Among the methods used to remove metals and their compounds from landfill leachates with low application costs and high efficiency are bioleaching and biosorption. The most effective bacteria used in the metal removal process are Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. The aim of the study was to determine the usefulness of the A. ferrooxidans and A. thiooxidans population in removing heavy metals from landfill leachate. In addition, development opportunities for bacterial population using landfill leachate as growth medium were identified. The substrate for the research was the raw leachate before the reverse osmosis process. In order to increase the efficiency of trace elements removal and recovery from leachate, variable combinations have been used which differ by the addition of sulfuric acid, A. ferrooxidans culture, A. thiooxidans culture, mixed culture containing populations of both bacteria, and elemental sulfur. Based on the research, it was found tha... [more]

Understanding of the metabolic pathways connected with a removal of micropollutant bisphenol A (BPA) may help to better design effective wastewater treatment processes. The aim of this study was to determine changes in gene expression in an aerobic granular sludge (AGS) community exposed to BPA. In the study, AGS adapted to BPA degradation was used. In this sludge, BPA was dosed; as a control sample, granules without BPA addition were used. mRNA was isolated from both samples and sequenced using the Illumina platform. Metatranscriptome analysis of AGS exposed to BPA indicated direct biodegradation as the main mechanism of BPA removal from wastewater. High expression of genes coding pilus and flagellin proteins in the BPA-exposed biomass indicated that exposition to BPA stimulated aggregation of microbial cells and formation of biofilm. In the BPA-exposed biomass, nitrogen was mainly used as an energy source, as indicated by the presence of genes coding nitrification enzymes and urease.... [more]

Cyanobacterial blooms and strains absorb carbon dioxide, drawing attention to its use as feed for animals and renewable energy sources. However, cyanobacteria can produce toxins and have a low heating value. Herein, we studied a cyanobacterial strain harvested during a bloom event and analyzed it to use as animal feed and a source of energy supply. The thermal properties and the contents of total nitrogen, protein, carbohydrate, fatty acids, lipid, and the presence of cyanotoxins were investigated in the Microcystis aeruginosa LTPNA 01 strain and in a bloom material. Microcystins (hepatotoxins) were not detected in this strain nor in the bloom material by liquid chromatography coupled to mass spectrometry. Thermogravimetric analysis showed that degradation reactions (devolatilization) initiated at around 180 °C, dropping from approximately 90% to 20% of the samples’ mass. Our work showed that despite presenting a low heating value, both biomass and non-toxic M. aeruginosa LTPNA 01 coul... [more]

The aim of the study was to evaluate the possibility of using the process of dark fermentation to convert kitchen waste into valuable volatile fatty acids in a semi-continuous process at different values of the organic loading rate (2.5 and 5.0 gVS/(L × d)) and hydraulic retention time (5 and 10 d) using anaerobic mixed microbial consortia. The experiments were performed in a bioreactor of working volume 8L with pH control. The maximum volatile fatty acids yield in a steady state (22.3 g/L) was achieved at the organic loading rate of 5.0 gVS/(L × d) and HRT of 10 days. The main products of dark fermentation were acetic and butyric acids, constituting, respectively, 35.2−47.7% and 24.1−30.0% of all identified volatile fatty acids. Additionally, at the beginning of the fermentation and in a steady-state condition, the microbial population analysis (16S rDNA) of the fermentation mixture with the most effective volatile fatty acids generation has been performed to monitor the DF microflora... [more]

Lignin-feeding insect gut is a natural ligninolytic microbial bank for the sustainable conversion of crop straw to biogas. However, limited studies have been done on highly efficient microbes. Here, an efficient ligninolytic strain Enterobacter hormaechei KA3 was isolated from the gut microbiomes of lignin-feeding Hypomeces squamosus Fabricius, and its effects on lignin degradation and anaerobic digestion were investigated. No research has been reported. Results showed that strain KA3 had better lignin-degrading ability for corn straw with a higher lignin-degrading rate (32.05%) and lignin peroxidase activity (585.2 U/L). Furthermore, the highest cumulative biogas yield (59.19 L/kg-VS) and methane yield (14.76 L/kg-VS) were obtained for KA3 inoculation, which increased by 20% and 31%, respectively, compared to CK. Higher removal rates of COD, TS, and vs. of 41.6%, 43.11%, and 66.59% were also found. Moreover, microbial community diversity increased as digestion time prolonged in TG, an... [more]

