Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Anaerobic Fungi : Past, Present, and Future
    Hess, Matthias ; Paul, Shyam S. ; Puniya, Anil K. ; Giezen, Mark van der; Shaw, Claire ; Edwards, Joan E. ; Fliegerová, Kateřina - \ 2020
    Frontiers in Microbiology 11 (2020). - ISSN 1664-302X
    anaerobic digestion - carbohydrate-active enzymes - food security - herbivores - methanogenesis - Neocallimastigomycota - rumen - sustainable agriculture

    Anaerobic fungi (AF) play an essential role in feed conversion due to their potent fiber degrading enzymes and invasive growth. Much has been learned about this unusual fungal phylum since the paradigm shifting work of Colin Orpin in the 1970s, when he characterized the first AF. Molecular approaches targeting specific phylogenetic marker genes have facilitated taxonomic classification of AF, which had been previously been complicated by the complex life cycles and associated morphologies. Although we now have a much better understanding of their diversity, it is believed that there are still numerous genera of AF that remain to be described in gut ecosystems. Recent marker-gene based studies have shown that fungal diversity in the herbivore gut is much like the bacterial population, driven by host phylogeny, host genetics and diet. Since AF are major contributors to the degradation of plant material ingested by the host animal, it is understandable that there has been great interest in exploring the enzymatic repertoire of these microorganisms in order to establish a better understanding of how AF, and their enzymes, can be used to improve host health and performance, while simultaneously reducing the ecological footprint of the livestock industry. A detailed understanding of AF and their interaction with other gut microbes as well as the host animal is essential, especially when production of affordable high-quality protein and other animal-based products needs to meet the demands of an increasing human population. Such a mechanistic understanding, leading to more sustainable livestock practices, will be possible with recently developed -omics technologies that have already provided first insights into the different contributions of the fungal and bacterial population in the rumen during plant cell wall hydrolysis.

    Effect of nickel, cobalt, and iron on methanogenesis from methanol and cometabolic conversion of 1,2-dichloroethene by Methanosarcina barkeri
    Paulo, Lara M. ; Hidayat, Mohamad R. ; Moretti, Giulio ; Stams, Alfons J.M. ; Sousa, Diana Z. - \ 2020
    Biotechnology and applied biochemistry 67 (2020)5. - ISSN 0885-4513 - p. 744 - 750.
    cometabolic dechlorination - metals - methanogenesis

    Methanogens are responsible for the last step in anaerobic digestion (AD), in which methane (a biofuel) is produced. Some methanogens can cometabolize chlorinated pollutants, contributing for their removal during AD. Methanogenic cofactors involved in cometabolic reductive dechlorination, such as F430 and cobalamin, contain metal ions (nickel, cobalt, iron) in their structure. We hypothesized that the supplementation of trace metals could improve methane production and the cometabolic dechlorination of 1,2-dichloroethene (DCE) by pure cultures of Methanosarcina barkeri. Nickel, cobalt, and iron were added to cultures of M. barkeri growing on methanol and methanol plus DCE. Metal amendment improved DCE dechlorination to vinyl chloride (VC): assays with 20 µM of Fe3+ showed the highest final concentration of VC (5× higher than in controls without Fe3+), but also in assays with 5.5 µM of Co2+ and 5 µM of Ni2+ VC formation was improved (3.5–4× higher than in controls without the respective metals). Dosing of metals could be useful to improve anaerobic removal of chlorinated compounds, and more importantly decrease the detrimental effect of DCE on methane production in anaerobic digesters.

    Anaerobic Degradation of Non-Methane Alkanes by "Candidatus Methanoliparia" in Hydrocarbon Seeps of the Gulf of Mexico
    Laso-Pérez, Rafael ; Hahn, Cedric ; Vliet, Daan M. van; Tegetmeyer, Halina E. ; Schubotz, Florence ; Smit, Nadine T. ; Pape, Thomas ; Sahling, Heiko ; Bohrmann, Gerhard ; Boetius, Antje ; Knittel, Katrin ; Wegener, Gunter - \ 2019
    mBio 10 (2019)4. - ISSN 2150-7511
    alkane degradation - archaea - methanogenesis - methyl-coenzyme M reductase - oil seeps

    Crude oil and gases in the seabed provide an important energy source for subsurface microorganisms. We investigated the role of archaea in the anaerobic degradation of non-methane alkanes in deep-sea oil seeps from the Gulf of Mexico. We identified microscopically the ethane and short-chain alkane oxidizers "Candidatus Argoarchaeum" and "Candidatus Syntrophoarchaeum" forming consortia with bacteria. Moreover, we found that the sediments contain large numbers of cells from the archaeal clade "Candidatus Methanoliparia," which was previously proposed to perform methanogenic alkane degradation. "Ca. Methanoliparia" occurred abundantly as single cells attached to oil droplets in sediments without apparent bacterial or archaeal partners. Metagenome-assembled genomes of "Ca. Methanoliparia" encode a complete methanogenesis pathway including a canonical methyl-coenzyme M reductase (MCR) but also a highly divergent MCR related to those of alkane-degrading archaea and pathways for the oxidation of long-chain alkyl units. Its metabolic genomic potential and its global detection in hydrocarbon reservoirs suggest that "Ca. Methanoliparia" is an important methanogenic alkane degrader in subsurface environments, producing methane by alkane disproportionation as a single organism.IMPORTANCE Oil-rich sediments from the Gulf of Mexico were found to contain diverse alkane-degrading groups of archaea. The symbiotic, consortium-forming "Candidatus Argoarchaeum" and "Candidatus Syntrophoarchaeum" are likely responsible for the degradation of ethane and short-chain alkanes, with the help of sulfate-reducing bacteria. "Ca. Methanoliparia" occurs as single cells associated with oil droplets. These archaea encode two phylogenetically different methyl-coenzyme M reductases that may allow this organism to thrive as a methanogen on a substrate of long-chain alkanes. Based on a library survey, we show that "Ca. Methanoliparia" is frequently detected in oil reservoirs and may be a key agent in the transformation of long-chain alkanes to methane. Our findings provide evidence for the important and diverse roles of archaea in alkane-rich marine habitats and support the notion of a significant functional versatility of the methyl coenzyme M reductase.

