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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Carbonate Adsorption to Ferrihydrite : Competitive Interaction with Phosphate for Use in Soil Systems
Mendez, Juan C. ; Hiemstra, Tjisse - \ 2019
ACS Earth and Space Chemistry 3 (2019)1. - p. 129 - 141.
CD model - competition - ferrihydrite - goethite - ion adsorption - nanoparticles - solubility - surface complexation

Carbonate (CO3) interacts with Fe-(hydr)oxide nanoparticles, affecting the availability and geochemical cycle of other important oxyanions in nature. Here, we studied the carbonate-phosphate interaction in closed systems with freshly prepared ferrihydrite (Fh), using batch experiments that cover a wide range of pH values, ionic strength, and CO3 and PO4 concentrations. The surface speciation of CO3 has been assessed by interpreting the ion competition with the Charge Distribution (CD) model, using CD coefficients derived from MO/DTF optimized geometries. Adsorption of CO3 occurs predominately via formation of bidentate inner-sphere complexes, either (=FeO)2CO or (=FeO)2CO··Na+. The latter complex is electrostatically promoted at high pH and in the presence of adsorbed PO4. Additionally, a minor complex is present at high CO3 loadings. The CD model, solely parametrized by measuring the pH-dependent PO4 adsorption as a function of the CO3 concentration, successfully predicts the CO3 adsorption to Fh in single-ion systems. The adsorption affinity of CO3 to Fh is higher than to goethite, particularly at high pH and CO3 loadings due to the enhanced formation (=FeO)2CO··Na+. The PO4 adsorption isotherm in 0.5 M NaHCO3 can be well described, being relevant for assessing the reactive surface area of the natural oxide fraction with soil extractions and CD modeling. Additionally, we have evaluated the enhanced Fh solubility due to Fe(III)-CO3 complex formation and resolved a new species (Fe(CO3)2(OH)2 3(aq)), which is dominant in closed systems at high pH. The measured solubility of our Fh agrees with the size-dependent solubility predicted using the surface Gibbs free energy of Fh.

Comparison of the functional properties of RuBisCO protein isolate extracted from sugar beet leaves with commercial whey protein and soy protein isolates
Martin, Anneke H. ; Castellani, Oscar ; Jong, Govardus A.H. de; Bovetto, Lionel ; Schmitt, Christophe - \ 2019
Journal of the Science of Food and Agriculture 99 (2019)4. - ISSN 0022-5142 - p. 1568 - 1576.
emulsion - gel - green leaf protein - solubility - sugar beet

Background: RuBisCO was extracted from sugar beet leaves using soft and food-compatible technologies. Proximate composition, solubility, emulsifying, foaming and gelling properties of the protein isolate were determined. All these properties were systematically benchmarked against commercial whey and soy protein isolates used in food applications. Results: RuBisCO protein isolate (RPI) contained 930 g kg−1 of crude protein. Protein solubility was higher than 80% at pH values lower than 4.0 or higher than 5.5. Foaming capacity of RPI was better at pH 4.0 than at pH 7.0. Interestingly, 10 g kg−1 protein foams were more stable (pH 7.0 and 4.0) than foams obtained with whey or soy protein. Moreover, 10 g kg−1 RPI emulsions at pH 4.0 or 7.0 exhibited good stability, being similar to whey protein isolate. Remarkable gelling properties were observed at pH 7.0, where 50 g kg−1 protein solutions of RPI formed self-supporting gels while more concentrated solutions were needed for whey or soy protein. Conclusion: RuBisCO showed comparable or superior functional properties to those of currently used whey and soy protein isolates. These results highlight the high potential of sugar beet leaf protein isolate as a nutritious and functional food ingredient to face global food security and protein supply.

