Atomic Layers of Graphene for Microbial Corrosion Prevention.

Graphene is a promising material for many biointerface applications in engineering, medical, and life-science domains. Here, we explore the protection ability of graphene atomic layers to metals exposed to aggressive sulfate-reducing bacteria implicated in corrosion. Although the graphene layers on copper (Cu) surfaces did not prevent the bacterial attachment and biofilm growth, they effectively restricted the biogenic sulfide attack. Interestingly, single-layered graphene (SLG) worsened the biogenic sulfide attack by 5-fold compared to bare Cu. In contrast, multilayered graphene (MLG) on Cu restricted the attack by 10-fold and 1.4-fold compared to SLG-Cu and bare Cu, respectively. We combined experimental and computational studies to discern the anomalous behavior of SLG-Cu compared to MLG-Cu. We also report that MLG on Ni offers superior protection ability compared to SLG. Finally, we demonstrate the effect of defects, including double vacancy defects and grain boundaries on the protection ability of atomic graphene layers.

Electricity from lignocellulosic substrates by thermophilic Geobacillus species.

Given our vast lignocellulosic biomass reserves and the difficulty in bioprocessing them without expensive pretreatment and fuel separation steps, the conversion of lignocellulosic biomass directly into electricity would be beneficial. Here we report the previously unexplored capabilities of thermophilic Geobacillus sp. strain WSUCF1 to generate electricity directly from such complex substrates in microbial fuel cells. This process obviates the need for exogenous enzymes and redox mediator supplements. Cyclic voltammetry and chromatography studies revealed the electrochemical signatures of riboflavin molecules that reflect mediated electron transfer capabilities of strain WSUCF1. Proteomics and genomics analysis corroborated that WSUCF1 biofilms uses type-II NADH dehydrogenase and demethylmenaquinone methyltransferase to transfer the electrons to conducting anode via the redox active pheromone lipoproteins localized at the cell membrane.

Valorization of methane from environmental engineering applications: A critical review.

Wastewater and waste management sectors alone account for 18% of the anthropogenic methane (CH4) emissions. This study presents a critical overview of methanotrophs ("methane oxidizing microorganisms") for valorizing typically discarded CH4 from environmental engineering applications, focusing on wastewater treatment plants. Methanotrophs can convert CH4 into valuable bioproducts including chemicals, biodiesel, DC electricity, polymers, and S-layers, all under ambient conditions. As discarded CH4 and its oxidation products can also be used as a carbon source in nitrification and annamox processes. Here we discuss modes of CH4 assimilation by methanotrophs in both natural and engineered systems. We also highlight the technical challenges and technological breakthroughs needed to enable targeted CH4 oxidation in wastewater treatment plants.

Electricity from methanol using indigenous methylotrophs from hydraulic fracturing flowback water.

Methanol solvents that are used in hydraulic fracturing often return back to the surface in the form of recalcitrant flowback water. Here, the indigenous methylotrophic bacteria from flowback water were enriched and used to generate electricity from methanol in a two-compartment microbial fuel cell (CH3OH-MFC). An identical MFC based on a tryptone-yeast extract (TY-MFC) was used as a control. CH3OH-MFC yielded a 2.7-fold thicker biofilm dominated by electrogenic species (81%) and higher power density (76 mW/m2) compared with TY-MFC (50 mW/m2). Illumina MiSeq sequencing of the 16S rRNA gene in TY-MFC revealed classes from Actinobacteria, Bacteroidia and γ-proteobacteria. The CH3OH-MFC yielded α-proteobacteria, ß-proteobacteria, γ-proteobacteria and Bacteroidia, with a dominant fraction of Rhodobacter sphaeroides (~29%). We discuss the potential pathways used by R. sphaeroides to maintain syntrophic cooperation with other bacterial and archaeal members to sustain CH3OH oxidation. Finally, we establish that a pure culture of R. sphaeroides 2.4.1 generates electricity directly from methanol.

Producing methane, methanol and electricity from organic waste of fermentation reaction using novel microbes.

