In Situ Engineering of Intracellular Hemoglobin for Implantable High-Performance Biofuel Cells.

The key challenge for the broad application of implantable biofuel cells (BFCs) is to achieve inorganic-organic composite biocompatibility while improving the activity and selectivity of the catalysts. We have fabricated nanoengineered red blood cells (NERBCs) by an environmentally friendly method by using red blood cells as the raw material and hemoglobin (Hb) embedded with ultrasmall hydroxyapatite (HAP, Ca10 (PO4 )6 (OH)2 ) as the functional BFC cathode material. The NERBCs showed greatly enhanced cell performance with high electrocatalytic activity, stability, and selectivity. The NERBCs maintained the original biological properties of the natural cell, while enhancing the catalytic oxygen reduction reaction (ORR) through the interaction between -OH groups in HAP and the Hb in RBCs. They also enabled direct electron transportation, eliminating the need for an electron-transfer mediator, and showed catalytic inactivity for glucose oxidation, thus potentially enabling the development of separator-free BFCs.

Agricultural anaerobic digestion power plants in Ireland and Germany: policy and practice.

The process of anaerobic digestion (AD) is valued as a carbon-neutral energy source, while simultaneously treating organic waste, making it safer for disposal or use as a fertilizer on agricultural land. The AD process in many European nations, such as Germany, has grown from use of small, localized digesters to the operation of large-scale treatment facilities, which contribute significantly to national renewable energy quotas. However, these large AD plants are costly to run and demand intensive farming of energy crops for feedstock. Current policy in Germany has transitioned to support funding for smaller digesters, while also limiting the use of energy crops. AD within Ireland, as a new technology, is affected by ambiguous governmental policies concerning waste and energy. A clear governmental strategy supporting on-site AD processing of agricultural waste will significantly reduce Ireland's carbon footprint, improve the safety and bioavailability of agricultural waste, and provide an indigenous renewable energy source. © 2016 Society of Chemical Industry.

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.

Glucose oxidase nanotube-based enzymatic biofuel cells with improved laccase biocathodes.

Glucose/O(2) biofuel cells (BFCs) with an improved power density and stability were developed, using glucose oxidase (GOD) nanotubes with polypyrrole (PPy)-carbon nanotubes (CNTs)-GOD layers deposited on their surface as an anode and a PPy-laccase-2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) film type cathode. The GOD nanotubes were fabricated within the nanopores of an anodized aluminum oxide membrane using a template-assisted layer-by-layer deposition method. These BFCs exhibited a higher volumetric power than the best performance reported previously; this was likely due to an increase in enzyme loading of GOD nanotubes and improved electrochemical properties of the PPy-CNTs-GOD layers. The stability of BFCs was closely related to the leakage of ABTS from the cathode. When the leakage of ABTS was suppressed, the power density of BFCs was nearly unchanged for at least 8 days under physiological conditions.

Conception and optimization of a membrane electrode assembly microbial fuel cell (MEA-MFC) for treatment of domestic wastewater.

A membrane electrode assembly (MEA) for microbial fuel cells (MEA-MFC) was developed for continuous electricity production while treating domestic wastewater concurrently. It was optimized via three upgraded versions (noted α, ß and γ) in terms of design (current collectors, hydrophilic separator nature) and operating conditions (hydraulic retention time, external resistance, aeration rate, recirculation). An overall rise of power by over 100% from version α to γ shows the importance of factors such as the choice of proper construction materials and prevention of short-circuits. A power of 2.5 mW was generated with a hydraulic retention time of 2.3 h when a Selemion proton exchange membrane was used as a hydrophilic separator in the MEA and 2.8 mW were attained with a reverse osmosis membrane. The MFC also showed a competitive value of internal resistance (≈40-50 Ω) as compared to the literature, especially considering its large volume (3 L). However, the operation of our system in a complete loop where the anolyte was allowed to trickle over the cathode (version γ) resulted in system failure.

Scaling up microbial fuel cells and other bioelectrochemical systems.

