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.

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Oligomerization and hydroxylation of green tea catechins by oxidative enzymes
Verloop, J.W. - \ 2016
University. Promotor(en): Harry Gruppen, co-promotor(en): Jean-Paul Vincken. - Wageningen : Wageningen University - ISBN 9789462577770 - 146 p.
green tea - oxidation - theaflavine - peroxidase - oxygenases - flavanols - phenolic compounds - catechol oxidase - mass spectrometry - maldi-tof - process control - groene thee - oxidatie - oxygenasen - flavanolen - fenolverbindingen - massaspectrometrie - procesbewaking

Black teas are known for their characteristic brown colour, bitter taste and astringent mouth feel. These sensory characteristics are mainly influenced by the phenolic oxidation products present in black tea. The oxidation of phenolics from green tea leaves during black tea manufacturing is an uncontrolled process. With the objective to make tea oxidation a more controlled process, the aim of this thesis was to understand the enzymatic oxidation reactions occurring during tea oxidation, and to enable more rapid analysis of complex mixtures of phenolics. By incubating green tea catechins with an exogenous tyrosinase, a black tea-like phenolic profile was obtained, enriched in theaflavins, which are important for quality of tea. Further oxidation of theaflavins yielded theatridimensins, in which an epicatechin is coupled to the benzotropolone ring of theaflavin. By using MS/MS on selected ions these theatridimensins were shown to occur in black tea. This MS method could also be used to distinguish isomeric procyanidins and dehydrocatechins based on MS2 fragments, as well as the different interflavanic configurations occurring in dehydrodicatechins. The dehydrocatechins were shown to occur in black tea as well. Besides these oligomerization reactions mediated by tyrosinase, oxidation of tea phenolics also comprised hydroxylation. The enzymatic activity from tea leaves responsible for this hydroxylation reaction, was found to be peroxidase. All findings were condensed into a new version of the ‘oxidative cascade hypothesis’, describing the oxidation reactions towards formation of a black tea.

Biotechnological removal of H2S and thiols from sour gas streams under haloalkaline conditions
Roman, P. - \ 2016
University. Promotor(en): Albert Janssen, co-promotor(en): Martijn Bijmans. - Wageningen : Wageningen University - ISBN 9789462577336 - 193 p.
desulfurization - biogas - bioreactors - methane - sulfides - oxidation - ontzwaveling - bioreactoren - methaan - sulfiden - oxidatie

Biotechnological removal of H2S and thiols from sour gas streams under haloalkaline conditions

Paweł Roman

Abstract

Biological removal of H2S from sour gas streams became popular in recent years because of high process efficiency and low operational costs. To expand the scope of these processes to gas streams containing volatile organosulfur compounds, like thiols, it is necessary to provide new insights into their impact on overall biodesulfurization process. In the current thesis multidisciplinary investigations are performed, such as investigations of inhibitory effects of organic sulfur compounds on sulfide-oxidizing biomass by biochemical and enzyme studies; modelling of the process performance and biological pathways; preparation of analytical tools for measuring unstable sulfur compounds under the process conditions; following the microbial dynamics. The research described in this thesis increases the understanding of the underlying processes occurring in biological gas desulfurization systems when organosulfur compounds are present in the feed gas and provides solutions how to cope with these compounds in full-scale gas biodesulfurization installations.

Exploring the ecophysiology of anaerobic communities of methanotrophic archaea and sulfate-reducing bacteria
Timmers, P.H.A. - \ 2015
University. Promotor(en): Fons Stams, co-promotor(en): Caroline Plugge. - Wageningen : Wageningen University - ISBN 9789462575820 - 181
sulfate reducing bacteria - methane - oxidation - anaerobic conditions - sulfates - marine sediments - microbial physiology - sulfaat reducerende bacteriën - methaan - oxidatie - anaërobe omstandigheden - sulfaten - mariene sedimenten - microbiële fysiologie

Anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SR) is a widespread occurring process in anoxic marine sediments. The process is performed by ANaerobic MEthane oxidizing archaea (ANME) and associated sulfate reducing bacteria (SRB). The ANME presumably oxidize methane through reverse methanogenesis. The associated SRB were thought to reduce sulfate using an interspecies electron carrier (IEC) derived from AOM. The product of methane oxidation that is transferred to the SRB is either a less reduced compound that acts as IEC or electrons are transferred directly (through nanowires or pili) or indirectly (through extracellular quinones). However, recent evidence emerged that ANME could perform both methane oxidation and sulfate reduction to produce sulfur, where the SRB disproportionate the produced sulfur. Little is known on the physiology and ecology of these ANME and associated SRB. The main reasons for this are the difficulties in lab cultivation and to perform in situ studies.