Resolubilization of Protein from Water-Insoluble Phlorotannin-Protein Complexes upon Acidification
Vissers, Anne M. ; Blok, Annelies E. ; Westphal, Adrie H. ; Hendriks, Wouter H. ; Gruppen, Harry ; Vincken, Jean Paul - \ 2017
Journal of Agricultural and Food Chemistry 65 (2017)44. - ISSN 0021-8561 - p. 9595 - 9602.
complexation - pH - phlorotannins - reversibility - solubility
Marine phlorotannins (PhT) from Laminaria digitata might protect feed proteins from ruminal digestion by formation of insoluble non-covalent tannin-protein complexes at rumen pH (6-7). Formation and disintegration of PhT-protein complexes was studied with β-casein (random coil) and bovine serum albumin (BSA, globular) at various pH. PhT had similar binding affinity for β-casein and BSA as pentagalloyl glucose, as studied by fluorescence quenching. The affinity of PhT for both proteins was independent of pH (3.0, 6.0, and 8.0). In the presence of PhT, the pH range for precipitation of tannin-protein complexes widened to 0.5-1.5 pH units around the isoelectric point (pI) of the protein. Complete protein resolubilization from insoluble PhT-protein complexes was achieved at pH 7 and 2 for β-casein and BSA, respectively. It was demonstrated that PhT modulate the solubility of proteins at neutral pH and that resolubilization of PhT-protein complexes at pH deviating from pI is mainly governed by the charge state of the protein.
The nutritive value of condensed wheat distillers solubles for cattle
Boever, J.L. De; Blok, M.C. ; Millet, S. ; Vanacker, J. ; Campeneere, S. De - \ 2016
Animal 10 (2016)12. - ISSN 1751-7311 - p. 1955 - 1964.
condensed wheat distillers solubles - digestibility - protein value - ruminants - solubility

The chemical composition and the energy and protein value of five batches of condensed distillers solubles (CDS) originating from wheat were determined. The net energy for lactation (NEL) was derived from digestion coefficients obtained with sheep. The true protein digested in the small intestine (DVE) and the rumen degradable protein balance (OEB) were based on the rumen degradation rate (kd D), the rumen undegradable fraction (U) and intestinal digestibility of undegraded protein (%DVBE) predicted by regression equations derived from a data set of 28 protein feeds with kd D, U and %DVBE determined in situ. The CDS is a by-product with a high, but very variable CP content (238 to 495 g/kg DM). The CP contained on average 81% amino acids, with glutamine as main component (on average 21.8% of CP) and a relatively good lysine proportion (3.0%). Further, CDS contains quite a lot of crude fat (mean±SD: 71±14 g/kg DM), glycerol (95±52 g/kg DM) and sugars (123±24 g/kg DM) resulting in a high organic matter digestibility (88.6±3.0%) and high NEL content (8.3±0.4 MJ/kg DM). The protein value showed a large variation, with DVE ranging from 122 to 244 g/kg DM and OEB from 50 to 204 g/kg DM. Wheat CDS is a rich source of minerals and trace elements with exception of calcium.

Suitability of analytical methods to measure solubility for the purpose of nanoregulation
Tantra, Ratna ; Bouwmeester, Hans ; Bolea, Eduardo ; Rey-Castro, Carlos ; David, Calin A. ; Dogné, Jean Michel ; Jarman, John ; Laborda, Francisco ; Laloy, Julie ; Robinson, Kenneth N. ; Undas, Anna K. ; Zande, Meike Van Der - \ 2016
Nanotoxicology 10 (2016)2. - ISSN 1743-5390 - p. 173 - 184.
Nanomaterials - regulation - solubility

Solubility is an important physicochemical parameter in nanoregulation. If nanomaterial is completely soluble, then from a risk assessment point of view, its disposal can be treated much in the same way as "ordinary" chemicals, which will simplify testing and characterisation regimes. This review assesses potential techniques for the measurement of nanomaterial solubility and evaluates the performance against a set of analytical criteria (based on satisfying the requirements as governed by the cosmetic regulation as well as the need to quantify the concentration of free (hydrated) ions). Our findings show that no universal method exists. A complementary approach is thus recommended, to comprise an atomic spectrometry-based method in conjunction with an electrochemical (or colorimetric) method. This article shows that although some techniques are more commonly used than others, a huge research gap remains, related with the need to ensure data reliability.

