisms as production hosts for lipid synthesis will enable an efficient and sustainable solution to produce lipids, decreasing reliance on traditional routes for production (either petrochemical or plant-derived) and supporting a circular bioeconomy. To realize this goal, continuous biomanufacturing processes must be developed to maximize productivity and minimize costs compared to traditional batch fermentation processes.

Results: Here, we utilized biofilms of the marine bacterium, Marinobacter atlanticus, to produce wax esters from succinate (i.

Performance of a combined electrotrophic and electrogenic biofilm operated under long-term, continuous cycling.

Objectives: Evaluate electrochemically active biofilms as high energy density rechargeable microbial batteries toward providing persistent power in applications where traditional battery technology is limiting (, remote monitoring applications).

Results: Here we demonstrated that an electrochemically active biofilm was able to store and release electrical charge for alternating charge/discharge cycles of up to 24 h periodicity (50% duty cycle) with no significant decrease in average current density (0.16 ± 0.

Marinobacter: A case study in bioelectrochemical chassis evaluation.

The junction of bioelectrochemical systems and synthetic biology opens the door to many potentially groundbreaking technologies. When developing these possibilities, choosing the correct chassis organism can save a great deal of engineering effort and, indeed, can mean the difference between success and failure. Choosing the correct chassis for a specific application requires a knowledge of the metabolic potential of the candidate organisms, as well as a clear delineation of the traits, required in the application.

Metagenomic and Metatranscriptomic Characterization of a Microbial Community That Catalyzes Both Energy-Generating and Energy-Storing Electrode Reactions.

Electroactive bacteria are living catalysts, mediating energy-generating reactions at anodes or energy storage reactions at cathodes via extracellular electron transfer (EET). The Cathode-ANode (CANode) biofilm community was recently shown to facilitate both reactions; however, the identities of the primary constituents and underlying molecular mechanisms remain unknown. Here, we used metagenomics and metatranscriptomics to characterize the CANode biofilm.

Evidence of a Streamlined Extracellular Electron Transfer Pathway from Biofilm Structure, Metabolic Stratification, and Long-Range Electron Transfer Parameters.

A strain of Geobacter sulfurreducens, an organism capable of respiring solid extracellular substrates, lacking four of five outer membrane cytochrome complexes ( strain) grows faster and produces greater current density than the wild type grown under identical conditions. To understand cellular and biofilm modifications in the strain responsible for this increased performance, biofilms grown using electrodes as terminal electron acceptors were sectioned and imaged using electron microscopy to determine changes in thickness and cell density, while parallel biofilms incubated in the presence of nitrogen and carbon isotopes were analyzed using NanoSIMS (nanoscale secondary ion mass spectrometry) to quantify and localize anabolic activity. Long-distance electron transfer parameters were measured for wild-type and biofilms spanning 5-μm gaps.

Biofilm structure, dynamics, and ecology of an upscaled biocathode wastewater microbial fuel cell.

A microbial fuel cell (MFC) system containing modular half-submerged biocathode was operated for 6 months in an 800 L flow-through system with domestic wastewater. For the first time, spatial and temporal differences in biofilm communities were examined on large three-dimensional electrodes in a wastewater MFC. Biocathode microbial community analysis showed a specialized biofilm community with electrogenic and electrotrophic taxa forming during operation, suggesting potentially opposing electrode reactions.

Nanoliter scale electrochemistry of natural and engineered electroactive bacteria.

Bacterial extracellular electron transfer (EET) is envisioned for use in applied biotechnologies, necessitating electrochemical characterization of natural and engineered electroactive biofilms under conditions similar to the target application, including small-scale biosensing or biosynthesis platforms, which is often distinct from standard 100 mL-scale stirred-batch bioelectrochemical test platforms used in the laboratory. Here, we adapted an eight chamber, nanoliter volume (500 nL) electrochemical flow cell to grow biofilms of both natural (Biocathode MCL community, Marinobacter atlanticus, and Shewanella oneidensis MR1) or genetically modified (S. oneidensis ΔMtr and S.

Activation of Protein Expression in Electroactive Biofilms.

Microbes that form biofilms on electrodes and generate electrical current responses could be integrated into devices to perform sensing, conduct signals, or act as living microprocessors. A challenge in working with these species is the ability to visualize biofilm formation and protein expression in real-time while also measuring current, which is not possible with typical bio-electrochemical reactors. Here, we present a three-dimensional-printed flow cell for simultaneous electrochemistry and fluorescence imaging.

Extracellular DNA Promotes Efficient Extracellular Electron Transfer by Pyocyanin in Pseudomonas aeruginosa Biofilms.

Redox cycling of extracellular electron shuttles can enable the metabolic activity of subpopulations within multicellular bacterial biofilms that lack direct access to electron acceptors or donors. How these shuttles catalyze extracellular electron transfer (EET) within biofilms without being lost to the environment has been a long-standing question. Here, we show that phenazines mediate efficient EET through interactions with extracellular DNA (eDNA) in Pseudomonas aeruginosa biofilms.

Spatially Resolved Chemical Analysis of Geobacter sulfurreducens Cell Surface.

Geobacter sulfurreducens is of interest for the highest efficiency of power generation and extremely long extracellular electron transfer (EET) between the bacterium and electrodes. Despite more than 15 years of intensive molecular biological research, there is still no clear answer which molecules are responsible for these processes. In the present work, we look at the problem from another (atomic) perspective and identify the location and shape of the compounds that are known to be conductive, particularly those containing Fe atoms.

Application of electrochemical surface plasmon resonance (ESPR) to the study of electroactive microbial biofilms.

