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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Anaerobic digestion of cellulose and hemicellulose in the presence of humic acids
Azman, Samet - \ 2016
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 - hemicellulosen - biomassa - hernieuwbare energie - energieterugwinning - 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
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
University. Promotor(en): Johan Sanders, co-promotor(en): Marieke Bruins; E. Ratnaningsih. - Wageningen : Wageningen University - ISBN 9789462576643 - 236 p.
biorefinery - biomass conversion - rubber - rubber plants - protein extraction - latex - hydrolysis - hydrophobicity - amino acids - wheat gluten - residual streams - biobased economy - bioraffinage - biomassaconversie - rubberplanten - eiwitextractie - hydrolyse - hydrofobiciteit - aminozuren - tarwegluten - reststromen

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.

Ketenanalyse en productverkenning voor valorisatie pelagische bijvangst en bijproducten
Broeze, J. ; Poelman, M. ; Kals, J. ; Rurangwa, E. ; Vogel-van den Bosch, H.M. de - \ 2015
Wageningen : Wageningen UR - Food & Biobased Research - ISBN 9789462577091 - 27 p.
bijvangst - reststromen - bioraffinage - vis - hydrolyse - veevoeder
Dit rapport presenteert een analyse naar alternatieve mogelijkheden voor verwaarding van visbijvangst ten opzichte van vismeel.

Het hier gerapporteerde onderzoek omvat een brede inventarisatie van mogelijkheden binnen de wettelijke kaders. Door middel van een expert-brainstorm en een inventarisatie van recente productinnovaties in de markt zijn de volgende ideeën gegenereerd:
A. afzet van beschadigde vis voor bewerkte voedseltoepassingen;
B. verwerking van huiden tot leder;
C. geur- en smaakstoffen op basis van vis-eiwitten; ook attractanten t.b.v. visvoer;
D. bioactieve peptiden (met gezondheidsbevorderende eigenschappen), te produceren door middel van (enzymatische of evt. zure) hydrolyse;
E. vis-eiwit als allergeen-vrij (afgezien van parvalbumin) alternatief voor koemelk en sojamelk (denk aan babyvoeding);
F. collageen voor bijvoorbeeld voeding, cosmetica of technische toepassingen;
G. fosfolipiden voor emulsies (zoals margarine);
H. visolie in voeding; geur en smaak kunnen gemaskeerd worden;
I. mineralen-vitamines-supplementen uit vis, o.a. selenium, vitamines a, d en e;
J. silage (auto-hydrolyse), waarbij de vissilage verder kan worden gescheiden in:
o eiwitten voor diervoeder (bijvoorbeeld nat voor varkens; droog voor pluimvee);
o olie scheiden/zuiveren.
Vanuit de sector zelf is idee (A) in de praktijk gebracht: beschadigde vis wordt succesvol in de bestaande markt afgezet. Dit idee is mede daarom in het project niet verder uitgewerkt.
Door het projectteam en vertegenwoordigers uit de pelagische sector zijn uit bovenstaande lijst drie opties geselecteerd voor verdere analyse:
1. Silage gericht op grondstof voor diervoeders (optie J).
2. Silage met winning van bioactieve peptiden (combinatie van opties D en J)
3. Milde hydrolyse gericht op winning van bio-actieve peptiden (optie D).

Het eerste opties betreft silage: onder toevoeging van zuur worden eiwitmoleculen opgeknipt tot onder andere peptiden en aminozuren. Het silage-product kan worden afgezet als veevoeder, bijvoorbeeld als alternatief voor sojameel. Helaas levert deze business case een negatief resultaat.

