Pollutant removal and bioelectricity generation from urban river sediment using a macrophyte cathode sediment microbial fuel cell (mSMFC).

Sediment microbial fuel cell (SMFC) efficacy depends highly on organic matter flux and dissolved oxygen (DO) at the anode and cathode, respectively. However, utilizing floating-macrophyte for elevated DO supply at the cathode has not been fully explored. Therefore, a novel floating-macrophyte implanted biocathode single-chamber SMFC (mSMFC) was developed for the simultaneous removal of pollutant and bioelectricity generation from polluted urban river sediment. With Lemna minor L. employed in mSMFC, high pollutant removal was feasible as opposed to the control bioreactor. Total COD, nitrate and sulfate removal reached 57%, 99%, and 99%, respectively. Maximum voltage output, power density, columbic efficiency, normalized energy recovery, and net energy production observed was 0.56 ±â€¯0.26 V, 86.06 mW m-3, 24.7%, 0.033 kWh m-3 and 0.020 kWh m-3, respectively. Alternatively, when floating-macrophyte (predominantly Pistia stratiotes) was employed in the catholyte, DO increased significantly to about 10 mg L-1 in the mSMFC. 16S rRNA gene sequencing revealed Euryarchaeota-(90.91%) and Proteobacteria-(59.68%) as the dominant phyla affiliated to archaea and bacteria, respectively. Pollutant removal mechanisms observed within the mSMFC included bioelectrochemical oxidation at the anode and reduction reaction and macrophyte hyperaccumulation at the cathode. The novel mSMFC system provided an effective approach for the removal of pollutant and bioelectricity generation.

Assessment of Bacterial Community Composition of Anaerobic Granular Sludge in Response to Short-Term Uranium Exposure.

The effect of 10-50 µM uranium (U(VI)) on the bacterial community of anaerobic granular sludge was investigated by 24-h exposure tests, after which the bacterial community was analyzed by high-throughput sequencing. The specific U(VI) reducing activity of the anaerobic granular sludge ranged between 3.1 to 19.7 µM U(VI) g-1(VSS) h-1, independently of the initial U(VI) concentration. Alpha diversity revealed that microbial richness and diversity was the highest for anaerobic granular sludge upon 10 µM uranium exposure. Compared with the original biomass, the phylum of Euryarchaeota was significantly affected, whereas the Bacteroidetes, Firmicutes, and Synergistetes phyla were only slightly affected. However, the abundance of Chloroflexi and Proteobacteria phyla clearly increased after 24 h uranium exposure. Based on the genus level analysis, significant differences appeared in the bacterial abundance after uranium exposure. The proportions of Pseudomonas, Acinetobacter, Parabacteroides, Brevundimonas, Sulfurovum, and Trichococcus increased significantly, while the abundance of Paludibacter and Erysipelotrichaceae incertae sedis decreased dramatically. This study shows a dynamic diversification of the bacterial composition as a response to a short time (24 h) U(VI) exposure (10-50 µM).

Bioactive fractions from the pasture legume Biserrula pelecinus L. have an anti-methanogenic effect against key rumen methanogens.

Methanogenic archaea (methanogens) are common inhabitants of the mammalian intestinal tract. In ruminants, they are responsible for producing abundant amounts of methane during digestion of food, but selected bioactive plants and compounds may inhibit this activity. Recently, we have identified that, Biserrula pelecinus L. (biserrula) is one such plant and the current study investigated the specific anti-methanogenic activity of the plant. Bioassay-guided extraction and fractionation, coupled with in vitro fermentation batch culture were used to select the most bioactive fractions of biserrula. The four fractions were then tested against five species of methanogens grown in pure culture. Fraction bioactivity was assessed by measuring methane production and amplification of the methanogen mcrA gene. Treatments that showed bioactivity were subcultured in fresh broth without the bioactive fraction to distinguish between static and cidal effects. All four fractions were active against pure cultures, but the F2 fraction was the most consistent inhibitor of both methane production and cell growth, affecting four species of methanogens and also producing equivocal-cidal effects on the methanogens. Other fractions had selective activity affecting only some methanogens, or reducing either methane production or methanogenic cell growth. In conclusion, the anti-methanogenic activity of biserrula can be linked to compounds contained in selected bioactive fractions, with the F2 fraction strongly affecting key rumen methanogens. Further study is required to identify the specific plant compounds in biserrula that are responsible for the anti-methanogenic activity. These findings will help devise novel strategies to control methanogen populations and activity in the rumen, and consequently contribute in reducing greenhouse gas emissions from ruminants.

Bioremediation of oily hypersaline soil and water via potassium and magnesium amendment.

