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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    Praktijkgerichte innovaties voor duurzame ruwvoerproductie: Opbrengst optimalisatie gras en snijmais
    Verloop, Koos ; Stienezen, Marcia ; Bufe, Conny ; Verhoeven, John ; Wesselink, Marie ; Rombout, Sjoerd ; Tjoonk, L. ; Strijkveen, Emiel ; Steinbusch, Maurice ; Keurentjes, B. ; Schils, Rene ; Middelkoop, Jantine van - \ 2019
    Beslisondersteunende hulpmiddelen voor de ruwvoerproductie in Nederland : Inventarisatie van online beslisondersteunende hulpmiddelen en analyse van het gebruik in de praktijk
    Bufe, Conny ; Wesselink, Marie ; Verhoeven, John ; Stienezen, Marcia ; Strijkveen, Emiel ; Steinbusch, Maurice ; Tjoonk, Leo ; Verloop, Koos - \ 2018
    Wageningen : Stichting Wageningen Research, Wageningen Plant Research (Stichting Wageningen Research, Wageningen Plant Research rapport WPR-876) - 35
    In-situ carboxylate recovery and simultaneous pH control with tailor-configured bipolar membrane electrodialysis during continuous mixed culture fermentation
    Arslan, D. ; Zhang, Y. ; Steinbusch, K.J.J. ; Diels, L. ; Hamelers, Hubertus V.M. ; Buisman, C.J.N. ; Wever, H. de - \ 2017
    Separation and Purification Technology 175 (2017). - ISSN 1383-5866 - p. 27 - 35.
    Bipolar membrane - Electrodialysis - Fermentation - ISPR - Short chain carboxylates

    Anaerobic fermentation of organic waste streams by mixed culture generates a mixture of short chain carboxylic acids. To avoid inhibitory effects of the acids or their consumption in internal conversion reactions in the mixed culture environment, in-situ recovery of acids can be beneficial. In this study, electrodialysis with bipolar membranes (EDBM) was applied to a mixed culture fermentation on organic waste streams using a novel EDBM stack with “direct contact” operation mode. We could demonstrate simultaneous recovery of carboxylates from the fermenter by the EDBM stack while in-situ generation and transport of hydroxyl ions to the fermenter allowed direct pH control. Experiments showed productivity increase after EDBM coupling to the fermenter, and complete elimination of external base consumption. It was also observed that EDBM was able to drive the mixed culture fermentation towards acetate and propionate type of carboxylates.

    Cumelabedrijven gevonden voor mobiele waterzuivering
    Ruijven, Jim van - \ 2016
    Methanol as an alternative electron donor in chain elongation for butyrate and caproate formation
    Chen, W.S. ; Ye, Y. ; Steinbusch, K.J.J. ; Strik, D.P.B.T.B. ; Buisman, C.J.N. - \ 2016
    Biomass and Bioenergy 93 (2016). - ISSN 0961-9534 - p. 201 - 208.
    Biorefinery - Butyrate - Caproate - Chain elongation - Methanol - Mixed culture fermentation

    Chain elongation is an emerging mixed culture biotechnology converting acetate into valuable biochemicals by using ethanol as an external electron donor. In this study we proposed to test another potential electron donor, methanol, in chain elongation. Methanol can be produced through the thermochemical conversion of lignocellulosic biowaste. Use of methanol in chain elongation integrates the lignocellulosic feedstocks and the thermochemical platform technologies into chain elongation. After such integration, the feedstocks for chain elongation are solely from 2nd generation biomass resources. A proof-of-principle study of chain elongation using methanol and acetate was performed in both a batch and a continuous experiment. In the batch experiment, butyrate (191 mMC) and caproate (3 mMC) production from methanol and acetate was observed. A mixed culture microbiome taken from a previous chain elongation reactor fed with ethanol was responsible for the observed organic acid production. The continuous experiment was performed in an upflow anaerobic bioreactor (UAB). The hydraulic retention time (HRT) was 36 h and the operational period lasted for 45 days. In the continuous experiment, butyrate production (Rate > 30 mMC/day) was observed; the caproate concentration was below the detection limit during the entire continuous operational period. In both experiments, methanol and acetate were both substrates contributing to the butyrate production. To the authors' current knowledge, this study is the first attempt at a mixed culture fermentation utilising methanol and acetate for biochemical production. Further research should focus on elevating the butyrate production rate and concentration in the continuous operation of methanol chain elongation, which may stimulate caproate formation.

