Polyethylene glycol hydrogel coatings for protection of electroactive bacteria against chemical shocks.

Loss of bioelectrochemical activity in low resource environments or from chemical toxin exposure is a significant limitation in microbial electrochemical cells (MxCs), necessitating the development of materials that can stabilize and protect electroactive biofilms. Here, polyethylene glycol (PEG) hydrogels were designed as protective coatings over anodic biofilms, and the effect of the hydrogel coatings on biofilm viability under oligotrophic conditions and ammonia-N (NH4+-N) shocks was investigated. Hydrogel deposition occurred through polymerization of PEG divinyl sulfone and PEG tetrathiol precursor molecules, generating crosslinked PEG coatings with long-term hydrolytic stability between pH values of 3 and 10. Simultaneous monitoring of coated and uncoated electrodes co-located within the same MxC anode chamber confirmed that the hydrogel did not compromise biofilm viability, while the coated anode sustained nearly a 4 × higher current density (0.44 A/m2) compared to the uncoated anode (0.12 A/m2) under oligotrophic conditions. Chemical interactions between NH4+-N and PEG hydrogels revealed that the hydrogels provided a diffusive barrier to NH4+-N transport. This enabled PEG-coated biofilms to generate higher current densities during NH4+-N shocks and faster recovery afterwards. These results indicate that PEG-based coatings can expand the non-ideal chemical environments that electroactive biofilms can reliably operate in.

Critical evaluation of heat extraction temperature on soluble microbial products (SMP) and extracellular polymeric substances (EPS) quantification in wastewater processes.

While soluble microbial products (SMP) and extracellular polymeric substances (EPS) in wastewater bioprocesses have been widely studied, a lack of standard quantification procedures make it difficult to compare results between studies. This study investigated the effect of temperature on SMP and EPS profiles for biological nutrient removal (BNR) sludges and aerobic membrane bioreactor sludge by adapting the commonly used heat extraction and centrifugation scheme, followed by colorimetric quantification of the carbohydrate and protein fractions using the phenol-sulfuric acid (PS) and the bicinchoninic acid (BCA) methods, respectively. To overcome known inconsistencies in colorimetry, total carbon (TC), total nitrogen (TN), and fluorometry analyses were performed in tandem. SMP samples marginally benefitted from heat extraction, owing to their mostly soluble nature, while EPS profiles were greatly influenced by temperature. 60 °C appears to be a suitable general-purpose extraction temperature near the lysis threshold for the sludges tested. The PS method's misestimation due to lack of specificity was observed and contrasted by TC analyses, while the TN analyses corroborated the BCA assays. Fluorometry proved to be a sensitive and rapid analytical method that provided semi-quantitative information on SMP and EPS constituents, particularly its proteinaceous components, with positive implications for robust wastewater process control.

Polymer Surface Dissection for Correlated Microscopic and Compositional Analysis of Bacterial Aggregates during Membrane Biofouling.

Multispecies biofilms are a common limitation in membrane bioreactors, causing membrane clogging, degradation, and failure. There is a poor understanding of biological fouling mechanisms in these systems due to the limited number of experimental techniques useful for probing microbial interactions at the membrane interface. Here, we develop a new experimental method, termed polymer surface dissection (PSD), to investigate multispecies assembly processes over membrane surfaces. The PSD method uses photodegradable polyethylene glycol hydrogels functionalized with bioaffinity ligands to bind and detach microscale, microbial aggregates from the membrane for microscopic observation. Subsequent exposure of the hydrogel to high resolution, patterned UV light allows for controlled release of any selected aggregate of desired size at high purity for DNA extraction. Follow-up 16S community analysis reveals aggregate composition, correlating microscopic images with the bacterial community structure. The optimized approach can isolate aggregates with microscale spatial precision and yields genomic DNA at sufficient quantity and quality for sequencing from aggregates with areas as low as 2000 µm2, without the need of culturing for sample enrichment. To demonstrate the value of the approach, PSD was used to reveal the composition of microscale aggregates of different sizes during early-stage biofouling of aerobic wastewater communities over PVDF membranes. Larger aggregates exhibited lower diversity of bacterial communities, and a shift in the community structure was found as aggregate size increased to areas between 25,000 and 45,000 µm2, below which aggregates were more enriched in Bacteroidetes and above which aggregates were more enriched with Proteobacteria. The findings demonstrate that community succession can be observed within microscale aggregates and that the PSD method is useful for identification and characterization of early colonizing bacteria that drive biofouling on membrane surfaces.