Scientific research has advanced on different microbial fuel cell (MFC) technologies in the laboratory at an amazing pace, with power densities having reached over 1 kW/m(3) (reactor volume) and to 6.9 W/m(2) (anode area) under optimal conditions. The main challenge is to bring these technologies out of the laboratory and engineer practical systems for bioenergy production at larger scales. Recent advances in new types of electrodes, a better understanding of the impact of membranes and separators on performance of these systems, and results from several new pilot-scale tests are all good indicators that commercialization of the technology could be possible within a few years. Some of the newest advances and future challenges are reviewed here with respect to practical applications of these MFCs for renewable energy production and other applications.

New applications and performance of bioelectrochemical systems.

Bioelectrochemical systems (BESs) are emerging technologies which use microorganisms to catalyze the reactions at the anode and/or cathode. BES research is advancing rapidly, and a whole range of applications using different electron donors and acceptors has already been developed. In this mini review, we focus on technological aspects of the expanding application of BESs. We will analyze the anode and cathode half-reactions in terms of their standard and actual potential and report the overpotentials of these half-reactions by comparing the reported potentials with their theoretical potentials. When combining anodes with cathodes in a BES, new bottlenecks and opportunities arise. For application of BESs, it is crucial to lower the internal energy losses and increase productivity at the same time. Membranes are a crucial element to obtain high efficiencies and pure products but increase the internal resistance of BESs. The comparison between production of fuels and chemicals in BESs and in present production processes should gain more attention in future BES research. By making this comparison, it will become clear if the scope of BESs can and should be further developed into the field of biorefineries.

Recovery of chromium, copper and vanadium combined with electricity generation in two-chambered microbial fuel cells.

Microbial fuel cells (MFCs) offer a promising solution towards recovery and treatment of heavy metal pollutants. In this study, two-chambered MFCs were employed for recovery of chromium, copper and vanadium (Cr (VI), Cu (II) and V (V)). One g/L concentrations of K2Cr2O7, CuCl2 and NaVO3 served as catholytes, while a mixed culture was used as anolyte. Cr (VI), Cu (II) and V (V) were reduced biologically into less toxic forms of Cr (III), Cu and V (IV) respectively. Power density and cathodic efficiency were calculated for each of the catholytes. Cr (VI) gave the maximum power density and cathodic efficiency due to its high redox potential. Current produced depended on the concentration of the catholyte. Over a period of time, biological reduction of catholytes lead to decrease in the metal concentrations, which demonstrated the application of MFC technology towards heavy metal treatment and recovery in a reasonably cost-effective manner.

Good policy follows good science: using criteria and indicators for assessing sustainable biofuel production.

Developing scientific criteria and indicators should play a critical role in charting a sustainable path for the rapidly developing biofuel industry. The challenge ahead in developing such criteria and indicators is to address the limitations on data and modeling.

Performance of trickling bed microbial fuel cell treating isopropyl alcohol vapor: Effects of shock-load and shut-down episodes.

This work investigates the enhancement in the removal efficiency of isopropyl alcohol (IPA) vapor by a hollow trickling-bed microbial fuel cell (TB-MFC) that can be achieved by certain modifications. The effects of shock load and shutdown on the performance of TB-MFC were evaluated. When organic loading (OL) of IPA was approximately 22.1-88.5 g m-3 h-1, the removal efficiency of 85.1-93.8% of the TB-MFC was achieved. With an empty bed residence time (EBRT) of 60 s and an inlet IPA concentration of 4.42 g m-3, the TB-MFC achieved its maximum EC of 150 g m-3 h-1, which was 1.7-4 times higher than reported for conventional biofiltration technology. A maximum closed-circuit voltage (CCV) of 173 mV and maximum power density (PDmax) of 53.2 mW m-3 were obtained under optimal conditions (IPA concentration = 0.73 g m-3; EBRT = 60 s). Short-term shutdown (seven days) did not cause significant changes in EC, CCV, and PDmax of the TB-MFC. This investigation establishes the feasibility of using a trickling-bed MFC to substantially increase the removal of IPA and handle shock-load and shut-down events. To increase EC and power output, this laboratory-scale TB-MFC could easily be scaled up by stacking anodes, and has great potential for future application in the field in various industries.