    Granular sludge formation and characterization in a chain elongation process
    Roghair, M. ; Strik, D.P.B.T.B. ; Steinbusch, K.J.J. ; Weusthuis, R.A. ; Bruins, M.E. ; Buisman, C.J.N. - \ 2016
    Process Biochemistry 51 (2016)10. - ISSN 1359-5113 - p. 1594 - 1598.
    Chain elongation is an open-culture biotechnological process which converts short chain fatty acids andan electron donor to medium chain fatty acids (MCFAs). With this letter we present the first observation ofgranular sludge formation in a chain elongation process. This discovery was made in a continuously stirredanaerobic reactor producing caproate (10.8 g L−1d−1) and heptanoate (1.8 g L−1d−1) as main MCFAs.Concurrently granular and suspended sludge were shaped and attributed to 85% and 15% respectively ofthe total sludge. Both sludge types showed equal product distributions and contributed similarly to MCFAproduction. Granules had irregular shapes, diameters up to ∼1.5 mm, settling velocities of 4–36 m h−1and contained micro-organisms with various shapes. The in-situ settler retained sludge in the bioreactorresulting in a SRT of 4.7 days at an HRT of 17 h. Granular sludge based chain elongation can be optimisedas a high rate biotechnological process.
    Selective short-chain carboxylates production : A review of control mechanisms to direct mixed culture fermentations
    Arslan, D. ; Steinbusch, K.J.J. ; Diels, L. ; Hamelers, H.V.M. ; Strik, D.P.B.T.B. ; Buisman, C.J.N. ; Wever, H. De - \ 2016
    Critical Reviews in Environmental Science and Technology 46 (2016)6. - ISSN 1064-3389 - p. 592 - 634.
    Biomass conversion - carboxylates - mixed culture fermentation - operational parameters - organic waste - volatile fatty acids

    Anaerobic digestion of organic residual streams can be directed to produce carboxylates such as acetate, propionate, and n-butyrate, which can be either directly used in industry or converted into other valuable compounds. This paper reviews the studies working with mixed culture conversion of organic substrates toward carboxylates. It draws connections between standard fermentation parameters and the carboxylate product concentrations and composition. The use of more concentrated carbohydrate-rich substrates, at longer residence times and at neutral pH ranges, stimulates total acid production. When increasing pH to the neutral range, acetate and propionate fractions are elevated. High propionate concentrations and fractions are infrequently reported and mainly appear on high-protein-containing feedstock. High n-butyrate fraction <70% is usually found when pH > 6, at longer retention times or organic loading rates, under CO2 atmosphere or on substrates with high lactate concentrations. The review concludes with prospects for further developments related to the carboxylate platform.

    Chain Elongation with Reactor Microbiomes: Open-Culture Biotechnology To Produce Biochemicals
    Angenent, L.T. ; Richter, H. ; Buckel, W. ; Spirito, C.M. ; Steinbusch, K.J.J. ; Plugge, C.M. ; Strik, D.P.B.T.B. ; Grootscholten, T.I.M. ; Buisman, C.J.N. ; Hamelers, H.V.M. - \ 2016
    Environmental Science and Technology 50 (2016)6. - ISSN 0013-936X - p. 2796 - 2810.