    Evaluation of the SF6 tracer technique for estimating methane emission rates with reference to dairy cows using a mechanistic model
    Berends, H. ; Gerrits, W.J.J. ; France, J. ; Ellis, J.L. ; Zijderveld, S.M. van; Dijkstra, J. - \ 2014
    Journal of Theoretical Biology 353 (2014). - ISSN 0022-5193 - p. 1 - 8.
    sulfur-hexafluoride tracer - chamber techniques - eructated gas - cattle - rumen - sheep - methanogenesis - performance - ruminants - digestion
    A dynamic, mechanistic model of the sulfur hexafluoride (SF6) tracer technique, used for estimating methane (CH4) emission rates from ruminants, was constructed to evaluate the accuracy of the technique. The model consists of six state variables and six zero-pools representing the quantities of SF6 and CH4 in rumen and hindgut fluid, in rumen and hindgut headspace, and in blood and collection canister. The model simulates flows of CH4 and SF6 through the body, subsequent eructation and exhalation and accumulation in a collection canister. The model predicts CH4 emission by multiplying the SF6 release rate of a permeation device in the rumen by the ratio of CH4:SF6 in collected air. This prediction is compared with the actual CH4 production rate, assumed to be continuous and used as a driving variable in the model. A sensitivity analysis was conducted to evaluate the effect of changes in several parameters. The predicted CH4 emission appeared sensitive to parameters affected by the difference in CH4:SF6 ratio in exhaled and eructed air respectively, viz., hindgut fractional passage rate and hindgut CH4 production. This is caused by the difference in solubility of CH4 and SF6 and by hindgut CH4 production. In addition, the predicted CH4 emission rate appeared sensitive to factors that affect proportions of exhaled and eructed air sampled, i.e., eructation time fraction, exhalation time fraction, and distance from sampling point to mouth/nostrils. Changes in rumen fractional passage rate, eructation rate, SF6 release rate, background values and air sampling rate did not noticeably affect the predicted CH4 emission. Simulations with 13CH4 as an alternative tracer show that the differences and sensitivity to parameters greatly disappear. The model is considered a useful tool to evaluate critical points in the SF6 technique. Data from in vivo experiments are needed to further evaluate model simulations.
    Evidence for a hydrogen-sink mechanism of (+)catechin-mediated emission reduction of the ruminant greenhouse gas methane
    Becker, P.M. ; Wikselaar, P.G. van; Franssen, M.C.R. ; Vos, C.H. de; Hall, R.D. ; Beekwilder, M.J. - \ 2014
    Metabolomics 10 (2014)2. - ISSN 1573-3882 - p. 179 - 189.
    rumen bacteria - fermentation - methanogenesis - perspective - metabolites - tannins - growth - acids
    Methane formation in the rumen is a major cause of greenhouse gas emission. Plant secondary compounds in ruminant diets, such as essential oils, saponins and tannins, are known to affect methane production. However, their methane-lowering properties have generally been associated with undesired side effects such as impaired feed digestibility. Here we show that microbial methane formation in diluted and buffered rumen fluid was significantly lowered in the presence of (+)-catechin, a natural polyphenol. This flavan-3-ol, a tannin precursor, decreased the production of methane in a dose-dependent manner, where 1.0 mol catechin prevented the emission of 1.2 mol methane. During methane mitigation, (+)-catechin was step-wise degraded via C- and A-ring cleavage and reductive dehydroxylation reactions, as indicated by LC-QToF-MS based metabolomic profiling and NMR-based metabolite identification. This accounted for the acceptance of six hydrogen atoms per catechin molecule. Consequently, catechin functions as an extensive hydrogen sink, thereby competing with methane production by rumen methanogens (TeX). Catechin therefore acts as an antireductant under the anaerobic test conditions, in contrast to its well-known antioxidant role during oxidative stress. The reductive degradation of catechin had no impact on the formation of ruminal fermentation products such as short-chain fatty acids in this model system. These results highlight the potential of plant secondary compounds to replace methane precursors as hydrogen sinks, and justify future scientific screening programs for similar, potentially more effective organic compounds
    Methane reduction by plant pigments and antioxidants in rumen fluid involves modifications, e.g. hydrogenatioor degradation of the active compoundsn,
    Becker, P.M. ; Wikselaar, P.G. van; Ilgenfritz, J. ; Beekwilder, M.J. ; Vos, R.C.H. de; Franz, C.H. ; Zitterl-Eglseer, K. - \ 2013
    Wiener Tierarztliche Monatsschrift 100 (2013). - ISSN 0043-535X - p. 295 - 305.