Bij de tweede optie, hydrolyse, worden eiwitketens ook opgeknipt in kleinere stukken, vooral peptiden. Maar hierbij wordt het proces beter gecontroleerd, zodat relatief grote hoeveelheden waardevolle specifieke peptide-moleculen worden gevormd. Hydrolyse kan ook worden uitgevoerd door toevoeging van zuur, maar dan bij gecontroleerde temperatuur en procestijd (het proces wordt gestopt door neutralisatie). Het meest doelgericht kunnen specifieke peptiden worden gevormd door gebruik van enzymen in plaats van zuur.
Hydrolysaten kunnen worden afgezet als voedselingrediënt (bijvoorbeeld met aangepaste technische eigenschappen), als gezondheidsbevorderend bio-actieve component (in voeding of als voedingssupplement) of voor diervoerdertoepassingen.
Hoewel wetgeving dat niet expliciet voorschrijft, wordt in dit rapport geconcludeerd dat voor humane consumptie de vis voor het hydrolyseproces moet worden gestript. Dit drijft de prijs voor het ingangsmateriaal aanzienlijk op.
Uit kosten-batenanalyses van zowel de veevoeder-optie als voor humane toepassingen volgt een positieve business case. Maar deze positieve uitkomsten zijn wel sterk afhankelijk van prijzen van zowel het ingangsmateriaal als de eindproducten. Omdat ontwikkeling van deze opties op basis van vis in de kinderschoenen staat, is amper informatie over afzetprijzen beschikbaar is. Omdat deze prijzen kritisch zijn voor een positieve business case, wordt aangeraden bij een eventuele vervolgontwikkeling ook mogelijke afnemers te betrekken.

Als laatste idee is nog gekeken naar een mogelijke tussenvorm tussen silage en hydrolyse: bioactieve moleculen uit silage. Helaas blijkt dat zelfs bij minimale hoeveelheid zuur (ondergrens wordt bepaald door eisen voor houdbaarheid) het product na enkele maanden bewaring te ver gehydrolyseerd is (meeste bio-actieve peptiden zijn afgebroken tot aminozuren). Dus, alleen door een beperkte (vooral qua tijd) hydrolysestap kan nog een product met bio-actieve waarde worden geproduceerd.

Geconcludeerd wordt dat milde hydrolyse het beste perspectief beidt. Toepassing voor zowel voedsel als diervoeders is mogelijk. Echter, voor voedingstoepassingen heeft bijvangst een nadeel ten opzichte van bijproduct van visverwerking omdat de vis gestript moet worden. Diervoedertoepassing past daarom beter.
Voor zowel voedings- als diervoedertoepassing zal ook de markt nog ontwikkeld moeten worden.
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 p.
pelagic fishery - marine fisheries - discards - fish silage - livestock feeding - bioactive compounds - hydrolysis - feed industry - pelagische visserij - zeevisserij - vissilage - veevoeding - bioactieve verbindingen - hydrolyse - veevoederindustrie
Kinetic modelling of enzymatic starch hydrolysis
Bednarska, K.A. - \ 2015
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
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 - 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.

Enzyme-assisted separation and hydrolysis of gluten : options for intensification
Hardt, N.A. - \ 2014
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 - 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.

Designed enzyme preparations for the hydrolysis of corn silage polysaccharides
Neumüller, K.G. - \ 2014
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 - research - biomass conversion
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
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
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).