    Chain elongation into medium-chain carboxylates, such as n-caproate and n-caprylate, with ethanol as an electron donor and with open cultures of microbial consortia (i.e., reactor microbiomes) under anaerobic conditions is being developed as a biotechnological production platform. The goal is to use the high thermodynamic efficiency of anaerobic fermentation to convert organic biomass or organic wastes into valuable biochemicals that can be extracted. Several liter-scale studies have been completed and a first pilot-plant study is underway. However, the underlying microbial pathways are not always well understood. In addition, an interdisciplinary approach with knowledge from fields ranging from microbiology and chemical separations to biochemistry and environmental engineering is required. To bring together research from different fields, we reviewed the literature starting with the microbiology and ending with the bioprocess engineering studies that already have been performed. Because understanding the microbial pathways is so important to predict and steer performance, we delved into a stoichiometric and thermodynamic model that sheds light on the effect of substrate ratios and environmental conditions on product formation. Finally, we ended with an outlook
    Selective short chain carboxylates production by mixed culture fermentation
    Arslan, D. - \ 2014
    Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): H. De Wever; Kirsten Steinbusch. - Wageningen : Wageningen University - ISBN 9789462571228 - 211
    fermentation - carboxylic acids - recovery - waste utilization - technology - fermentatie - carbonzuren - terugwinning - afvalhergebruik - technologie


    Surfactants are produced and used in the formulation of many different commercial products. After use, these compounds end up in wastewater treatment plants (WWTPs) or in the environment. Although many surfactants can be degraded in aerobic conditions, anaerobic conditions are also common in Nature and in WWTPs. For achieving nutrients removal from wastewater, biological removal of nitrogen and phosphorus can be performed in a WWTP using the anaerobic-anoxic-aerobic (A2/O) concept. Using the A2/O process sequence, surfactants can be degraded anaerobically before reaching the aerobic compartment. In the anoxic compartment, facultative anaerobic bacteria can degrade surfactants by using nitrate/nitrite as electron acceptor. However, not much is known about surfactant-degrading denitrifying bacteria. In this thesis, Pseudomonas stutzeri strain SN1 and Pseudomonas nitroreducens strain SN2 were isolated from activated sludge of a WWTP with the A2/O process, using the anionic surfactant sodium dodecyl sulfate (SDS) as sole carbon and energy source. Both strains were able to completely degrade SDS coupled to nitrate reduction to dinitrogen gas (Chapter II).

    In the A2/O process, the diversity of bacterial communities involved in the degradation of surfactants may differ between anoxic and oxic compartments, where two different electron acceptors are involved. Surfactants can directly affect the biological activity of microorganisms present in WWTPs and disturb the treatment efficiency. In this way, increased concentrations of surfactants may give rise to a different bacterial diversity selection in anaerobic, anoxic and oxic conditions. The degradation of the anionic surfactant sodium lauryl ether sulfate (SLES) in aerobic conditions is known, but not in denitrifying conditions. In this thesis, the bacterial diversity of enrichments cultures able to degrade different concentrations of SLES in anoxic and aerobic conditions was determined. Aeromonas hydrophila strain S7, Pseudomonas stutzeri strain S8 and Pseudomonas nitroreducens strain S11 were isolated from anoxic enrichments. Comamonas testosteroni strain S13 and Acinetobacter sp. S15 were isolated from aerobic enrichments (Chapter III). SLES initial degradation steps by pure bacterial cultures were previously investigated, but much is still unknown about how the cleavage of ether bonds from chemical compounds is catalyzed by bacterial enzymes. Aeromonas hydrophila strain S7, Pseudomonas stutzeri strain S8 and Pseudomonas nitroreducens strain S11 are able to use SLES in anoxic conditions coupled to nitrate reduction (Chapter III). SLES degradation in anoxic conditions was compared between the three strains. P. nitroreducens strain S11 was found to be the best SLES degrader in anoxic conditions and also to be an excellent aerobic SLES degrader (Chapter IV). Sulfatases and ether cleaving enzymes were probably used by P. nitroreducens strain S11 in both conditions, although differences between SLES degradation in aerobic and anoxic conditions indicated that ether cleavage and following SLES complete degradation is faster under aerobic conditions.

