Staff Publications

Staff Publications

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

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

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

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

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    Anaerobic digestion of cellulose and hemicellulose in the presence of humic acids
    Azman, Samet - \ 2016
    Wageningen University. Promotor(en): Fons Stams; Grietje Zeeman, co-promotor(en): Caroline Plugge. - Wageningen : Wageningen University - ISBN 9789462579613 - 189
    humic acids - hydrolysis - anaerobic digestion - cellulose - hemicelluloses - biomass - renewable energy - energy recovery - biogas - fermentation - bioprocess engineering - humuszuren - hydrolyse - anaërobe afbraak - cellulose - hemicellulosen - biomassa - hernieuwbare energie - energieterugwinning - biogas - fermentatie - bioproceskunde

    Research on the hydrolysis step of the AD became more important with the increased use of recalcitrant waste products such as manure, sewage sludge and agricultural biomass for biogas production. Hydrolysis is often the rate limiting step of the overall AD. Hydrolysis enhancement is one of the required steps to optimise biogas production. Despite the progress to overcome the limitations of hydrolysis, inhibition of hydrolysis is still poorly researched. Humic acid-like molecules (HA) are one of the inhibitors of the anaerobic hydrolysis and their effect on the overall AD process is generally overlooked.

    In this thesis, the HA inhibition on anaerobic digestion of cellulosic material and mitigation strategies, using cation and enzyme addition, to overcome the inhibition were investigated. In addition, the microbial community dynamics during AD in the presence and absence of HA were examined. In this scope, in Chapter 2, we reviewed the literature and pinpointed the urgent need for comprehensive studies on the role of hydrolytic microorganisms and environmental factors that effects their abundance within biogas plants. Consequently, the hydrolysis mechanism and involved hydrolytic enzymes were discussed. The overall discussion showed that a holistic approach, including microbiological and engineering studies should be chosen to disclose the role of hydrolytic microbes within biogas reactors. In Chapter 3 and, Chapter 4 the effect of HA on anaerobic cellulose hydrolysis and methanogenesis, in batch wise incubations is reported, respectively. Our results showed that pulse addition of 5 g L-1 HA caused a 50 % decrease in hydrolysis rate of anaerobic cellulose degradation (Chapter 3). Moreover, VFA accumulation was observed in the presence of HA during the anaerobic cellulose degradation, which indicated the possible inhibition of HA on methanogenesis. Based on the results of Chapter 3, pure cultures of methanogens and a mixed culture were tested to study the vulnerability of methanogenesis to HA inhibition. Hydrogenotrophic methanogenesis in pure cultures was inhibited by more than 75% in the presence of 1 g L-1 HA whereas, acetoclastic methanogenesis by Methanosaeta concilii was only slightly affected by HA up to 3 g L-1. When methanogenic granular sludge was incubated with HA, the specific methanogenic activity tests showed less inhibition, when compared to the pure cultures of methanogens. HA inhibition was also observed during long-term CSTR operation at an HRT of 20 days, 35°C and a mixture of cellulose and xylan as a subtrate (Chapter 6). 8 g L-1 HA inhibited the hydrolysis efficiency of the cellulose and xylan digestion by 40 % and concomitantly reduced the methane yields.

    Mitigation of the HA inhibition is required to increase the hydrolysis efficiency and methane yields of cellulosic biomass digestion. Therefore, two different strategies were tested for their potential use as mitigation agents, viz. addition of cations such as, calcium magnesium and iron (Chapter 3 and Chapter 6) and addition of hydrolytic enzymes (Chapter 6). Addition of magnesium, calcium and iron salts mitigated the HA inhibition and hydrolysis efficiencies reached up to 75, 65 and 72%, respectively, compared to the control groups in the batch wise incubations (Chapter 3). However, in long term CSTR operations, calcium addition did not show a positive effect on hydrolysis inhibition. On the other hand, enzyme addition helped to reverse the negative effect of HA.

    The microbial communities involved in AD were also studied. Chapter 5 and Chapter 6 dealt with microbial community analyses with 16S rRNA next generation sequencing. In Chapter 5, five replicate reactors were monitored during the start-up period. Transient feeding strategy was used to acclimatise anaerobic sludge to efficient cellulose and xylan degradation. During the experiment, Bacteriodales, Clostridiales and Anaerolineales became dominant bacterial populations while, Methanobacteriaceae and Methanospirillaceae were the dominant archaeal populations within the reactors. In Chapter 6, the microbial population dynamics in the presence and absence of HA were monitored. Microbiological analyses showed that the abundance of hydrolytic/fermentative bacterial groups such as Clostridiales, Bacteroidales and Anaerolineales was significantly lowered by the presence of HA. HA also affected the archaeal populations. Mostly hydrogenotrophic methanogens were negatively affected by HA.

    In conclusion, this thesis confirms that HA inhibit the hydrolysis and methanogenesis within both batch incubations and CSTR systems. Microbial populations were also affected by HA. Therefore, hydrolytic enzyme addition can be an option to mitigate HA inhibition and enhance hydrolysis and methanogenesis during conversion of biomass to biogas.

