Bioelectricity generation using two chamber microbial fuel cell treating wastewater from food processing

Electricity generation from microbial fuel cells which treat food processing wastewater was investigated in this study. Anaerobic anode and aerobic cathode chambers were separated by a proton exchange membrane in a two-compartment MFC reactor. Buffer solutions and food industry wastewater were used as electrolytes in the anode and cathode chambers, respectively. The produced voltage and current intensity were measured using a digital multimeter. Effluents from the anode compartment were tested for COD, BOD₅, NH₃, P, TSS, VSS, SO₄ and alkalinity. The maximum current density and power production were measured 527 mA/m² and 230 mW/m² in the anode area, respectively, at operation organic loading (OLR) of 0.364 g COD/l.d. At OLR of 0.182 g COD/l.d, maximum voltage and columbic efficiency production were recorded 0.475 V and 21%, respectively. Maximum removal efficiency of COD, BOD₅, NH₃, P, TSS, VSS, SO₄ and alkalinity were 86, 79, 73, 18, 68, 62, 30 and 58%, respectively. The results indicated that catalysts and mediator-less microbial fuel cells (CAML-MFC) can be considered as a better choice for simple and complete energy conversion from the wastewater of such industries and also this could be considered as a new method to offset wastewater treatment plant operating costs.     

Morphogenetic fields in embryogenesis, regeneration, and cancer: Non-local control of complex patterning

Establishment of shape during embryonic development, and the maintenance of shape against injury or tumorigenesis, requires constant coordination of cell behaviors toward the patterning needs of the host organism. Molecular cell biology and genetics have made great strides in understanding the mechanisms that regulate cell function. However, generalized rational control of shape is still largely beyond our current capabilities. Significant instructive signals function at long range to provide positional information and other cues to regulate organism-wide systems properties like anatomical polarity and size control. Is complex morphogenesis best understood as the emergent property of local cell interactions, or as the outcome of a computational process that is guided by a physically encoded map or template of the final goal state? Here I review recent data and molecular mechanisms relevant to morphogenetic fields: large-scale systems of physical properties that have been proposed to store patterning information during embryogenesis, regenerative repair, and cancer suppression that ultimately controls anatomy. Placing special emphasis on the role of endogenous bioelectric signals as an important component of the morphogenetic field, I speculate on novel approaches for the computational modeling and control of these fields with applications to synthetic biology, regenerative medicine, and evolutionary developmental biology.     

Unveiling the morphogenetic code: A new path at the intersection of physical energies and chemical signaling

In this editorial, we discuss the remarkable role of physical energies in the control of cell signaling networks and in the specification of the architectural plan of both somatic and stem cells. In particular, we focus on the biological relevance of bioelectricity in the pattern control that orchestrates both developmental and regenerative pathways. To this end, the narrative starts from the dawn of the first studies on animal electricity, reconsidering the pioneer work of Harold Saxton Burr in the light of the current achievements. We finally discuss the most recent evidence showing that bioelectric signaling is an essential component of the informational processes that control pattern specification during embryogenesis, regeneration, or even malignant transformation. We conclude that there is now mounting evidence for the existence of a Morphogenetic Code, and that deciphering this code may lead to unprecedented opportunities for the development of novel paradigms of cure in regenerative and precision medicine.     

A greenhouse gas indicator for bioenergy: some theoretical issues with practical implications

