Bhushan Awate, Rebecca J. Steidl, Thilo Hamlischer, Gemma Reguera. Unwanted metabolites produced during fermentations reduce titers and productivity and increase the cost of downstream purification of the targeted product.
As a result, the economic feasibility of otherwise attractive fermentations is low. Using ethanol fermentation by the consolidated bioprocessing cellulolytic bacterium Cellulomonas uda, cathodic and anodic biofilms in single chamber microbial fuel cells demonstrate the effectiveness of anodic electro-fermentations at maximizing titers and productivity in a single-chamber microbial electrolysis cell SCMEC without the need for metabolic engineering of the fermentative microbe.
The performance of the SCMEC platform relied on the genetic improvements of anode biofilms of the exoelectrogen Geobacter sulfurreducens that prevented the oxidation of cathodic hydrogen and improved lactate oxidation. Cathodic and anodic biofilms in single chamber microbial fuel cells, a hybrid bioanode was designed that maximized the removal of organic acids in the fermentation broth. The targeted approach increased cellobiose consumption rates and ethanol titers, yields, and productivity three-fold or more, prevented pH imbalances and reduced batch-to-batch variability.
In addition, the sugar substrate was fully consumed and ethanol was enriched in the broth during the electro-fermentation, http://square-games.de/anzeige-aufgeben-er-sucht-sie.php its downstream purification.
Such improvements and the possibility of scaling up SCMEC configurations highlight the potential of anodic electro-fermentations to stimulate fermentative bacteria beyond their natural capacity and to levels required for industrial implementation. Stimulation of electro-fermentation in single-chamber microbial electrolysis cells driven by genetically engineered anode biofilms.
T1 - Stimulation of electro-fermentation in single-chamber microbial electrolysis more info driven by genetically engineered anode biofilms. N2 - Unwanted metabolites produced during fermentations reduce titers and productivity and increase the cost of downstream purification of http://square-games.de/leute-kennenlernen-witten.php targeted product.
AB - Unwanted metabolites produced during fermentations reduce titers and productivity and increase read article cost of downstream purification of the targeted product.
Stimulation of electro-fermentation in single-chamber microbial electrolysis cells driven by genetically engineered anode biofilms Bhushan Awate, Rebecca J. Abstract Unwanted metabolites produced during fermentations reduce titers and productivity and increase the cost http://square-games.de/frauen-treffen-nrw.php downstream purification of the targeted product.
Journal of Power Sources. Journal of Power Sources Awate, Bhushan ; Steidl, Rebecca J. Access to Document Link to publication in Scopus. Link to citation list in Scopus.
To receive news and publication updates for BioMed Research International, enter your email address in the box below. This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use, distribution, and cathodic and anodic biofilms in single chamber microbial fuel cells in any medium, provided the original work is properly cited.
Microbial Fuel cells MFCs have been proposed for nutrient removal and energy recovery from different wastes. In this study the anaerobic digestate was used to feed H-type MFC reactors, one with a graphite anode preconditioned with Geobacter sulfurreducens and the other with an unconditioned graphite anode.
The data demonstrate that the digestate acts as a carbon source, and even in the absence of anode preconditioning, electroactive bacteria colonise the anodic chamber, producing a maximum power density of Overall, these results demonstrate that MFCs can be used to recover anammox bacteria from natural sources, and it may represent a promising bioremediation unit in anaerobic digestor plants for the simultaneous nitrogen removal and electricity generation using digestate as substrate.
AD is accomplished through a series of complex microorganisms-driven this web page breaking down organic substances into CO 2 and volatile fatty acids acidogenesis that are then converted to biogas methanogenesis.
The remaining fraction in the digester is a nutrient-rich sludge, the digestate. Although transformation of nitrogen compounds occurs in AD, the nitrogen content remains high in the digestate making this by-product suitable to be used as fertilizer.
However, accumulation of biogas plants in small agriculture area or regions of intensive dairy cattle farming may lead to an oversupply of digestate. Indeed, digestate-based fertilization, when exceeding the need of crops, contributes to eutrophication of land and water bodies [ 12 ].