Residual solid and liquid streams from the one-pot CRUDE (Conversion of Raw and Untreated Disposal into Ethanol) process were treated with two separate biochemical routes for renewable energy transformation. The solid residual stream was subjected to thermophilic anaerobic digestion (TAD), which produced 95 ±â€¯7 L methane kg-1 volatile solid with an overall energy efficiency of 12.9 ±â€¯1.7%. A methanotroph, Methyloferula sp., was deployed for oxidation of mixed TAD biogas into methanol. The residual liquid stream from CRUDE process was used in a Microbial Fuel Cell (MFC) to produce electricity. Material balance calculations confirmed the integration of biochemical routes (i.e. CRUDE, TAD, and MFC) for developing a sustainable approach of energy regeneration. The current work demonstrates the utilization of different residual streams originated after food waste processing to release minimal organic load to the environment.

Extremophiles for microbial-electrochemistry applications: A critical review.

Extremophiles, notably archaea and bacteria, offer a good platform for treating industrial waste streams that were previously perceived as hostile to the model organisms in microbial electrochemical systems (MESs). Here we present a critical overview of the fundamental and applied biology aspects of halophiles and thermophiles in MESs. The current study suggests that extremophiles enable the MES operations under a seemingly harsh conditions imposed by the physical (pressure, radiation, and temperature) and geochemical extremes (oxygen levels, pH, and salinity). We highlight a need to identify the underpinning mechanisms that define the exceptional electrocatalytic performance of extremophiles in MESs.

Hexagonal Boron Nitride: The Thinnest Insulating Barrier to Microbial Corrosion.

We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the thinnest insulating barrier to microbial corrosion induced by the sulfate-reducing bacteria Desulfovibrio alaskensis G20. We used electrochemical methods to assess the corrosion resistance of SL-hBN on copper against the effects of both the planktonic and sessile forms of the sulfate-reducing bacteria. Cyclic voltammetry results show that SL-hBN-Cu is effective in suppressing corrosion effects of the planktonic cells at potentials as high as 0.2 V ( vs Ag/AgCl). The peak anodic current for the SL-hBN coatings is ∼36 times lower than that of bare Cu. Linear polarization resistance tests confirm that the SL-hBN coatings serve as a barrier against corrosive effects of the G20 biofilm when compared to bare Cu. The SL-hBN serves as an impermeable barrier to aggressive metabolites and offers ∼91% corrosion inhibition efficiency, which is comparable to much thicker commercial coatings such as polyaniline. In addition to impermeability, the insulating nature of SL-hBN suppresses galvanic effects and improves its ability to combat microbial corrosion.

Comparative performances of microbial capacitive deionization cell and microbial fuel cell fed with produced water from the Bakken shale.

This study evaluates and compares the performance of microbial fuel cells (MFCs) and microbial capacitive deionization cells (MCDCs) fed with wastewater produced from the Bakken shale. The produced water was characterized by high levels of dissolved solids and chemical oxygen demand (COD). Two-compartment MFCs and three-compartment MCDCs were evaluated under batch-fed mode using mixed microbial consortia in the anode, ferricyanide in the cathode, and produced water as the electrolyte in the anode and capacitive deionization units. COD removal in the MFCs was 88%, while that in the MCDCs was limited to 76%. The lower performance of the MCDCs was due to the large impedance (6600 Ω cm2) compared with the MFCs (870 Ω cm2). However, the MCDCs achieved two-fold higher removal of dissolved solids. Both the MFCs and MCDCs suffered from a higher impedance induced by fouling in the latter stages of the operation.

Simultaneous hydrolysis and fermentation of unprocessed food waste into ethanol using thermophilic anaerobic bacteria.