Effect of Methanethiol Concentration on Sulfur Production in Biological Desulfurization Systems under Haloalkaline Conditions
Roman, P. ; Veltman, R. ; Bijmans, M.F.M. ; Keesman, K.J. ; Janssen, A.J.H. - \ 2015
Environmental Science and Technology 49 (2015)15. - ISSN 0013-936X - p. 9212 - 9221.
natron-alkaline conditions - sulfide oxidation - oxidizing bacteria - aqueous-solutions - soda lakes - lab-scale - bioreactors - solubility - kinetics - polysulfides
Bioremoval of H2S from 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 organic sulfur compounds, like thiols, it is necessary to provide new insights into their impact on overall biodesulfurization process. Published data on the effect of thiols on biodesulfurization processes are scarce. In this study, we investigated the effect of methanethiol on the selectivity for sulfur production in a bioreactor integrated with a gas absorber. This is the first time that the inhibition of biological sulfur formation by methanethiol is investigated. In our reactor system, inhibition of sulfur production started to occur at a methanethiol loading rate of 0.3 mmol L–1 d–1. The experimental results were also described by a mathematical model that includes recent findings on the mode of biomass inhibition by methanethiol. We also found that the negative effect of methanethiol can be mitigated by lowering the salinity of the bioreactor medium. Furthermore, we developed a novel approach to measure the biological activity by sulfide measurements using UV-spectrophotometry. On the basis of this measurement method, it is possible to accurately estimate the unknown kinetic parameters in the mathematical model.
Speciation of trace metals and their uptake by rice in paddy soils
Pan, Y. - \ 2015
Wageningen University. Promotor(en): Rob Comans, co-promotor(en): Gerwin Koopmans; J. Song. - Wageningen : Wageningen University - ISBN 9789462572744
oryza sativa - rijst - padigronden - sporenelementen - voedingsstoffenopname (planten) - bodemchemie - natte rijst - oplosbaarheid - rice - paddy soils - trace elements - nutrient uptake - soil chemistry - flooded rice - solubility

Rice (Oryza sativa L.) is the most important staple food in South and Southeast Asia and plays a crucial role in food security. However, with fast urbanization and industrialization and economic growth in these parts of the world, the production and quality of rice has become an increasing concern, because contamination of paddy soils with trace metals in industrialized areas can lead to yield reduction of rice, a decline in the nutritional quality of the rice, and an accumulation of trace metals in rice grains. In this PhD thesis, I used a combination of experimental research and mechanistic modeling to investigate the solubility of trace metals in paddy soils exposed to alternating flooding and drainage conditions and to link trace metal solubility to the uptake by rice plants over time. This work contributes to the understanding of how redox chemistry affects the solubility of trace metals in flooded soil and sediment systems and provides a tool for the measurement of the free trace metal concentrations in flooded soil and sediment systems in situ in the form of the field DMT.

Fractionation of five technical lignins by selective extraction in green solvents and characterization of isolated fractions
Boeriu, C.G. ; Fitigau, F. ; Gosselink, R.J.A. ; Frissen, A.E. ; Stoutjesdijk, J.H. ; Peter, F. - \ 2014
Industrial Crops and Products 62 (2014). - ISSN 0926-6690 - p. 481 - 490.
antioxidant activities - structural features - alcell(r) lignin - molecular-weight - kraft lignin - solubility - spectroscopy - prediction - ethanol - wood
Lignins from softwood, hardwood, grass and wheat straw were fractionated by selective extraction at ambient temperature using green solvents like acetone/water solutions of 10, 30, 50, 70 and 90% (v/v) acetone and ethyl acetate. A comparison between the isolated fractions and unfractionated lignins was made in terms of extraction yield, lignin solubility factor, molecular weight distribution and functional group composition. Low molecular weight (LMW) lignin fractions with narrow dispersity are obtained by extraction with ethyl acetate and acetone–water solution containing 30% acetone, with yields depending on the type and the functional group content of lignins. A significant amount (56%) of the organosolv hardwood lignin with low molecular weight (Mw = 1868 g/mol) and low dispersity was isolated from ethyl acetate. Insoluble fractions with very high molecular weight (Mw between 10 and 17 kg/mol) are obtained in low yield from acetone–water solutions with 50, 70 and 90% acetone. LMW lignins are in general less condensed and have lower aliphatic hydroxyl content than parent lignins while the HMW fractions have a higher content of condensed hydroxyls. Principal component analysis on the chemical composition of lignins and isolated fractions determined from 31P NMR data showed the high heterogeneity of the technical lignins. Partial least squares models based on FT-IR spectral data were developed to predict the functional group content determined by quantitative 31P NMR analysis of technical lignins and lignin fractions. This approach can be used to develop simple, rapid and accurate analytical tools to monitor and control the selective fractionation of lignin.