Efficient recovery of phosphorus and sulfur from Anaerobic Membrane Bioreactor (AnMBR) permeate using chemical addition of iron and evaluation of its nutrient availability for plant uptake.

Anaerobic membrane bioreactors (AnMBRs) represent an emerging environmental biotechnology platform with the potential to simultaneously recover water, energy, and nutrients from concentrated wastewaters. The removal and beneficial capture of nutrients from AnMBR permeate has yet to be fully explored, therefore this study sought to foster iron phosphate recovery through a tertiary coagulation process, as well as characterize the recovered nutrient product (RNP) and assess its net phosphorus release, diffusion, and availability for plant uptake. One of the primary goals of this study was to optimize the dose of the coagulant, ferric chloride, and coagulant aid, aluminum chlorohydrate (ACH), for continuous application to the coagulation-flocculation-sedimentation (CFS) unit of an AnMBR pilot plant treating municipal wastewater, through controlled bench-scale jar tests. Anaerobic systems present unique challenges for nutrient capture, including high, dissolved hydrogen sulfide concentrations, along with settleability issues. The addition of the coagulant aid increases settleability, while enhancing phosphorus removal by up to 20%, decreasing iron demand. Water quality analysis indicated that a variety of factors affect nutrient capture, including the COD (chemical oxygen demand) concentration of the permeate and the limiting coagulant dose. COD >200 mg/L was shown to decrease the phosphorus removal efficiency by up to 15%. A combination of inductively coupled plasma optical emission spectrometer (ICP-OES) elemental analysis, inductively coupled plasma mass spectrometer (ICP-MS) elemental analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES) spectroscopy analysis was used to characterize the P-rich RNP which revealed a 2.58% w/w phosphorus content and the lack of a well-defined crystalline structure. Detailed studies on resin extractable phosphorus to assess the plant uptake potential also demonstrated that iron-based P-rich RNPs may not be an effective fertilizer product, as they can act as a phosphorus sink in some agricultural systems instead of a source.

Long-term microbial community dynamics in a pilot-scale gas sparged anaerobic membrane bioreactor treating municipal wastewater under seasonal variations.

This study evaluates the microbial community development in the suspended sludge within a pilot-scale gas sparged Anaerobic membrane bioreactor (AnMBR) under ambient conditions, as well as understand the influence of microbial signatures in the influent municipal wastewater on the bioreactor using amplicon sequence analysis. The predominant bacterial phyla comprised of Bacteroidetes, Proteobacteria, Firmicutes, and Chloroflexi demonstrated resiliency with ambient temperature operation over a period of 472 days. Acetoclastic Methanosaeta were predominant during most of the AnMBR operation. Beta diversity analysis indicated that the microbial communities present in the influent wastewater did not affect the AnMBR core microbiome. Syntrophic microbial interactions were evidenced by the presence of the members from Synergistales, Anaerolineales, Clostridiales, and Syntrophobacterales. The proliferation of sulfate reducing bacteria (SRB) along with sulfate reduction underscored the competition of SRB in the AnMBR. Operational and environmental variables did not greatly alter the core bacterial population based on canonical correspondence analysis.

A comparative pilot-scale evaluation of gas-sparged and granular activated carbon-fluidized anaerobic membrane bioreactors for domestic wastewater treatment.

