Titel Deelnemers "Korte inhoud" "The effect of high pressure homogenization on pectin: Importance of pectin source and pH" "Avi Shpigelman, Clare Kyomugasho, Stefanie Christiaens, Ann Van Loey, Marc Hendrickx" "Pectin is a common, heterogeneous, and structurally complex polysaccharide present in plant cell walls that is naturally present in staple foods and commonly used in the food and biomedical industry. Pectin is known to be sensitive to process induced chemical changes that can result in various effects on its functionality. This worked aimed at better understanding the effects of high pressure homogenization (HPH), an emerging technology that can be used to influence rheological/textural properties and reduce the microbial activity of liquid food systems in a continuous process, on pectin. Our results show that the previously suggested depolymerization of pectin is dependent on its source, most likely due to the presence of neutral sugar (NS) side chains. While citrus pectin (poor in NS) was depolymerized by HPH, apple pectin (richer in NS and having a more compact structure) was not. The depolymerization only occurred to pectins above a specific Mw threshold, resulting in the possibility of utilization of this method for the production of a more uniform pectin. Additionally, an effect for pH was noticed. At pH 6.3, the HPH induced conformational changes resulted in a more compact structure (for both pectins), while at pH 4.4 no conformational changes were noticed. HPH did not result in changes in the degree of methoxylation of both pectins and also no change in the amount of reducing sugars was noted." "Structural prediction and characterization of Canavalia grandiflora (ConGF) lectin complexed with MMP1 : unveiling the antiglioma potential of legume lectins" "Rodrigo Bainy Leal, Josiane Mann, Vanir Reis Pinto-Junior, Messias Vital Oliveira, Vinicius Jose Da Silva Osterne, Ingrid Alessandra Victoria Wolin, Ana Paula Machado Nascimento, Priscilla Gomes Welter, Valeria Maria Sousa Ferreira, Alice Araujo Silva, Rodrigo Lopes Seeger, Kyria Santiago Nascimento, Benildo Sousa Cavada" "A glioblastoma (GBM) is a highly malignant primary brain tumor with a poor prognosis because of its invasiveness and high resistance to current therapies. In GBMs, abnormal glycosylation patterns are associated with malignancy, which allows for the use of lectins as tools for recognition and therapy. More specifically, lectins can interact with glycan structures found on the malignant cell surface. In this context, the present work aimed to investigate the antiglioma potential of ConGF, a lectin purified from Canavalia grandiflora seeds, against C6 cells. The treatment of C6 cells with ConGF impaired the mitochondrial transmembrane potential, reduced cell viability, and induced morphological changes. ConGF also induced massive autophagy, as evaluated by acridine orange (AO) staining and LC3AB-II expression, but without prominent propidium iodide (PI) labeling. The mechanism of action appears to involve the carbohydrate-binding capacity of ConGF, and in silico studies suggested that the lectin can interact with the glycan structures of matrix metalloproteinase 1 (MMP1), a prominent protein found in malignant cells, likely explaining the observed effects." "The Prader-Willi syndrome proteins MAGEL2 and necdin regulate leptin receptor cell surface abundance through ubiquitination pathways" "Leentje De Ceuninck, Delphine Masschaele, Jan Tavernier" "Effect of de-methylesterification on network development and nature of Ca2+-pectin gels: Towards understanding structure–function relations of pectin" "Ilse Fraeye, Ruth Cardinaels, Ann Van Loey, Paula Moldenaers, Marc Hendrickx" "Pectins of varying degree and pattern of methylesterification were produced through controlled de-esterification of highly esterified citrus pectin, using carrot pectin methylesterase (PME) (P-pectins), Aspergillus aculeatus PME (F-pectins) or sodium hydroxide saponification (C-pectins). Estimation of the degree of methylesterification (DM) and quantification of the pattern of methylester distribution in terms of absolute degree of blockiness (DBₐbₛ) enabled the characterisation of pectins. Characterised pectins were used for the preparation of Ca²⁺-pectin gels with varying calcium ion (Ca²⁺) concentration. The rheological characteristics of produced gels were evaluated by means of small-amplitude oscillatory tests. During gel formation, gel strength was monitored so as to allow assessment of network development. Based on the evaluation of mechanical spectra, the nature of the cured gels was established. Depending on Ca²⁺ concentration as well as DM and DBₐbₛ, gels prepared from specific C-pectins (48≥DM≥26%; 9≤DBₐbₛ≤37%) and F-pectins (64≥DM≥29%; 9≤DBₐbₛ≤50%) showed a striking decrease of the gel strength with time, while gel networks produced from other pectins either displayed a continuous increase of the gel strength or verged towards pseudo-equilibrium within the observation time of 5h. Furthermore, the DM, DBₐbₛ and Ca²⁺ concentration influenced the evolution of Ca²⁺-pectin networks from “structured liquids” to “strong gels”. Based on the experimental results, specific mechanisms of