Ten hydrocarbonoclastic halobacterial species and 5 haloarchaeal species that had been isolated on a mineral medium with oil as the sole carbon source grew better and consumed more crude oil, as measured by gas-liquid chromatography, in media receiving between 0.50 and 0.75 mol/L KCl and between 1.50 and 2.25 mol/L MgSO4. Chemical analysis revealed that within a certain limit, the higher the KCl and MgSO4 concentrations in the medium, the more K⁺ and Mg²âº, respectively, was accumulated by cells of all the tested halobacteria and haloarchaea. Also, in experiments in which total natural microbial consortia in hypersaline soil and water samples were directly used as inocula, the consumption of hydrocarbons was enhanced in the presence of the above given concentrations of KCl and MgSO4. It was concluded that amendment with calculated concentrations of K⁺ and Mg²âº could be a promising practice for hydrocarbon bioremediation in hypersaline environments.

Analyses of n-alkanes degrading community dynamics of a high-temperature methanogenic consortium enriched from production water of a petroleum reservoir by a combination of molecular techniques.

Despite the knowledge on anaerobic degradation of hydrocarbons and signature metabolites in the oil reservoirs, little is known about the functioning microbes and the related biochemical pathways involved, especially about the methanogenic communities. In the present study, a methanogenic consortium enriched from high-temperature oil reservoir production water and incubated at 55 °C with a mixture of long chain n-alkanes (C(15)-C(20)) as the sole carbon and energy sources was characterized. Biodegradation of n-alkanes was observed as methane production in the alkanes-amended methanogenic enrichment reached 141.47 µmol above the controls after 749 days of incubation, corresponding to 17 % of the theoretical total. GC-MS analysis confirmed the presence of putative downstream metabolites probably from the anaerobic biodegradation of n-alkanes and indicating an incomplete conversion of the n-alkanes to methane. Enrichment cultures taken at different incubation times were subjected to microbial community analysis. Both 16S rRNA gene clone libraries and DGGE profiles showed that alkanes-degrading community was dynamic during incubation. The dominant bacterial species in the enrichment cultures were affiliated with Firmicutes members clustering with thermophilic syntrophic bacteria of the genera Moorella sp. and Gelria sp. Other represented within the bacterial community were members of the Leptospiraceae, Thermodesulfobiaceae, Thermotogaceae, Chloroflexi, Bacteroidetes and Candidate Division OP1. The archaeal community was predominantly represented by members of the phyla Crenarchaeota and Euryarchaeota. Corresponding sequences within the Euryarchaeota were associated with methanogens clustering with orders Methanomicrobiales, Methanosarcinales and Methanobacteriales. On the other hand, PCR amplification for detection of functional genes encoding the alkylsuccinate synthase α-subunit (assA) was positive in the enrichment cultures. Moreover, the appearance of a new assA gene sequence identified in day 749 supported the establishment of a functioning microbial species in the enrichment. Our results indicate that n-alkanes are converted to methane slowly by a microbial community enriched from oilfield production water and fumarate addition is most likely the initial activation step of n-alkanes degradation under thermophilic methanogenic conditions.

Microbial processes in oil fields: culprits, problems, and opportunities.

Our understanding of the phylogenetic diversity, metabolic capabilities, ecological roles, and community dynamics of oil reservoir microbial communities is far from complete. The lack of appreciation of the microbiology of oil reservoirs can lead to detrimental consequences such as souring or plugging. In contrast, knowledge of the microbiology of oil reservoirs can be used to enhance productivity and recovery efficiency. It is clear that (1) nitrate and/or nitrite addition controls H2S production, (2) oxygen injection stimulates hydrocarbon metabolism and helps mobilize crude oil, (3) injection of fermentative bacteria and carbohydrates generates large amounts of acids, gases, and solvents that increases oil recovery particularly in carbonate formations, and (4) nutrient injection stimulates microbial growth preferentially in high permeability zones and improves volumetric sweep efficiency and oil recovery. Biosurfactants significantly lower the interfacial tension between oil and water and large amounts of biosurfactant can be made in situ. However, it is still uncertain whether in situ biosurfactant production can be induced on the scale needed for economic oil recovery. Commercial microbial paraffin control technologies slow the rate of decline in oil production and extend the operational life of marginal oil fields. Microbial technologies are often applied in marginal fields where the risk of implementation is low. However, more quantitative assessments of the efficacy of microbial oil recovery will be needed before microbial oil recovery gains widespread acceptance.

Characterization of long-chain fatty-acid-degrading syntrophic associations from a biodegraded oil reservoir.