    Anaerobic treatment of municipal wastewater in a UASB-Digester system : temperature effect on system performance, hydrolysis and methanogenesis
    Zhang, Lei - \ 2016
    Wageningen University. Promotor(en): Grietje Zeeman; Huub Rijnaarts, co-promotor(en): Tim Hendrickx. - Wageningen : Wageningen University - ISBN 9789462579798 - 165
    municipal wastewater - anaerobic digesters - hydrolysis - temperature - water treatment sludge - sludges - water treatment - sewage sludge - sewage - stedelijk afvalwater - anaërobe verteerders - hydrolyse - temperatuur - waterzuiveringsslib - slib - waterzuivering - rioolslib - rioolwater

    A novel treatment chain for low strength domestic sewage includes low temperature anaerobic treatment as the main process. It can improve the energy efficiency of sewage treatment compared with conventional aerobic sewage treatment. A combination of an Upflow Anaerobic Sludge Blanket reactor and a sludge digester, a UASB-digester system, was proven to be one of the successful anaerobic systems to challenge temperatures as low as 10°C and organic matter concentrations in the range of 382 and 1054 mg chemical oxygen demand (COD)/l. The UASB is operated at low sewage temperature (10°C) and high loading rate. The produced non-stabilised sludge in the UASB is recirculated over the mesophilic digester (35°C) to convert organic solids to methane gas and produce anaerobic biomass fed back into the UASB reactor, where it converts dissolved COD at the low temperature of the waste water.

    The effect of sludge recirculation rate and sludge transfer point on the performance of a UASB-digester treating domestic sewage at 15 ˚C was studied in this research. The results show increased total COD removal efficiency when increasing the sludge recirculation rate from 1% to 2.6% of the influent flow rate. Methane gas production increases with the sludge recirculation rate, in the range of 1 to 12.5% of the influent flow rate. A higher sludge transfer point results in an increased suspended COD removal efficiency and a higher VSS concentration of the UASB sludge bed.

    Co-digestion was applied for improving soluble COD removal efficiency of a UASB-digester system, operated at low temperatures and treating domestic sewage with a high dissolved/suspended COD ratio. Glucose was chosen as a model co-substrate and added to the sludge digester to produce additional methanogenic biomass, which was continuously recycled to inoculate the UASB reactor. Methane production in the UASB reactor almost doubles and soluble COD removal efficiency equals the biodegradability of the influent dissolved COD, due to a twofold increase in methanogenic capacity, when applying co-digestion 16% of influent organic loading rate. Therefore, co-digestion is a suitable approach to support a UASB-digester for treatment of low temperature domestic sewage.

    A pilot scale UASB-digester (130 + 50 L) was studied to treat domestic wastewater at temperatures of 10-20°C at an HRT of 6 h in the UASB reactor and 15 h in the digester. The results show a stable COD removal efficiency of 60 ± 4.6% during the operation at 12.5 to 20°C. COD removal efficiency decreases to 51.5 ± 5.5% at 10°C. The decreased COD removal efficiency is attributed to an increased influent COD load, leading to insufficient methanogenic capacity of the UASB reactor at such low temperature. Suspended COD removal efficiency was 76.0 ± 9.1% at 10-20°C. The effluent COD concentration is 90 ± 23 mg/L at temperatures between 12.5 and 20°C, while soluble COD removal efficiency fluctuates due to variation in the influent COD concentration. 80% of the influent biodegradable COD is recovered as methane gas (including dissolved methane).

    Low temperature (10-25°C) hydrolysis after applying a short pre-hydrolysis at 35°C was studied compared with those without the pre-hydrolysis. Batch experiments were executed using cellulose and tributyrin as model substrates for carbohydrates and lipids. Low temperature anaerobic hydrolysis rate constants increase by a factor 1.5 - 10 after applying a short anaerobic pre-hydrolysis at 35°C. The hydrolytic activity of the supernatant collected from the digestate after batch digestion of cellulose and tributyrin at 35°C was higher than that of the supernatants collected from the low temperature (≤ 25°C) digestates. The observed hydrolysis in the UASB of a UASB-digester system, treating domestic sewage at low temperatures (10-20°C) is in line with the elevated hydrolytic activity of mesophilic supernatant.

    Effects of temperature and temperature shocks on specific methanogenic activity (SMA), and acetate affinity of the digester sludge were studied. Digester sludge from a UASB (12.5°C)-digester (35°C) system, was fed with acetate at constant temperatures of 10-35°C and at varying temperatures from 35°C to 25, to 15 to 10°C. The results show no lag phase in methane production rate when applying temperature shocks of 35°C to 25, 15, and 10°C. The temperature dependency of the SMA of the digester sludge after the temperature shocks was similar to the one at constant temperatures. Acetate affinity of the digester sludge was high at the applied temperatures (10-35°C). Latter is consistent with the finding of no VFA in the effluent of the UASB-digester, treating low strength, and low temperature (12.5°C) domestic wastewater.

    The UASB-digester system to treat low strength, low temperature domestic sewage was provided with a proof-of-principle, and its essential underlying anaerobic processes were sufficiently elucidated to make the technology ready for further scaling up and demonstration in practice.