Isoflavone extraction from okara using water as extractant
Jankowiak, L. ; Kantzas, N. ; Boom, R.M. ; Goot, A.J. van der - \ 2014
Food Chemistry 160 (2014). - ISSN 0308-8146 - p. 371 - 378.
defatted soybean flakes - soy foods - solubility - soymilk - ph - temperature - stability - genistein - daidzein - proteins
We here report on the use of water as a ‘green’ extraction solvent for the isolation of isoflavones from okara, a by-product of soymilk production. At a low liquid-to-solid ratio of 20 to 1 and 20 °C, 47% of the isoflavones that can be extracted with 70% aqueous ethanol were extracted. The malonyl-glucosides were fully recovered with a ratio of 20 to 1, while ß-glucosides were recovered with an increased liquid-to-solid ratio of 40 to 1. The extraction of aglycones was better at higher ratios, but leveled off before reaching a 100% yield. Temperature hardly affected the total amount of isoflavones. At a 20 to 1 ratio, 20 °C, and pH 10, there was no significant difference (p > 0.05) between isoflavone extraction in water and in 70% aqueous ethanol. The results suggest that water may be used as a green alternative for separation of isoflavones from okara.
Glutamic acid production from wheat by-products using enzymatic and acid hydrolysis
Sari, Y.W. ; Alting, A.C. ; Floris, R. ; Sanders, J.P.M. ; Bruins, M.E. - \ 2014
Biomass and Bioenergy 67 (2014). - ISSN 0961-9534 - p. 451 - 459.
bio-based chemicals - amino-acids - protein - gluten - deamidation - biomass - solubility
Glutamic acid (Glu) has potential as feedstock for bulk chemicals production. It has also been listed as one of the top twelve chemicals derived from biomass. Large amounts of cheaper Glu can be made available by enabling its production from biomass by-products, such as wheat dried distillers grains with solubles (DDGS) derived from ethanol production. The aim of this study was to develop a new method for Glu production from biomass. Wheat gluten was used to represent wheat DDGS. To reduce chemicals usage, several methods were evaluated. These included enzymatic, dilute acid, and a combination of enzymatic and dilute acid hydrolysis. The separate enzymatic and dilute acid hydrolysis (1 M HCl; 95 °C) resulted in yields of 48% and 46% Glu, respectively. However, the combination of enzymatic and dilute acid hydrolysis resulted in a much higher yield of 70% Glu and 10% pyroglutamic acid thereby opening up new possibilities for the industrial production of Glu from biomass
Sensitivity analysis of mechanistic models for estimating ammonia emission from dairy cow urine puddles
Snoek, J.W. ; Stigter, J.D. ; Ogink, N.W.M. ; Groot Koerkamp, P.W.G. - \ 2014
Biosystems Engineering 121 (2014). - ISSN 1537-5110 - p. 12 - 24.
volatile weak electrolytes - aqueous-solutions - mass-transfer - computer-model - swine manure - volatilization - solubility - release - house - temperature
Ammonia (NH3) emission can cause acidification and eutrophication of the environment, is an indirect source of nitrous oxide, and is a precursor of fine dust. The current mechanistic NH3 emission base model for explaining and predicting NH3 emissions from dairy cow houses with cubicles, a floor and slurry pit is based on measured data from a limited number of studies. It requires input values for numerous variables, but the empirical equations for the model parameters in the literature vary. Furthermore, many of the input variables cannot be assessed accurately, and their actual influence on the prediction is unknown. We aimed to improve NH3 emission modelling, by assessing the contribution to the variation in NH3 emission of each input variable and each model parameter related to a single urine puddle. We did so for 27 candidate models, created by each possible combination of three equations per model parameter: the acid dissociation constant, Henry’s law constant, and the mass transfer coefficient. After analysing each candidate model with a Global Sensitivity Analysis we found that at least 71% of the model variation in NH3 emission for each candidate model was explained by five puddle related input variables: pH, depth, area, initial urea concentration and temperature. NH3 emission was not sensitive to the other four variables: air temperature, air velocity, maximum rate of urea conversion and the MichaeliseMenten constant for urea conversion. Based on these results we recommend simplifying the model structurally and reducing the number of input variables.