    bacteria - methanogenesis - anthocyanins - cleavage - bilberry - bisdemethoxycurcumin - demethoxycurcumin - resveratrol - inhibition - emissions
    Methane is a major greenhouse gas, and ruminants cause about a quarter of all anthropogenic methane emissions. The objective of this study was to testplant secondary products in terms of their effects on methane production, and to follow active compounds analytically during incubation. In a simplifi ed model of ruminal methane production, a glycerol tripolylactate served as a central metabolites-generating and hydrogen-releasing substrate for rumen prokaryotes. The experimental additives, tested for their interfering potential with methane production, comprised bilberry fruit extract, tomato paste, paprika powder, grape seed extract, turmeric powder, curcumin, catechin, ferulic acid, ferulic acid ethyl ester and resveratrol. Being an unsaturated compound, fumarate, a competing electron acceptor to methane precursors, served as a well-described methane-reducing compound among the experimental additives in the in vitro tests. Methanemitigating effi ciencies were calculated by subtraction of the methane quantity produced in fl asks with the interfering additives from the quantity measured without any additive. Grape seed extract, bilberry fruit extract, turmeric powder, ferulic acid, catechin, and resveratrol reduced the production of methane in vitro. Grape seed extract, bilberry fruit extract, catechin, and resveratrol decreased methane formation to a higher extent than fumarate when added at comparable concentrations. Analysis of the secondary compounds in the assays by means of HPLC and revealed a considerably and in most cases significant (p
    Dietary nitrate supplementation reduces methane emission in beef cattle fed sugarcane-based diets
    Hulshof, R.B.A. ; Berndt, A. ; Gerrits, W.J.J. ; Dijkstra, J. ; Zijderveld, S.M. van; Newbold, J.R. ; Perdok, H.B. - \ 2012
    Journal of Animal Science 90 (2012)7. - ISSN 0021-8812 - p. 2317 - 2323.
    rumen fermentation - sheep - methanogenesis - manipulation - mitigation - livestock - nitrite - dairy - urea - wall
    The objective of this study was to determine the effect of dietary nitrate on methane emission and rumen fermentation parameters in Nellore × Guzera (Bos indicus) beef cattle fed a sugarcane based diet. The experiment was conducted with 16 steers weighing 283 ± 49 kg (mean ± SD), 6 rumen cannulated and 10 intact steers, in a cross-over design. The animals were blocked according to BW and presence or absence of rumen cannula and randomly allocated to either the nitrate diet (22 g nitrate/kg DM) or the control diet made isonitrogenous by the addition of urea. The diets consisted of freshly chopped sugarcane and concentrate (60:40 on DM basis), fed as a mixed ration. A 16-d adaptation period was used to allow the rumen microbes to adapt to dietary nitrate. Methane emission was measured using the sulfur hexafluoride tracer technique. Dry matter intake (P = 0.09) tended to be less when nitrate was present in the diet compared with the control, 6.60 and 7.05 kg/d DMI, respectively. The daily methane production was reduced (P <0.01) by 32% when steers were fed the nitrate diet (85 g/d) compared with the urea diet (125 g/d). Methane emission per kilogram DMI was 27% less (P <0.01) on the nitrate diet (13.3 g methane/kg DMI) than on the control diet (18.2 g methane/kg DMI). Methane losses as a fraction of gross energy intake (GEI) were less (P <0.01) on the nitrate diet (4.2% of GEI) than on the control diet (5.9% of GEI). Nitrate mitigated enteric methane production by 87% of the theoretical potential. The rumen fluid ammonia-nitrogen (NH3-N) concentration was significantly greater (P <0.05) for the nitrate diet. The total concentration of VFA was not affected (P = 0.61) by nitrate in the diet, while the proportion of acetic acid tended to be greater (P = 0.09), propionic acid less (P = 0.06) and acetate/propionate ratio tended to be greater (P = 0.06) for the nitrate diet. Dietary nitrate reduced enteric methane emission in beef cattle fed sugarcane based diet.