A new direction in the use of lactic acid bacteria inoculants is their application for renewable raw materials ensiling for biogas production. The aim of the study was to demonstrate the possibility of stimulating the synthesis of propionic acid in the process of co-fermentation of selected strains of Lactobacillus buchneri and L. diolivorans as well as L. buchneri and Pediococcus acidilactici. L. buchneri KKP 2047p and P. acidilactici KKP 2065p were characterized by the special capabilities for both synthesis and metabolism of 1,2-propanediol. L. diolivorans KKP 2057p stands out for the ability to metabolize 1,2-propanediol to propionic acid. As a result of the co-fermentation a concentration of propionic acid was obtained at least 1.5 times higher in the final stage of culture in comparison to cultivating individual species of bacteria separately. The results of in vitro experiments were applied in agricultural practice, by application of two lactic acid bacteria inoculants in ensili... [more]

The aim of the study was to investigate the process of electrostatic fabrication of cellulose acetate (CA) nanofibers containing methylene blue (MB) as a photosensitizer. The electrical, physicochemical, and biocidal properties of the prepared material were given. CA nanofibers were prepared by electrospinning method using a solvent mixture of acetone and distilled water (9:1 vv−1) and different concentrations of CA (i.e., 10−21%). Additionally, methylene blue was implemented into the polymer solution with a CA concentration of 17% to obtain fibers with photo-bactericidal properties. Pure electrospun CA fibers were more uniform than fibers with MB (i.e., ribbon shape). Fiber diameters did not exceed 900 nm for the tested polymer solutions and flow rate below 1.0 mL h−1. The polymer properties (i.e., concentration, resistivity) and other parameters of the process (i.e., flow rate, an applied voltage) strongly influenced the size of the fibers. Plasma treatment of nanofibers resulted in... [more]

Anode modification is a useful method to increase the performance of microbial fuel cells (MFCs). By using the electrochemical deposition method, Fe3O4 and polypyrrole (PPy) were polymerized on a carbon felt anode to prepare Fe3O4-PPy composite modified anodes. In order to ascertain the effect of electrodeposition time on characteristics of the modified electrode, the preparation time of the modified electrode was adjusted. The modified anodes were used in MFCs, and their performances were evaluated by analyzing the electricity generation performance and sewage treatment capacity of MFCs. Experimental results indicated that the Fe3O4-PPy composite modified anodes could enhance the power production capacity and sewage treatment efficiency of MFC effectively. In particular, when the deposition time was 50 min, the modified anode could significantly improve the MFC performance. In this case, the steady-state current density of MFC increased by 59.5% in comparison with that of the MFC with... [more]

Anaerobic digestion with corn straw faces the problems of difficult degradation, long fermentation time and acid accumulation in the high concentration of feedstocks. In order to speed up the process of methane production, corn straw treated with sodium hydroxide was used in thermophilic (50 °C) anaerobic digestion, and the effects of biochar addition on the performance of methane production and the microbial community were analyzed. The results showed that the cumulative methane production of all treatment groups reached over 75% of the theoretical methane yield in 7 days and the addition of 4% biochar increased the cumulative methane production by 6.75% compared to the control group. The addition of biochar also decreased the number of biogas and methane production peaks from 2 to 1, and had a positive effect on shortening the digestion start-up period and reducing the fluctuation of biogas production during the digestion process. The addition of 4% biochar increased the abundance of... [more]

The present work describes a self-sustaining bioelectrochemical system that adopts simple cell configurations and operates in uncontrolled ambient surroundings. The microbial fuel cell (MFC) was comprised of white-rot fungus of Phanaerochaete chrysosporium fed with oil palm empty fruit bunch (EFB) as the substrate. This fungal strain degrades lignin by producing ligninolytic enzymes such as laccase, which demonstrates a specific affinity for oxygen as its electron acceptor. By simply pairing zinc and the air electrode in a membraneless, single-chamber, 250-mL enclosure, electricity could be harvested. The microbial zinc/air cell is capable of sustaining a 1 mA discharge current continuously for 44 days (i.e., discharge capacity of 1056 mAh). The role of the metabolic activities of P. chrysosporium on EFB towards the MFC’s performance is supported by linear sweep voltammetry measurement and scanning electron microscopy observations. The ability of the MFC to sustain its discharge for a... [more]