Anaerobic methane oxidation is a process that is at the border of what is energetically possible for sustaining life, which makes it hard to cultivate the responsible organisms. Estimates of the Gibbs free energy yields are between -18 and -35 kJ mol-1 and growth rates between 1.1 and 7.5 months, depending on the environment. AOM therefore operates close to thermodynamic equilibrium and is highly dependent on substrate and product concentrations. In chapter 2, we obtained faster growth rates at elevated methane partial pressure as compared to ambient pressure. The increase in partial pressure increased the solubility of methane and thus the energy yield for the organisms. In chapter 6, we showed higher AOM activity and growth of ANME under thermodynamically favorable sulfate and sulfide concentrations. The problems in studying the process in situ in complex environments comes from difficulties in differentiation of reversible processes. In most studies, methane oxidation is monitored by labelled CO2 formation from labelled methane. Methanogens can perform trace methane oxidation (TMO)during net methanogenesis, which also results in the production of labelled CO2 from labelled methane. When AOM becomes less favorable, the anaerobic back flux of AOM becomes significant, leading to the production of measurable amounts of methane. In chapter 2 and chapter 3, we were able to differentiate between AOM and TMO in long-term incubations.

Another challenge is related to the detection of ANME in complex environments. The phylogenetic distance between and within ANME clades is large. In chapter 5, we discussed the difficulties in primer and probe design for selective detection of ANME without targeting closely related methanogens. Furthermore, it is not known if even more ANME species and clades have yet to be discovered that are not detected with the primers and probes used thus far. In chapter 3, we found indications that besides ANME-2a/b, ANME-2d archaea were also able to perform AOM coupled to sulfate reduction in freshwater conditions. The finding of ANME-2a/b in freshwater shows that ANME archaea are ubiquitously distributed and not only occur in marine sediments. In chapter 6, we confirmed that different ANME clades show niche separation based on the presence of methane and different sulfate and sulfide concentrations. In chapter 2, we obtained indications that ANME-2c grows at high methane partial pressure. More research on the ecophysiology could help in understanding occurrence and activity of ANME in different environments.

Many different SRB have been found so far to form close associations with ANME. Most fall within the Desulfosarcina/Desulfococcus (DSS) clade and only for two enrichment cultures the dominant partner of ANME-2a/b was determined to belong to a specific group with the DSS named SEEP-SRB1. In chapter 2, we found more evidence that a group outside the DSS clade, SEEP-SRB2, could also associate with ANME-2a/b and that Eel-1 members are not directly involved in AOM. In chapter 4, we enriched for SRB within the DSS clade on alternative substrates besides methane, but we were unable to show that these are involved in AOM. Therefore, more research on the sulfate-reducing partner is needed to understand the metabolic interactions between ANME and SRB.

Anaerobic oxidation of methane : evaluation of alternative conditions
Suarez Zuluaga, D.A. - \ 2015
University. Promotor(en): Cees Buisman, co-promotor(en): Jan Weijma. - Wageningen : Wageningen University - ISBN 9789462574823 - 131
microorganisms - methane - oxidation - sulfates - reduction - bioreactors - micro-organismen - methaan - oxidatie - sulfaten - reductie - bioreactoren

Microorganisms capable of performing anaerobic oxidation of methane (AOM) coupled to sulphate reduction have high doubling times which make their enrichment difficult. However, due to higher energy gain, they might be rapidly enriched using alternative electron acceptors. In chapter 2, it was shown that up to 50 times higher conversion rates were obtained with thiosulphate when compared to sulphate. However, it was also presented that thiosulphate was not be exclusively used by microorganisms that reduce it, but that it was also disproportionated into sulphate and sulphide (Chapter 2).

In Chapter 3, a 5 litre membrane bioreactor was fed not only with methane and sulphate but also with acetate and thiosulphate. As previous experiments using these additional substrates had allowed to obtain either faster conversion rates or enrichment of methanotrophic microorganisms; it was expected that AOM rates in the reactor would increase relatively fast. However, the microorganisms that were enriched were not AOM related. They microbial community that showed the highest activity rates in the reactor was comprised by thiosulphate disproportionated bacteria and green sulphur bacteria. The former disproportionated thiosulphate into sulphate and sulphide while the latter converted the sulphide into elemental sulphur.