Two significantly different pilot-scale AnMBRs were used to treat screened domestic wastewater for over one year. Both systems similarly reduced BOD5 and COD by 86-90% within a 13-32 °C temperature range and at comparable COD loading rates of 1.3-1.4 kg-COD m-3 d-1 and membrane fluxes of 7.6-7.9 L m-2 h-1 (LMH). However, the GAC-fluidized AnMBR achieved these results at a 65% shorter hydraulic retention time than the gas-sparged AnMBR. The gas-sparged AnMBR was able to operate at a similar operating permeability with greater reactor concentrations of suspended solids and colloidal organics than the GAC-fluidized AnMBR. Also, the membranes were damaged more in the GAC-fluidized system. To better capture the relative advantages of each system a hybrid AnMBR comprised of a GAC-fluidized bioreactor connected to a separate gas-sparged ultrafiltration membrane system is proposed. This will likely be more effective, efficient, robust, resilient, and cost-effective.

Long-Term Performance of a Pilot-Scale Gas-Sparged Anaerobic Membrane Bioreactor under Ambient Temperatures for Holistic Wastewater Treatment.

Concerns regarding ambient temperature operation, dissolved methane recovery, and nutrient removal have limited the implementation of anaerobic membrane bioreactors (AnMBRs) for domestic wastewater treatment. This study addresses these challenges using a pilot-scale gas-sparged AnMBR, with post-treatment recovery of dissolved methane and nutrients. Operating under ambient temperatures for 472 days, the AnMBR achieved an average effluent quality of 58 ± 27 mg/L COD and 25 ± 12 mg/L BOD5 at temperatures ranging from 12.7 to 31.5 °C. The average total methane yield was 0.14 ± 0.06 L-CH4/g-COD fed, with 42% of the total methane dissolved in the permeate. Dissolved methane removal using a hollow fiber membrane contactor achieved an average removal efficiency of 70 ± 5%, producing effluent dissolved methane concentrations of 3.8 ± 0.94 mg/L. The methane recovered from gaseous and dissolved fractions could generate an estimated 72.8% of the power required for energy neutrality. Nutrient recovery was accomplished using coagulation, flocculation, and sedimentation for removal of sulfide and phosphorus, followed by a clinoptilolite ion-exchange column for removal of ammonia, producing effluent concentrations of 0.7 ± 1.7 mg-S/L, 0.43 ± 0.29 mg-P/L and 0.05 ± 0.05 mg-N/L. The successful integration of AnMBRs in a treatment train that addresses the critical challenges of dissolved methane and nutrients demonstrates the viability of the technology in achieving holistic wastewater treatment.

Simultaneous fermentation of cellulose and current production with an enriched mixed culture of thermophilic bacteria in a microbial electrolysis cell.

An enriched mixed culture of thermophilic (60°C) bacteria was assembled for the purpose of using cellulose to produce current in thermophilic microbial electrolysis cells (MECs). Cellulose was fermented into sugars and acids before being consumed by anode-respiring bacteria (ARB) for current production. Current densities (j) were sustained at 6.5 ± 0.2 A m-2 in duplicate reactors with a coulombic efficiency (CE) of 84 ± 0.3%, a coulombic recovery (CR) of 54 ± 11% and without production of CH4 . Low-scan rate cyclic voltammetry (LSCV) revealed a mid-point potential (Eka ) of -0.17 V versus SHE. Pyrosequencing analysis of the V4 hypervariable region of 16S rDNA and scanning electron microscopy present an enriched thermophilic microbial community consisting mainly of the phylum Firmicutes with the Thermoanaerobacter (46 ± 13%) and Thermincola (28 ± 14%) genera occupying the biofilm anode in high relative abundance and Tepidmicrobium (38 ± 6%) and Moorella (11 ± 8%) genera present in high relative abundance in the bulk medium. The Thermoanaerobacter (15 ± 16%) and Brevibacillus (21 ± 30%) genera were also present in the bulk medium; however, their relative abundance varied by reactor. This study indicates that thermophilic consortia can obtain high CE and CR, while sustaining high current densities from cellulose in MECs.

Enhancing anaerobic digestion of food waste through biochemical methane potential assays at different substrate: inoculum ratios.