    Biological formation of caproate and caprylate from acetate: fuel and chemical production from low grade biomass
    Steinbusch, K.J.J. ; Hamelers, H.V.M. ; Plugge, C.M. ; Buisman, C.J.N. - \ 2011
    Energy & Environmental Science 4 (2011)1. - ISSN 1754-5692 - p. 216 - 224.
    fermentative hydrogen-production - fatty-acids - clostridium-kluyveri - carboxylic-acids - mixed cultures - bacteria - ethanol - 2-bromoethanesulfonate - methanogenesis - ketonization
    This research introduces an alternative mixed culture fermentation technology for anaerobic digestion to recover valuable products from low grade biomass. In this mixed culture fermentation, organic waste streams are converted to caproate and caprylate as precursors for biodiesel or chemicals. It was found that acetate, as the main intermediate of anaerobic digestion, can be elongated to medium chain fatty acids with six and eight carbon atoms. Mixed microbial communities were able to produce 8.17 g l-1 caproate and 0.32 g l-1 caprylate under methanogenesis-suppressed conditions in a stable batch reactor run. The highest production rate was 25.6 mM C caproate per day with a product yield of 0.6 mol C per mol C. This elongation process occurred with both ethanol and hydrogen as electron donors, demonstrating the flexibility of the process. Microbial characterization revealed that the microbial populations were stable and dominated by relatives of Clostridium kluyveri
    Hydrogenotrophic Sulfate Reduction in a Gas-Lift Bioreactor Operated at 9 degrees C
    Nevatalo, L.M. ; Bijmans, M.F.M. ; Lens, P.N.L. ; Kaksonen, A.H. ; Puhakka, J.A. - \ 2010
    Journal of Microbiology and Biotechnology 20 (2010)3. - ISSN 1017-7825 - p. 615 - 621.
    reducing bacteria - retention time - carbon-dioxide - growth-rate - sp-nov - reactor - temperature - methanogenesis - oxidation - sulfide
    The viability of low-temperature sulfate reduction with hydrogen as electron donor was studied with a bench-scale gas-lift bioreactor (GLB) operated at 9 degrees C. Prior to the GLB experiment, the temperature range of sulfate reduction of the inoculum was assayed. The results of the temperature gradient assay indicated that the inoculum was a psychrotolerant mesophilic enrichment culture that had an optimal temperature for sulfate reduction of 31 degrees C, and minimum and maximum temperatures of 7 degrees C and 41 degrees C, respectively. In the GLB experiment at 9 degrees C, a sulfate reduction rate of 500-600 mg l(-1) d(-1), corresponding to a specific activity of 173 mg SO42- g VSS-1 d(-1), was obtained. The electron flow from the consumed H-2-gas to sulfate reduction varied between 27% and 52%, whereas the electron flow to acetate production decreased steadily from 15% to 5%. No methane was produced. Acetate was produced from CO2 and H-2 by homoacetogenic bacteria. Acetate supported the growth of some heterotrophic sulfate-reducing bacteria. The sulfate reduction rate in the GLB was limited by the slow biomass growth rate at 9 degrees C and low biomass retention in the reactor. Nevertheless, this study demonstrated the potential sulfate reduction rate of psychrotolerant sulfate-reducing mesophiles at suboptimal temperature.
    Nitrate and sulfate: effective alternative hydrogen sinks for mitigation of ruminal methane production in sheep
    Zijderveld, S.M. van; Gerrits, W.J.J. ; Apajalahti, J.A. ; Newbold, J.R. ; Dijkstra, J. ; Leng, R.A. ; Perdok, H.B. - \ 2010
    Journal of Dairy Science 93 (2010)12. - ISSN 0022-0302 - p. 5856 - 5866.
    real-time pcr - fumaric-acid - feed-intake - in-vitro - rumen - methanogenesis - emissions - reduction - nitrogen - cattle
    Twenty male crossbred Texel lambs were used in a 2 x 2 factorial design experiment to assess the effect of dietary addition of nitrate (2.6% of dry matter) and sulfate (2.6% of dry matter) on enteric methane emissions, rumen volatile fatty acid concentrations, rumen microbial composition, and the occurrence of methemoglobinemia. Lambs were gradually introduced to nitrate and sulfate in a corn silage-based diet over a period of 4 wk, and methane production was subsequently determined in respiration chambers. Diets were given at 95% of the lowest ad libitum intake observed within one block in the week before methane yield was measured to ensure equal feed intake of animals between treatments. All diets were formulated to be isonitrogenous. Methane production decreased with both supplements (nitrate: -32%, sulfate: -16%, and nitrate + sulfate: -47% relative to control). The decrease in methane production due to nitrate feeding was most pronounced in the period immediately after feeding, whereas the decrease in methane yield due to sulfate feeding was observed during the entire day. Methane-suppressing effects of nitrate and sulfate were independent and additive. The highest methemoglobin value observed in the blood of the nitrate-fed animals was 7% of hemoglobin. When nitrate was fed in combination with sulfate, methemoglobin remained below the detection limit of 2% of hemoglobin. Dietary nitrate decreased heat production (-7%), whereas supplementation with sulfate increased heat production (+3%). Feeding nitrate or sulfate had no effects on volatile fatty acid concentrations in rumen fluid samples taken 24 h after feeding, except for the molar proportion of branched-chain volatile fatty acids, which was higher when sulfate was fed and lower when nitrate was fed, but not different when both products were included in the diet. The total number of rumen bacteria increased as a result of sulfate inclusion in the diet. The number of methanogens was reduced when nitrate was fed. Enhanced levels of sulfate in the diet increased the number of sulfate-reducing bacteria. The number of protozoa was not affected by nitrate or sulfate addition. Supplementation of a diet with nitrate and sulfate is an effective means for mitigating enteric methane emissions from sheep.