The one-pot CRUDE (Conversion of Raw and Untreated Disposal into Ethanol) process was developed for simultaneous hydrolysis and fermentation of unprocessed food waste into ethanol using thermophilic (growing at 65°C) anaerobic bacteria. Unlike existing waste to energy technologies, the CRUDE process obviates the need for any pre-treatment or enzyme addition. A High-Temperature-High-Pressure (HTHP) distillation technique was also applied that facilitated efficient use of fermentation medium, inoculum recycling, and in-situ ethanol collection. For material balancing of the process, each characterized component was represented in terms of C-mol. Recovery of 94% carbon at the end confirmed the operational efficiency of CRUDE process. The overall energy retaining efficiency calculated from sugars to ethanol was 1262.7kJdryweightkg-1 of volatile solids using HTHP. These results suggest that the CRUDE process can be a starting point for the development of a commercial ethanol production process.

Integrated membrane and microbial fuel cell technologies for enabling energy-efficient effluent Re-use in power plants.

Municipal wastewater is an attractive alternative to freshwater sources to meet the cooling water needs of thermal power plants. Here we offer an energy-efficient integrated microbial fuel cell (MFC)/ultrafiltration (UF) process to purify primary clarifier effluent from a municipal wastewater treatment plant for use as cooling water. The microbial fuel cell was shown to significantly reduce chemical oxygen demand (COD) in the primary settled wastewater effluent upstream of the UF module, while eliminating the energy demand required to deliver dissolved oxygen in conventional aerobic treatment. We investigated surface modification of the UF membranes to control fouling. Two promising hydrophilic monomers were identified in a high-throughput search: zwitterion (2-(Methacryloyloxy)-ethyl-dimethyl-(3-sulfopropyl ammoniumhydroxide, abbreviated BET SO3-), and amine (2-(Methacryloyloxy) ethyl trimethylammonium chloride, abbreviated N(CH3)3+). Monomers were grafted using UV-induced polymerization on commercial poly (ether sulfone) membranes. Filtration of MFC effluent by membranes modified with BET SO3- and N(CH3)3+ exhibited a lower rate of resistance increase and lower energy consumption than the commercially available membrane. The MFC/UF process produced high quality cooling water that meets the Electrical Power Research Institute (EPRI) recommendations for COD, a suite of metals (Fe, Al, Cu, Zn, Si, Mn, S, Ca and Mg), and offered extremely low corrosion rates (<0.05 mm/yr). A series of AC and DC diagnostic tests were used to evaluate the MFC performance.

Potential water resource impacts of hydraulic fracturing from unconventional oil production in the Bakken shale.

Modern drilling techniques, notably horizontal drilling and hydraulic fracturing, have enabled unconventional oil production (UOP) from the previously inaccessible Bakken Shale Formation located throughout Montana, North Dakota (ND) and the Canadian province of Saskatchewan. The majority of UOP from the Bakken shale occurs in ND, strengthening its oil industry and businesses, job market, and its gross domestic product. However, similar to UOP from other low-permeability shales, UOP from the Bakken shale can result in environmental and human health effects. For example, UOP from the ND Bakken shale generates a voluminous amount of saline wastewater including produced and flowback water that are characterized by unusual levels of total dissolved solids (350 g/L) and elevated levels of toxic and radioactive substances. Currently, 95% of the saline wastewater is piped or trucked onsite prior to disposal into Class II injection wells. Oil and gas wastewater (OGW) spills that occur during transport to injection sites can potentially result in drinking water resource contamination. This study presents a critical review of potential water resource impacts due to deterministic (freshwater withdrawals and produced water management) and probabilistic events (spills due to leaking pipelines and truck accidents) related to UOP from the Bakken shale in ND.

Electricity generation from defective tomatoes.

The United States faces a significant burden in treating 0.61billionkg of defective tomatoes (culls) every year. We present a proof-of-concept for generating electricity from culled tomatoes in microbial-electrochemical systems (MESs). This study delineates impedance behavior of the culled tomatoes in MESs and compares its impedance spectra with that of soluble substrates (dextrose, acetate, and wastewater). A series of AC and DC diagnostic tests have revealed the superior performance of the culled tomatoes compared to the pure substrates. Cyclic voltammetry results have indicated the active role of indigenous, diffusible redox-active pigments in the culled tomatoes on overall electricity production. Electrochemical impedance spectroscopy results have elucidated the role of peel and seed on the oxidation behavior of the culled tomatoes.