Fluctuation of electrode potential based on molecular regulation induced diversity of electrogenesis behavior in multiple equilibrium microbial fuel cell.

In this study, the electrogenesis behaviors and mechanisms in multiple equilibrium microbial fuel cells (MEMFCs) which volatile fatty acids as multiple electron donors are investigated. The electrochemical property and energy recovery can be enhanced in propionic acid dominant systems (HPr-D-MEMFCs) which compares to butyric acid dominant systems (HBu-D-MEMFCs), increase power density from 0.04 to 0.43 W/m2 and energy recovery efficiency from 2.07 to 5.44%, respectively. With isotope experiment analysis, the fluctuation of electrode potentials induce diverse electrogenesis pathways that high utilization efficiencies and bioconversion efficiency of hybrid acids observed in HPr-D-MEMFCs which different with HAc-D-MEMFCs and HBu-D-MEMFCs. In addition, the electrochemical and microbial community variation of MEMFCs reveal that the direct interspecies electron transfer stimulated with higher electric double layer capacitance, and activities of exoelectrogens enhanced with high relative abundance in HPr-D-MEMFCs. The findings present an intensive study in electrogenesis, providing a promising way to promote energy recovery and further extend its application value.

Optimizing the performance of organics and nutrient removal in constructed wetland-microbial fuel cell systems.

No studies have reported the operation optimization of constructed wetland-microbial fuel cell (CW-MFC) systems in terms of pollutant removal under the influence of multiple factors. Multifactor orthogonal experiment (L25(55)) was designed in this study to investigate the influence of multiple factors on the CW-MFC performance and determine the optimal operating conditions for the organics and nutrient removal. The tested factors include volume ratio of granular graphite in the substrates (A), dissolved oxygen (DO) concentration in the cathode zone (B), hydraulic retention time (HRT) (C), effluent reflux ratio (D), and external resistance (E). The results showed that the sequence and degree of the influence of the tested factors were C** > B** > E** > D* > A for chemical oxygen demand (CODCr) removal, C** > B** > D* > E > A for ammonia nitrogen (NH3-N) removal, C** > D** > B** > E* > A* for total nitrogen (TN) removal, and C** > D* > B > A > E for total phosphorus (TP) removal (* denotes significant influence (0.01 < p < 0.05) and ** denotes extremely significant influence (p ≤ 0.01)). HRT was found to be the most influential factor for pollutant removal in CW-MFCs with a contribution of over 50% for CODCr, NH3-N and TP removal, and over 45% for TN removal. The optimal operating conditions for CODCr, NH3-N, TN and TP removal in CW-MFCs were quite different from each other. Comprehensively considering the treatment efficiency of pollutant, treatment capacity of wastewater, and energy consumption from artificial aeration, the selected comprehensive optimal operating conditions for CW-MFCs were A = 20%, B = 1.5 mg/L, C = 1.5 days, D = 50%, and E ≤ 250 Ω. Moreover, incorporating the MFC significantly enhanced the organics and nitrogen removal in CWs by 8.72-11.04% CODCr and 9.78-12.04% TN.

A novel photoactive and three-dimensional stainless steel anode dramatically enhances the current density of bioelectrochemical systems.

This study reports a high-performance 3D stainless-steel photoanode (3D SS photoanode) for bioelectrochemical systems (BESs). The 3D SS photoanode consists of 3D carbon-coated SS felt bioactive side and a flat α-Fe2O3-coated SS plate photoactive side. Without light illumination, the electrode reached a current density of 26.2 ±â€¯1.9 A m-2, which was already one of the highest current densities reported thus far. Under illumination, the current density of the electrode was further increased to 46.5 ±â€¯2.9 A m-2. The mechanism of the photo-enhanced current production can be attributed to the reduced charge-transfer resistance between electrode surface and the biofilm with illumination. It was also found that long-term light illumination can enhance the biofilm formation on the 3D SS photoanode. These findings demonstrate that using the synergistic effect of photocatalysis and microbial electrocatalysis is an efficient way to boost the current production of the existing high-performance 3D anodes for BESs.