    Enrichment of anaerobic methanotrophs in sulfate-reducing membrane bioreactors
    Meulepas, R.J.W. ; Jagersma, C.G. ; Gieteling, J. ; Buisman, C.J.N. ; Stams, A.J.M. ; Lens, P.N.L. - \ 2009
    Biotechnology and Bioengineering 104 (2009)3. - ISSN 0006-3592 - p. 458 - 470.
    16s ribosomal-rna - continuous-flow bioreactor - methane oxidation rates - marine-sediments - carbon-monoxide - waste-water - archaea - methanogenesis - consumption - reduction
    Anaerobic oxidation of methane (AOM) in marine sediments is coupled to sulfate reduction (SR). AOM is mediated by distinct groups of archaea, called anaerobic methanotrophs (ANME). ANME co-exist with sulfate-reducing bacteria, which are also involved in AOM coupled SR. The microorganisms involved in AOM coupled to SR are extremely difficult to grow in vitro. Here, a novel well-mixed submerged-membrane bioreactor system is used to grow and enrich the microorganisms mediating AOM coupled to SR. Four reactors were inoculated with sediment sampled in the Eckernförde Bay (Baltic Sea) and operated at a methane and sulfate loading rate of 4.8 L L(-1) day(-1) (196 mmol L(-1) day(-1)) and 3.0 mmol L(-1) day(-1). Two bioreactors were controlled at 15 degrees C and two at 30 degrees C, one reactor at 30 degrees C contained also anaerobic granular sludge. At 15 degrees C, the volumetric AOM and SR rates doubled approximately every 3.8 months. After 884 days, an enrichment culture was obtained with an AOM and SR rate of 1.0 mmol g(volatile suspended solids) (-1) day(-1) (286 micromol g(dry weight) (-1) day(-1)). No increase in AOM and SR was observed in the two bioreactors operated at 30 degrees C. The microbial community of one of the 15 degrees C reactors was analyzed. ANME-2a became the dominant archaea. This study showed that sulfate reduction with methane as electron donor is possible in well-mixed bioreactors and that the submerged-membrane bioreactor system is an excellent system to enrich slow-growing microorganisms, like methanotrophic archaea
    High rate sulfate reduction at pH 6 in a Ph-auxostat submerged membrane bioreactor fed with formate
    Bijmans, M.F.M. ; Peeters, T.W.T. ; Lens, P.N.L. ; Buisman, C.J.N. - \ 2008
    Water Research 42 (2008)10-11. - ISSN 0043-1354 - p. 2439 - 2448.
    afvalwaterbehandeling - industrieel afval - bioreactoren - membranen - filtratie - sulfaat reducerende bacteriën - sulfaatreductie - waste water treatment - industrial wastes - bioreactors - membranes - filtration - sulfate reducing bacteria - sulfate reduction - gas-lift reactor - reducing bacteria - hydrogen-sulfide - carbon-dioxide - growth - methanogenesis - conversion - removal - sludge - water
    Many industrial waste and process waters contain high concentrations of sulfate, which can be removed by sulfate-reducing bacteria (SRB). This paper reports on mesophilic (30 °C) sulfate reduction at pH 6 with formate as electron donor in a membrane bioreactor with a pH-auxostat dosing system. A mixed microbial community from full-scale industrial wastewater treatment bioreactors operated at pH 7 was used as inoculum. The pH-auxostat enabled the bacteria to convert sulfate at a volumetric activity of 302 mmol sulfate reduced per liter per day and a specific activity of 110 mmol sulfate reduced per gram volatile suspended solids per day. Biomass grew in 15 days from 0.2 to 4 g volatile suspended solids per liter. This study shows that it is possible to reduce sulfate at pH 6 with formate as electron donor at a high volumetric and specific activity with inocula from full-scale industrial wastewater treatment bioreactors operated at neutral pH. The combination of a membrane bioreactor and a pH-auxostat is a useful research tool to study processes with unknown growth rates at maximum activities.