Food waste has a high energy potential that can be converted into useful energy in the form of methane via anaerobic digestion. Biochemical Methane Potential assays (BMPs) were conducted to quantify the impacts on methane production of different ratios of food waste. Anaerobic digester sludge (ADS) was used as the inoculum, and BMPs were performed at food waste:inoculum ratios of 0.42, 1.42, and 3.0g chemical oxygen demand/g volatile solids (VS). The 1.42 ratio had the highest CH4-COD recovery: 90% of the initial total chemical oxygen demand (TCOD) was from food waste, followed by ratios 0.42 and 3.0 at 69% and 57%, respectively. Addition of food waste above 0.42 caused a lag time for CH4 production that increased with higher ratios, which highlighted the negative impacts of overloading with food waste. The Gompertz equation was able to represent the results well, and it gave lag times of 0, 3.6 and 30days and maximum methane productions of 370, 910, and 1950mL for ratios 0.42, 1.42 and 3.0, respectively. While ratio 3.0 endured a long lag phase and low VSS destruction, ratio 1.42 achieved satisfactory results for all performance criteria. These results provide practical guidance on food-waste-to-inoculum ratios that can lead to optimizing methanogenic yield.

Electrochemical techniques reveal that total ammonium stress increases electron flow to anode respiration in mixed-species bacterial anode biofilms.

When anode-respiring bacteria (ARB) respire electrons to an anode in microbial electrochemical cells (MXCs), they harvest only a small amount of free energy. This means that ARB must have a high substrate-oxidation rate coupled with a high ratio of electrons used for respiration compared to total electrons removed by substrate utilization. It also means that they are especially susceptible to inhibition that slows anode respiration or lowers their biomass yield. Using several electrochemical techniques, we show that a relatively high total ammonium-nitrogen (TAN) concentration (2.2 g TAN/L) induced significant stress on the ARB biofilms, lowering their true yield and forcing the ARB to boost the ratio of electrons respired per electrons consumed from the substrate. In particular, a higher respiration rate, measured as current density (j), was associated with slower growth and a lower net yield, compared to an ARB biofilm grown with a lower ammonium concentration (0.2 g TAN/L). Further increases in influent TAN (to 3 and then to 4.4 g TAN/L) caused nearly complete inhibition of anode respiration. However, the ARB could recover from high-TAN inhibition after a shift of the MXC's feed to 0.2 g TAN/L. In summary, ARB biofilms were inhibited by a high TAN concentration, but could divert more electron flow toward anode respiration with modest inhibition and recover when severe inhibition was relieved. Biotechnol. Bioeng. 2017;114: 1151-1159. © 2017 Wiley Periodicals, Inc.

Archaea and Bacteria Acclimate to High Total Ammonia in a Methanogenic Reactor Treating Swine Waste.

Inhibition by ammonium at concentrations above 1000 mgN/L is known to harm the methanogenesis phase of anaerobic digestion. We anaerobically digested swine waste and achieved steady state COD-removal efficiency of around 52% with no fatty-acid or H2 accumulation. As the anaerobic microbial community adapted to the gradual increase of total ammonia-N (NH3-N) from 890 ± 295 to 2040 ± 30 mg/L, the Bacterial and Archaeal communities became less diverse. Phylotypes most closely related to hydrogenotrophic Methanoculleus (36.4%) and Methanobrevibacter (11.6%), along with acetoclastic Methanosaeta (29.3%), became the most abundant Archaeal sequences during acclimation. This was accompanied by a sharp increase in the relative abundances of phylotypes most closely related to acetogens and fatty-acid producers (Clostridium, Coprococcus, and Sphaerochaeta) and syntrophic fatty-acid Bacteria (Syntrophomonas, Clostridium, Clostridiaceae species, and Cloacamonaceae species) that have metabolic capabilities for butyrate and propionate fermentation, as well as for reverse acetogenesis. Our results provide evidence countering a prevailing theory that acetoclastic methanogens are selectively inhibited when the total ammonia-N concentration is greater than ~1000 mgN/L. Instead, acetoclastic and hydrogenotrophic methanogens coexisted in the presence of total ammonia-N of ~2000 mgN/L by establishing syntrophic relationships with fatty-acid fermenters, as well as homoacetogens able to carry out forward and reverse acetogenesis.