    Biorefinery of proteins from rubber plantation residues
    Widyarani, R. - \ 2016
    Wageningen University. Promotor(en): Johan Sanders, co-promotor(en): Marieke Bruins; E. Ratnaningsih. - Wageningen : Wageningen University - ISBN 9789462576643 - 236
    biorefinery - biomass conversion - rubber - rubber plants - protein extraction - latex - hydrolysis - hydrophobicity - amino acids - wheat gluten - residual streams - biobased economy - bioraffinage - biomassaconversie - rubber - rubberplanten - eiwitextractie - latex - hydrolyse - hydrofobiciteit - aminozuren - tarwegluten - reststromen - biobased economy

    Biorefinery of rubber tree side streams could add economic value and income for farmers, who already grow the trees for latex production. The objective of this research was to design a process for the recovery of proteinaceous fractions from rubber tree. The aimed applications were expected to be suitable for local use, particularly in Indonesia, being one of the world’s largest rubber producers. Rubber seed was selected as a model biomass based on its availability (21-144 kg-protein/ha) and its oil content that enables the combination of protein and biodiesel productions within a biorefinery framework. Experimental works were focused on three parts: separation of protein and oil from rubber seed kernel, enzymatic hydrolysis of rubber seed protein into amino acids, and separation of amino acids from hydrolysate. Using alkaline extraction, up to 80% protein from the total original amount of protein in the kernel could be recovered in the extract, comparable to protein recoveries from other oilseeds and oilseed cakes. Seed type and pre-treatment had the most influence on protein recovery. Following protein extraction, the extracted proteins were recovered via isoelectric precipitation, resulting in rubber seed protein concentrate that can be used as such or can be processed further. Different protease combinations were used to hydrolyse rubber seed protein concentrate. After 24 h hydrolysis of rubber seed protein, up to 53% degree of hydrolysis and 35% protein recovery as free amino acids could be achieved. Combination of Pronase + Peptidase R resulted in the highest recovery and concentration of hydrophobic amino acids (phenylalanine, leucine, isoleucine, tyrosine, tryptophan, valine, methionine, and proline) in the hydrolysate. Some hydrophobic amino acids are essential in human and farm animal diets, therefore they can potentially be applied as a group in food and feed. Ethanol was used as an anti-solvent for selective precipitation of amino acids. Ethanol was able to selectively increase the hydrophobic amino acid fraction in rubber seed protein hydrolysate from 59% (mol/mol) in the starting material to 76% in the supernatant. Leucine and valine contributed most to this increase. The results of this study show that rubber seed proteins can be applied locally as animal feed or in industries for technical applications.

    Pelagic fish discards : technical report on opportunities for silage valorisation
    Rurangwa, E. ; Poelman, M. ; Broeze, J. ; Bosch, Heleen van den - \ 2015
    Yerseke : IMARES (Report / IMARES C197/15) - 30
    pelagic fishery - marine fisheries - discards - fish silage - livestock feeding - bioactive compounds - hydrolysis - feed industry - pelagische visserij - zeevisserij - discards - vissilage - veevoeding - bioactieve verbindingen - hydrolyse - veevoederindustrie
    How Does Alkali Aid Protein Extraction in Green Tea Leaf Residue: A Basis for Integrated Biorefinery of Leaves
    Zhang, C. ; Sanders, J.P.M. ; Xiao, T.T. ; Bruins, M.E. - \ 2015
    PLoS ONE 10 (2015)7. - ISSN 1932-6203
    functional-properties - antioxidant activity - sugar-beet - cell-walls - cellulose - pectins - biomass - acid - degradation - hydrolysis
    Leaf protein can be obtained cost-efficiently by alkaline extraction, but overuse of chemicals and low quality of (denatured) protein limits its application. The research objective was to investigate how alkali aids protein extraction of green tea leaf residue, and use these results for further improvements in alkaline protein biorefinery. Protein extraction yield was studied for correlation to morphology of leaf tissue structure, protein solubility and hydrolysis degree, and yields of non-protein components obtained at various conditions. Alkaline protein extraction was not facilitated by increased solubility or hydrolysis of protein, but positively correlated to leaf tissue disruption. HG pectin, RGII pectin, and organic acids were extracted before protein extraction, which was followed by the extraction of cellulose and hemi-cellulose. RGI pectin and lignin were both linear to protein yield. The yields of these two components were 80% and 25% respectively when 95% protein was extracted, which indicated that RGI pectin is more likely to be the key limitation to leaf protein extraction. An integrated biorefinery was designed based on these results. Introduction
    Kinetic modelling of enzymatic starch hydrolysis
    Bednarska, K.A. - \ 2015
    Wageningen University. Promotor(en): Tiny van Boekel; Remko Boom, co-promotor(en): Anja Janssen. - Wageningen : Wageningen University - ISBN 9789462573086 - 159
    hydrolyse - enzymen - zetmeel - stochastische modellen - verwerking - hydrolysis - enzymes - starch - stochastic models - processing

    Kinetic modelling of enzymatic starch hydrolysis – a summary

    K.A. Bednarska

    The dissertation entitled ‘Kinetic modelling of enzymatic starch hydrolysis’ describes the enzymatic hydrolysis and kinetic modelling of liquefaction and saccharification of wheat starch. After the background information about the enzymes, the substrate and the basics of the model in the first chapter, we describe a model predicting the outcome of wheat starch liquefaction by α-amylase from Bacillus licheniformis at 50°C in chapter 2. We demonstrate the ability of the model to predict starch hydrolysis products larger than the oligosaccharides considered in the existing models. The model in its extended version follows all the products of wheat starch hydrolysis separately, and despite the quantitative differences, the qualitative predictions are satisfactory. We also show that the difference between the experimental and computed data might stem from the inaccuracy of the subsite map.