Molecular methods were used to characterize stearate- and heptadecanoate-degrading methanogenic consortia enriched from a low-temperature biodegraded oil field. Stearate- and heptadecanoate-degrading cultures formed acetate. Growth on heptadecanoate was also accompanied by the production of propionate. These fermentation products were transiently accumulated at the beginning of the exponential phase and were further consumed with the concomitant production of methane. Clone libraries of bacterial and archaeal 16S rRNA genes were generated for each stable enrichment. Our 16S rRNA gene-cloning analysis combined with fluorescence in situ hybridization revealed that the predominant microorganisms in the associations were affiliated with a clone cluster close to the genus Syntrophus in the class "Deltaproteobacteria" and with the methanogenic genera Methanocalculus and Methanosaeta. Confocal scanning laser microscopy showed that the bacterial and archaeal cells formed compact aggregates around the insoluble substrates. No layered structure was observed in the aggregate organization. This study reports the presence of new fatty-acid-degrading syntrophic consortia in oil fields and our results suggest that such associations may have an important ecological role in oil fields under methanogenic conditions.

Methanogenic potential of tailings samples from oil sands extraction plants.

Approximately 20% of Canada's oil supply now comes from the extraction of bitumen from the oil sands deposits in northeastern Alberta. The oil sands are strip-mined, and the bitumen is typically separated from sand and clays by an alkaline hot water extraction process. The rapidly expanding oil sands industry has millions of cubic metres of tailings for disposal and large areas of land to reclaim. There are estimates that the consolidation of the mature fine tails (MFT) in the settling ponds will take about 150 years. Some of the settling ponds are now evolving microbially produced methane, a greenhouse gas. To hasten consolidation, gypsum (CaSO4 x 2H2O) is added to MFT, yielding materials called consolidated or composite tailings (CT). Sulfate from the gypsum has the potential to stimulate sulfate-reducing bacteria (SRB) to out-compete methanogens, thereby stopping methanogenesis. This investigation examined three MFT and four CT samples from three oil sands extractions companies. Each was found to contain methanogens and SRB. Serum bottle microcosm studies showed sulfate in the CT samples stopped methane production. However, if the microcosms were amended with readily utilizable electron donors, the sulfate was consumed, and when it reached approximately 20 mg/L, methane production began. Some unamended microcosms were incubated for 372 days, with no methane production detected. This work showed that each MFT and CT sample has the potential to become methanogenic, but in the absence of exogenous electron donors, the added sulfate can inhibit methanogenesis for a long time.

Ruminal methanogenesis as influenced by individual fatty acids supplemented to complete ruminant diets.

The objective of the present study was to investigate the effects of seven different pure fatty acids on rumen fermentation using the rumen simulation technique (RUSITEC). The fatty acids were supplied to a complete ruminant diet at a proportion of 50 g x kg(-1) dietary dry matter and compared with an unsupplemented control. Methane release and methanogenic counts were suppressed by the fatty acids C12 : 0, C14 : 0 and C18 : 2 whereas C8 : 0, C10 : 0, C16 : 0 and C18 : 0 showed no corresponding effects. Apart from C12 : 0 and C18 : 2, C8 : 0 and C10 : 0 also adversely affected ciliate protozoa suggesting independence from the methane-suppressing effect of medium-chain fatty acids (MCFA). Although MCFA but not C18 : 2 reduced ruminal fibre degradation, the influence on other fermentation traits remained low. In conclusion, the supply of certain fatty acids to ruminant diets seems to have the potential to reduce methane release.

Methanogens and sulfate-reducing bacteria in oil sands fine tailings waste.

In the past decade, the large tailings pond (Mildred Lake Settling Basin) on the Syncrude Canada Ltd. lease near Fort McMurray, Alta., has gone methanogenic. Currently, about 60%-80% of the flux of gas across the surface of the tailings pond is methane. As well as adding to greenhouse gas emissions, the production of methane in the fine tailings zone of this and other settling basins may affect the performance of these settling basins and impact reclamation options. Enumeration studies found methanogens (10(5)-10(6) MPN/g) within the fine tailings zone of various oil sands waste settling basins. SRB were also present (10(4)-10(5) MPN/g) with elevated numbers when sulfate was available. The methanogenic population was robust, and sample storage up to 9 months at 4 degrees C did not cause the MPN values to change. Nor was the ability of the consortium to produce methane delayed or less efficient after storage. Under laboratory conditions, fine tailings samples released 0.10-0.25 mL CH4 (at STP)/mL fine tailings. The addition of sulfate inhibited methanogenesis by stimulating bacterial competition.

Microbiology of petroleum reservoirs.

Although the importance of bacterial activities in oil reservoirs was recognized a long time ago, our knowledge of the nature and diversity of bacteria growing in these ecosystems is still poor, and their metabolic activities in situ largely ignored. This paper reviews our current knowledge about these bacteria and emphasises the importance of the petrochemical and geochemical characteristics in understanding their presence in such environments.

Characterization of microbial communities in anaerobic bioreactors using molecular probes.