A manganese oxide-coated cylindrical graphite cathode with a zinc anode was developed to treat wastewater containing selenite in a dual-chambered microbial fuel cell. COD and selenite removal in the anodic chamber by Bacillus cereus with energy generation were evaluated in batch mode. A manganese dioxide-coated graphite cathode was tested for its surface morphology and chemical composition using scanning electron microscopy and dispersive energy analysis of X-rays. Compared to the non-coated graphite electrode, up to 69% enhancement was observed in the manganese dioxide-coated electrode voltage generation with 150 ppm selenite concentration. The fuel cell achieved a maximum power density of 1.29 W/m2 with 91% selenite reduction and up to 74% COD (initial COD of 120 mg/L) removal for an initial selenite concentration from 100 to 150 ppm. The current study demonstrated the possibility of a modified cathode in enhancing energy generation and the use of microbial fuel cell technology to tr... [more]

Microbial fuel cell (MFC) technology is anticipated to be a practical alternative to the activated sludge technique for treating domestic and industrial effluents. The relevant literature mainly focuses on developing the systems and materials for maximum power output, whereas understanding the fundamental electrochemical characteristics is inadequate. This experimental study uses a double-chamber MFC having graphite electrodes and an anion-exchange membrane to investigate the electrochemical process limitations and the potential of bioelectricity generation and dairy effluent treatment. The results revealed an 81% reduction in the chemical oxygen demand (COD) in 10 days of cell operation, with an initial COD loading of 4520 mg/L. The third day recorded the highest open circuit voltage of 396 mV, and the maximum power density of 36.39 mW/m2 was achieved at a current density of 0.30 A/m2. The electrochemical impedance spectroscopy analysis disclosed that the activation polarization of th... [more]

The Future of Energy is focused on the consolidation of new energy technologies. Among them, Fuel Cells (FCs) are on the Energy Agenda due to their potential to reduce the demand for fossil fuel and greenhouse gas emissions, their higher efficiency (as fuel cells do not use combustion, their efficiency is not linked to their maximum operating temperature) and simplicity and absence of moving parts. Additionally, low-power FCs have been identified as the target technology to replace conventional batteries in portable applications, which can have recreational, professional, and military purposes. More recently, low-power FCs have also been identified as an alternative to conventional batteries for medical devices and have been used in the medical field both in implantable devices and as micro-power sources. The most used power supply for implantable medical devices (IMD) is lithium batteries. However, despite its higher lifetime, this is far from enough to meet the patient’s needs since... [more]

In this paper, we presented a novel microbial fuel cell (bMFC) structure, with a bipolar membrane separating the anode and cathode chambers. A bipolar membrane divides the bMFC into anode and cathode chambers. The bipolar membrane comprises anion and cation exchange layers. The anode chamber side has the cation exchange layer, while the cathode chamber side has the anion exchange layer. The anode chamber of the bMFC was loaded with Shewanella oneidensis MR-1 and lactic acid, while the cathode chamber was loaded with pure water and iron (III) hydroxide. The bMFC generated electrons for 20 days at a maximum current density of 30 mA/m2 and the ohmic resistance value was estimated to be 500 Ω. During the operation of the bMFC, both the anode and cathode chambers kept anaerobic conditions. There was no platinum catalyst in the cathode chamber, which is required for the reaction of protons with oxygen. Therefore, oxygen could not serve as an electron acceptor in the bMFC. We considered a bMF... [more]

This study evaluated different strategies to increase gas−liquid mass transfer in a randomly packed gas stirred tank reactor (GSTR) continuously fed with second cheese whey (SCW), at thermophilic condition (55 °C), for the purpose of carrying out in situ biogas upgrading. Two different H2 addition rates (1.18 and 1.47 LH2 LR−1 d−1) and three different biogas recirculation rates (118, 176 and 235 L LR−1 d−1) were applied. The higher recirculation rate showed the best upgrading performance; H2 utilization efficiency averaged 88%, and the CH4 concentration in biogas increased from 49.3% during conventional anaerobic digestion to 75%, with a methane evolution rate of 0.37 LCH4 LR−1 d−1. The microbial community samples were collected at the end of each experimental phase, as well as one of the thermophilic sludge used as inoculum; metanogenomic analysis was performed using Illumina-based 16S sequencing. The whole microbial community composition was kept quite stable throughout the conventio... [more]