    In the following chapters the model is used to find a better description of the hydrolysis data at two temperatures (50°C and 80°C), by varying the energy values of the subsite map and evaluating the inhibition. We hypothesize that a subsite map that is based on the cleavage patterns of linear, short molecules does not account for the complexity of hydrolysis of amylopectin. The branched structure of amylopectin molecules influences the composition of the hydrolysis products by restricting the access to some of the bonds. The presence of branches creates steric obstacles for the enzyme. The used α-amylase has difficulties hydrolysing and accommodating α-(1,6)-glycosidic bonds, which imposes on the hydrolysis of the α-(1,4)-glycosidic bonds located in its proximity. On this basis, we analyse the subsite maps in detail and suggest which of the subsites are crucial when making predictions about the product composition of starch hydrolysates. On top of that we propose new subsite maps that allow a quantitative description of the experimental data.

    After the model was shown to work at different experimental conditions, we also test it at increased the dry matter content during wheat starch hydrolysis. We follow both the liquefaction by BLA and the saccharification process by glucoamylase from Aspergillus niger at low moisture content. The liquefaction model, is used to predict all of the products of wheat starch hydrolysis at higher dry matter contents (30-60 w/w%). The liquefaction model also creates the substrate matrices representing maltodextrins to be used in the saccharification model. The saccharification of liquefacts to glucose is followed with a new mechanistic model, also using the assumptions of the subsite theory. The saccharification model predicts all of the reaction products using the subsite maps of glucoamylase available in literature.

    The findings described in the thesis are summarized and put in context in the general discussion. We demonstrate how the parameters of the liquefaction model at low moisture contents were chosen. The outcomes of the model are also compared with the experimental data at 30-60 w/w%. Next, we test our liquefaction model with starch hydrolysis data at 5 and 60 w/w% taken from literature, to verify both the approach we used and the validity of the parameters we obtained in previous chapters. The method used to improve the subsite maps is also tested on another enzyme, Bacillus amyloliquefaciens α-amylase. After discussing the factors that influence saccharification at high dry matter contents, we conclude the chapter with describing the potential of stochastic modelling and its practical use.

    Valorization of jatropha fruit biomass for energy applications
    Marasabessy, A. - \ 2015
    Wageningen University. Promotor(en): Johan Sanders, co-promotor(en): Ruud Weusthuis; M. Moeis. - Wageningen : Wageningen University - ISBN 9789462572614 - 147
    landbouwbijproducten - jatropha curcas - bio-energie - bioraffinage - biobrandstoffen - economische aspecten - extractie - fractionering - hydrolyse - indonesië - agricultural byproducts - jatropha curcas - bioenergy - biorefinery - biofuels - economic aspects - extraction - fractionation - hydrolysis - indonesia

    Valorization of Jatropha fruit biomass for

    energy applications

    Ahmad Marasabessy

    Thesis Abstract

    Our research objectives were to develop sustainable technologies of Jatropha oil extraction and Jatropha biomass fractionation within a framework of bioconversions (enzymatic and microbial processings). Microbial extraction of oil from Jatropha kernels using whole cells of Bacillus pumilus yields 73% oil, and this is comparable to the known processes such as by using expeller or by enzymatic extraction. The bacterium facilitates oil liberation via degradation of hemicelluloses therefore the majority of Jatropha proteins were preserved in the solid phase of the extraction residues. In investigating the effect of dilute sulfuric acid pretreatment on the enzymatic digestibility of the lignocellulosic components of Jatropha fruit biomass, we found that the seed shell and the seed cake were more recalcitrant to dilute sulfuric acid pretreatments than the fruit hull. A pretreatment of the fruit hull at optimum conditions (10% solid loading, 0.9% sulfuric acid, 30 min, 178 oC) followed by neutralization and a 24-h enzymatic hydrolysis with cellulases (GC220) liberated 100% pentoses (71% yield and 29% degradation to furfural) and 83% hexoses (78% yield and 5% degradation to 5-hydroxymethylfurfural). The fruit hull hydrolyzate can be used as a substrate for Saccharomyces cerevisiae to produce ethanol in SSF process. Our economic analysis in the retrospectives showed that valorization of the fruit biomass into variuos products (oil, protein isolate, lignin, biogas, bio-oil, etc.) using the most known techniques (pretreatment, hydrolysis, fermentation, extraction, separation, anaerobic digestion, pyrolysis) could improve the economy value of this biofuel crop significantly.