Heat-Induced Aggregation of Whey Proteins in Aqueous Solutions below Their Isoelectric Point
Cornacchia, L. ; Forquenot de la Fortelle, C. ; Venema, P. - \ 2014
Journal of Agricultural and Food Chemistry 62 (2014). - ISSN 0021-8561 - p. 733 - 741.
bovine beta-lactoglobulin - disulfide bonds - interchange reactions - thermal-denaturation - alpha-lactalbumin - particulate gels - induced gelation - ionic-strength - ph 2 - solubility
Processing beverages containing high concentrations of globular proteins represents a technological challenge due to their instability during heating caused by protein aggregation and gelation. Aggregation of whey protein mixtures was investigated in aqueous model systems at pH 3.5, 4.0, and 4.5 at heating conditions resembling conventional industrial treatment (90 °C for 30 s). The extent of aggregation progressively decreased moving away from the pI. Protein aggregates became smaller and had a more open structure compared to higher pH values. Significant loss of protein dispersibility occurred at pH 4.0 and 4.5 above the denaturation T of whey protein (~70 °C), at which aggregation was caused by intermolecular hydrophobic interactions. Accessible thiol groups were detected in the heat-treated systems, with a higher intensity at higher pH and increasing extent of aggregation. Intermolecular -S-S- bonding played only a minor role in the aggregation at all conditions studied.
Unique characteristics of Pb in soil contaminated by red lead anti-corrosion paint
Brokbartold, M. ; Temminghoff, E.J.M. ; Weng, L. ; Marschner, B. - \ 2013
Soil and Sediment Contamination 22 (2013)8. - ISSN 1532-0383 - p. 839 - 855.
donnan membrane technique - chemical speciation - southern thailand - trace-metals - solubility - cd - exposure - cadmium - nigeria - copper
Red lead (Pb3O4) has been extensively used in the past in anti-corrosion paints for the protection of steel constructions such as electricity pylons or bridges. Until recently, little has been known about the behavior of these Pb compounds in soils. Therefore, three pylon soils and six red lead anti-corrosion paints were characterized in terms of solubility, Pb mineral composition, extractability, sorption and desorption, and the chemical speciation of Pb in soil extracts. The pylon soils were characterized by moderate total Pb concentrations (˜700 mg kg-1), while NH4NO3 extractable Pb was exceptionally high (up to 15% of total Pb). In soil extracts, the free Pb2+ fraction ranged from 33 to 81% of total soluble Pb. The equilibrium concentration of Pb derived from Pb3O4 in ultra-pure water reached 68.5 mg L-1. This high solubility explains the observed high extractability in soils and contradicts earlier reports of much lower water solubilities of the compound.
Estimation of abraham solvation equation coefficients for hydrogen bond formation from abraham solvation parameters for solute activity and basicity
Noort, P.C.M. van - \ 2013
Chemosphere 90 (2013)2. - ISSN 0045-6535 - p. 344 - 348.
free-energy relationship - 298 k - partition-coefficients - organic-compounds - ionic liquids - lfer analysis - solubility - vapors - gases - water
Abraham solvation equations find widespread use in environmental chemistry and pharmaco-chemistry. The coefficients in these equations, which are solvent (system) descriptors, are usually determined by fitting experimental data. To simplify the determination of these coefficients in Abraham solvation equations, this study derives equations, based on Abraham solvation parameters for hydrogen acidity and basicity of the solvents involved, to estimate the value of the coefficients for hydrogen bond formation. These equations were applied to calculate Abraham solvation parameters for hydrogen acidity and basicity for polyoxymethylene, polyacrylate, sodium dodecylsulfate, some ionic liquids, alkanoyl phosphatidyl cholines, and lipids for which fitted values for Abraham coefficients for hydrogen bond formation were available
Continuous bioscorodite crystallization in CSTRs for arsenic removal and disposal
Gonzalez-Contreras, P.A. ; Weijma, J. ; Buisman, C.J.N. - \ 2012
Water Research 46 (2012)18. - ISSN 0043-1354 - p. 5883 - 5892.