Chapter 4, unlike the previous chapters, focused on studying the occurrence of AOM in a fresh water ecosystem. Such system was located next to a natural gas source which captured methane for domestic purposes. It was presented how, with the different electron acceptors added, AOM and trace methane oxidation occurred. However, net AOM was only measured in the presence of sulphate as electron acceptor. Furthermore, the microorganisms that were enriched in the presence of methane and sulphate were also detected.

There are several hypotheses which attempted to explain the AOM coupled to sulphate reduction. One of them indicates that it is a process that involves two microorganisms working in a syntrophic relationship. The first microorganism would convert the methane into carbon dioxide and pass the electrons to the second one. Consequently, the second microorganism would convert the sulphate into hydrogen sulphide. In such a structure, the way that electrons are released by the conversion performed by the first microorganism is unknown. It is possible, that electrons are not transfer via electron shuttles or chemical compounds, but that they are transferred directly from one microorganism to the other. A methodology which could be used to determine if the AOM consortia uses direct electron transfer mechanisms was evaluated in Chapter 5. Different kinds of granular biomass were used for this evaluation and, the granule types that would potentially be capable of using direct electron transfer mechanisms were detected.

Plasma geactiveerd water veelbelovend voor de glastuinbouw : inzet als ontsmettings- of gewasbeschermingsmiddel
Kierkels, T. ; Hofland-Zijlstra, J.D. ; Broek, R.C.F.M. van den - \ 2015
Onder Glas 12 (2015)4. - p. 54 - 55.
glastuinbouw - gewasbescherming - ontsmettingsmiddelen - reactieve zuurstof soorten - oxidatie - proeven - biociden - duurzaamheid (sustainability) - greenhouse horticulture - plant protection - disinfectants - reactive oxygen species - oxidation - trials - biocides - sustainability
De eerste proeven met plasma geactiveerd water zijn veelbelovend. In het lab worden Erwinia en Botrytis afgedood of sterk teruggedrongen. Daarmee kan het plasma geactiveerde water wellicht een alternatief vormen voor ontsmetting met chloor. Daarnaast zijn er ook mogelijkheden om het gewas te beschermen tegen ongewenste organismen. Een groot samenwerkingsverband verkent de mogelijkheden verder.
Investigations into the biosynthesis, regulation, and self-resistance of toxoflavin in Pseudomonas protegens Pf-5
Philmus, B. ; Shaffer, B.T. ; Kidarsa, T.A. ; Yan, Q. ; Raaijmakers, J.M. ; Begley, T.P. ; Loper, J.E. - \ 2015
ChemBioChem 16 (2015)12. - ISSN 1439-4227 - p. 1782 - 1790.
formylglycine-generating enzyme - fluorescens pf-5 - burkholderia-glumae - pyoluteorin - cocovenenans - expression - oxidation - system - rice - gaca
Pseudomonas spp. are prolific producers of natural products from many structural classes. Here we show that the soil bacterium Pseudomonas protegens Pf-5 is capable of producing trace levels of the triazine natural product toxoflavin (1) under microaerobic conditions. We evaluated toxoflavin production by derivatives of Pf-5 with deletions in specific biosynthesis genes, which led us to propose a revised biosynthetic pathway for toxoflavin that shares the first two steps with riboflavin biosynthesis. We also report that toxM, which is not present in the well-characterized cluster of Burkholderia glumae, encodes a monooxygenase that degrades toxoflavin. The toxoflavin degradation product of ToxM is identical to that of TflA, the toxoflavin lyase from Paenibacillus polymyxa. Toxoflavin production by P. protegens causes inhibition of several plant-pathogenic bacteria, and introduction of toxM into the toxoflavin-sensitive strain Pseudomonas syringae DC3000 results in resistance to toxoflavin.
Verwijderen gewasbeschermingsmiddelen : duurproef actief koolfilter
Ruijven, J.P.M. van; Staaij, M. van der; Os, E.A. van; Beerling, E.A.M. - \ 2015
glastuinbouw - gewasbescherming - milieueffect - chemische bestrijding - lozing - oppervlaktewaterkwaliteit - oxidatie - koolstof - actieve kool - filters - greenhouse horticulture - plant protection - environmental impact - chemical control - disposal - surface water quality - oxidation - carbon - activated carbon
Met de aankomende verplichting tot het toepassen van zuiveringstechnieken voor het verwijderen van gewasbeschermingsmiddelen uit glastuinbouw lozingswater in gedachten, worden in het IDC Water verschillende technieken op effectiviteit onderzocht. Eerdere (kortdurende) proeven hebben goede resultaten laten zien van de combinatie geavanceerde oxidatie met actief koolstof.
Modeling studies of biological gas desulfurization under haloalkaline conditions
Klok, J.B.M. - \ 2015
University. Promotor(en): Albert Janssen, co-promotor(en): Karel Keesman. - Wageningen : Wageningen University - ISBN 9789462572980 - 158
biogas - aardgas - ontzwaveling - sulfiden - oxidatie - bioreactoren - wiskundige modellen - simulatiemodellen - natural gas - desulfurization - sulfides - oxidation - bioreactors - mathematical models - simulation models