    Analysis of by-product formation and sugar monomerization in sugarcane bagasse pretreated at pilot plant scale: Differences between autohydrolysis, alkaline and acid pretreatment
    Pol, E.C. van der; Bakker, R. ; Zeeland, A.N.T. van; Sanchez Garcia, D. ; Punt, A.M. ; Eggink, G. - \ 2015
    Bioresource Technology 181 (2015). - ISSN 0960-8524 - p. 114 - 123.
    saccharomyces-cerevisiae - degradation-products - wet oxidation - hydrolysis - ethanol - fermentations - cellulose - glucose - biomass
    Sugarcane bagasse is an interesting feedstock for the biobased economy since a large fraction is polymerized sugars. Autohydrolysis, alkaline and acid pretreatment conditions combined with enzyme hydrolysis were used on lignocellulose rich bagasse to acquire monomeric. By-products found after pretreatment included acetic, glycolic and coumaric acid in concentrations up to 40, 21 and 2.5 g/kg dry weight bagasse respectively. Alkaline pretreated material contained up to 45 g/kg bagasse DW of sodium. Acid and autohydrolysis pretreatment results in a furan formation of 14 g/kg and 25 g/kg DW bagasse respectively. Enzyme monomerization efficiencies of pretreated solid material after 72 h were 81% for acid pretreatment, 77% for autohydrolysis and 57% for alkaline pretreatment. Solid material was washed with superheated water to decrease the amount of by-products. Washing decreased organic acid, phenol and furan concentrations in solid material by at least 60%, without a major sugar loss.
    Lignin pyrolysis for profitable lignocellulosic biorefineries
    Wild, P.J. de; Gosselink, R.J.A. ; Huijgen, W.J.J. - \ 2014
    Biofuels Bioproducts and Biorefining 8 (2014)5. - ISSN 1932-104X - p. 645 - 657.
    wheat-straw - organosolv lignin - biomass - phenols - separation - valorization - pretreatment - hydrolysis - conversion - chemicals
    Bio-based industries (pulp and paper and biorefineries) produce > 50 Mt/yr of lignin that results from fractionation of lignocellulosic biomass. Lignin is world's second biopolymer and a major potential source for production of performance materials and aromatic chemicals. Lignin valorization is a key-issue for enhanced profitability of sustainable bio-based industries. Despite a myriad of potential applications for lignin and decades of research, its heterogeneity and recalcitrance still preclude commercial value-added applications. Most lignin is utilized for heat and power. Unconventional solutions are needed to better exploit lignin's potential. Organosolv lignins are especially suitable as feedstock for high-value chemicals. At ECN, a lignin biorefinery approach (LIBRA) has been developed, involving a dedicated lignin pyrolysis protocol that is robust, continuous, and capable of processing different lignins. Typical product yields are 20% gas, 35% char, and 45% oil. The oil contains approximately 45% oligomeric phenolic substances, 23% monomeric phenols, and 33% water. The future perspective is scale-up of the process to produce larger lignin pyrolysis oil samples for separation, purification, and industrial application tests. Presently, small lignin pyrolysis oil samples are investigated as feedstock for extracting high-value chemicals, as a substitute for phenol in several applications, and as a feedstock for hydrotreating. The biochar is tested as growth enhancer and as substitute for carbon-black in rubber. Regarding the large lignin side streams from (future) bio-based industries, the LIBRA pyrolysis technology has ample potential to increase the profitability of lignocellulosic biorefineries provided that for both the liquid product and the solid char value-added applications are developed.
    Determination of the Influence of Substrate Concentration on Enzyme Selectivity Using Whey Protein Isolate and Bacillus licheniformis Protease
    Butré, C.I. ; Sforza, S. ; Gruppen, H. ; Wierenga, P.A. - \ 2014
    Journal of Agricultural and Food Chemistry 62 (2014)42. - ISSN 0021-8561 - p. 10230 - 10239.
    beta-lactoglobulin - functional-properties - mass-spectrometry - hydrolysis - peptide - endopeptidase - sequence - casein - model
    Increasing substrate concentration during enzymatic protein hydrolysis results in a decrease in hydrolysis rate. To test if changes in the mechanism of hydrolysis also occur, the enzyme selectivity was determined. The selectivity is defined quantitatively as the relative rate of hydrolysis of each cleavage site in the protein. It was determined from the identification and quantification of the peptides present in the hydrolysates. Solutions of 0.1–10% (w/v) whey protein isolate (WPI) were hydrolyzed by Bacillus licheniformis protease at constant enzyme-to-substrate ratio. The cleavage sites were divided into five groups, from very high (>10%) to very low selectivity (
    Enzyme-assisted separation and hydrolysis of gluten : options for intensification
    Hardt, N.A. - \ 2014
    Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Atze Jan van der Goot. - Wageningen : Wageningen University - ISBN 9789462571228 - 165
    gluten - graaneiwitten - scheiding - enzymen - hydrolyse - voedseltechniek - watergehalte - watergebruik - gluten - cereal proteins - separation - enzymes - hydrolysis - food engineering - water content - water use

    The food industry is one of the largest water consumers in industry. Using large amounts of water, however, is undesirable from an environmental point of view because freshwater is a scarce good in many regions of the world and undesirable from an economic point of view because high water loadings require high amounts of energy for dehydration and signify high amounts of wastewater. This thesis uses wheat, one of the major crops in human nutrition, to study the influence of low water concentrations on two relevant processes in wheat processing:

    The separation of starch and gluten. Separation is often performed using 10–15 L water per kg dry matter. Instead, starch and gluten can be separated by inducing shear using 0.5 L water per kg dry matter. In this thesis we make use of xylanases to hydrolyze arabinoxylan present in wheat, thereby releasing the water associated with arabinoxylan. In doing so, shear-induced starch–gluten separation is performed at even more concentrated conditions. The influence of arabinoxylan hydrolysis in wheat dough at low water contents is studied in chapters 2 and 3.The hydrolysis of gluten. Hydrolysis is currently performed using approximately 4 L water per kg dry mater. In this thesis we perform gluten hydrolysis at solid concentrations of up to 70%, thereby investigating the changes in the hydrolysis reaction and the functionality of the resulting hydrolysates. Wheat gluten hydrolysis at low water contents is studied in chapters 4, 5 and 6.

    This thesis consists of seven chapters. Chapter 1 gives a general introduction of the thesis. In chapter 2, wheat dough rheology at low water contents below 40% and the influence of xylanases is studied. A reduction in water content from 43.5–44.8% (representing optimal Farinograph water absorption) to 34% (the lowest water content where a dough forms) results in a non-linear increase in the dough consistency, elastic modulus G’, and a decrease in the maximum creep compliance Jc,max of 1–2 orders of magnitude. Addition of xylanases has the same effect on the dough consistency, G’ and Jc,max as an increase in water content of 2–5% (on a water basis). Tan δ is hardly and Jel not influenced by xylanase addition showing that the influence of xylanases on the mechanism of hydration is negligible.