    Although surfactants can be toxic to microorganisms, surfactant-degrading bacteria are known to be resistant to high surfactants concentration, in aerobic conditions. This was not previously investigated using surfactant-degrading denitrifying bacteria. Surfactant-resistant bacteria, with the ability to couple surfactant degradation to nitrate reduction, can be very useful for degrading the surfactants arriving to the anoxic compartments of a WWTP at high concentration. In this thesis, high concentrations of SDS and SLES were used to investigate the effect of these on SDS/SLES-degrading bacteria (P. stutzeri strain SN1, P. nitroreducens strain SN2, P. stutzeri strain S8 and P. nitroreducens strain S11), under anoxic conditions (Chapter V). P. stutzeri strain SN1 was inhibited by increasing SDS and SLES concentrations, after degrading a certain amount of the surfactants. Overall, P. nitroreducens strains showed to be more resistant to high surfactant concentrations compared to P. stutzeri strains. Nevertheless, high concentrations of SDS and SLES did not inhibit growth and nitrate reduction ability of any of the tested Pseudomonas sp..

    Protein domains represent the evolutionary conserved autonomously folding functional building blocks of the proteins. Prediction of protein domains from genomes can be used for species classification and validation of known physiological abilities. P. nitroreducens are facultative anaerobic bacteria from the P. aeruginosa group, which can degrade complex compounds. P. nitroreducens DSM 14399T shares with P. nitroreducens strain SN2 the ability for SDS degradation in anoxic conditions. For increasing the insight into P. nitroreducens DSM 14399T phylogenetic classification and physiological properties (e.g. SDS degradation) its genome was sequenced, annotated and compared to other Pseudomonas spp. genomes. This was performed by comparing functional profiles, based on protein domains presence or absence, with physiological data (Chapter VI). Functional profile comparison confirmed P. nitroreducens classification. Protein domain analysis and genes annotation validated SDS degradation by P. nitroreducens DSM 14399T. This study showed that protein domains prediction and functional profiles comparison can be used for studying and comparing different Pseudomonas species at the physiological level.

    Two-stage medium chain fatty acid (MCFA) production from municipal solid waste and ethanol
    Grootscholten, T.I.M. ; Strik, D.P.B.T.B. ; Steinbusch, K.J.J. ; Buisman, C.J.N. ; Hamelers, B. - \ 2014
    Applied Energy 116 (2014)1. - ISSN 0306-2619 - p. 223 - 229.
    clostridium-kluyveri - carboxylic-acids - carbon-dioxide - elongation - biomass - inhibition - caprylate - caproate - bacteria - acetate
    Chain elongation is an anaerobic fermentation that produces medium chain fatty acids (MCFAs) from volatile fatty acids and ethanol. These MCFAs can be used as biochemical building blocks for fuel production and other chemical processes. Producing MCFAs from the organic fraction of municipal solid waste (OFMSW) is attractive because it combines waste treatment with biochemical production. We investigated whether higher MCFA production rates can be achieved from OFMSW by applying a two-stage conversion, consisting of the OFMSW acidification step followed by chain elongation, compared to a single-stage system. We obtained higher MCFA production rates with a two-stage system than with a single-stage system. The obtained caproate concentrations were above the solubility of caproic acid in water. Furthermore, this work discussed competitive processes for MCFA production and shows how these processes can be controlled in a two-stage system. Finally an outlook was given on research required to prevent too much production of the intermediate co-product butyrate instead of MCFAs, which occurred several times during the experiment.
    Macrophage Specific Caspase-1/11 Deficiency Protects against Cholesterol Crystallization and Hepatic Inflammation in Hyperlipidemic Mice
    Hendrikx, T. ; Bieghs, V. ; Walenbergh, S.M.A. ; Gorp, P.J. van; Verheyen, F. ; Jeurissen, M.L.J. ; Steinbusch, M.M.F. ; Vaes, N. ; Binder, C.J. ; Koek, G.H. ; Stienstra, R. ; Netea, M.G. ; Hofker, M.H. ; Shiri-Sverdlov, R. - \ 2013
    PLoS ONE 8 (2013)12. - ISSN 1932-6203 - 10 p.