One of the most promising techniques to reduce nitrogen content from ammonia-rich wastewaters is the anaerobic ammonium oxidation ANAMMOX. Nitrogen removal under anaerobic conditions is driven by a group of anammox bacteria, which are affiliated to the order Brocadialeswithin the phylum of Planctomycetes [ 3 ].
The advantages of the anammox process, over the conventional method of nitrification and denitrification, include the lower oxygen demand and the absence of external carbon sources requirements. However, a critical aspect limiting the application of article source process in large bioreactors is the requirement of long start-up periods caused by the slow growth rate doubling time approximately weeks of sprüche kann flirten ich anammox bacteria and by the absence of conventional microbiological techniques for their cultivation [ 4 ].
Several methods have been proposed to obtain enrichment of anammox bacteria [ 4 — 9 ]; however, cultivation still poses a serious challenge. Nitrogen removal from wastewater has been studied in microbial fuel cells MFCselectrochemical devices that catalyse the conversion of chemical oxygen demand into electricity through the metabolic activity of microorganisms [ 10 ]. Typically in the anodic chamber, microorganisms cathodic and anodic biofilms in single chamber microbial fuel cells the organic matter and the electrons are donated to the anode.
These electrons are subsequently transferred, through an electric circuit, to the cathode electrode where they reduce terminal click acceptors.
Several bacteria have naturally evolved strategies to transfer electrons outside the cell surface and this feature has allowed the use of these microorganisms in MFCs. The main quality of electroactive bacteria in the MFC system is the ability to transfer electrons from the microbial cell to an electrode instead of the natural redox partner [ 11 ]. Different microorganisms, either gram-positive or gram-negative, can exchange electrons with electrodes and this is accomplished by different mechanisms: In most cases, bacteria may use more than one mechanism.
For example, in Shewanella oneidensis the electrons may hop from the cell-surface c -type cytochrome, which is part of a multiprotein complex that transferred click to see more electrons from the faz online partnersuche to the cell surface, to an external acceptor directly or via a flavin produced by the cell itself.
Geobacter sulfurreducens has many c-type cytochromes exposed to cathodic and anodic biofilms in single chamber microbial fuel cells cell surface among which OmcZ appears cathodic and anodic biofilms in single chamber microbial fuel cells be the key element for electron transfer. Additionally, the conductive pili ensure the long-range electron transfer dating 4 the typical multilayer G.
However, when MFCs are inoculated with a mixed culture, bacterial community analysis of the anodic biofilms revealed a great diversity in electroactive bacteria, regardless of the substrate type. This finding suggests a potential existence of other unknown species contributing to electricity generation through a variety of ways beyond the accepted Geobacter or Shewanella species [ click at this page ].
In addition to electricity production, the microbial metabolism can be used to produce valuable products or to remove unwanted compounds [ 14 ]. Accordingly, in cathodic and anodic biofilms in single chamber microbial fuel cells development of MFC, nitrogen removal has been considered as an added endpoint. Nitrate reduction at the cathode of MFC read article been demonstrated by different experimental approaches including the use of a potentiostat-poised half-cell in which nitrogen was completely reduced to N 2 gas in the absence check this out any organic substance electron donors [ 15 ].
More recently, a variety of denitrifying This web page reactors have been designed: Please click for source MFC, with the cathode exposed to air air-cathodeand two-chamber MFC, with ferricyanide catholyte were also tested for ammonia removal from swine wastewater [ 1920 ].
Ammonia and COD removal rates by single-chamber MFC were significantly improved by doubling the gas diffusion area [ 22 ]. In this study we investigated the possibility of biological ammonia removal with current generation in MFC reactors from digestate.
This was accomplished by feeding MFC reactors in batch mode with anaerobic digestate from agricultural by-products and cow manure. Electrical and chemical performances of both cells were investigated. Additionally, the presence of anammox bacteria in the digestate and their establishment in the MFC conditions had been assessed by molecular methods. Our results demonstrate that MFC reactors allow the development of digestate-derived biofilms that contribute to the simultaneous generation of electricity and nitrogen removal from the digestate.