    In chapter 3, shear-induced starch–gluten separation with the help of xylanases is studied at water contents from 43.5% to 34%. Addition of xylanases at the standard water content of 43.5% results in a slurry without any separation. As a result, lower water contents are used. At water contents below 40%, the local formation of gluten clusters is observed with and without xylanases addition. However, opposed to shear-induced separation at 43.5% water without xylanase, the gluten patches do not migrate to the center of the cone because of the densely packed dough and an inhomogeneity in the shear field. Nevertheless, gluten clusters can be concentrated up to 60% (N×5.7) protein. Similar to chapter 2, xylanase addition allows water savings of 3–5% (on a water basis).

    Chapter 4 introduces enzymatic wheat gluten hydrolysis at high solid concentrations and describes the influence of high-solid hydrolysis on the resulting functional properties of the gluten hydrolysates. Wheat gluten can be hydrolyzed at solid concentrations of up to 60% (w/w). The water solubility of the dried hydrolysates is independent of the solid concentration during hydrolysis, just like the foam stabilizing properties at degrees of hydrolysis (DH%) below 8% At DH% above 8%, high solid concentrations even increase the foam stabilizing properties of the resulting hydrolysates, which is related to the presence of more peptides with a molecular mass >25 kDa. Furthermore, an increase in solid concentration results in an increase of the volumetric productivity.

    Despite the advantages of high-solid gluten hydrolysis, we also observe lower hydrolysis rates in high-solid gluten hydrolysis compared to low-solid gluten hydrolysis at constant enzyme-to-substrate ratios. The factors causing this hydrolysis rate limitation are investigated in chapter 5. It is shown that enzyme inhibition, the water activity, and mass transfer limitations do not impede the hydrolysis up to 50% solids. However, the hydrolysis rate limitation can be explained by a second-order enzyme auto-inactivation rate along with the higher enzyme concentrations used. At solid concentrations above 50%, the hydrolysis rate further decreases due to mass transfer limitations. Furthermore, the addition of enzyme after 24 h at high solid concentrations hardly increases the DH%, suggesting that the maximum attainable DH% decreases at high solid concentrations. This DH% limitation is explained by a reduced enzyme activity due to a decline in water activity.

    Based on the findings in chapters 4 and 5, a direct hydrolysis of gluten present in wheat flour at high solid concentrations is investigated in chapter 6, thereby omitting the starch–gluten separation. At a constant protein concentration, the protease activity is higher for wheat flour hydrolysis (at 40% total solids) than for vital wheat gluten hydrolysis (at 7.2% total solids) in the initial 6 h of hydrolysis, despite the high starch content in wheat flour and consequently lower water content. This is related to the starch granules in wheat flour, preventing the aggregation of (native) gluten. At wheat flour concentrations above 50% and for longer reaction times the positive effect of starch disappears. This is explained by mass transfer limitations and reduced water activities in the wheat flour slurry or dough, respectively.

    Chapter 7 summarizes and generalizes the main findings of this thesis and compares the current status in starch–gluten separation and gluten hydrolysis with the concentrated separation and hydrolysis processes developed in this study. Water and energy savings of at least 50% are possible when separating and hydrolyzing at concentrated conditions. In the end, future prospects in high-solid wheat gluten hydrolysis are briefly discussed.

    Purification, Characterization, and Prebiotic Properties of Pectic Oligosaccharides from Orange Peel Wastes
    Gómez, B. ; Gullón, B. ; Remoroza, C.A. ; Schols, H.A. ; Parajó, J.C. ; Alonso, J.L. - \ 2014
    Journal of Agricultural and Food Chemistry 62 (2014)40. - ISSN 0021-8561 - p. 9769 - 9782.
    in-vitro fermentation - butyrate-producing bacteria - human fecal microbiota - human gut - polysaccharides - fermentability - pretreatment - hydrolysis - product - acid
    Pectic oligosaccharides (POS) were obtained by hydrothermal treatment of orange peel wastes (OPW) and purified by membrane filtration to yield a refined product containing 90 wt % of the target products. AraOS (DP 3–21), GalOS (DP 5–12), and OGalA (DP 2–12, with variable DM) were identified in POS mixtures, but long-chain products were also present. The prebiotic potential of the concentrate was assessed by in vitro fermentation using human fecal inocula. For comparative purposes, similar experiments were performed using orange pectin and commercial fructo-oligosaccharides (FOS) as substrates for fermentation. The dynamics of selected microbial populations was assessed by fluorescent in situ hybridization (FISH). Gas generation, pH, and short-chain fatty acid (SCFA) production were also measured. Under the tested conditions, all of the considered substrates were utilized by the microbiota, and fermentation resulted in increased numbers of all the bacterial groups, but the final profile of the microbial population depended on the considered carbon source. POS boosted particularly the numbers of bifidobacteria and lactobacilli, so that the ratio between the joint counts of both genera and the total cell number increased from 17% in the inocula to 27% upon fermentation. SCFA generation from POS fermentation was similar to that observed with FOS, but pectin fermentation resulted in reduced butyrate generation.
    Designed enzyme preparations for the hydrolysis of corn silage polysaccharides
    Neumüller, K.G. - \ 2014
    Wageningen University. Promotor(en): Harry Gruppen; Henk Schols, co-promotor(en): H. Streekstra. - Wageningen : Wageningen University - ISBN 9789462570832 - 150
    maïskuilvoer - xylaan - industriële enzymen - hydrolyse - biogas - onderzoek - biomassaconversie - biobased economy - maize silage - xylan - industrial enzymes - hydrolysis - biogas - research - biomass conversion - biobased economy
    This thesis describes the design of hemicellulolytic enzyme preparations with high activity towards the rather recalcitrant xylan present in corn silage, a major biogas feedstock. Also, recalcitrance factors towards the enzymatic conversion of xylans, varying in type and level of substitution, are addressed.
    Introducing enzyme selectivity as a quantitative parameter to describe the effects of substrate concentration on protein hydrolysis
    Butré, C.I. - \ 2014
    Wageningen University. Promotor(en): Harry Gruppen, co-promotor(en): Peter Wierenga; Stefano Sforza. - Wageningen : Wageningen University - ISBN 9789462570238 - 199
    eiwitten - eiwittechnologie - eiwitafbraak - hydrolyse - enzymen - concentratie - proteins - protein engineering - protein degradation - hydrolysis - enzymes - concentration