The microbial community structure of twenty-one single-phase and one two-phase full-scale anaerobic sewage sludge digesters was evaluated using oligonucleotide probes complementary to conserved tracts of the 16S rRNAs of phylogenetically defined groups of methanogens and sulfate-reducing bacteria. These probe results were interpreted in combination with results from traditional chemical analyses and metabolic activity assays. It was determined that methanogens in "healthy" mesophilic, single-phase sewage sludge digesters accounted for approximately 8-12% of the total community and that Methanosarcinales and Methanomicrobiales constituted the majority of the total methanogen population. Methanobacteriales and Methanococcales played a relatively minor role in the digesters. Phylogenetic groups of mesophilic, Gram-negative sulfate-reducing bacteria were consistently present at significant levels: Desulfovibrio and Desulfobulbus spp. were the dominant sulfate-reducing populations, Desulfobacter and Desulfobacterium spp. were present at lower levels, and Desulfosarcina, Desulfococcus, and Desulfobotulus spp. were absent. Sulfate reduction by one or more of these populations played a significant role in all digesters evaluated in this study. In addition, sulfate-reducing bacteria played a role in favoring methanogenesis by providing their substrates. The analysis of the two-phase digester indicated that true phase separation was not accomplished: significant levels of active methanogens were present in the first phase. It was determined that the dominant populations in the second phase were different from those in the single-phase digesters.

Isolation and characterization of a dimethyl sulfide-degrading methanogen, Methanolobus siciliae HI350, from an oil well, characterization of M. siciliae T4/MT, and emendation of M. siciliae.

We isolated strain HI350 from a gas and oil well in the Gulf of Mexico, characterized it, and found that it is closely related to Methanolobus siciliae T4/MT (T = type strain), which we also characterized. The previously published characterization of the type strain of M. siciliae was limited to the optimum temperature for growth, and our characterization suggested the species description given below. Cells are irregular, nonmotile, coccoid, and 1.5 to 3 microns in diameter. The catabolic substrates used include methanol, trimethylamine, and dimethyl sulfide, but not H2-CO2, formate, or acetate. Growth is fastest in the presence of 0.4 to 0.6 M Na+, in the presence of 60 to 200 mM Mg2+, at pH 6.5 to 6.8, and at 40 degrees C. Growth on trimethylamine is stimulated by yeast extract. An electrophoretic analysis confirmed that strain HI350 is closely related to strain T4/MT and indicated that major changes in the intracellular proteins of M. siciliae HI350 occur when the growth substrate is switched between dimethyl sulfide and trimethylamine.

Incidence of methanogenic bacteria in a sigmoidoscopy population: an association of methanogenic bacteria and diverticulosis.

This study determined the incidence and concentration of methane-producing bacteria in tap water enema samples of 130 individuals taken before sigmoidoscopy. The number of subjects classified in five major colonic groups were as follows: normal colon 36, diverticulosis 57, inflammatory bowel disease 11, colon polyps 34, and colon cancer 11. Some patients were placed in more than one category. Ninety four of the subjects or 72% had methanogenic bacteria ranging in concentration from 6 to about 3 X 10(10)/g dry weight of faeces. The predominant methanogen in all groups was Methanobrevibacter smithii. Chi-square analysis showed that the incidence of methanogens in concentrations of 10(7)/g dry weight of faeces or greater in patients with diverticulosis (58%) was significantly greater than in normal patients (25%). High methanogen concentrations are associated with excretion of methane in the breath.

[Ecologic conditions for the spread of methane-forming bacteria in the petroleum strata of Apsheron]. / Ekologicheskie usloviia rasprostraneniia metanoobrazuiushchikh bakterii v neftianykh plastakh Apsherona.

The distribution of methan producing bacteria was studied in oil bearing strata of the Apsheron Peninsula and was shown to depend on ecological conditions: the total mineralization of stratal water, the content of hydrogen sulfide, sulfates, the pH, the extent of penetration of surface waters. The bacteria was found in 11 among 14 stratal water samples taken from the studied oil deposits. The flooding of oil collectors with surface waters was shown to be one of the factors responsible for the distribution of methane producing bacteria in the stratal waters of oil deposits. Methane producing cenoses were found in stratal water whose mineralization varied from 17 to 84.8 g per litre and the content of hydrogen sulfide varied from 0 to 585 mg per litre. Most of the samples contained also sulfate reducing bacteria which grew in a medium with lactate, as well as fermenting microorganisms which grew in the presence of peptone and glucose and supplied methane producing bacteria with their substrates, viz. H2, CO2 and acetate. Preliminary experiments in which methane was produced from oil via a two-stage process suggest that flooding favours the formation of oil oxidation products in the strata and these products serve as substrates for the growth of microbial cenoses producing methane.