Electrochemical surface plasmon resonance (ESPR) monitors faradaic processes optically by the change in refractive index that occurs with a change in redox state at the electrode surface. Here we apply ESPR to investigate the anode-grown Geobacter sulfurreducens biofilm (GSB), a model system used to study electroactive microbial biofilms (EABFs) which perform electrochemical reactions using electrodes as metabolic electron acceptors or donors. A substantial body of evidence indicates that electron transfer reactions among hemes of c-type cytochromes (c-Cyt) play major roles in the extracellular electron transfer (EET) pathways that connect intracellular metabolic processes of cells in an EABF to the electrode surface.

Internal Redox Polarity of an Individual G. sulfurreducens Bacterial Cell Attached to an Inorganic Substrate.

Bacterial cell polarity is an internal asymmetric distribution of subcellular components, including proteins, lipids, and other molecules that correlates with the cell ability to sense energy and metabolite sources, chemical signals, quorum signals, toxins, and movement in the desired directions. This ability also plays central role in cell attachment to various surfaces and biofilm formation. Mechanisms and factors controlling formation of this cell internal asymmetry are not completely understood.

Redox-gradient driven electron transport in a mixed community anodic biofilm.

Here, we describe the long-distance (multi-cell-length) extracellular electron transport (LD-EET) that occurs in an anode-grown mixed community biofilm (MCB) enriched from river sediment that contains 3%-45% Geobacter spp. High signal-to-noise temperature-dependent electrochemical gating measurements (EGM) using interdigitated microelectrode arrays reveal a peak-shaped electrical conductivity vs. potential dependency, indicating MCB acts as a redox conductor, similar to pure culture anode-grown Geobacter sulfurreducens biofilms (GSB).

On the relationship between long-distance and heterogeneous electron transfer in electrode-grown Geobacter sulfurreducens biofilms.

The ability of certain microorganisms to live in a multi-cell thick, electrode-grown biofilm by utilizing the electrode as a metabolic electron acceptor or donor requires electron transfer across cell membranes, through the biofilm, and across the biofilm/electrode interface. Even for the most studied system, anode-grown Geobacter sulfurreducens, the mechanisms underpinning each process and how they connect is largely unresolved. Here we report on G.

Correction to Comparison of Nonprecious Metal Cathode Materials for Methane Production by Electromethanogenesis.

[This corrects the article DOI: 10.1021/sc400520x.].

Biofilm as a redox conductor: a systematic study of the moisture and temperature dependence of its electrical properties.

Some microbial biofilms are electrically conductive. However, the mechanism of electron transport remains unclear. Here, we show that μm-scale long-distance electron transport through electrode-grown Geobacter sulfurreducens biofilms occurs via redox conduction, as determined by electrical measurements performed under varied hydration states and temperatures.

Thermally activated long range electron transport in living biofilms.

Microbial biofilms grown utilizing electrodes as metabolic electron acceptors or donors are a new class of biomaterials with distinct electronic properties. Here we report that electron transport through living electrode-grown Geobacter sulfurreducens biofilms is a thermally activated process with incoherent redox conductivity. The temperature dependency of this process is consistent with electron-transfer reactions involving hemes of c-type cytochromes known to play important roles in G.

Effects of constant or dynamic low anode potentials on microbial community development in bioelectrochemical systems.

In bioelectrochemical systems, exoelectrogenic bacteria respire with anode electrodes as their extracellular electron acceptor; therefore, lower anode potentials can reduce the energy gain to each microbe and select against ones that are not able to respire at a lower potential range. Often fully developed anode communities are compared across bioelectrochemical systems with set anode potentials or fixed external resistances as different operational conditions. However, the comparative effect of the resulting constantly low versus dynamically low anode potentials on the development of anode microbial communities as well as the final cathode microbial communities has not been directly demonstrated.

Alamethicin suppresses methanogenesis and promotes acetogenesis in bioelectrochemical systems.

Microbial electrosynthesis (MES) systems with mixed cultures often generate a variety of gaseous and soluble chemicals. Methane is the primary end product in mixed-culture MES because it is the thermodynamically most favorable reduction product of CO2. Here, we show that the peptaibol alamethicin selectively suppressed the growth of methanogens in mixed-culture MES systems, resulting in a shift of the solution and cathode communities to an acetate-producing system dominated by Sporomusa, a known acetogenic genus in MES systems.

The presence of hydrogenotrophic methanogens in the inoculum improves methane gas production in microbial electrolysis cells.

High current densities in microbial electrolysis cells (MECs) result from the predominance of various Geobacter species on the anode, but it is not known if archaeal communities similarly converge to one specific genus. MECs were examined here on the basis of maximum methane production and current density relative to the inoculum community structure. We used anaerobic digester (AD) sludge dominated by acetoclastic Methanosaeta, and an anaerobic bog sediment where hydrogenotrophic methanogens were detected.

Examination of protein degradation in continuous flow, microbial electrolysis cells treating fermentation wastewater.

Cellulose fermentation wastewaters (FWWs) contain short chain volatile fatty acids and alcohols, but they also have high concentrations of proteins. Hydrogen gas production from FWW was examined using continuous flow microbial electrolysis cells (MECs), with a focus on fate of the protein. H2 production rates were 0.

Exoelectrogenic biofilm as a template for sustainable formation of a catalytic mesoporous structure.

Mesoporous structures can increase catalytic activity by maximizing the ratio of surface area to volume, but current synthesis techniques utilize expensive polymers and toxic chemicals. A Geobacter sulfurreducens biofilm was used as a sustainable template to form mesoporous Pd structures while eliminating the need for synthetic chemicals. The bulk of the biofilm material was removed by thermal treatments after nanoparticle formation, producing a catalytic Pd mesoporous (pore size 9.