Autogenerative high pressure digestion : biogass production and upgrading in a single step
Lindeboom, R.E.F. - \ 2014
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 - digestion - pressure - methane production - carbon dioxide - starch - hydrolysis
Transformation reactions in TOXSWA : transformation reactions of plant protection products in surface water
Deneer, J.W. ; Beltman, W.H.J. ; Adriaanse, P.I. - \ 2010
Wageningen : Alterra (Alterra-rapport 2074) - 94
pesticiden - hydrolyse - fotolyse - biotransformatie - oppervlaktewater - pesticides - hydrolysis - photolysis - biotransformation - surface water
This report aims to give a general description of transformation processes for future use in the TOXSWA model. Hydrolysis, photolysis and biotic transformation are described as distinct processes, employing separate rate constants. Additionally, a way to introduce into TOXSWA the daily variation of pH and temperature is proposed.
Biomass pre-treatment for hydrogen fermentation
Lips, S.J.J. ; Bakker, R.R. - \ 2010
waterstof - ruwe grondstoffen - voorbehandeling - hydrolyse - biobased economy - biobrandstoffen - reststromen - hydrogen - raw materials - pretreatment - hydrolysis - biofuels - residual streams
Poster met onderzoeksinformatie over het project HYVOLUTION. Als restproducten gebruikt worden voor de productie van biowaterstof, moeten ze voorbehandeld worden.
Hydrolysis inhibition of complex biowaste
Vasconcelos Fernandes, T. - \ 2010
University. Promotor(en): Jules van Lier, co-promotor(en): Grietje Zeeman. - [S.l.] : S.n. - ISBN 9789085856818 - 182
agrarische afvalstoffen - dierlijke meststoffen - drijfmest - biomassa - hydrolyse - verwerking - anaërobe behandeling - anaërobe afbraak - afvalverwerking - biogas - biomassaconversie - agricultural wastes - animal manures - slurries - biomass - hydrolysis - processing - anaerobic treatment - anaerobic digestion - waste treatment - biomass conversion
The increasing demand of renewable energy sources and reuse of wastes, challenges our society for better technological solutions for energy production. Co-digestion of agricultural biowaste, such as animal manure and plant residues, offers an interesting contribution to the renewable energy strategies. The biogas plants, where the complex substrates, such as agricultural biowaste, get converted into biogas, are then able to produce electricity and heat, which can be used in the farm and delivered to the main electricity grid. Moreover, due to its decentralised nature, the implementation of small-scale biogas plants can supply renewable energy to people without the need for large-scale infrastructural networks such as electricity grids, thereby solving part of the populations’ energy demands.
The production of biogas from complex biowaste is rate-limited by the hydrolysis step of the anaerobic digestion process. However the hydrolysis step has been poorly described and not very well understood, resulting in non-optimized anaerobic digester volumes. Due to that, a review on the anaerobic hydrolysis step is in this thesis presented, together with ways to accelerate the hydrolysis, either by mitigating the revealed inhibiting compounds, by pre-treating difficultly hydrolysable substrates, or as is nowadays also applied, by adding hydrolytic enzymes to full scale biogas co-digestion plants.
In this thesis two compounds were studied in terms of its inhibiting effect on hydrolysis: ammonia nitrogen and Humic Matter (HM). Ammonia nitrogen did not show an inhibiting effect on anaerobic hydrolysis. On the other hand Humic acids-like (HAL) and Fulvic acids-like (FAL) extracted from fesh cow manure and silage maize, and in this thesis extensively described in terms of its chemical characteristics, showed a strong inhibiting effect on the hydrolysis step.
Plant matter is high in lignocellulosic biomass. Lignocellulosic biomass consists of lignin, which is resistant to anaerobic degradation, cellulose and hemicelluloses. Pre-treatment of plant material, is particularly important in order to increase biogas production during co-digestion of manure. Calcium hydroxide pre-treatment was shown, in this thesis, to improve the biodegradability of lignocellulosic biomass, especially for high lignin content substrates. Maleic acid generated the highest percentage of dissolved COD during pre-treatment, however its high market price makes it not so attractive as calcium hydroxyde.
Enzyme addition has recently gained the attention of biogas plants’ operators in order to accelerate hydrolysis, however further research is needed.