The generation of energy through the transformation of polluting waste is a widely explored field and offers advances in green technologies. One of the promising technologies is Microbial Fuel Cells (MFCs). These cells can contain electroactive microorganisms that transform organic waste into electricity by transferring electrons from their metabolism. In this study, a new bacterium capable of producing electricity from the waste of the poultry sector and using copper electrodes, called Av_G1, was identified and isolated. It is phylogenetically related to Citrobacter freundii and Citrobacter Murlinae. This new strain was identified molecularly, biochemically, and phylogenetically; its physiological and morphological characteristics were also studied through a Scanning Electron Microscope (SEM). Biochemical determination was performed using Simmons Citrate Agar, Lysine Iron Medium (L.I.A.), Motility/Ornithine Test, Methyl Red indicator, Enzymes: oxidase and catalase, and Gram stain test... [more]

The microbial enhanced oil recovery (MEOR) method is an eco-friendly and economical alternative technology. The technology involves a variety of uncertainties, and its success depends on controlling microbial growth and metabolism. Though a few numerical studies have been carried out to reduce the uncertainties, no attempt has been made to consider temperature, pressure, and salinity in an integrated manner. In this study, a new modeling method incorporating these environmental impacts was proposed, and MEOR analysis was performed. As a result, accurate modeling was possible to prevent overestimating the performance of MEOR. In addition, oil recovery was maximized through sensitivity analysis and optimization based on an integrative model. Finally, applying MEOR to an actual reservoir model showed a 7% increase in oil recovery compared to waterflooding. This result proved the practical applicability of the method.

This study explored the effect of eight antimicrobials on the efficiency of biogas production in the anaerobic digestion (AD) process of cattle manure. The microbiome involved in AD, presence and number of genes mcrA, MSC and MST specific for Archaea, and antibiotic resistance genes (ARGs) concentration in digestate (D) were examined. Supplementation of antibiotics to substrate significantly lowered biogas production. Amoxicillin caused a 75% decrease in CH4 production in comparison with the control samples. Enrofloxacin, tetracycline, oxytetracycline, and chlortetracycline reduced the amount of biogas produced by 36, 39, 45 and 53%, respectively. High-throughput sequencing of 16S rRNA results revealed that bacteria dominated the Archaea microorganisms in all samples. Moreover, antibiotics led to a decrease in the abundance of the genes mcrA, MSC, MST, and induced an increase in the number of tetracyclines resistance genes. Antibiotics decreased the efficiency of the AD process and low... [more]

Olive mill wastewater (OMW), which is generated during olive oil production, has detrimental effects on the environment due to its high organic load and phenolic compounds content. OMW is difficult to biodegrade, but represents a valuable resource of nutrients for microbial growth. In this study, yeast strains were screened for their growth on phenolic compounds usually found in OMW and responsible for antimicrobial effects. Candida tropicalis ATCC 750 demonstrated an extraordinary capacity to grow in phenolics and was chosen for further experiments with OMW-based medium. The effects of nitrogen supplementation, the pH, and the stirring rate on cellular growth, OMW-components consumption, and added-value compounds production were studied in batch cultures in Erlenmeyer flasks and in a bioreactor. Candida tropicalis was able to reduce 68% of the organic load (chemical oxygen demand) and 39% of the total phenols of OMW in optimized conditions in bioreactor experiments, producing lipase (... [more]

In this work, the effect of the external load on the current and power generation, as well as on the pollutant removal by microbial fuel cells (MFCs), has been studied by step-wise modifying the external load. The load changes included a direct scan, in which the external resistance was increased from 120 Ω to 3300 Ω, and a subsequent reverse scan, in which the external resistance was decreased back to 120 Ω. The reduction in the current, experienced when increasing the external resistance, was maintained even in the reverse scan when the external resistance was step-wise decreased. Regarding the power exerted, when the external resistance was increased below the value of the internal resistance, an enhancement in the power exerted was observed. However, when operating near the value of the internal resistance, a stable power exerted of about 1.6 µW was reached. These current and power responses can be explained by the change in population distribution, which shifts to a more fermentat... [more]