The effect of pH and buffer concentration on anode biofilms of Thermincola ferriacetica.

We assessed the effects of pH and buffer concentration on current production and growth of biofilms of Thermincola ferriacetica - a thermophilic, Gram-positive, anode-respiring bacterium (ARB) - grown on anodes poised at a potential of -0.06V vs. SHE in microbial electrolysis cells (MECs) at 60°C. T. ferriacetica generated current in the pH range of 5.2 to 8.3 with acetate as the electron donor and 50mM bicarbonate buffer. Maximum current density was reduced by ~80% at pH5.2 and ~14% at 7.0 compared to pH8.3. Increasing bicarbonate buffer concentrations from 10mM to 100mM resulted in an increase in the current density by 40±6%, from 6.8±1.1 to 11.2±2.7Am(-2), supporting that more buffer alleviated pH depression within T. ferriacetica biofilms. Confocal laser scanning microscopy (CLSM) images indicated that higher bicarbonate buffer concentrations resulted in larger live biofilm thicknesses: from 68±20µm at 10mM bicarbonate to >150µm at 100mM, supporting that buffer availability was a strong influence on biofilm thickness. In comparison to mesophilic Geobacter sulfurreducens biofilms, the faster transport rates at higher temperature and the ability to grow at relatively lower pH allowed T. ferriacetica to produce higher current densities with lower buffer concentrations.

Impact of Ammonium on Syntrophic Organohalide-Respiring and Fermenting Microbial Communities.

Syntrophic interactions between organohalide-respiring and fermentative microorganisms are critical for effective bioremediation of halogenated compounds. This work investigated the effect of ammonium concentration (up to 4 g liter(-1) NH4 (+)-N) on trichloroethene-reducing Dehalococcoides mccartyi and Geobacteraceae in microbial communities fed lactate and methanol. We found that production of ethene by D. mccartyi occurred in mineral medium containing ≤2 g liter(-1) NH4 (+)-N and in landfill leachate. For the partial reduction of trichloroethene (TCE) to cis-dichloroethene (cis-DCE) at ≥1 g liter(-1) NH4 (+)-N, organohalide-respiring dynamics shifted from D. mccartyi and Geobacteraceae to mainly D. mccartyi. An increasing concentration of ammonium was coupled to lower metabolic rates, longer lag times, and lower gene abundances for all microbial processes studied. The methanol fermentation pathway to acetate and H2 was conserved, regardless of the ammonium concentration provided. However, lactate fermentation shifted from propionic to acetogenic at concentrations of ≥2 g liter(-1) NH4 (+)-N. Our study findings strongly support a tolerance of D. mccartyi to high ammonium concentrations, highlighting the feasibility of organohalide respiration in ammonium-contaminated subsurface environments. IMPORTANCE Contamination with ammonium and chlorinated solvents has been reported in numerous subsurface environments, and these chemicals bring significant challenges for in situ bioremediation. Dehalococcoides mccartyi is able to reduce the chlorinated solvent trichloroethene to the nontoxic end product ethene. Fermentative bacteria are of central importance for organohalide respiration and bioremediation to provide D. mccartyi with H2, their electron donor, acetate, their carbon source, and other micronutrients. In this study, we found that high concentrations of ammonium negatively correlated with rates of trichloroethene reductive dehalogenation and fermentation. However, detoxification of trichloroethene to nontoxic ethene occurred even at ammonium concentrations typical of those found in animal waste (up to 2 g liter(-1) NH4 (+)-N). To date, hundreds of subsurface environments have been bioremediated through the unique metabolic capability of D. mccartyi. These findings extend our knowledge of D. mccartyi and provide insight for bioremediation of sites contaminated with chlorinated solvents and ammonium.