Abstract

Biogas, synthesis and natural gas streams often require treatment because of the presence of gaseous hydrogen sulphide (H2S). About 25 years ago, a biotechnological gas treatment process was developed as an alternative to the conventionally applied technologies. This process is known as the Thiopaq process and offers a number of advantages compared to the existing physical-chemical processes. Depending on the process conditions, H2S is oxidized to elemental bio-sulfur (90-94 mol%) and sulphate (6-10 mol%). In order to enable cost effective large scale applications, the selectivity for sulfur production should be increased to more than 97 mol%. Hence, a better understanding of the combined effect of abiotic and biological reaction kinetics and the relation to hydrodynamic characteristics is required.

The first part of this PhD study focuses on biological reaction kinetics and biological pathways for sulphide oxidation that occur in the process at haloalkaline conditions. It was found that two different sulfide oxidizing enzyme systems are present in haloalkaline sulfide oxidizing bacteria. It has been hypothesized that the different enzymatic routes are determined by the process conditions. Both enzyme systems were taken into account to propose and validate a new physiological mathematical model that can handle multi-substrates and multi-products.

In the second part of the thesis, this model was evaluated via a normalized sensitivity method and it was demonstrated that certain key parameters affect the activity of the biomass at different substrate levels. Furthermore, from CSTR simulations it has been demonstrated that non-linear effects are of importance when scaling up from lab-scale to full-scale industrial units.

Finally, the developed kinetic models have been incorporated in a full-scale biodesulfurization model that includes the effects of turbulent flow regimes and mass transfer of oxygen. This enables us to better understand the overall process. Moreover, the model can also be used as a tool to design model-based control strategies which will lead to better overall process performance, i.e. maximize sulfur production and minimize chemical consumption rates.