Quick start-up and performance of microbial fuel cell enhanced with a polydiallyldimethylammonium chloride modified carbon felt anode.

It is of significant importance to simultaneously shorten the start-up time and enhance the electricity generation performance for practical application of microbial fuel cell (MFC). In this paper, the polydiallyldimethylammonium chloride (PDDA) modified carbon felt (PDDA-CF) electrode was prepared and used as the anode of PDDA-MFC. The anode significantly enhanced the start-up speed and electricity generation and dye wastewater degradation performances of the PDDA-MFC. The start-up time of PDDA-MFC is only 9 h, which is only 7.5% that of the unmodified carbon felt anode MFC (CF-MFC). The charge transfer resistance, the maximum output voltage and the maximum output power density of PDDA-MFC were 9.7 Ω, 741 mV and 537.8 mW m-2 respectively, which were 70.3% lower than, 1.7 times and 3.3 times greater than those of CF-MFC respectively. In addition, the color and chemical oxygen demand (COD) removal rates of Reactive Brilliant Red X-3B for PDDA-MFC reached 95.94% and 64.24% at 24 h respectively, which were 41.5% and 51.2% higher than those of CF-MFC respectively. Due to the electrostatic attraction of PDDA, the adhesion and metabolic mass transfer rate of exoelectrogens are accelerated, thus the PDDA-CF electrode has excellent electrochemical properties and bio-affinity. This paper provides a new idea to enhance the start-up speed and performance of MFC simultaneously.

Safety evaluation for a biodiesel process using prion-contaminated animal fat as a source.

BACKGROUND: Due to the bovine spongiform encephalopathy (BSE), specified risk material (SRM) as well as animal meat and bone meal (MBM) are banned from the food and feed chain because of a possible infection with pathogenic prions (PrP(Sc)). Nowadays, prions are widely accepted to be responsible for TSE(transmissible spongiform encephalopathies)-caused illnesses like BSE and scrapie, and especially for the occurrence of the new variant of CJD in humans. Presently, SRM and MBM are burnt under high temperatures to avoid any hazards for humans, animals or the environment. The aim of this study was to evaluate a method using animal fat separated from Category I material which includes SRM and the carcasses of TSE-infected animals, or animals suspected of being infected with TSE, as a source for producing biodiesel by transesterification, analogous to the biodiesel process using vegetable oil. METHODS: For this purpose, animal fat was spiked with scrapie-infected hamster brain equivalents--as representative for a TSE-infected animal--and the biodiesel manufacturing process was downscaled and performed under lab-scale conditions. RESULTS AND DISCUSSION: The results analysed by Western blotting showed clearly that almost each single step of the process leads to a significant reduction of the concentration of the pathogenic prion protein (PrP(Sc)) in the main and side-products. CONCLUSION: The data revealed that the biodiesel production, even from material with a high concentration of pathogenic prions, can be considered as safe. RECOMMENDATIONS AND OUTLOOK: The obtained results indicated that biodiesel produced from prion-contaminated fat was safe under the tested process conditions. However, it has to be pointed out that the results cannot be generalized because a different process control using other conditions may lead to different results and then has to be analysed independently. It is clear that the production of biodiesel from high risk material represents a more economic usage than the combustion of such material.

Surgical Ablation of Atrial Fibrillation Using Energy Sources.

Surgical ablation, concomitant with other operations, is an option for treatment in patients with chronic atrial fibrillation. The aim of this study is to present a literature review on surgical ablation of atrial fibrillation in patients undergoing cardiac surgery, considering energy sources and return to sinus rhythm. A comprehensive survey was performed in the literature on surgical ablation of atrial fibrillation considering energy sources, sample size, study type, outcome (early and late), and return to sinus rhythm. Analyzing studies with immediate results (n=5), the percentage of return to sinus rhythm ranged from 73% to 96%, while those with long-term results (n=20) (from 12 months on) ranged from 62% to 97.7%. In both of them, there was subsequent clinical improvement of patients who underwent ablation, regardless of the energy source used. Surgical ablation of atrial fibrillation is essential for the treatment of this arrhythmia. With current technology, it may be minimally invasive, making it mandatory to perform a procedure in an attempt to revert to sinus rhythm in patients requiring heart surgery.