Evaluating biochemical methane production from brewer's spent yeast.

Anaerobic digestion treatment of brewer's spent yeast (SY) is a viable option for bioenergy capture. The biochemical methane potential (BMP) assay was performed with three different samples (SY1, SY2, and SY3) and SY1 dilutions (75, 50, and 25 % on a v/v basis). Gompertz-equation parameters denoted slow degradability of SY1 with methane production rates of 14.59-4.63 mL/day and lag phases of 10.72-19.7 days. Performance and kinetic parameters were obtained with the Gompertz equation and the first-order hydrolysis model with SY2 and SY3 diluted 25 % and SY1 50 %. A SY2 25 % gave a 17 % of TCOD conversion to methane as well as shorter lag phase (<1 day). Average estimated hydrolysis constant for SY was 0.0141 (±0.003) day(-1), and SY2 25 % was more appropriate for faster methane production. Methane capture and biogas composition were dependent upon the SY source, and co-digestion (or dilution) can be advantageous.

Total Value of Phosphorus Recovery.

Phosphorus (P) is a critical, geographically concentrated, nonrenewable resource necessary to support global food production. In excess (e.g., due to runoff or wastewater discharges), P is also a primary cause of eutrophication. To reconcile the simultaneous shortage and overabundance of P, lost P flows must be recovered and reused, alongside improvements in P-use efficiency. While this motivation is increasingly being recognized, little P recovery is practiced today, as recovered P generally cannot compete with the relatively low cost of mined P. Therefore, P is often captured to prevent its release into the environment without beneficial recovery and reuse. However, additional incentives for P recovery emerge when accounting for the total value of P recovery. This article provides a comprehensive overview of the range of benefits of recovering P from waste streams, i.e., the total value of recovering P. This approach accounts for P products, as well as other assets that are associated with P and can be recovered in parallel, such as energy, nitrogen, metals and minerals, and water. Additionally, P recovery provides valuable services to society and the environment by protecting and improving environmental quality, enhancing efficiency of waste treatment facilities, and improving food security and social equity. The needs to make P recovery a reality are also discussed, including business models, bottlenecks, and policy and education strategies.

Selective fermentation of carbohydrate and protein fractions of Scenedesmus, and biohydrogenation of its lipid fraction for enhanced recovery of saturated fatty acids.

Biofuels derived from microalgae have promise as carbon-neutral replacements for petroleum. However, difficulty extracting microalgae-derived lipids and the co-extraction of non-lipid components add major costs that detract from the benefits of microalgae-based biofuel. Selective fermentation could alleviate these problems by managing microbial degradation so that carbohydrates and proteins are hydrolyzed and fermented, but lipids remain intact. We evaluated selective fermentation of Scenedesmus biomass in batch experiments buffered at pH 5.5, 7, or 9. Carbohydrates were fermented up to 45% within the first 6 days, protein fermentation followed after about 20 days, and lipids (measured as fatty acid methyl esters, FAME) were conserved. Fermentation of the non-lipid components generated volatile fatty acids, with acetate, butyrate, and propionate being the dominant products. Selective fermentation of Scenedesmus biomass increased the amount of extractable FAME and the ratio of FAME to crude lipids. It also led to biohydrogenation of unsaturated FAME to more desirable saturated FAME (especially to C16:0 and C18:0), and the degree of saturation was inversely related to the accumulation of hydrogen gas after fermentation. Moreover, the microbial communities after selective fermentation were enriched in bacteria from families known to perform biohydrogenation, i.e., Porphyromonadaceae and Ruminococcaceae. Thus, this study provides proof-of-concept that selective fermentation can improve the quantity and quality of lipids that can be extracted from Scenedesmus.

Application of microbial electrolysis cells to treat spent yeast from an alcoholic fermentation.