However, since the substrate influences the bacterial diversity in the anode biofilm additional studies are needed to compare different types of digestate as well as to better understand the physical and biological mechanisms that can affect MFC performances in full-scale application systems.
The digestate was the effluent of an anaerobic digestion plant treating agricultural wastes and cow manure Azienda Agricola Bruni, Sutri, VT, Italy.
It was representative of a typical effluent of this kind of power plant in Italy [ 24 ]. All experiments were performed using H-type MFC. Anodic chambers were flushed with N 2 gas to maintain kennenlernen sprüche internet conditions. Feed solution digestate-based feeding was 1: Two MFC reactors operated under the same condition and configuration except the anode: Current was measured using the same instrument in a chronoamperometric mode, and Coulombic Efficiency CE was calculated as where was the total electric charge calculated cathodic and anodic biofilms in single chamber microbial fuel cells integrating the current over time and was the theoretical amount of electric charge available based on the total COD removal in the MFC section of the reactor [ 26 ].
Power, calculated as was normalized with respect to both the projected surface area of the cathode power density and the volume of the liquid media volumetric power density. The internal resistance value coincides with the value of the external resistance that maximizes load power consumption and drawing typical polarization curves by using the VSP instrument. The obtained solution was cooled, blended with NaOH, and distilled using the Kjeldahl method. Nitrites and nitrates were determined by ion chromatography, using a DX instrument Dionex.
At the end of the experimental procedure day 49 the graphite anode was cut into three sections. PCR amplification was carried out using the following primers: All primer sets were tested for sensitivity, optimal annealing, temperature, and primer efficiency with proper positive and negative controls.
The positive control for the anammox 16S rRNA gene amplification was a plasmid containing the sequence of the anammox 16S rRNA gene obtained in this study. The phylogenetic tree was obtained using the multiple alignment program for amino acid or nucleotide sequences MAFFT version 7.
Data were collected and analysed with the Axiovision 4. Samples for SEM analysis were fixed in 2. After rinsing in phosphate buffer, the samples were dehydrated in a series of graded ethanol and air-dried.
In order to determine whether the resident microbial community of the digestate can convert organic matter into electricity while reducing nitrogen content we set up H-type MFCs with the two-chamber separated by proton exchange membranes Figure 1. The latter was obtained from an MFC operated with G.
The initial digestate was diluted in order to obtain more favourable conditions for the growth of the resident bacteria and to reduce the introduction of toxic compounds that may inhibit bacterial activity [ 34 — 36 ].
During the first month the reactors behaved differently: Additionally, the rapid increase of CCV observed following feeding strongly suggested that it was due to the activity of the anode-associated biofilm. In the first three weeks, after reaching the peak, the CCV decreased with a different rate, whereas from day 28 to the end of operation the CCV cycles were more homogeneous.
This may be due to the presence of an evolving bacterial population in the anodic chamber that reached the equilibrium after weeks cathodic and anodic biofilms in single chamber microbial fuel cells operation. To synchronize the two reactors, the fifth feeding was postponed by one week, after which weekly feeding was restored.
After the start-up period MFC-C reached a reproducible maximum power computed by 2 of 0. The substrate type influences the MFC performance, not only in terms of bacterial community but also in the maximum power and Coulombic Efficiency.
Therefore, the time required to achieve the maximum cell voltage observed in our MFC systems is in accordance with the composition of the digestate-like medium supplemented with acetate. It has been reported that methanogens, by competing with electroactive bacteria for substrates, can reduce the performance of MFCs [ 37 ]. Nonetheless, in both reactors we did not detect CH 4 production, neither in the start-up period nor during operation regime, suggesting that methanogenesis did not take place in the MFCs or it was very low.
Since the digestate was collected in the final stage of biogas production it may be that methanogenesis was exhausted although we cannot exclude that digestate-based medium in MFC conditions outcompeted methanogens while favoring colonization of electrogenic bacteria.
