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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    We will mail you new results for this query: keywords==enzymatic-hydrolysis
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Kinetics of Acid Hydrolysis of Water-Soluble Spruce O-Acetyl Galactoglucomannans
Xu, C. ; Pranovich, A. ; Vahasalo, L. ; Hemming, J. ; Holmbom, B. ; Schols, H.A. ; Willfor, S. - \ 2008
Journal of Agricultural and Food Chemistry 56 (2008)7. - ISSN 0021-8561 - p. 2429 - 2435.
molecular-weight changes - thermomechanical pulp - enzymatic-hydrolysis - degradation - chitosan - depolymerization - polysaccharides - products - polymers
Water-soluble O-acetyl galactoglucomannan (GGM) is a softwood-derived polysaccharide, which can be extracted on an industrial scale from wood or mechanical pulping waters and now is available in kilogram scale for research and development of value-added products. To develop applications of GGM, information is needed on its stability in acidic conditions. The kinetics of acid hydrolysis of GGM was studied at temperatures up to 90 °C in the pH range of 1¿3. Molar mass and molar mass distribution were determined using size exclusion chromatography with multiangle laser light scattering and refractive index detection. The molar mass of GGM decreased considerably with treatment time at temperatures above 70 °C and pH below 2. The molar mass distribution broadened with hydrolysis time. A first-order kinetic model was found to match the acid hydrolysis. The reaction rate constants at various pH values and temperatures were calculated on the basis of the first-order kinetic model. Furthermore, the activation energy, E, was obtained from the Arrhenius plot. The activation energy E was 150 kJ mol¿1 for acid hydrolysis of spruce GGM. The apparent rate constant during acid hydrolysis increased by a factor of 10 with a decrease in pH by 1 unit, regardless of temperature. In addition, gas chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were applied to study the released GGM monomers and oligomers. Keywords: Kinetics; acid hydrolysis; galactoglucomannans; oligosaccharides; stability.
Towards an optimal process for gelatinisation and hydrolysis of highly concentrated starch-water mixtures with alpha-amylase from B. licheniformis
Baks, T. ; Kappen, F.H.J. ; Janssen, A.E.M. ; Boom, R.M. - \ 2008
Journal of Cereal Science 47 (2008)2. - ISSN 0733-5210 - p. 214 - 225.
twin-screw extruder - wheat-starch - enzymatic-hydrolysis - extrusion-cooking - corn starch - sago starch - model - liquefaction - degradation - kinetics
The enzymatic hydrolysis of starch is usually carried out with 30¿35 w/w% starch in water. Higher substrate concentrations (50¿70 w/w%) were reached by using a twin-screw extruder for gelatinisation and for mixing enzyme with gelatinised starch prior to enzymatic hydrolysis in a batch reactor. The aim of this study was to determine which parameters are important for gelatinisation of wheat starch and to investigate the effects of different extrusion conditions on the enzymatic hydrolysis. After extrusion, the degree of gelatinisation was measured. During hydrolysis, the carbohydrate composition, the dextrose equivalent (DE) and the alpha-amylase activity were measured. Gelatinisation measurements showed that mechanical forces lowered the temperature required for complete gelatinisation. During hydrolysis experiments, high DEs were observed even if starch was not completely gelatinised during extrusion. Due to high substrate concentrations, the residual alpha-amylase activity remained high throughout enzymatic hydrolysis, although high temperatures were used. Increased substrate concentrations did not affect the carbohydrate composition of the product. Furthermore, the time required for the batch hydrolysis step could be varied by choosing a different enzyme-to-substrate ratio. This article provides a basis for detailed optimisation of this process to develop an industrial-scale process at high substrate concentrations.
A generic model for glucose production from various cellulose sources by a commercial cellulase complex
Drissen, R.E.T. ; Maas, R.H.W. ; Maarel, M.J. van der; Kabel, M.A. ; Schols, H.A. ; Tramper, J. ; Beeftink, H.H. - \ 2007
Biocatalysis and Biotransformation 25 (2007)6. - ISSN 1024-2422 - p. 419 - 429.
research-and-development - pretreated wheat-straw - enzymatic-hydrolysis - simultaneous saccharification - aspergillus-niger - saccharomyces-cerevisiae - fermentation process - ethanol - lignocellulose - technology
The kinetics of cellulose hydrolysis by commercially available Cellubrix were described mathematically, with Avicel and wheat straw as substrates. It was demonstrated that hydrolysis could be described by three reactions: direct glucose formation and indirect glucose formation via cellobiose. Hydrolysis did not involve any soluble oligomers apart from low amounts of cellobiose. Phenomena included in the mathematical model were substrate limitation, adsorption of enzyme onto substrate, glucose inhibition, temperature dependency of reaction rates, and thermal enzyme inactivation. In addition, substrate heterogeneity was described by a recalcitrance constant. Model parameters refer to both enzyme characteristics and substrate-specific characteristics. Quantitative model development was carried out on the basis of Avicel hydrolysis. In order to describe wheat straw hydrolysis, wheat straw specific parameter values were measured. Updating the pertinent parameters for wheat straw yielded a satisfactory description of wheat straw hydrolysis, thus underlining the generic potential of the model.