Energy and nutrient recovery for municipal wastewater treatment: How to design a feasible plant layout?
Khiewwijit, R. ; Temmink, B.G. ; Rijnaarts, H.H.M. ; Keesman, K.J. - \ 2015
Environmental Modelling & Software 68 (2015). - ISSN 1364-8152 - p. 156 - 165.
autotrophic nitrogen removal - sensitivity analysis - models - phosphorus - parameters - resources - oxidation - sewage - future - urine
Activated sludge systems are commonly used for robust and efficient treatment of municipal wastewater. However, these systems cannot achieve their maximum potential to recover valuable resources from wastewater. This study demonstrates a procedure to design a feasible novel configuration for maximizing energy and nutrient recovery. A simulation model was developed based on literature data and recent experimental research using steady-state energy and mass balances with conversions. The analysis showed that in the Netherlands, proposed configuration consists of four technologies: bioflocculation, cold partial nitritation/Anammox, P recovery, and anaerobic digestion. Results indicate the possibility to increase net energy yield up to 0.24 kWh/m3 of wastewater, while reducing carbon emissions by 35%. Moreover, sensitivity analysis points out the dominant influence of wastewater organic matter on energy production and consumption. This study provides a good starting point for the design of promising layouts that will improve sustainability of municipal wastewater management in the future.
Electricity generation by a plant microbial fuel cell with an integrated oxygen reducing biocathode
Wetser, K. ; Sudirjo, E. ; Buisman, C.J.N. ; Strik, D.P.B.T.B. - \ 2015
Applied energy 137 (2015). - ISSN 0306-2619 - p. 151 - 157.
determine performance - living plants - reduction - oxidation - biofilms - system
In this study we show that a chemical ferricyanide cathode can be replaced by a biological oxygen reducing cathode in a plant microbial fuel cell (PMFC) with a new record power output. A biocathode was successfully integrated in a PMFC and operated for 151 days. Plants growth continued and the power density increased reaching a maximum power output of 679 mW/m2 plant growth area (PGA) in a 10 min polarization. The two week record average power densities was 240 mW/m2 PGA. The new records were reached due to the high redox potential of oxygen reduction which was effectively catalyzed by microorganisms in the cathode. This resulted in a 127 mV higher cathode potential of the PMFC with a biocathode than a PMFC with a ferricyanide cathode. We also found that substrate availability in the anode likely limits the current generation. This work is crucial for PMFC application as it shows that PMFC can be a completely sustainable biotechnology with an improved power output.
Oxygen restriction as challenge test reveals early high-fat-diet-induced changes in glucose and lipid metabolism
Duivenvoorde, L.P.M. ; Schothorst, E.M. van; Derous, D. ; Stelt, I. van der; Masania, J. ; Rabbani, N. ; Thornalley, P.J. ; Keijer, J. - \ 2015
Pflugers Archiv-European Journal of Physiology 467 (2015)6. - ISSN 0031-6768 - p. 1179 - 1193.
adipose-tissue - gene-expression - intermittent hypoxia - energy-expenditure - insulin-resistance - transcriptional regulation - mass-spectrometry - mice - obesity - oxidation
Challenge tests stress homeostasis and may reveal deviations in health that remain masked under unchallenged conditions. Ideally, challenge tests are non-invasive and applicable in an early phase of an animal experiment. Oxygen restriction (OxR; based on ambient, mild normobaric hypoxia) is a non-invasive challenge test that measures the flexibility to adapt metabolism. Metabolic inflexibility is one of the hallmarks of the metabolic syndrome. To test whether OxR can be used to reveal early diet-induced health effects, we exposed mice to a low-fat (LF) or high-fat (HF) diet for only 5 days. The response to OxR was assessed by calorimetric measurements, followed by analysis of gene expression in liver and epididymal white adipose tissue (eWAT) and serum markers for e.g. protein glycation and oxidation. Although HF feeding increased body weight, HF and LF mice did not differ in indirect calorimetric values under normoxic conditions and in a fasting state. Exposure to OxR; however, increased oxygen consumption and lipid oxidation in HF mice versus LF mice. Furthermore, OxR induced gluconeogenesis and an antioxidant response in the liver of HF mice, whereas it induced de novo lipogenesis and an antioxidant response in eWAT of LF mice, indicating that HF and LF mice differed in their adaptation to OxR. OxR also increased serum markers of protein glycation and oxidation in HF mice, whereas these changes were absent in LF mice. Cumulatively, OxR is a promising new method to test food products on potential beneficial effects for human health.
Zn sorption to biogenic bixbyite-like Mn2O3 produced by Bacillus CUA isolated from soil: XAFS study with constraints on sorption mechanism
Zhang, Z.J. ; Yin, H. ; Tan, W.F. ; Koopal, L.K. ; Zheng, L.R. ; Feng, X.H. ; Liu, F. - \ 2014
Chemical Geology 389 (2014). - ISSN 0009-2541 - p. 82 - 90.
adsorption-desorption reversibility - manganite gamma-mnooh - pseudomonas-putida - mn-oxides - hexagonal-birnessite - bacterial biofilm - marine bacillus - zinc sorption - strain sg-1 - oxidation