Background, aim, and scope  The expectations with respect to biomass as a resource for sustainable energy are sky-high. Many industrialized countries have adopted ambitious policy targets and have introduced financial measures to stimulate the production or use of bioenergy. Meanwhile, the side-effects and associated risks have been pointed out as well. To be able to make a well-informed decision, the Dutch government has expressed the intention to include sustainability criteria into relevant policy instruments. Main features  Among other criteria, it has been proposed to calculate a so-called life-cycle-based greenhouse gas (GHG) indicator, which expresses the reduction of GHG emissions of a bio-based fuel chain in comparison with a fossil-based fuel chain. Life-cycle-based biofuel studies persistently have problems with the handling of biogenic carbon balances and with the treatment of coproducts and recycling. In life-cycle assessments (LCAs) of agricultural products, a distinction between “negative” and “positive” emissions may be relevant. In particular, carbon dioxide, as a naturally occurring compound or an anthropogenic emission, takes part in the so-called geochemical carbon cycle. The most appropriate way to treat carbon cycles is to view them as genuine cycles and, thus, at the systems level, subtract the fixation of CO₂ during tree growth from the CO₂ emitted during waste treatment of discarded wood and to quantify the CH₄ emitted. In solving the multifunctionality problem, two steps may be distinguished. The first concerns the modeling of the product system studied in the inventory analysis. In this step, system boundaries are set, processes are described, and process flows are quantified. Multifunctionality problems can be identified and the model of the product system is drafted. The second step concerns solving the remaining multifunctionality problems. For this step, various ways of solving the multifunctionality problem have been proposed and applied, on the basis of mass, energy, economic value, avoided burdens, etc. As the GHG indicator may constitute the basis for granting subsidies to stimulate the use of bioenergy, for example, and as the method for the GHG indicator provides no guidelines on the handling of biogenic CO₂ and guidelines for solving multifunctionality problems such as with coproducts and recycling that leave room for various choices, this study analyzed whether the current GHG indicator provides results that are a robust basis for granting such subsidies. Results  For the robustness check, a hypothetical case study on wood residue-based electricity was set up in order to illustrate what the effects of different solutions and choices for the two steps mentioned may be. The case dealt with the production of wood pellets (residues of the wood industry) that are cofired in a coal-fired power plant. The functional unit is 1 kWh of electricity. Three possibilities for the places of the multifunctional process, two possibilities for whether or not to include biogenic CO₂, and four possibilities for the allocation method were distinguished and calculated. Varying the options for these three choices in this way appears to have a huge effect on the GHG indicator, while no clear pattern seems to emerge. Discussion  The results found for this hypothetical case indicate that there are several methodological choices that have not sufficiently been fixed by the presently available standards and guidelines for LCA and GHG assessment of bioenergy systems. In particular, we have focused on issues related to biogenic CO₂ and allocation, two issues that play a prominent role in the assessment of bioenergy systems. Moreover, we have demonstrated with a small hypothetical case study that these are not only issues that might theoretically show up, but that they play a decisive role in practice. Conclusions  The present (Dutch) GHG indicator lacks robustness, which will raise problems for providing a sound basis for granting subsidies. This situation can, however, be improved by reducing the freedom of choices for the handling of biogenic CO₂ and allocation to an absolute minimum. Recommendations and perspectives  Even then, however, differences could appear due to different definitions, data sources, and method interpretations. It thus appears that two kinds of guidance are needed: (1) the LCA methodology itself should be expanded with guidelines for those issues that follow from science, logic, or consensus; (2) in the policy regulation that demands LCA to be the basis of the decision, additional guidelines should be specified that perhaps do not (yet) have the status of being scientifically proven or generally agreed upon, but that serve as a set of temporary extra guidelines.

Bioelectric signaling in regeneration: Mechanisms of ionic controls of growth and form

The ability to control pattern formation is critical for the both the embryonic development of complex structures as well as for the regeneration/repair of damaged or missing tissues and organs. In addition to chemical gradients and gene regulatory networks, endogenous ion flows are key regulators of cell behavior. Not only do bioelectric cues provide information needed for the initial development of structures, they also enable the robust restoration of normal pattern after injury. In order to expand our basic understanding of morphogenetic processes responsible for the repair of complex anatomy, we need to identify the roles of endogenous voltage gradients, ion flows, and electric fields. In complement to the current focus on molecular genetics, decoding the information transduced by bioelectric cues enhances our knowledge of the dynamic control of growth and pattern formation. Recent advances in science and technology place us in an exciting time to elucidate the interplay between molecular-genetic inputs and important biophysical cues that direct the creation of tissues and organs. Moving forward, these new insights enable additional approaches to direct cell behavior and may result in profound advances in augmentation of regenerative capacity.     