Maximum power transfer curves Figure 3 a and polarization curves Figures cathodic and anodic biofilms in single chamber microbial fuel cells b and 3 c for both the MFCs were carried out in correspondence of CCV peak values at the sixth batch cycle when the reactors reached stable performances. The maximum power generation reached a peak value of 0. Conversely, in the MFC-U the digestate-resident microbial population might prefer slightly higher resistance conditions to better exploit the substrate as a result of the competition with the electrogenic bacteria.
Overall, the electrochemical measurements showed comparable performances between the reactors demonstrating that electrogenic bacteria were present in the digestate and possibly selected by MFC conditions. The absence of any gas development in both reactors allowed us to exclude methanogenic processes as the main cause of the resulting low Coulombic Efficiency. On the contrary, it could be attributed to the initial presence of nitrates, sulphates, and other terminal electron acceptors in the digestate.
Ammonia in the cathodic chamber was always found at negligible level disfavouring the hypothesis of the ammonium ion transit to the cathodic chamber through the membrane [ 39 ]. Ammonia volatilization in the cathodic chamber can be also excluded since no oxygen was insufflated and the cathodic pH was neutral.
Although, nitrogen consumption in the cells could be in part justified by the synthesis of new biomass in the anodic chamber, other mechanisms could be involved. According to the literature ammonia consumption in MFC can be also explained by several different specific pathways such as nitrification-denitrification, anammox, and nitrite reduction by lithotrophic ammonia oxidizers or by specific processes of ammonia oxidation coupled to electricity generation.
Taking into consideration the lower Coulombic Efficiency and total COD consumption calculated for the unconditioned cell with respect to the conditioned one, electricity generation from direct ammonia oxidation appeared to be negligible. At the same time, since dissolved oxygen in the anodic chambers was always lower than 0.
Collectively our results suggest that H-type MFC reactors fed with digestate-based medium allowed the development of a microbial consortium able to oxidize ammonia anaerobically, as proposed in other studies [ 40 ]. However, further experiments are needed to better investigate the nitrogen removal mechanism and to evaluate the maximum nitrogen amount potentially degradable in such systems. The morphology of the biofilm grown on the electrodes surface was analysed by scanning electron microscope SEM and fluorescence microscopy.
SEM analysis showed that anodes from both reactors were covered by bacterial biofilm Figures 5 a and 5 d. Close-up images Figures 5 b — 5 e revealed a different bacterial morphology with a cathodic and anodic biofilms in single chamber microbial fuel cells of bacilli, often tightly embedded into the biofilm matrix Figure 5 partnersuche schortens. Accordingly, MFC-C images at higher magnification revealed the presence of a multilayered biofilm in all the fields examined.
On the contrary, MFC-U biofilm showed composite morphology with smooth and rough areas with bacteria mainly located on the surface of the matrix. Additionally, MFC-U biofilm showed the presence of complex aggregates, probably due to the entrapped digestate sediments. These different morphologies could be due to the fact that biofilm in MFC-C partnersuche uckermark kostenlos previously colonized by G.
The fraction of live bacteria was slightly higher in MFC-U than in MFC-C, probably due to the fact that the anodic biofilm in the latter was one month older than the former.
Although the staining procedure cannot rigorously distinguish live and dead cells, check this out it is based on membrane permeability, the fraction of live bacteria in these reactors appeared much lower than previously described [ 13 ].
Some differences may account for this result such as anode materials graphite cathodic and anodic biofilms in single chamber microbial fuel cells carbon cloth and the age of the biofilm.
Nonetheless, current generation in the two reactors was similar to that reported by the aforementioned studies, suggesting that the anode biofilms developed from digestate are efficient in electricity production.
Additionally, the presence of a subpopulation of dead cells in-between the metabolically active cells cathodic and anodic biofilms in single chamber microbial fuel cells the electrode surface did not appear to significantly dampen electron transfer possibly due to long-range electrons transfer via the conductive pili [ 12 ].