Although most reported biogenic Mn oxides are hexagonal birnessites, other types of biogenic Mn oxides also commonly occur in the environment. Compared to hexagonal birnessites, the sorption characteristics and the underlying mechanism of adsorption of heavy-metal ions to those of the other biogenic Mn oxides are still rarely addressed. A strain of Mn-oxidizing bacteria isolated from Claypani-Udic Argosols was identified as Bacillus with 16S rRNA sequencing analysis. The bacterial Mn(II) oxidation product is a poorly crystallized bixbyite-like Mn2O3 (alpha-Mn2O3). The maximum adsorption capacities of Zn(II) onto the biogenic Mn oxide at pH 6.00 and pH 4.00 were 663 mmol/kg and 629 mmol/kg, respectively. The complex structure of adsorbed Zn2+ was constrained using Zn EXAFS analysis, combined with structural parameters of the biogenic Mn oxide with alternately arranged regular and distorted MnO6 octahedra obtained through multiple-FEFF fitting of Mn EXAFS data. At a relatively low Zn2+ loading (100 mmol/kg, pH 6.00), Zn2+ adsorbed onto the biogenic Mn oxide with two types of tetrahedrally coordinated complexes, i.e. (1) coordinated with one regular/distorted MnO6 octahedron as a monodentate-mononuclear complex and (2) with two MnO6 octahedra (two regular, two distorted or a regular and a distorted) as a bidentate-binuclear complex. While, at a relatively high Zn2+ loading (556 mmol/kg, pH 4.00; 635 mmol/kg, pH 6.00), two types of octahedrally coordinated complexes are constrained, i.e. (1) coordinated with one regular/distorted MnO6 octahedron as a monodentate-mononuclear complex and (2) with one regular MnO6 octahedron as a bidentate mononuclear complex. This research extends further understanding on the formation of biogenic Mn oxides in the environment and the adsorption mechanism of heavy metals onto low-valence Mn oxides with distorted structures. The application of low valence biogenic Mn oxides to efficiently remove heavy metals from water is also shown to be promising. (C) 2014 Elsevier B.V. All rights reserved.
Analysis of Palmitoyl Apo-astaxanthinals, Apo-astaxanthinones, and their Epoxides by UHPLC-PDA-ESI-MS
Weesepoel, Y.J.A. ; Gruppen, H. ; Bruijn, W.J.C. de; Vincken, J.P. - \ 2014
Journal of Agricultural and Food Chemistry 62 (2014)42. - ISSN 0021-8561 - p. 10254 - 10263.
beta-carotene degradation - mass-spectrometry - hypochlorous acid - haematococcus-pluvialis - products - myeloperoxidase - autoxidation - stability - oxidation - esters
Food products enriched with fatty acid-esterified xanthophylls may result in deviating dietary apo-carotenoids. Therefore, free astaxanthin and its mono- and dipalmitate esters were subjected to two degradation processes in a methanolic model system: light-accelerated autoxidation and hypochlorous acid/hypochlorite (HOCl/OCl–) bleaching. Reversed phase ultrahigh-performance liquid chromatography photodiode array with in-line electrospray ionization mass spectrometry (RP-UHPLC-PDA-ESI-MS) was used for assessment of degradation products. Apo-astaxanthinals and -astaxanthinones containing 3 (apo-9) to 10 (apo-8') conjugated double bonds were found upon autoxidation for all three types of astaxanthin (except free apo-8'-astaxanthinal). Fragmentation of [M + H]+ and [M + Na]+ parent masses of apo-astaxanthins from dipalmitate astaxanthin indicated palmitate esterification. Astaxanthin monopalmitate degradation resulted in a mixture of free and palmitate apo-astaxanthins. HOCl/OCl– rapidly converted the astaxanthins into a mixture of epoxy-apo-9- and epoxy-apo-13-astaxanthinones. The palmitate ester bond was hardly affected by autoxidation, whereas for HOCl/OCl– the ester bond of the apo-astaxanthin palmitoyl esters was degraded.
Technologieën voor verwijdering gewasbeschermingsmiddelen
Beerling, E.A.M. - \ 2014
gewasbescherming - chemische bestrijding - milieueffect - cost effective analysis - afvalverwerking - oxidatie - scheidingsapparaten - bioremediëring - adsorptie - plant protection - chemical control - environmental impact - cost effectiveness analysis - waste treatment - oxidation - separators - bioremediation - adsorption
Mogelijk geschikte technieken om chemische gewasbeschermingsmiddelen te verwijderen zodat ze niet het milieu verontreiningen worden geïnventariseerd met behulp van onafhankelijke experts uit de watersector (o.a. KWR, Wetsus, Mannen van de Wit en Stowa)
Microbiological and geochemical dynamics of the subsurface: chemical oxidation and bioremediation of organic contaminants
Sutton, N.B. - \ 2014
University. Promotor(en): Huub Rijnaarts, co-promotor(en): Tim Grotenhuis. - Wageningen : Wageningen University - ISBN 9789462570269 - 295
bodemverontreiniging - biologische processen - geochemie - bioremediëring - microbiologie - ecotoxicologie - oxidatie - biodegradatie - microbiologie van de ondergrond - soil pollution - biological processes - geochemistry - bioremediation - microbiology - ecotoxicology - oxidation - biodegradation - subsurface microbiology