ferrous iron oxidation - low ph - scorodite - precipitation - solubility - kinetics - batch
In CSTRs, ferrous iron was biologically oxidized followed by crystallization of scorodite (FeAsO4·2H2O) at pH 1.2 and 72 °C. The CSTRs were fed with 2.8 g L-1 arsenate and 2.4 g L-1 ferrous and operated at an HRT of 40 h, without seed addition or crystal recirculation. Both oxidation and crystallization were stable for periods up to 200 days. The arsenic removal efficiency was higher than 99% at feed Fe/As molar ratios between 1 and 2, resulting in effluents with 29 ± 18 mg As L-1. Arsenic removal decreased to 40% at feed Fe/As molar ratios between 2 and 5. Microorganisms were not affected by arsenic concentrations up to 2.8 g As5+ L-1. The bioscorodite solid yield was 3.2 g/g arsenic removed. Bioscorodite crystals precipitated as aggregates, causing scaling on the glass wall of the reactor. The observed morphology through SE microscopy of the precipitates appeared amorphous but XRD analysis confirmed that these were crystalline scorodite. Arsenic leaching of bioscorodite was 0.4 mg L-1 after 100 days under TCLP conditions, but when jarosite had been co-precipitated leaching was higher at 0.8 g L-1. The robustness of the continuous process, the high removal efficiency and the very low arsenic leaching rates from bioscorodite sludge make the process very suitable for arsenic removal and disposal.
Bioscorodite Crystallization in an Airlift Reactor for Arsenic Removal
Gonzalez-Contreras, P.A. ; Weijma, J. ; Buisman, C.J.N. - \ 2012
Crystal Growth and Design 12 (2012)5. - ISSN 1528-7483 - p. 2699 - 2706.
atmospheric-pressure conditions - sulfate-solutions - scorodite - feaso4.2h2o - solubility - precipitation - stability - biooxidation - minerals
Bioscorodite (FeAsO4·2H2O) crystals were crystallized in an airlift reactor fed at pH 1.2 and 72 °C. Arsenic removal was limited by the biological ferrous iron oxidation. In continuous operation, the iron oxidation initially was 30% and increased to 80% in few days when the iron and dissolved oxygen concentration were increased. The bioscorodite yield was 3 g/g of arsenic removed. The first precipitates were identified as scorodite having a dipyramidal octahedron habit with an Fe/As molar ratio of 1.55. The stability test (TCLP) classified the crystals as suitable for storage with a leached arsenic concentration of 0.5 mg L–1 after 60 days. Settling rates of bioscorodite crystals between 50 and 140 m h–1 were measured. Size distribution frequency indicates that bioscorodite crystals grew from an average size of 30 µm during batch operation to 160 µm at the end of the continuous operation phase. The morphology and size of the crystals guarantee their free-flowing nature, avoiding scaling. The biggest and most stable crystals can be harvested by sedimentation, to select the material best suited for final disposal.
High-Calorific Biogas Production by Selective CO2 Retention at Autogenerated Biogas Pressures up to 20 Bar
Lindeboom, R.E.F. ; Weijma, J. ; Lier, J.B. van - \ 2012
Environmental Science and Technology 46 (2012)3. - ISSN 0013-936X - p. 1895 - 1902.
anaerobic-digestion - methane enrichment - thermodynamic model - waste-water - low ph - solubility - bacteria - sludge - energy - bog
Autogenerative high pressure digestion (AHED) is a novel configuration of anaerobic digestion, in which micro-organisms produce autogenerated biogas pressures up to 90 bar with >90% CH4-content in a single step reactor. The less than 10% CO2-content was postulated to be resulting from proportionally more CO2 dissolution relative to CH4 at increasing pressure. However, at 90 bar of total pressure Henry's law also predicts dissolution of 81% of produced CH4. Therefore, in the present research we studied whether CO2 can be selectively retained in solution at moderately high pressures up to 20 bar, aiming to produce high-calorific biogas with >90% methane. Experiments were performed in an 8 L closed fed-batch pressure digester fed with acetate as the substrate. Experimental results confirmed CH4 distribution over gas and liquid phase according to Henry's law, but the CO2-content of the biogas was only 1-2%, at pH 7, that is, much lower than expected. By varying the ratio between acid neutralizing capacity (ANC) and total inorganic carbon (TICproduced) of the substrate between 0 and 1, the biogas CO2-content could be controlled independently of pressure. However, by decreasing the ANC relative to the TICproduced CO2 accumulation in the aqueous medium caused acidification to pH 5, but remarkably, acetic acid was still converted into CH4 at a rate comparable to neutral conditions.