Myopotential inhibition of unipolar lithium pacemakers.

The effect of isometric upper extremity exercise on pacemaker function was evaluated in 27 patients who remained pacemaker-dependent during testing. Inhibition was demonstrated in eight (31 percent) of which five were symptomatic. Based on design of the sensing amplifier and return to an all-metal housing in the unipolar lithium pulse generators, myopotential inhibition is being recognized as one cause of symptomatic pacemaker inhibition that is more common than generally appreciated. A method of evaluation and management options for symptomatic patients are discussed. Routine testing of all patients should be performed at the time of a regular office evaluation. If one model pulse generator appears to be particularly prone to myopotential inhibition, this knowledge should be considered in the choice of future pacing systems.

Approaches to the artificial heart. Invited speaker.

Over the last two decades, the implantable artificial heart has evolved from an idea to a device capable of completely supporting the circulation for periods now exceeding 5 months. Although initial animal studies were limited by thromboembolism and device breakage, the usual causes of death in experimental animals are now infection, atrioventricular valve obstruction, elastomer bladder calcification, or inadequate cardiac output because of the relatively rapid growth of the young calves. As a result of the bulky nature of the energy converter and the substantial risk of infection with large diameter percutaneous tubes, clinical use of their air-powered artificial hearts will be limited to patients who are awaiting or being prepared for heart transplantation. Artificial hearts with implanted energy converters are being developed for permanent heart replacement. These devices require well-designed, durable mechanical components and sophisticated control systems. Although initial designs centered around thermal engines powered by a completely implantable nuclear energy source, the excessive cost and potential dangers have shifted the focus away from the nuclear system. Several electrically driven artificial hearts, based on samarium-cobalt magnet brushless direct-current motors, are now undergoing bench testing and will be ready for long-term animal studies within 2 years. This research will culminate with the availability of an "off-the-shelf" electrically powered artificial heart for use in patients with a wide range of nonrepairable forms of end-stage heart disease.

Clinical experience with the isotopic cardiac pacemaker.

Clinical experience with isotopic pacemakers in 59 patients is compared with that in 77 control patients having conventional chemical battery-powered pulse generators. The review covers a 51/2-year period. Statistical analysis of the two series is impossible because of the numerous variables such as age, type of disease, number of controls, types of test and control pulse generators, dates of insertion, and protocol regulations. However, there were pulse generator failures in the control group, but not in the test group. Though not proven in this study, the isotopic cardiac pacer is likely to last longer than conventional chemical battery-powered units, and could provide lifetime pacing for many patients. The risk of carcinogenesis is minimal and seems negligible in older patients. The isotopic cardiac pacer, in spite of restrictions of the Nuclear Regulatory Commission, should be considered for any patient with a life expectancy of 10 or more years. Paradoxically, it might be indicated in older rather than younger patients.

MFC-cascade stacks maximise COD reduction and avoid voltage reversal under adverse conditions.

Six continuous-flow Microbial Fuel Cells (MFCs) configured as a vertical cascade and tested under different electrical connections are presented. When in parallel, stable operation and higher power and current densities than individual MFCs were observed, despite substrate imbalances. The cascading dynamic allowed for a cumulative COD reduction of >95% in approximately 5.7h, equivalent to 7.97 kg COD m(-3) d(-1). Under a series configuration, the stack exhibited considerable losses until correct fluidic/electrical insulation of the units was applied, upon which the stack also exhibited superior performance. In both electrical configurations, the 6 MFC system was systematically starved for up to 15 d, with no significant performance degradation. The results from the 14-month trials, demonstrate that cascade-stacking of small units can result in enhanced electricity production (vs single large units) and treatment rates without using expensive catalysts. It is also demonstrated that substrate imbalances and starvation do not necessarily result in cell-voltage reversal.