    Anaerobic microbial LCFA degradation in bioreactors
    Sousa, D.Z. ; Pereira, M.A. ; Alves, J.I. ; Smidt, H. ; Stams, A.J.M. ; Alves, M.M. - \ 2008
    Water Science and Technology 57 (2008)3. - ISSN 0273-1223 - p. 439 - 444.
    afvalwater - industrieel afval - vetzuren met een lange keten - voedselindustrie - anaërobe afbraak - bioreactoren - clostridiaceae - methanobacterium - palmitaten - waste water - industrial wastes - long chain fatty acids - food industry - anaerobic digestion - bioreactors - clostridiaceae - methanobacterium - palmitates - chain fatty-acids - sludge - nov. - methanogenesis - inhibition - bacterium - digestion - coculture - acetate
    This paper reviews recent results obtained on long-chain fatty acids (LCFA) anaerobic degradation. Two LCFA were used as model substrates: oleate, a mono-unsaturated LCFA, and palmitate, a saturated LCFA, both abundant in LCFA-rich wastewaters. 16S rRNA gene analysis of sludge samples submitted to continuous oleate- and palmitate-feeding followed by batch degradation of the accumulated LCFA demonstrated that bacterial communities were dominated by members of the Clostridiaceae and Syntrophomonadaceae families. Archaeal populations were mainly comprised of hydrogen-consuming microorganisms belonging to the genus Methanobacterium, and acetate-utilizers from the genera Methanosaeta and Methanosarcina. Enrichment cultures growing on oleate and palmitate, in the absence or presence of sulfate, gave more insight into the major players involved in the degradation of unsaturated and saturated LCFA. Syntrophomonas-related species were identified as predominant microorganisms in all the enrichment cultures. Microorganisms clustering within the family Syntrophobacteraceae were identified in the methanogenic and sulfate-reducing enrichments growing on palmitate. Distinct bacterial consortia were developed in oleate and palmitate enrichments, and observed differences might be related to the different degrees of saturation of these two LCFA. A new obligately syntrophic bacterium, Syntrophomonas zehnderi, was isolated from an oleate-degrading culture and its presence in oleate-degrading sludges detected by 16S rRNA gene cloning and sequencing
    Syntrophic growth on formate: a new microbial niche in anoxic environments
    Dolfing, J. ; Jiang, B. ; Henstra, A.M. ; Stams, A.J.M. ; Plugge, C.M. - \ 2008
    Applied and Environmental Microbiology 74 (2008)19. - ISSN 0099-2240 - p. 6126 - 6131.
    methane production - acetate oxidation - signal peptides - bacteria - methanogenesis - life - metabolism - archaea - association - prediction
    Anaerobic syntrophic associations of fermentative bacteria and methanogenic archaea operate at the thermodynamic limits of life. The interspecies transfer of electrons from formate or hydrogen as a substrate for the methanogens is key. Contrary requirements of syntrophs and methanogens for growth-sustaining product and substrate concentrations keep the formate and hydrogen concentrations low and within a narrow range. Since formate is a direct substrate for methanogens, a niche for microorganisms that grow by the conversion of formate to hydrogen plus bicarbonate--or vice versa--may seem unlikely. Here we report experimental evidence for growth on formate by syntrophic communities of (i) Moorella sp. strain AMP in coculture with a thermophilic hydrogen-consuming Methanothermobacter species and of (ii) Desulfovibrio sp. strain G11 in coculture with a mesophilic hydrogen consumer, Methanobrevibacter arboriphilus AZ. In pure culture, neither Moorella sp. strain AMP, nor Desulfovibrio sp. strain G11, nor the methanogens grow on formate alone. These results imply the existence of a previously unrecognized microbial niche in anoxic environments
    Acidification of methanol-fed anaerobic granular sludge bioreactors by cobalt deprivation: Induction and microbial community dynamics
    Gonzalez Fermoso, F. ; Collins, G. ; Bartacek, J. ; O'Flaherty, V. ; Lens, P.N.L. - \ 2008
    Biotechnology and Bioengineering 99 (2008)1. - ISSN 0006-3592 - p. 49 - 58.
    uasb reactors - in-situ - oligonucleotide probes - degradation - methanogenesis - conversion - bacteria - hybridization - competition - archaea
    The acidification of mesophilic (30 degrees C) methanol-fed upflow anaerobic sludge bed (UASB) reactors induced by cobalt deprivation from the influent was investigated by coupling the reactor performance (pH 7.0; organic loading rate 4.5 g COD . L-1 . d(-1)) to the microbial ecology of the bioreactor sludge. The latter was investigated by specific methanogenic activity (SMA) measurements and fluorescence in situ hybridization (FISH) to quantify the abundance of key organisms over time. This study hypothesized that Under cobalt limiting conditions, the SMA on methanol of the sludge gradually decreases, which ultimately results in methanol accumulation in the reactor effluent. Once the methanol accumulation surpasses a threshold value (about 8.5 mM for the sludge investigated), reactor acidification occurs because acetogens outcompete methylothrophic methanogens at these elevated methanol concentrations. Methanogens present in granular sludge at the time of the acidification do not use methanol as the direct substrate and are unable to degrade acetate. Methylotrophic/acetoclastic methanogenic activity was found to be lost within 10 days of reactor operation, coinciding with the disappearance of the Methanosarcina population. The loss of SMA on methanol can thus be used as an accurate parameter to predict reactor acidification of methanol-fed UASB reactors operating under cobalt limiting conditions.