Ca²⁺ interactions with pectins were (also) considered." "Improved heat stability of whey protein isolate stabilized emulsions via dry heat treatment of WPI and low methoxyl pectin : effect of pectin concentration, pH, and ionic strength" "Arima Diah Setiowati, Serveh Saeedi, Wahyu Wijaya, Paul Van der Meeren" "Cotyledon pectin molecular interconversions explain pectin solubilization during cooking of common beans (Phaseolus vulgaris)" "Claire Chigwedere, Clare Kyomugasho, Andrea Pallares Pallares, Ann Van Loey, Tara Grauwet, Marc Hendrickx" "Dynamics of pectin extractability in cotyledons and seed coats were explored for mechanistic insight into pectin changes due to aging and cooking of beans. In addition, changes in mineral distribution during cooking were determined in order to investigate their retention in the matrix. Pre-soaked fresh and aged beans were cooked in demineralized water for different times and the cotyledons, seed coats and cooking water were lyophilized. From cotyledon and seed coat powders, alcohol insoluble residue (AIR) was extracted and sequentially fractionated into water-, chelator- and sodium carbonate-extractable pectin (WEP, CEP and NEP, respectively). Characterization of pectin in AIR and pectin fractions revealed inherent structural differences between cotyledon and seed coat pectin with the latter exhibiting a lower degree of methylesterification (DM) and being more linear. Due to aging, WEP decreased whilst NEP substantially increased and the CEP fraction and DM of pectin in AIR did not change significantly, suggesting a more crucial role of increased covalent bonding than cation-mediated crosslinking in aging-induced hardening of beans. During cooking, some NEP was converted into WEP and no pectin depolymerization was observed from molar mass distribution profiles. Pectin changes due to aging and cooking of beans were more pronounced in the cotyledon compared to the seed coat. Whilst Ca2+, Fe2+ and Zn2+ were largely retained in the bean matrix during cooking, Mg2+ was largely leached from cotyledons into the cooking water. In conclusion, aging-induced hardening of beans and softening during cooking were found to be premised on interconversion of pectin fractions in cotyledons." "Pectin Fine Structure and the Rheological Characteristics of Ca2+-pectin Gels: Towards understanding structure - function relations of pectin" "Eugenie Doungla Ngouemazong" "Pectin, a plant cell wall polysaccharide, is a natural multifunctional ingredient in a wide range of food systems, imparting desirable textural and rheological properties. The use of pectin is often related to its Ca2+ gel-forming ability. The rheological characteristics of Ca2+-pectin gels, particularly gel stiffness, are determined by the structural features of pectins linear homogalacturonan domain. The application of structurally modified pectins depends on their functionality and, hence, on a detailed understanding of pectin structure function relations, the latter being the subject of the present study.First, the effect of partial demethylesterification of homogalacturonan on the rheological characteristics of Ca2+-pectin gels was studied. Pectins of various degrees and patterns of methylesterification (DM and PM, respectively) were produced through controlled de-esterification of highly esterified citrus pectin using chemical saponification, fungal pectin methylesterase (PME) or plant PME. The PM was quantified using the indicative parameter absolute degree of blockiness (DBabs). Mathematical relations between DM and DBabs of the pectins produced through the different de-esterification methods clearly revealed the differences in the distribution patterns of methylesters. The characterised pectins were then used for the preparation of Ca2+-pectin gels with varied Ca2+ concentration. The rheological characteristics (gel development, nature and stiffness) of the produced gels were evaluated by means of small-amplitude oscillatory tests. The gels characteristics varied with Ca2+ concentration as well as with DM and DBabs for the three de-esterification methods. Depending on DBabs (for the three de-esterification methods), the increase in gel stiffness was related not only to an increase in the number of junction zones per pectin chain, but also to an increase in the size of the junction zones and the number of dimerised chains occurring in the gels. In the second part, the influence of partial depolymerisation of rhamnogalacturonan I side chains on pectin functionality was investigated. Water-soluble pectin was extracted from carrot and part of it was subjected to a controlled carrot PME treatment, thereby producing de-esterified pectin. Both pectins were subsequently treated with a mixture of endo-arabinanase and α-L-arabinofuranosidase. The partial debranching of pectin resulted in a reduction of the Ara content by approximately 50%. Gels produced from semi-dilute solutions of the partially debranched pectins showed development profiles similar to those of the corresponding non-debranched polymers. Yet, the former gels showed lower gel stiffness, poorer gel elastic character and a weaker nature as compared to the latter. These observations suggest that, next