Spent yeast (SY), a major challenge for the brewing industry, was treated using a microbial electrolysis cell to recover energy. Concentrations of SY from bench alcoholic fermentation and ethanol were tested, ranging from 750 to 1500mgCOD/L and 0 to 2400mgCOD/L respectively. COD removal efficiency (RE), coulombic efficiency (CE), coulombic recovery (CR), hydrogen production and current density were evaluated. The best treatment condition was 750mgCOD/LSY+1200mgCOD/L ethanol giving higher COD RE, CE, CR (90±1%, 90±2% and 81±1% respectively), as compared with 1500mgCOD/LSY (76±2%, 63±7% and 48±4% respectively); ethanol addition was significantly favorable (p value=0.011), possibly due to electron availability and SY autolysis. 1500mgCOD/LSY+1200mgCOD/L ethanol achieved higher current density (222.0±31.3A/m(3)) and hydrogen production (2.18±0.66 [Formula: see text] ) but with lower efficiencies (87±2% COD RE, 71.0±.4% CE). Future work should focus on electron sinks, acclimation and optimizing SY breakdown.

Characterization of Electrical Current-Generation Capabilities from Thermophilic Bacterium Thermoanaerobacter pseudethanolicus Using Xylose, Glucose, Cellobiose, or Acetate with Fixed Anode Potentials.

Thermoanaerobacter pseudethanolicus 39E (ATCC 33223), a thermophilic, Fe(III)-reducing, and fermentative bacterium, was evaluated for its ability to produce current from four electron donors-xylose, glucose, cellobiose, and acetate-with a fixed anode potential (+ 0.042 V vs SHE) in a microbial electrochemical cell (MXC). Under thermophilic conditions (60 °C), T. pseudethanolicus produced high current densities from xylose (5.8 ± 2.4 A m(-2)), glucose (4.3 ± 1.9 A m(-2)), and cellobiose (5.2 ± 1.6 A m(-2)). It produced insignificant current when grown with acetate, but consumed the acetate produced from sugar fermentation to produce electrical current. Low-scan cyclic voltammetry (LSCV) revealed a sigmoidal response with a midpoint potential of -0.17 V vs SHE. Coulombic efficiency (CE) varied by electron donor, with xylose at 34.8% ± 0.7%, glucose at 65.3% ± 1.0%, and cellobiose at 27.7% ± 1.5%. Anode respiration was sustained over a pH range of 5.4-8.3, with higher current densities observed at higher pH values. Scanning electron microscopy showed a well-developed biofilm of T. pseudethanolicus on the anode, and confocal laser scanning microscopy demonstrated a maximum biofilm thickness (Lf) greater than ~150 µm for the glucose-fed biofilm.

Draft Genome Sequence of the Gram-Positive Thermophilic Iron Reducer Thermincola ferriacetica Strain Z-0001T.

A 3.19-Mbp draft genome of the Gram-positive thermophilic iron-reducing Firmicutes isolate from the Peptococcaceae family, Thermincola ferriacetica Z-0001, was assembled at ~100× coverage from 100-bp paired-end Illumina reads. The draft genome contains 3,274 predicted genes (3,187 protein coding genes) and putative multiheme c-type cytochromes.

Effects of pre-fermentation and pulsed-electric-field treatment of primary sludge in microbial electrochemical cells.

The aim of this study was to investigate the combination of two technologies - pulsed electric field (PEF) pre-treatment and semi-continuous pre-fermentation of primary sludge (PS) - to produce volatile fatty acids (VFAs) as the electron donor for microbial electrolysis cells (MECs). Pre-fermentation with a 3-day solids retention time (SRT) led to the maximum generation of VFAs, with or without pretreatment of the PS through pulsed-electric-fields (PEF). PEF treatment before fermentation enhanced the accumulation of the preferred VFA, acetate, by 2.6-fold. Correspondingly, MEC anodes fed with centrate from 3-day pre-fermentation of PEF-treated PS had a maximum current density ∼3.1 A/m(2), which was 2.4-fold greater than the control pre-fermented centrate. Over the full duration of batch MEC experiments, using pre-fermented centrate led to successful performance in terms of Coulombic efficiency (95%), Coulombic recovery (80%), and COD-removal efficiency (85%).