    Hydrogenogenic CO Conversion in a Moderately Thermophilic (55 C) Sulfate-Fed Gas Lift Reactor: Competition for CO-Derived H2
    Sipma, J. ; Lettinga, G. ; Stams, A.J.M. ; Lens, P.N.L. - \ 2006
    Biotechnology Progress 22 (2006)5. - ISSN 8756-7938 - p. 1327 - 1334.
    carbon-monoxide conversion - anaerobic bioreactor sludges - growth - reduction - methanogenesis - methanol - energy - 2-bromoethanesulfonate - chloroform - bacteria
    Thermophilic (55 °C) sulfate reduction in a gas lift reactor fed with CO gas as the sole electron donor was investigated. The reactor was inoculated with mesophilic granular sludge with a high activity of CO conversion to hydrogen and carbon dioxide at 55 °C. Strong competition for H2 was observed between methanogens and sulfate reducers, while the homoacetogens present consumed only small amounts of H2. The methanogens appeared to be more sensitive to pH and temperature shocks imposed to the reactor, but could not be completely eliminated. The fast growth rates of the methanogens (generation time of 4.5 h) enabled them to recover fast from shocks, and they rapidly consumed more than 90% of the CO-derived H2. Nevertheless, steep increases in sulfide production in periods with low methane production suggests that once methanogenesis is eliminated, sulfate reduction with CO-rich gas as electron donor has great potential for thermophilic biodesulfurization
    NO Removal in Continuous BioDeNOx Reactors: Fe(II)EDTA2- Regeneration, Biomass Growth, and EDTA Degradation
    Maas, P.M.F. van der; Brink, P. van den; Utomo, S. ; Klapwijk, A. ; Lens, P.N.L. - \ 2006
    Biotechnology and Bioengineering 94 (2006)3. - ISSN 0006-3592 - p. 575 - 584.
    nitric-oxide - ethylenediaminetetraacetic acid - biological denitrification - reduction - absorption - iron - methanogenesis - oxidation - kinetics - sulfide
    BioDeNOx is a novel technique for NOx removal from industrial flue gases. In principle, BioDeNOx is based on NO absorption into an aqueous Fe(II)EDTA2- solution combined with biological regeneration of that scrubber liquor in a bioreactor. The technical and economical feasibility of the BioDeNOx concept is strongly determined by high rate biological regeneration of the aqueous Fe(II)EDTA2- scrubber liquor and by EDTA degradation. This investigation deals with the Fe(II)EDTA2- regeneration capacity and EDTA degradation in a lab-scale BioDeNOx reactor (10-20 mM Fe(II)EDTA2-, pH 7.2 ± 0.2, 55°C), treating an artificial flue gas (1.5 m3/h) containing 60-155 ppm NO and 3.5-3.9% O2. The results obtained show a contradiction between the optimal redox state of the aqueous FeEDTA solution for NO absorption and the biological regeneration. A low redox potential (below -150 mV vs. Ag/AgCl) is needed to obtain a maximal NO removal efficiency from the gas phase via Fe(II)EDTA2- absorption. Fe(III)EDTA- reduction was found to be too slow to keep all FeEDTA in the reduced state. Stimulation of Fe(III)EDTA- reduction via periodical sulfide additions (2 mM spikes twice a week for the conditions applied in this study) was found to be necessary to regenerate the Fe(II)EDTA2- scrubber liquor and to achieve stable operation at redox potentials below -150 mV (pH 7.2 ± 0.2). However, redox potentials of below -200 mV should be avoided since sulfide accumulation is unwanted because it is toxic for NO reduction. Very low values for biomass growth rate and yield, respectively, 0.043/d and 0.009 mg protein per mg ethanol, were observed. This might be due to substrate limitations, that is the electron acceptors NO and presumably polysulfide, or to physiological stress conditions induced by the EDTA rich medium or by radicals formed in the scrubber upon the oxidation of Fe(II)EDTA2- by oxygen present in the flue gas. Radicals possibly also induce EDTA degradation, which occurs at a substantial rate: 2.1 (±0.1) mM/d under the conditions investigated
    Dispersed plug flow model for upflow anaerobic sludge bed reactors with focus on granular sludge dynamics
    Kalyuzhnyi, S.V. ; Fedorovich, V.V. ; Lens, P.N.L. - \ 2006
    Journal of Industrial Microbiology and Biotechnology 33 (2006)3. - ISSN 1367-5435 - p. 221 - 237.