Biobutanol from wheat straw
Lopez Contreras, A.M. ; Bakker, R.R. ; Wal, H. van der; Houweling-Tan, G.B.N. ; Claassen, P.A.M. - \ 2009
tarwestro - fermentatie - hydrolyse - butanol - biobrandstoffen - biobased economy - wheat straw - fermentation - hydrolysis - biofuels
Poster met onderzoeksinformatie over de productie van biobutanol uit tarwestro door middel van het aceton-butanol-ethanol (ABE) fermantatieproces.
Microbial conversion of lignocellulose-derived carbohydrates into bioethanol and lactic acid
Maas, R.H.W. - \ 2008
University. Promotor(en): Gerrit Eggink, co-promotor(en): Ruud Weusthuis. - [S.l.] : S.n. - ISBN 9789085048718 - 158
tarwestro - lignocellulose - lignocellulosehoudend afval - microbiële afbraak - conversie - melkzuur - fermentatie - hydrolyse - bio-energie - bioethanol - wheat straw - lignocellulosic wastes - microbial degradation - conversion - lactic acid - fermentation - hydrolysis - bioenergy
Houtachtige biomassa (rest)stromen kan één van de duurzame alternatieven gaan worden voor aardolie omdat het kan dienen als grondstof voor de productie van biobrandstoffen en bulkchemicaliën. Belangrijk voordeel van deze technologie is dat er geen gebruik hoeft te worden gemaakt van plantaardige producten die geschikt zijn voor voedseldoeleinden. Binnen het huidige onderzoek zijn we erin geslaagd om op grote schaal houtachtige biomassa zoals stro via verschillende fysisch-chemische behandelingen en een enzymatische hydrolyse af te breken tot enkelvoudige suikers. Deze suikers werden door verschillende soorten micro-organismen omgezet naar gewenste producten zoals ethanol voor biobrandstoftoepassing of melkzuur als bouwsteen voor de productie van biologisch afbreekbaar plastic. De delen van het stro welke niet door de micro-organismen konden worden omgezet werden gebruikt voor biogasproductie of fungeerden als brandstof voor het verkrijgen van warmte en elektriciteit. Een productieproces waarbij, via een combinatie van verschillende voorbehandelingen, stro door bacteriën efficiënt werd omgezet naar melkzuur werd gepatenteerd.
Process development for gelatinisation and enzymatic hydrolysis of starch at high concentrations
Baks, T. - \ 2007
University. Promotor(en): Remko Boom, co-promotor(en): Anja Janssen. - [S.l.] : s.n. - ISBN 9789085046943 - 208
zetmeel - verwerking - hydrolyse - alfa-amylase - starch - processing - hydrolysis - alpha-amylase - cum laude
cum laude graduation (with distinction) Enzymatic hydrolysis of starch is encountered in day-to-day life for instance in the dishwasher during removal of stains with detergents or in our mouth during chewing of starch-based foods in the presence of saliva. The reaction is also important for the (food) industry, for example for the production of beer or bio-ethanol. In industry, it is usually preceded by gelatinisation to make the starch molecules available for the enzymes. Both gelatinisation and hydrolysis are usually carried out at a starch concentrations of 30 weight-%. Increasing the starch concentration during these processes can lead to a higher productivity, lower energy consumption, lower use of water and a higher enzyme stability. However, the drawback is that the gelatinisation temperature and the viscosity increase at these conditions. By using the proper process equipment, it is possible to overcome these drawbacks and to perform the gelatinisation and hydrolysis at high starch concentrations leading to the advantages mentioned above. The purpose of this study was therefore to develop a process for gelatinisation and enzymatic hydrolysis of wheat starch at high starch concentrations (more than 40 weight-%). Besides the development of such a process, analysis methods were developed to measure the main process parameters at these conditions.
Hydrogen from biomass
Claassen, P.A.M. ; Vrije, G.J. de - \ 2006
Wageningen : Agrotechnology & Food Sciences Group (Report / Agrotechnology and Food Sciences Group 725) - ISBN 9085850231 - 42
waterstof - biomassa - biologische productie - fermentatie - hydrolyse - micro-organismen - energiebronnen - vervangbare hulpbronnen - miscanthus - biobased economy - biobrandstoffen - hydrogen - biomass - biological production - fermentation - hydrolysis - microorganisms - energy sources - renewable resources - biofuels
Hydrogen is generally regarded as the energy carrier of the future. The development of a process for hydrogen production from biomass complies with the policy of the Dutch government to obtain more renewable energy from biomass. This report describes the progress of the BWP II project, phase 2 of the Biological Hydrogen Production programme.
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