Autogenerative high pressure digestion: anaerobic digestion and biogas upgrading in a single step reactor system
Lindeboom, R.E.F. ; Fermoso, F.G. ; Weijma, J. ; Zagt, K. ; Lier, J.B. van - \ 2011
Water Science and Technology 64 (2011)3. - ISSN 0273-1223 - p. 647 - 653.
biogas - gasproductie - biochemische omzettingen - methaan - anaërobe afbraak - drukbehandeling - kooldioxide - oplosbaarheid - anaërobe behandeling - afvalwaterbehandeling - biobased economy - gas production - biochemical pathways - methane - anaerobic digestion - pressure treatment - carbon dioxide - solubility - anaerobic treatment - waste water treatment
Conventional anaerobic digestion is a widely applied technology to produce biogas from organic wastes and residues. The biogas calorific value depends on the CH4 content which generally ranges between 55 and 65%. Biogas upgrading to so-called ‘green gas’, with natural gas quality, generally proceeds with add-on technologies, applicable only for biogas flows >100 m3/h. In the concept of autogenerative high pressure digestion (AHPD), methanogenic biomass builds up pressure inside the reactor. Since CO2 has a higher solubility than CH4, it will proportion more to the liquid phase at higher pressures. Therefore, AHPD biogas is characterised by a high CH4 content, reaching equilibrium values between 90 and 95% at a pressure of 3–90 bar. In addition, also H2S and NH3 are theoretically more soluble in the bulk liquid than CO2. Moreover, the water content of the already compressed biogas is calculated to have a dew point
Zn-Ni sulfide selective precipitation: The role of supersaturation
Sampaio, R.M.M. ; Timmers, R.A. ; Kocks, N. ; Andre, V. ; Duarte, M.T. ; Hullebusch, E.D. van; Farges, F. ; Lens, P.N.L. - \ 2010
Separation and Purification Technology 74 (2010)1. - ISSN 1383-5866 - p. 108 - 118.
acid-mine drainage - nickel sulfide - zinc-sulfide - homogeneous precipitation - metal sulfides - stirred-tank - kinetics - surface - solubility - transition
The selective removal of Zn with Na2S from a mixture of Zn and Ni was studied in a continuously stirred tank reactor. At pH 5 and pS 18 the selectivity was improved from 61% to 99% by reducing the supersaturation at the dosing points by means of the reduction of the influent concentrations. The particle size distribution (PSD) of the precipitates increased as the supersaturation decreased up to a mode of about 22 mu m at pH 5. PSD values on the 100-200 mu m range were obtained when the sulfide was dosed through a polytetrafluoroethylene (Teflon) membrane at low supersaturation. Zn precipitated as sphalerite, whereas Ni mainly formed amorphous particles with a pH dependent stoichiometry.
Effect of neutrase, alcalase, and papain hydrolysis of whey protein concentrates on iron uptake by Caco-2 cells
Ou, K.Q. ; Liu, Y.Z. ; Zhang, L.B. ; Yang, X.G. ; Huang, Z.W. ; Nout, M.J.R. ; Liang, J. - \ 2010
Journal of Agricultural and Food Chemistry 58 (2010)8. - ISSN 0021-8561 - p. 4894 - 4900.
in-vitro digestion - enzymatic-hydrolysis - culture model - phytic acid - milk - peptides - availability - bioavailability - dialyzability - solubility
Effects of enzymatic hydrolysates of whey protein concentrates (WPC) on iron absorption were studied using in vitro digestion combined with Caco-2 cell models for improved iron absorption. Neutrase- and papain-treated WPC could improve iron absorption; especially hydrolysates by Neutrase could significantly increase iron absorption to 12.8% compared to 3.8% in the control. Hydrolysates by alcalase had negative effects to the lowest at 0.57%. Two new bands at molecular weights (MW) around and below 10 kDa occurred at tricine-SDS-PAGE of hydrolysates by Neutrase, and one new band at MW below 10 kDa occurred in hydrolysates by papain. No new band was observed in hydrolysates by alcalase. Concentration of free amino acids indicated that, except for tyrosine and phenylalanine, amino acids in papain-treated hydrolysates were higher than that of alcalase, and no cysteine and proline were found in hydrolysates by alcalase. The results suggested that hydrolysate by Neutrase-treated WPC is a promising facilitator for iron absorption. Peptides of MW around and lower than 10 kDa and aspartic acid, serine, glutamic acid, glycin, cysteine, histidine, and proline may be contributors to enhancement
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