    nonalcoholic steatohepatitis - il-1-beta production - nlrp3 inflammasomes - nalp3 inflammasome - gut microbiota - autophagy - activation - atherosclerosis - crystals - disease
    Background & Aims: While non-alcoholic steatohepatitis (NASH) is characterized by hepatic steatosis combined with inflammation, the mechanisms triggering hepatic inflammation are unknown. In Ldlr(-/-) mice, we have previously shown that lysosomal cholesterol accumulation in Kupffer cells (KCs) correlates with hepatic inflammation and cholesterol crystallization. Previously, cholesterol crystals have been shown to induce the activation of inflammasomes. Inflammasomes are protein complexes that induce the processing and release of pro-inflammatory cytokines IL-1b and IL-18 via caspase-1 activation. Whereas caspase-1 activation is independent of caspase-11 in the canonical pathway of inflammasome activation, caspase-11 was found to trigger caspase-1-dependent IL-1b and IL-18 in response to non-canonical inflammasome activators. So far, it has not been investigated whether inflammasome activation stimulates the formation of cholesterol crystals. We hypothesized that inflammasome activation in KCs stimulates cholesterol crystallization, thereby leading to hepatic inflammation. Methods: Ldlr(-/-) mice were transplanted (tp) with wild-type (Wt) or caspase-1/11(-/-) (dKO) bone marrow and fed either regular chow or a high-fat, high-cholesterol (HFC) diet for 12 weeks. In vitro, bone marrow derived macrophages (BMDM) from wt or caspase-1/11(-/-) mice were incubated with oxLDL for 24h and autophagy was assessed. Results: In line with our hypothesis, caspase-1/11(-/-)-tp mice had less severe hepatic inflammation than Wt-tp animals, as evident from liver histology and gene expression analysis in isolated KCs. Mechanistically, KCs from caspase-1/11(-/-)-tp mice showed less cholesterol crystals, enhanced cholesterol efflux and increased autophagy. In wt BMDM, oxLDL incubation led to disturbed autophagy activity whereas BMDM from caspase-1/11(-/-) mice had normal autophagy activity. Conclusion: Altogether, these data suggest a vicious cycle whereby disturbed autophagy and decreased cholesterol efflux leads to newly formed cholesterol crystals and thereby maintain hepatic inflammation during NASH by further activating the inflammasome.
    Bioelectrochemical production of caproate and caprylate from acetate
    Eerten-Jansen, M.C.A.A. van; Heijne, A. ter; Grootscholten, T.I.M. ; Steinbusch, K.J.J. ; Sleutels, T.H.J.A. ; Hamelers, B. ; Buisman, C.J.N. - \ 2013
    Correction to Bioelectrochemical Production of Caproate and Caprylate from Acetate by Mixed Cultures
    Eerten-Jansen, M.C.A.A. van; Heijne, A. ter; Grootscholten, T.I.M. ; Steinbusch, K.J.J. ; Sleutels, T.H.J.A. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2013
    ACS sustainable chemistry & engineering 1 (2013)8. - ISSN 2168-0485 - p. 1069 - 1069.
    Selective carboxylate production by controlling hydrogen, carbon dioxide and substrate concentrations in mixed culture fermentation
    Arslan, D. ; Steinbusch, K.J.J. ; Diels, L. ; Wever, H. de; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2013
    Bioresource Technology 136 (2013). - ISSN 0960-8524 - p. 452 - 460.
    sequencing batch reactor - biohydrogen production - biological production - waste-water - bacteria - glucose - acid - bioconversion - butyrate - caproate
    This research demonstrated the selective production of n-butyrate from mixed culture by applying 2 bar carbon dioxide into the headspace of batch fermenters or by increasing the initial substrate concentration. The effect of increasing initial substrate concentration was investigated at 8, 13.5 and 23 g COD/L with potato processing waste stream. Within 1 week of incubation, n-butyrate fraction selectively increased up to 83% by applying 2 bar hydrogen or 78% by applying carbon dioxide into the headspace whereas it was only 59% in the control reactor. Although the fraction of n-butyrate was elevated, the concentration remained lower than in the control. Both the highest concentration and fraction of n-butyrate were observed under the highest initial substrate concentration without headspace addition. The concentration was 10 g COD/L with 73% fraction. The operational conditions obtained from batch experiments for selective n-butyrate production were validated in a continuous process.