    To understand the differences in peptide composition that result from variations in the conditions of enzymatic hydrolysis of proteins (e.g. substrate concentration) the mechanism of hydrolysis needs to be understood in detail. Therefore, methods and tools were developed to characterize and quantify the peptides formed during enzymatic protein hydrolysis. The information obtained was used to introduce a novel quantitative parameter: the selectivity of the enzyme towards the individual cleavage sites in the substrate, within the given specificity of the enzyme applied. The selectivity describes the rate of hydrolysis of a cleavage site compared to the rate of hydrolysis of all cleavage sites in the parental protein. Large differences in the selectivity of the enzyme towards the cleavage sites after the same type of amino acid residues in a protein were found. For β-lactoglobulin hydrolyzed by Bacillus licheniformis protease the selectivity was found to vary between 0.003 % and 17 % or even 0 for some cleavage sites. The effects of increasing substrate concentration and pH on the hydrolysis were studied. An increase in substrate concentration results in lower kinetics of hydrolysis, related to the available amount of water. This also resulted in significant changes in the enzyme selectivity towards the cleavage sites for which the enzyme has a high selectivity. Changing the pH of hydrolysis resulted in large changes in the kinetics of hydrolysis as well as in the enzyme selectivity. Due to the detailed analysis of the peptide composition, certain a-specific peptides were identified. It was shown that these originate from spontaneous cleavage of formed peptides. The changes in the mechanism of hydrolysis were compared to simulation data. The simulation data were obtained from a stochastic model based on random selection of the substrate and the cleavage site, given the specificity of the enzyme. A quite good agreement was obtained between simulated and experimental data. The parameters and methods developed in this study to describe the mechanism of hydrolysis can potentially be used for more complex systems.

    Guidance proposal for using available DegT50 values for estimation of degradation rates of plant protection products in Dutch surface water and sediment
    Boesten, J.J.T.I. ; Adriaanse, P.I. ; Horst, M.M.S. ter; Tiktak, A. ; Linden, A.M.A. van der - \ 2014
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-werkdocument 284) - 42
    oppervlaktewaterkwaliteit - pesticiden - degradatie - chemische afbraak - verontreinigde sedimenten - lichtregiem - hydrolyse - fotolyse - algen - waterplanten - waterverontreiniging - surface water quality - pesticides - degradation - chemical degradation - contaminated sediments - light regime - hydrolysis - photolysis - algae - aquatic plants - water pollution
    The degradation rate of plant protection products and their transformation products in surface water and sediment may influence their concentrations in Dutch surface water. Therefore the estimation of these rates may be an important part of the assessment of the exposure of aquatic organisms. We propose a stepped sequence of studies for estimating the rate in water going from simple and conservative to more sophisticated and more realistic studies. The sequence includes: - studies on hydrolysis and photolysis; - studies with fresh surface water in the dark; - water-sediment studies in the dark or in light; - studies with algae and macrophytes; - outdoor studies in realistic surface water systems. The usefulness of these studies for the exposure assessment in Dutch surface water is discussed.
    Water holding capacity and enzymatic modification of pressed potato fibres
    Ramasamy, U. - \ 2014
    Wageningen University. Promotor(en): Harry Gruppen, co-promotor(en): Mirjam Kabel. - Wageningen : Wageningen University - ISBN 9789461739643 - 156
    aardappelpulp - aardappelen - vezels - celwandstoffen - polysacchariden - waterbergend vermogen - hydrolyse - enzymen - potato pulp - potatoes - fibres - cell wall components - polysaccharides - water holding capacity - hydrolysis - enzymes

    Cell wall polysaccharides (CWPs) contribute to the water holding capacity (WHC) of fibre rich feeds, such as pressed potato fibres (PPF). However, the role of CWPs on the WHC of PPF was unidentified so far.

    PPF was characterized to be abundant in arabinogalactan (AG) linked rhamnogalacturonan-I (RG-I), homogalacturonan (HG) and cellulose, next to which xyloglucan (XG) contributed the most of the hemicellulosic CWPs. The CWP network in potatoes was loosened upon starch extraction of potatoes and solubilized HG-RG-I-AG.

    Analyses of the WHCs upon enzyme treatments indicated that the WHC of PPF was mainly caused by a network of insoluble, non-cellulosic CWPs such as pectic CWPs (HG-RG-I-AG) and XG. Findings in this thesis showed that AGs were better degraded than xyloglucans (XGs). Since XGs were found to be equally important in contributing to the WHC as AGs, the substantial removal of AGs, as well as XGs, should be advantageous to lower the WHC.