Comparison of methods to determine the degree of gelatinisation for both high and low starch concentrations
Baks, T. ; Ngene, I.S. ; Soest, J.J.G. van; Janssen, A.E.M. ; Boom, R.M. - \ 2007
Carbohydrate Polymers 67 (2007)4. - ISSN 0144-8617 - p. 481 - 490.
differential scanning calorimetry - high hydrostatic-pressure - partial molar volumes - potato starches - water-content - wheat-starch - birefringence measurements - crystalline polymorph - phase-transformations - enzymatic-hydrolysis
A general procedure was developed to measure the degree of gelatinisation in samples over a broad concentration range. Measurements based on birefringence, DSC (Differential scanning calorimetry), X-ray and amylose-iodine complex formation were used. If a 10 w/w % wheat starch-water mixture was used, each method resulted in approximately the same degree of gelatinisation vs. temperature curve. In case the gelatinisation of a 60 w/w % wheat starch-water mixture was followed as a function of the temperature, each method resulted in a different degree of gelatinisation vs. temperature curve. DSC and X-ray measurements are preferred, because they can be used to determine when the final stage of the gelatinisation process has been completed. Birefringence and amylose-iodine complex formation measurements are suitable alternatives if DSC and X-ray equipment is not available, but will lead to different results. The differences between the methods can be explained by considering the phenomena that take place during the gelatinisation at limiting water conditions. Based on the experimental data obtained with DSC and X-ray measurements, the gelatinisation of 10 w/w % and 60 w/w % wheat starch-water mixtures started at the same temperature (approximately 50 °C). However, complete gelatinisation was reached at different temperatures (approximately 75 °C and 115 °C for, respectively, 10 w/w % and 60 w/w % wheat starch-water mixtures) according to the experimental DSC and X-ray data. These results are in accordance with independent DSC measurements that were carried out. The Flory equation was adapted to provide a quantitative explanation for the curves describing the degree of starch gelatinisation as a function of the starch-water ratio and the temperature. The gelatinisation curves that were obtained with the model are in good agreement with the experimentally determined curves. The parameters Tm0, ¿Hu and ¿12 that resulted in the lowest sum of the squared residuals are 291 ± 63 °C, 29.2 ± 3.9 kJ/mol and 0.53 ± 0.05 (95% confidence interval). These values agree with other values reported in literature
Opposite Contributions of Glycinin- and ß-Conglycinin-Derived Peptides to the Aggregation Behavior of Soy Protein Isolate Hydrolysates
Kuipers, B.J.H. ; Koningsveld, G.A. van; Alting, A.C. ; Driehuis, F. ; Voragen, A.G.J. ; Gruppen, H. - \ 2006
Food Biophysics 1 (2006)4. - ISSN 1557-1858 - p. 178 - 188.
heat-induced gelation - soybean proteins - structural characteristics - emulsifying properties - enzymatic-hydrolysis - limited proteolysis - physical-properties - alpha-lactalbumin - gel properties - whey proteins
The aggregation behavior as a function of pH was studied for hydrolysates obtained by hydrolysis of soy protein isolate (SPI) and glycinin- and ß-conglycinin-rich protein fractions with subtilisin Carlsberg. The substrates were hydrolyzed up to degrees of hydrolysis (DH) of 2.2% and 6.5%. Compared with nonhydrolyzed SPI, a decrease in solubility was observed for the hydrolysates of SPI [0.8% (w/v) protein, I¿=¿0.03 M] around neutral pH. At pH 8.0, glycinin hydrolysates had a much lower solubility (~43% and 60%, respectively, for DH 2.2% and 6.5%) than SPI and ß-conglycinin-derived hydrolysates, which were almost completely soluble. Peptides that aggregated were all larger than 5 kDa, and as estimated by size-exclusion chromatography their composition was almost independent of the aggregation pH. The solubility of hydrolysates of SPIs with a varying glycinin and ß-conglycinin composition showed that glycinin-derived peptides are the driving force for the lower solubility of SPI hydrolysates. The solubility of SPI hydrolysates at pH 8.0 was shown not to be the sum of that of glycinin and ß-conglycinin hydrolysates. Assuming that the separate hydrolysis of glycinin and ß-conglycinin did not differ from that in the mixture (SPI), this indicates that ß-conglycinin-derived peptides have the ability to inhibit glycinin-derived peptide aggregation.