to Ca2+ cross-links, the presence of long Ara-containing side chains plays an important role in the rheological characteristics of Ca2+-pectin gels.In practice, partially demethylesterified pectins reveal PMs resulting from both controlled and uncontrolled de-esterification reactions. In the last part of this study, an attempt was made to assess the effect of such mixed PMs on the rheological characteristics of Ca2+-pectin gels, using polygalacturonic acid (poly-D-GalA) as a model for debranched pectin. First, an uncontrolled PM was induced through partial chemical methylesterification. Subsequently, controlled de-esterification (through chemical saponification, fungal PME or plant PME) was imposed on the resulting polymer to yield partially methylesterified poly-D-GalAs (referred to as mPGAs) of various DM and mixed PM. The final PMs of the mPGAs depended not only on the extent and method of the de-esterification process but also on the PM resulting from the initial uncontrolled methylesterification. The same held true for the rheological characteristics of the derived gels. The experimental results also indicate that extremely short non-cooperative junction zones can contribute to the stiffness of Ca2+-mPGA gels.In conclusion, besides Ca2+ concentration, the structural features of both homogalacturonan and rhamnogalacturonan I are responsible for the rheological characteristics of Ca2+-pectin gels. In addition, all modification processes of pectins homogalacturonan are suggested to crucially define the rheological properties of Ca2+-pectin gels. Insights gained from the structure function relations of pectin will enable to explore potential applications of Ca2+-highly methylesterified pectin systems and broaden the use of low-methylesterified pectins. However, the determination of the exact size and number of the junction zones that characterise pectin gels remains a challenge." "Fine-tuning the properties of pectin calcium gels by control of pectin fine structure, gel composition and environmental conditions" "Ilse Fraeye, Thomas Duvetter, Eugenie Doungla Ngouemazong, Ann Van Loey, Marc Hendrickx" "Pectin is abundantly used in the food industry. In jams and jellies, confectionary products and bakery fillings, it is applied as a gelling agent. The characteristics of the final gel depend on many factors, especially the food system composition (e.g. pectin concentration, pH, soluble solids) and the chemical fine structure of pectin. Detailed insight into how these variables affect gel properties allows fine-tuning of gel characteristics in order to meet the functionality required for each individual food application. This review focuses specifically on pectin-calcium gels." "Recombinant kiwi pectin methylesterase inhibitor: Purification and characterization of the interaction with plant pectin methylesterase during thermal and high-pressure processing" "Avi Shpigelman, Tina Verrijssen, Clare Kyomugasho, Ann Van Loey, Chris Michiels, Marc Hendrickx" "Recombinant kiwi pectin methylesterase inhibitor (rPMEI) with a six-histidine tag at the C-terminus was successfully expressed in Pichia pastoris GS115 strains. rPMEI was purified using pectin methylesterase (PME)-CNBr-affinity chromatography or nickel affinity chromatography. The purified rPMEI had a slightly higher molecular weight than the kiwi PMEI probably due to the presence of added six histidines and some glycosylation. The expression in P. pastoris did not result in changes in the inhibitory activity of rPMEI, nor did it significantly change the complexation with PME under thermal and high pressure processing conditions compared to kiwi PMEI. While thermal treatment of an equimolar PME–rPMEI complex resulted in the aggregation of PME and rPMEI as an entity, high-pressure processing led to the dissociation of PME–rPMEI complex resulting in the presence of free rPMEI after processing. The obtained results presented a viable option for utilization of recombinant PMEI for control of PME activity.The discovery of a pectin methylesterase inhibitor (PMEI) in kiwi fruit opened an additional way to control PME activity, although the industrial application is inhibited by the low yield obtainable from kiwi. For a possible utilization of PMEI in large scale production, recombinant PMEI (rPMEI) was modified with an additional six-histidine tag, expressed and studied. Our results showed that the expression of rPMEI with the additional six-histidine tag allows a feasible large scale purification of the inhibitor using nickel affinity chromatography without negatively affecting the inhibitory activity nor significantly changing the complexation with PME compared to kiwi PMEI. Thus the combination of rPMEI with high-pressure treatment can be exploited to process food systems where cloud stability is of importance but the high pressure itself is insufficient to completely inhibit the PME." "Recombinant kiwi pectin methylesterase inhibitor: Purification and characterization of the interaction with plant pectin methylesterase during thermal and high-pressure processing" "Xiaohong Mei, Avi Shpigelman, Tina Verrijssen, Clare Kyomugasho, Yunbo Luo, Ann Van Loey, Chris Michiels, Kunlun Huang, Marc Hendrickx"