    Other than lowering the WHC, the use of a pectinase-rich preparation improved the recovery of starch from potatoes by the degradation of mainly pectic CWPs, in particular pectic AG side chains and HG. The degradation of arabinan was observed to be inhibited by components in potato juice (PJ).

    Synergistic action of enzyme preparations towards recalcitrant corn silage polysaccharides
    Neumüller, K.G. ; Streekstra, H. ; Schols, H.A. ; Gruppen, H. - \ 2014
    Biomass and Bioenergy 60 (2014). - ISSN 0961-9534 - p. 88 - 97.
    talaromyces-emersonii - wheat-straw - hydrolysis - pretreatment - ethanol - plant - lignocellulose - fermentation - efficiency - conversion
    Corn silage, its water unextractable solids (WUS) and enzyme recalcitrant solids (ErCS) and an industrial corn silage-based anaerobic fermentation residue (AFR) represent corn substrates with different levels of recalcitrance. Compositional analysis reveals different levels of arabinoxylan substitution for WUS, ErCS and AFR, being most pronounced regarding acetic acid, glucuronic acid- and arabinose content. By screening for enzymatic degradation of WUS, ErCS and AFR, enzyme preparations exhibiting high conversion rates were identified. Furthermore significant synergistic effects were detected by blending Aspergillus niger/Talaromyces emersonii culture filtrates with various enzymes. These findings clearly highlight a necessity for a combinatorial use of enzyme preparations towards substrates with high recalcitrance characteristics to reach high degrees of degradation. Enzyme blends were identified, outperforming the individual commercial preparations. These enzyme preparations provide a basis for new, designed enzyme mixtures for corn polysaccharide degradation as a source of necessary, accessory enzyme activities.
    Autogenerative high pressure digestion : biogass production and upgrading in a single step
    Lindeboom, R.E.F. - \ 2014
    Wageningen University. Promotor(en): Jules van Lier, co-promotor(en): Jan Weijma; Caroline Plugge. - Wageningen : Wageningen University - ISBN 9789461738608 - 208
    biogas - spijsvertering - druk - methaanproductie - kooldioxide - zetmeel - hydrolyse - biogas - digestion - pressure - methane production - carbon dioxide - starch - hydrolysis
    Effect of charged polysaccharides on the techno-functional properties of fractions obtained from algae soluble protein isolate
    Schwenzfeier, A. ; Wierenga, P.A. ; Eppink, M.H.M. ; Gruppen, H. - \ 2014
    Food Hydrocolloids 35 (2014). - ISSN 0268-005X - p. 9 - 18.
    in-water emulsions - diffusing wave spectroscopy - tetraselmis sp - adsorption - microalgae - dissociation - hydrolysis - stability
    It has been suggested previously that charged polysaccharides present in algae soluble protein isolate (ASPI) contribute to its foaming and emulsifying properties. In this study ASPI was fractioned into one fraction enriched in uronic acids (the building blocks of charged polysaccharides, [ASPI-UA]), one enriched in protein (ASPI-P) and one containing small, dissociated (glyco-)proteins (ASPI-S). Emulsions prepared using ASPI-UA were stable against flocculation between pH 3e7, while ASPI-P and ASPI-S showed decreased emulsion stabilities around pH 5. This indicates the importance of the charged polysaccharides present in ASPI for emulsion stability at pH 5. For the foaming properties of ASPI no effect of charged polysaccharides was observed. Instead, ASPI-S showed considerably higher foam stabilities at pH 5e7 than the other fractions. These results suggest that dependent on the application charged polysaccharides or dissociated (glyco-) proteins can contribute to ASPI’s techno-functional properties. Its further fractionation yields a fraction with improved emulsion stability and a fraction with improved foaming properties.
    The effects of temperature, moisture, duration of incubation time, calcium level, and soaking with water or citric acid on in vitro phytate degradation in a wheat-barley-rye-soybean meal-based diet
    Esmaeilipour, O. ; Krimpen, M.M. van; Jongbloed, A.W. ; Jonge, L.H. de; Bikker, P. - \ 2013
    Animal Feed Science and Technology 183 (2013)3-4. - ISSN 0377-8401 - p. 168 - 174.
    aspergillus-niger phytase - phosphorus availability - microbial phytase - pigs - performance - supplementation - digestibility - hydrolysis - retention - broilers
    Three in vitro experiments were carried out to determine the effect of temperature, moisture content, duration of incubation, Ca level, soaking with water or citric acid onphytate degradation in a wheat-barley-rye-soybean meal-based broiler diet. In experiment 1, phytase activity of individual feed ingredients and 4 low-P broiler diets, containing 2, 4, 8, and 12 g Ca per kg diet, respectively, were measured in the presence or absence of sodium phytate or soybean meal. By using sodium phytate as substrate, phytase activity of rye, wheat, barley and soybean meal was 3350, 1170, 580 and 30 FTU/kg, respectively (P0.05). In experiment 2, the effect of 2 moisture levels (0.25 and 50%), 3 temperatures (70,75 and 80 degrees C) and 3 durations of incubation (2, 4, and 8 min) on the residual phytase activity of diet 1 (basal diet) were evaluated as a 2 x 3 x 3 factorial arrangement with 3 replicates per treatment. The loss of activity of intrinsic phytase increased from 0.25 at 70 degrees C to 0.61 at 80 degrees C (P
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