Verontreiniging van de ondergrond als gevolg van stedelijke en industriële activiteiten vormt een ernstig milieurisico. Om deze locaties te zuiveren en in hun oorspronkelijke staat te herstellen is het noodzakelijk dat efficiënte saneringstechnologieën ontwikkeld worden. Echter, de aanwezigheid en de behandeling van deze verontreinigingen biedt ook mogelijkheden voor wetenschappelijk onderzoek naar fundamentele onderwerpen op het gebied van de microbiële ecologie en bodemgeochemie. Dit proefschrift beschrijft in situ chemische oxidatie (ISCO) en in situ bioremediatie (ISB) van organische verontreinigingen
Nutritional Composition of Shea Products and Chemical Properties of Shea Butter: A Review
Honfo, G.F. ; Akissoe, N. ; Linnemann, A.R. ; Soumanou, M. ; Boekel, M.A.J.S. van - \ 2014
Critical Reviews in Food Science and Nutrition 54 (2014)5. - ISSN 1040-8398 - p. 673 - 686.
vitellaria-paradoxa - african countries - vegetable-oils - fat - extraction - olive - acid - tocopherols - oxidation - catechins
Increasing demand of shea products (kernels and butter) has led to the assessment of the state-of-the-art of these products. In this review, attention has been focused on macronutrients and micronutrients of pulp, kernels, and butter of shea tree and also the physicochemical properties of shea butter. Surveying the literature revealed that the pulp is rich in vitamin C (196.1 mg/100 g); consumption of 50 g covers 332% and 98% of the recommended daily intake (RDI) of children (4–8 years old) and pregnant women, respectively. The kernels contain a high level of fat (17.4–59.1 g/100 g dry weight). Fat extraction is mainly done by traditional methods that involve roasting and pressing of the kernels, churning the obtained liquid with water, boiling, sieving, and cooling. The fat (butter) is used in food preparation and medicinal and cosmetics industries. Its biochemical properties indicate some antioxidant and anti-inflammatory activities. Large variations are observed in the reported values for the composition of shea products. Recommendations for future research are presented to improve the quality and the shelf-life of the butter. In addition, more attention should be given to the accuracy and precision in experimental analyses to obtain more reliable information about biological variation.
The influence of spatiotemporal variability and adaptations to hypoxia on empirical relationships between soil acidity and vegetation
Cirkel, D.G. ; Witte, J.P.M. ; Bodegom, P.M. van; Nijp, J.J. ; Zee, S.E.A.T.M. van der - \ 2014
Ecohydrology 7 (2014)1. - ISSN 1936-0584 - p. 21 - 32.
bodemchemie - bodemaciditeit - vegetatietypen - bodem-plant relaties - soortensamenstelling - plantenfysiologie - rizosfeer - wetlands - heterogeniteit - ecohydrologie - ruimtelijke variatie - soil chemistry - soil acidity - vegetation types - soil plant relationships - species composition - plant physiology - rhizosphere - heterogeneity - ecohydrology - spatial variation - ellenberg indicator values - field-measurements - plant ecology - ph changes - iron - regression - diversity - diffusion - oxidation
Soil acidity is well known to affect the species composition of natural vegetation. The physiological adaptations of plants to soil acidity and related toxicity effects and nutrient deficiencies are, however, complex, manifold and hard to measure. Therefore, generally applicable quantifications of mechanistic plant responses to soil acidity are still not available. An alternative is the semi-quantitative and integrated response variable ‘indicator value for soil acidity’ (Rm). Although relationships between measured soil pH and Rm from various studies are usually strong, they often show systematic bias and still contain high residual variances. On the basis of a well-documented national dataset consisting of 91 vegetation plots and a dataset with detailed, within-plot, pH measurements taken at three periods during the growing season, it is shown that strong spatiotemporal variation of soil pH can be a critical source of systematic errors and statistical noise. The larger part of variation, however, could be explained by the moisture status of plots. For instance, Spearman's rho decreased from 93% for dry plots and 87% for moist plots to 59% for wet plots. The loss of relation between soil pH and Rm in the moderately acid to alkaline range at increasingly wetter plots is probably due to the establishment of aerenchyma-containing species, which are able to control their rhizosphere acidity. Adaptation to one site factor (oxygen deficit) apparently may induce indifference for other environmental factors (Fe2+, soil pH). For predictions of vegetation response to soil acidity, it is thus important to take the wetness of plots into account
Relationship between soil properties and the bias of N2O reduction by acetylene inhibition technique for analyzing soil denitrification potential
Qin, S.P. ; Yuan, H.J. ; Dong, W.X. ; Hu, C.S. ; Oenema, O. ; Zhang, Y.M. - \ 2013
Soil Biology and Biochemistry 66 (2013). - ISSN 0038-0717 - p. 182 - 187.
nitrous-oxide reduction - pseudomonas-aeruginosa - cultures - catchment - oxidation - sediments - nitrate - manure - assay - no