Starch hydrolysis under low water conditions: a conceptual process design
Veen, M.E. van der; Veelaert, S. ; Goot, A.J. van der; Boom, R.M. - \ 2006
Journal of Food Engineering 75 (2006)2. - ISSN 0260-8774 - p. 178 - 186.
thermostable alpha-amylase - niger glucoamylase-i - twin-screw extruder - enzymatic-hydrolysis - extrusion-cooking - corn starch - reactor - kinetics - glucose - liquefaction
A process concept is presented for the hydrolysis of starch to glucose in highly concentrated systems. Depending on the moisture content, the process consists of two or three stages. The two-stage process comprises combined thermal and enzymatic liquefaction, followed by enzymatic saccharification. The three-stage process starts with shear induced melting of starch, followed by enzymatic liquefaction and saccharification. At a low moisture content, the shear stress needed to completely melt corn starch is so high that significant enzyme inactivation cannot be avoided, which leads to a need for separating starch melting and liquefaction in two separate processing steps. Assuming the use of currently available enzymes, the final product composition was estimated to contain 69-93% glucose, starting with respectively 65% and 35% dry starch. These results showed that the formation of side-products, mainly isomaltose and isomaltotriose, increased with increasing dry matter content. Increasing the dry matter content from 35% to 65% resulted in increasing reactor productivity of 17%, while the amount of water that should be removed from the system was reduced by 87%. (c) 2005 Elsevier Ltd. All rights reserved.
Characterisation and foaming properties of hydrolysates derived from rapeseed isolate
Larré, C. ; Mulder, W.J. ; Sánchez-Vioque, R. ; Lazko, J. ; Bérot, S. ; Guéguen, J. ; Popineau, Y. - \ 2006
Colloids and Surfaces. B: Biointerfaces 49 (2006)1. - ISSN 0927-7765 - p. 40 - 48.
brassica-napus l. - emulsifying properties - functional-properties - enzymatic-hydrolysis - beta-lactoglobulin - plant-proteins - peptides - gluten - albumin - whey
Two hydrolysis methods used to obtain rapeseed isolate derivates were compared: chemical hydrolysis performed under alkaline conditions and pepsic proteolysis performed under acidic conditions. The mean molecular weights obtained for the hydrolysates varied from 26 to 2.5 kDa, depending on the level of hydrolysis. Further characterisation showed that, at the same level of hydrolysis, the chemical hydrolysates differed by their charges and hydrophobicity from those derived from enzymatic digestion. Analysis of the foaming properties showed, for both cases, that a limited degree of hydrolysis, around 3%, was sufficient to optimise the foaming properties of the isolate despite the different physicochemical properties of the peptides generated. The study of foaming properties at basic, neutral and acidic pHs showed that the hydrolysate solutions yielded dense foams which drained slowly and which maintained a very stable volume under the three pH conditions tested.
Production of glucose syrups in highly concentrated systems
Veen, M.E. van der; Goot, A.J. van der; Boom, R.M. - \ 2005
Biotechnology Progress 21 (2005)2. - ISSN 8756-7938 - p. 598 - 602.
enzymatic-hydrolysis - alpha-glucosidase - kinetic-model - wheat-starch - glucoamylase - optimization - mechanism - extruder - reactor
We have investigated the hydrolysis of maltodextrins in a high concentration (up to 70%), by means of enzymatic and acid catalysis. The study revealed that the equilibrium compositions of the catalyzed reactions were kinetically determined by the selectivity of the catalyst, the substrate concentration and the reaction time. A model comprising a set of two kinetic equations was used to describe the hydrolysis and condensation reactions of glucoamylase-catalyzed reactions, even to highly concentrated systems. Increased substrate concentration resulted in the formation of more condensation products. The enzyme inhibition was low and was found to be independent of the substrate concentration.
Shear induced inactivation of a-amylase in a plain shear field
Veen, M.E. van der; Iersel, D.G. van; Goot, A.J. van der; Boom, R.M. - \ 2004
Biotechnology Progress 20 (2004)4. - ISSN 8756-7938 - p. 1140 - 1145.
twin-screw extruder - enzymatic-hydrolysis - starch - deactivation - cellulase - reactor - transglutaminase - kinetics - enzymes - beta
A newly developed shearing device was used to study shear-induced inactivation of thermostable alpha-amylase in a plain shear field, under conditions comparable to extrusion. The results show that the inactivation can be described well with a first-order process, in which the inactivation energy largely depends on the shear stress, instead of specific mechanical energy or strain history. The resulting dependency of the rate of inactivation on the shear stress is very strong and nonlinear, which leads to the conclusion that in many cases the maximally applied shear stress determines the inactivation. Quantification of the inactivation rates gives design criteria for the application of enzymes in more viscous systems than conventionally used, provided that the reactor is designed such that no peak shear stresses occur.
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