Electric organ discharges of the gymnotiform fishes: III. Brachyhypopomus

We measured and mapped the electric fields produced by three species of neotropical electric fish of the genus Brachyhypopomus (Gymnotiformes, Rham phichthyoidea, Hypopomidae), formerly Hypopomus. These species produce biphasic pulsed discharges from myogenic electric organs. Spatio-temporal false-color maps of the electric organ discharges measured on the skin show that the electric field is not a simple dipole in Brachyhypopomus. Instead, the dipole center moves rostro-caudally during the 1st phase (P1) of the electric organ discharge, and is stationary during the 2nd phase (P2). Except at the head and tip of tail, electric field lines rotate in the lateral and dorso-ventral planes. Rostro-caudal differences in field amplitude, field lines, and spatial stability suggest that different parts of the electric organ have undergone selection for different functions; the rostral portions seem specialized for electrosensory processing, whereas the caudal portions show adaptations for d.c. signal balancing and mate attraction as well. Computer animations of the electric field images described in this paper are available on web sites http://www.bbb.caltech.edu/ElectricFish or http://www.fiu.edu/∼stoddard/electricfish.html. Accepted: 22 September 1998     

Growth across scales: Dynamic signaling impacts tissue size and shape

Organ and tissue growth result from an integration of biophysical communication across biological scales, both in time and space. In this review, we highlight new insight into the dynamic connections between control mechanisms operating at different length scales. First, we consider how the dynamics of chemical and electrical signaling in the shape of gradients or waves affect spatiotemporal signal interpretation. Then, we discuss the mechanics underlying dynamic cell behavior during oriented tissue growth, followed by the connections between signaling at the tissue and organismal levels.     

Bioelectric and biosynthetic aspects of cell polarity inAllomyces macrogynus

Summary In contrast to all filamentous fungi examined to date, vegetative hyphae ofAllomyces macrogynus, whether extending or not, produced an outward flow of positive electrical current, at a maximum of 0.16 A cm^–2 around 40 m behind the apex, as measured with a vibrating probe. Inward currents of up to 0.55 A cm^–2 were recorded around the rhizoids. Increases in outward current were observed in hyphae pre-grown under oxygen deficiency and then allowed to widen backwards to the hyphal base in sufficient oxygen. When spores were germinated in an applied electrical field they produced rhizoids predominantly towards the anode. Hyphae were produced initially towards the cathode but later bent around towards the anode. Experiments with a range of chemicals provided no evidence for the involvement of calcium in vegetative growth and development inA. macrogynus. Polyoxin and nikkomycin, inhibitors of chitin synthesis, had no effect on swimming zoospores, but inhibited wall formation of cysts, rhizoids and forward and backward growing hyphae.     

Electricity generation from synthesis gas by microbial processes: CO fermentation and microbial fuel cell technology

A microbiological process was established to harvest electricity from the carbon monoxide (CO). A CO fermenter was enriched with CO as the sole carbon source. The DGGE/DNA sequencing results showed that Acetobacterium spp. were enriched from the anaerobic digester fluid. After the fermenter was operated under continuous mode, the products were then continuously fed to the microbial fuel cell (MFC) to generate electricity. Even though the conversion yield was quite low, this study proved that synthesis gas (syn-gas) can be converted to electricity with the aid of microbes that do not possess the drawbacks of metal catalysts of conventional methods.     

A single chamber stackable microbial fuel cell with air cathode

A single chamber stackable microbial fuel cell (SCS-MFC) comprising four MFC units was developed. When operated separately, each unit generated a volumetric power density (P_max,V) of 26.2 W/m³ at 5.8 mA or 475 mV. The total columbic efficiency was 40% for each unit. Parallel connection of four units produced the same level of power output (P_max,V of 22.8 W/m³ at 27 mA), which was approximately four times higher than a single unit alone. Series connection of four units, however, only generated a maximum power output of 14.7 W/m³ at 730 mV, which was less than the expected value. This energy loss appeared to be caused by lateral current flow between two units, particularly in the middle of the system. The cathode was found to be the major limiting factor in our system. Compared to the stacked operation of multiple separate MFCs, our single chamber reactor does not require a delicate water distribution system and thus is more easily implemented in pre-existing wastewater treatment facilities with serpentine flow paths, such as fixed-bed reactors, with minimal infrastructure changes.