The acetylene inhibition technique (AIT) has been widely used to measure soil denitrification potential (SDP), but has been criticized also for underestimating the actual SDP due to limitations of the AIT. Possible effects of soil properties on the bias of the AIT-derived SDP have not been thoroughly investigated yet. The study presented here therefore aimed at quantifying the relationships between soil texture and nutrient contents and the bias of AIT-derived SDP. A total of 26 soils with a wide range of clay and nutrient contents were incubated according to the standard procedure of AIT for assaying SDP. Incubation flasks were made anaerobic by gas substitution with pure helium (99.999%). Changes in the N-2 and N2O concentrations in the He headspace were measured using gas chromatography. The emission rates of N2O and N-2 were calculated to quantify the bias of the AIT-derived SDP (expressed as the percentage of the actual SDP that was not accounted for by AIT). The results showed that the bias ranged from 8 to 98%. The bias was negatively correlated (P <0.05) with the clay, silt, organic matter and nutrient contents of the soils. These results indicate that the bias of the AIT-derived SDP was higher in low-fertility soils than in fertile soils. We recommend that soil properties are taken into account when interpreting results of AIT-derived SDP values. (C) 2013 Elsevier Ltd. All rights reserved.
Transformation of hydroxycarbonate green rust into crystalline iron (hydr)oxides: Influences of reaction conditions and underlying mechanisms
Wang, Xiaoming ; Liu, Fan ; Tan, W. ; Feng, Xionghan ; Koopal, L.K. - \ 2013
Chemical Geology 351 (2013). - ISSN 0009-2541 - p. 57 - 65.
containing aqueous-media - mossbauer-spectroscopy - pourbaix diagram - ferrihydrite - oxidation - carbonate - fougerite - hydroxide - phosphate - oxyhydroxides
Green rusts (GRs) are found as intermediate products between FeII hydroxides and FeIII oxyhydroxides in various anoxic environments. The transformation of hydroxycarbonate green rust GR1(CO32-) by air oxidation at different conditions and the underlying mechanisms were investigated using X-ray diffraction (XRD) including Rietveld qualitative analyses, chemical composition analysis, pH and Eh determination, and transmission electron microscopy. At the synthesis stage, the formation of GR1(CO32-) was completed when the suspension pH attained a minimum and the ratio n(FeII)/n(Fetotal) in the mineral attained a maximum. At the subsequent transformation stage, a dissolution–oxidation–reprecipitation process was observed, in which GR1(CO32-) firstly dissolves to less crystalline iron hydroxide and Fe2+, and is then oxidized to crystalline iron (hydr)oxides. When the pH increases from 6.5 to 10 at 25 °C, the transformation rate and oxidation rate of GR1(CO32-) gradually decrease, the final products change from lepidocrocite to goethite and magnetite, and the crystallite size of goethite gradually increases with pH. When temperature increases from 15 °C to 45 °C at about pH 7.7–8.8, the dissolution–reprecipitation rate of GR1(CO32-) gradually increases while the oxidation rate decreases, and the final products also change from lepidocrocite to goethite and magnetite. When the airflow rate increases from 0 to 0.1 m3 h-1 at 25 °C, the oxidation rate gradually increases, the final products vary from goethite to lepidocrocite and their crystallite sizes and crystallinity gradually decrease. In general, the Fe2+ oxidation rate is governed by pH, temperature and O2 concentration. When the oxidation rate increases, the products follow the order from magnetite to goethite to lepidocrocite, and the crystallite size and the crystallinity decrease.
Short term, high fat-feeding induced changes in white adipose tissue gene expression are highly predictive for long term changes
Voigt, A. ; Agnew, K. ; Schothorst, E.M. van; Keijer, J. ; Klaus, S. - \ 2013
Molecular Nutrition & Food Research 57 (2013)8. - ISSN 1613-4125 - p. 1423 - 1434.
diet-induced obesity - epigallocatechin gallate - uncoupling protein-1 - insulin-resistance - mice - microarray - oxidation - efficiency - adipocytes - alpha
Scope - We aimed to evaluate the predictability of short-term (5 days) changes in epididymal white adipose tissue (eWAT) gene expression for long-term (12 weeks) changes induced by high-fat diet (HFD) feeding. Methods and results - Mice were fed semisynthetic diets containing 10 (low-fat diet) or 40 (HFD) energy% of fat. Global gene expression in eWAT was analyzed using microarrays and confirmed by quantitative PCR. As expected, HFD feeding resulted in increased body fat accumulation and reduced glucose tolerance after 12 weeks. A total of 4678 transcripts were significantly changed by HFD after 12 weeks and 973 after 5 days, with an overlap of 764 transcripts encoding 549 genes. Of these, 79% were downregulated and 21% were upregulated by HFD, all in the same direction and highly correlated (r2 = 0.90) between the time points. Pathway analysis showed downregulation of the main identified processes: lipid metabolism, carbohydrate metabolism, and oxidative phosphorylation. Mest (mesoderm-specific transcript) was highly upregulated, confirming its role as an early marker of fat cell expansion. Conclusion - The high predictive value of short-term gene expression changes for long-term effects of high fat feeding is a promising step to establish robust early biomarkers that could shorten animal trials to assess health-promoting food compounds.
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