Soil microbial fuel cells (SMFCs) are a promising cost-effective power source for on-demand electricity generation applications. So far, reported SMFC configurations are usually bulky and hard to setup. In this study, a low-cost portable plugged-type SMFC (PSMFC) was designed and fabricated for on-demand micropower generation. The PSMFC can be activated just by plugging into natural wet soil, which is easy to access in the natural condition. The PSMFC uses carbon-based electrodes for cost-effectiveness. After setting the PSMFC into the soil to activate, it started to produce electricity after 1 h and reached the power density of 7.3 mW/m2 after 48 h. The proposed PSMFC can potentially generate electricity for remote sensors or soil sensing systems.

The aim of the study is to identify and determine the role of microbial degradation taking place in dusty deposits in potential threats (i.e., destruction of protective coatings and development of corrosion) to the means of transport in conditions of transshipment of energy biomass. This paper presents the results of research on the impact of powdery fractions of wood biomass and biomass obtained from oil plants in the degradation of paint coatings and corrosion processes. During the research, exposure to simulated port climate, OM, SEM, and EDS studies were used. It has been found that the presence of the fraction containing protein compounds and amino acids (e.g., dust of rapeseed meal) stimulates the growth of microorganisms whose metabolism products favour the destruction of protective coatings and the development of corrosion. Under the same conditions, the destruction of protective zinc coatings has been observed. It was found that already 14 days of exposure to oily biomass depo... [more]

Unharvested hardwoods are abundant in eastern Canada, due to the low quality of their fiber and the absence of outlets in conventional wood transformation industries. The objective of this study was to assess the biochemical and thermochemical energy conversion potential of decaying hardwoods and compare their relationships with external and internal indicators of tree degradation. We characterized how wood-decay processes altered the physical and chemical properties of these woods and affected their digestibility yield and their performance according to indexes of stability and efficiency of combustion. DNA analysis on wood samples was also performed to determine the relative abundance of white-rot fungi compared to that of other saprotrophs. All properties stayed within the range of variations allowing the wood to remain suitable for conversion into bioenergy, even with increased decay. We found no significant differences in the physical and chemical properties that are crucial for e... [more]

Maize forms the basis of Mexican food. As a result, approximately six million tons of corncob are produced each year, which represents an environmental issue, as well as a potential feedstock for biogas production. This research aimed to analyze the taxonomic and functional shift in the microbiome of the fermenters using a whole metagenome shotgun approach. Two strategies were used to understand the microbial community at the beginning and the end of anaerobic digestion: (i) phylogenetic analysis to infer the presence and coverage of clade-specific markers to assign taxonomy and (ii) the recovery of the individual genomes from the samples using the binning of the assembled scaffolds. The results showed that anaerobic digestion brought some noticeable changes and the main microbial community was composed of Corynebacterium variable, Desulfovibrio desulfuricans, Vibrio furnissii, Shewanella spp., Actinoplanes spp., Pseudoxanthomonas spp., Saccharomonospora azurea, Agromyces spp., Serinic... [more]

In this study, the production of polyhydroxyalkanoated PHA-rich microbial biomass as a novel feed additive in aquaculture was investigated at a lab-scale. Bio-based volatile fatty acids (VFAs), obtained from the acidogenic fermentation of agricultural residues in existing anaerobic digestion plants, were used as carbon and energy to cultivate the PHA-rich microbial biomass. The experimental activities were carried out using Thauera sp. Sel9 as pure strain, which was grown in a continuous stirred-tank reactor (CSTR) operated at three different hydraulic retention times (HRT). The highest productivity obtained of biomass cells was 0.69 g/L day, operating at one day HRT while the observed PHAs production yield was 0.14 gPHA/g soluble COD removed. At these conditions, the PHA concentration in the microbial cells was 41%. Although the sulfur amino acids were available at high concentrations and above the typical concentration found in fishmeal, the amino acids profile of the obtained biomas... [more]