    uasb-reactor - sulfate reduction - cheese whey - liquid flow - blanket - digestion - wastewater - glucose - methanogenesis - competition
    A new approach to model upflow anaerobic sludge bed (UASB)-reactors, referred to as a one-dimensional dispersed plug flow model, was developed. This model focusses on the granular sludge dynamics along the reactor height, based on the balance between dispersion, sedimentation and convection using one-dimensional (with regard to reactor height) equations. A universal description of both the fluid hydrodynamics and granular sludge dynamics was elaborated by applying known physical laws and empirical relations derived from experimental observations. In addition, the developed model includes: (1) multiple-reaction stoichiometry, (2) microbial growth kinetics, (3) equilibrium chemistry in the liquid phase, (4) major solid-liquid-gas interactions, and (5) material balances for dissolved and solid components along the reactor height. The integrated model has been validated with a set of experimental data on the start-up, operation performance, sludge dynamics, and solute intermediate concentration profiles of a UASB reactor treating cheese whey [Yan et al. (1989) Biol Wastes 27:289¿305; Yan et al. (1993) Biotechnol Bioeng 41:700¿706]. A sensitivity analysis of the model, performed with regard to the seed sludge characteristics and the key model parameters, showed that the output of the dispersed plug flow model was most influenced by the sludge settleability characteristics and the growth properties (especially ¿m) of both protein-degrading bacteria and acetotrophic methanogens
    Influence of pH shocks on trace netal dynamics and performance of methanol fed granular sludge bioreactors
    Zandvoort, M.H. ; Hullebusch, E.D. van; Peerbolte, A. ; Golubnic, S. ; Lettinga, G. ; Lens, P.N.L. - \ 2005
    Biodegradation 16 (2005)6. - ISSN 0923-9820 - p. 549 - 567.
    sequential extraction procedure - degradation - reactors - cobalt - methanogenesis - speciation - sediments - acetate - nickel - growth
    The influence of pH shocks on the trace metal dynamics and performance of methanol fed upflow anaerobic granular sludge bed (UASB) reactors was investigated. For this purpose, two UASB reactors were operated with metal pre-loaded granular sludge (1mM Co, Ni and Fe; 30°C; 96h) at an organic loading rate (OLR) of 5gCOD l reactor-1d-1. One UASB reactor (R1) was inoculated with sludge that originated from a full scale reactor treating alcohol distillery wastewater, while the other reactor (R2) was inoculated with sludge from a full scale reactor treating paper mill wastewater. A 30h pH shock (pH 5) strongly affected the metal retention dynamics within the granular sludge bed in both reactors. Iron losses in soluble form with the effluent were considerable: 2.3 and 2.9% for R1 and R2, respectively, based on initial iron content in the reactors, while losses of cobalt and nickel in soluble form were limited. Sequential extraction of the metals from the sludge showed that cobalt, nickel, iron and sulfur were translocated from the residual to the organic/sulfide fraction during the pH shock in R2, increasing 34, 47, 109 and 41% in the organic/sulfide fraction, respectively. This is likely due to the modification of the iron sulfide precipitate stability, which influences the extractability of iron and trace metals. Such a translocation was not observed for the R1 sludge during the first 30h pH shock, but a second 4day pH shock induced significant losses of cobalt (18%), iron (29%) and sulfur (29%) from the organic/sulfide fraction, likely due to iron sulfide dissolution and concomitant release of cobalt. After the 30h pH shock, VFA accumulated in the R2 effluent, whereas both VFA and methanol accumulated in R1 after the 4day pH shock. The formed VFA, mainly acetate, were not converted to methane due to the loss of methanogenic activity of the sludge on acetate. The VFA accumulation gradually disappeared, which is likely to be related to out-competition of acetogens by methanogens. Zinc, copper and manganese supply did not have a clear effect on the acetate removal and methanol conversion, but zinc may have induced the onset of methanol degradation after day 152 in R1.
    Enzymatic versus Nonenzymatic Conversions during the Reduction of EDTA-Chelated Fe(III) in BioDeNOx Reactors
    Maas, P.M.F. van der; Peng, S. ; Klapwijk, A. ; Lens, P.N.L. - \ 2005
    Environmental Science and Technology 39 (2005)8. - ISSN 0013-936X - p. 2616 - 2623.
    microbial fuel-cells - dissimilatory fe(iii) - reducing bacteria - iron - oxidation - environments - mechanisms - metals - sludge - methanogenesis
    Reduction of EDTA-chelated Fe(III) is one of the core processes in the BioDeNOx process, a chemically enhanced technique for biological NOx removal from industrial flue gases. The capacity of Escherichia coli, three mixed cultures from full scale methanogenic granular sludge reactors, one denitrifying sludge, and a BioDeNOx sludge to reduce Fe(III)EDTA- (25 mM) was determined at 37 and 55°C using batch experiments. Addition of catalytic amounts of sulfide greatly accelerated Fe(III)EDTA- reduction, indicating that biological Fe(III)EDTA - reduction is not a direct, enzymatic conversion but an indirect reduction with involvement of an electron-mediating compound, presumably polysulfides. It is suggested that not thermophilic dissimilatory iron-reducing bacteria but reducers of elemental sulfur or polysulfides are primarily involved in the reduction of EDTA-chelated Fe(III) in BioDeNOx reactors.
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