    Improving medium chain fatty acid productivity using chain elongation by reducing the hydraulic retention time in an upflow anaerobic filter
    Grootscholten, T.I.M. ; Steinbusch, K.J.J. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2013
    Bioresource Technology 136 (2013). - ISSN 0960-8524 - p. 735 - 738.
    clostridium-kluyveri - carboxylic-acids - ethanol - biomass - fermentation - inhibition - reduction
    The expansion of biofuel production can lead to an array of negative environmental impacts. Therefore, the European Union (EU) has recently imposed sustainability criteria on biofuel production in the Renewable Energy Directive (RED). In this article, we analyse the effectiveness of the sustainability criteria for climate change mitigation and biodiversity conservation. We first use a global agriculture and forestry model to investigate environmental effects of the EU member states National Renewable Energy Action Plans (NREAPs) without sustainability criteria. We conclude that these targets would drive losses of 2.2 Mha of highly biodiverse areas and generate 95 Mt CO 2 eq of additional greenhouse gas (GHG) emissions. However, in a second step, we demonstrate that the EU biofuel demand could be satisfied ‘sustainably’ according to RED despite its negative environmental effects. This is because the majority of global crop production is produced ‘sustainably’ in the sense of RED and can provide more than 10 times the total European biofuel demand in 2020 if reallocated from sectors without sustainability criteria. This finding points to a potential policy failure of applying sustainability regulation to a single sector in a single region. To be effective this policy needs to be more complete in targeting a wider scope of agricultural commodities and more comprehensive in its membership of countries.
    High rate heptanoate production from propionate and ethanol using chain elongation
    Grootscholten, T.I.M. ; Steinbusch, K.J.J. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2013
    Bioresource Technology 136 (2013). - ISSN 0960-8524 - p. 715 - 718.
    castor-oil - bacteria - acetate - acids
    Heptanoate (or enanthate), a saturated mono-carboxylate with seven carbon atoms, is a commercially produced biochemical building block with versatile applications. Currently, heptanoate is mainly derived from the oxidation of heptaldehyde, which can be obtained after pyrolysis of castor oil. The objective of this investigation was to achieve efficient high rate heptanoate production using a mixed culture chain elongation process based on propionate and ethanol. An efficient high rate heptanoate production using chain elongation could offer an alternative for heptanoate production from castor oil. The investigation was performed in an upflow anaerobic filter with a hydraulic retention time of 17 h. A heptanoate production rate of 4.5 g l-1 d-1 was achieved with a heptanoate concentration of 3.2 g l-1. These results show sufficient potential to consider this approach as an alternative for heptanoate production from castor oil. Future research should make heptanoate production from propionate and ethanol more cost-effective.
    Bioelectrochemical production of caproate and caprylate from acetate by mixed cultures
    Eerten-Jansen, M.C.A.A. van; Heijne, A. ter; Grootscholten, T.I.M. ; Steinbusch, K.J.J. ; Sleutels, T.H.J.A. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2013
    ACS sustainable chemistry & engineering 1 (2013)5. - ISSN 2168-0485 - p. 513 - 518.
    microbial electrolysis cells - fuel-cells - hydrogen - biomass - conversion - ethanol - reduction - transport - membranes - butyrate
    The use of mixed cultures to convert waste biomass into medium chain fatty acids, precursors for renewable fuels or chemicals, is a promising route. To convert waste biomass into medium chain fatty acids, an external electron donor in the form of hydrogen or ethanol needs to be added. This study investigated whether the cathode of a bioelectrochemical system can be used as the electron donor for the conversion of acetate into medium chain fatty acids. We show that medium chain fatty acids were produced in a bioelectrochemical system at -0.9 V vs. NHE cathode potential, without addition of an external mediator. Caproate, butyrate and smaller fractions of caprylate were the main products formed from acetate. In-situ produced hydrogen was likely involved as an electron donor for the reduction of acetate. Electron and carbon balances revealed that 45% of the electrons in electric current and acetate, and 31% of the carbon from acetate were recovered in the formed products. This study showed for the first time production of medium chain fatty acids caproate and caprylate from acetate at the cathode of bioelectrochemical systems, and offers new opportunities for application of bioelectrochemical systems.
    Chain elongation of acetate and ethanol in an upflow anaerobic filter for high rate MCFA production
    Grootscholten, T.I.M. ; Steinbusch, K.J.J. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2013
    Bioresource Technology 135 (2013). - ISSN 0960-8524 - p. 440 - 445.
    mixed cultures - liquid fuels - reactor - digestion - caproate - hydrogen - biomass - waste
    Recently, interest has regained for medium chain fatty acids (MCFAs) as a low cost feedstock for bio-based chemical and fuel production processes. To become cost-effective, the volumetric MCFA production rate by chain elongation should increase to comparable rates of other fermentation processes. We investigate the MCFA production process at a hydraulic retention time of 17 h in an upflow anaerobic filter to improve the volumetric MCFA production rate. This approach resulted in a MCFA production with a volumetric production rate of 16.6 g l-1 d-1, which is more than seven times higher than the current production rate. Moreover the rate is now in the range of other fermentation processes like methane, butanol and ethanol production. Increasing the ethanol load lead to higher volumetric production rates and a high MCFA selectivity of 91%. During operation, methane percentages lower than 0.1% were detected in the headspace of reactor.
    Object recognition testing: Rodent species, strains, housing conditions, and estrous cycle
    Goethem, N.P. van; Rutten, K. ; Staay, F.J. van der; Jans, L.A.W. ; Akkerman, S. ; Steinbusch, H.W.M. ; Blokland, A. ; Klooster, J.W. ; Prickaerts, J. - \ 2012
    Behavioural Brain Research 232 (2012)2. - ISSN 0166-4328 - p. 323 - 334.
    acute tryptophan depletion - one-trial test - sex-differences - wistar rats - memory performance - spatial memory - mouse strains - maze tests - mice - task
    The object recognition task (ORT) allows assessing learning and memory processes in rodents. In this study, two areas in which knowledge about the ORT could be extended were addressed; i.e. generality to species and strains, and intervening variables including housing and estrous cycle. Regarding generality to species and strains, the ORT performance of golden hamsters was assessed. The hamsters showed sufficient exploration times, object recognition performance, and a retention-interval dependent decline similar to rats and mice. Subsequently, we tested three mouse strains which have not been described before in the ORT; i.e. OF1, NMRI, and SJL mice. OF1 and NMRI strains performed equally well, whereas the SJL strain showed low exploration times and no memory retention. Therefore, the SJL strain is unsuited for ORT experiments using a 1 h retention interval and a fixed (3 min) trial duration. Furthermore, the sensitivity to a pharmacological memory deficit model (scopolamine) was tested in three rat strains. Each strain showed a dose dependent relationship, but the least effective dose of scopolamine differed among the three strains, the effect being greater in the order of Wistar, Long-Evans, Hooded Lister rats. Finally, to investigate potential intervening variables in the ORT, the effects of housing conditions and estrous cycle were investigated with rats. Single housing resulted in absolute higher performance than social housing. Furthermore, females in pro-estrus/estrus showed better performance compared to females in metestrus/di-estrus. Taken together, object recognition appears to be a common ability of rodent species, but different strains have different memory capacities and sensitivities to scopolamine, individual housing leads to higher performance, and performance of females is dependent on the estrous cycle phase. Thus, rodent species, strain, housing, and estrous cycle should be taken into consideration in ORT studies.
    Proceedings 2nd international PlantPower Symposium 2012
    Strik, D.P.B.T.B. ; Reas, S. ; Helder, M. ; Mos, Y. ; Schrama, N. ; Steinbusch, K.J.J. ; Wetser, K. ; Fennema, S. ; Snel, J. ; Kuijken, R. ; Hamelers, H.V.M. - \ 2012
    Wageningen : Wageningen University, Sub-deparment of Environmental Technology - 122
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