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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    Green Compressed Fluid Technologies To Extract Antioxidants and Lipids from Galdieria phlegrea in a Biorefinery Approach
    Imbimbo, Paola ; Bueno, Monica ; Elia, Luigi D'; Pollio, Antonino ; Ibañez, Elena ; Olivieri, Giuseppe ; Monti, Daria Maria - \ 2020
    ACS sustainable chemistry & engineering 8 (2020)7. - ISSN 2168-0485 - p. 2939 - 2947.
    biorefinery - carotenoids - compressed fluid technologies - Galdieria phlegrea - lipids - microalgae - phycocyanin

    A green cascade approach was used to recover phycocyanins, carotenoids and lipids from Galdiera phlegrea. Phycocyanin extraction was performed by high pressure homogenization and purified by ultrafiltration, whereas carotenoids were obtained by a pressurized liquid extraction and lipids by supercritical fluid extraction. The second step of this innovative, green, and cost-effective procedure is able to improve the recovery of zeaxanthin and β-carotene up to 40%, without affecting the quality of compounds and avoiding the use of organic solvents and the drying processes. The isolated carotenoids were active as antioxidants, as clearly shown by their protective activity on a cell-based model. The lipid yield was increased by 12% with respect to conventional methods.

    Application of Volatile Organic Compound Analysis in a Nutritional Intervention Study: Differential Responses during Five Hours Following Consumption of a High- and a Low-Fat Dairy Drink
    Hageman, Jeske H.J. ; Nieuwenhuizen, Arie G. ; Ruth, Saskia M. van; Hageman, Jos A. ; Keijer, Jaap - \ 2019
    Molecular Nutrition & Food Research 63 (2019)20. - ISSN 1613-4125
    breath analysis - breathomics - inter- and intraindividual variation - lipids - volatile organic compounds (VOCs)

    Scope: Exhaled volatile organic compounds (VOCs) are a possible relevant target for noninvasive assessment of metabolic responses. Using a breathomics approach, it is aimed to explore whether lipid intake influences VOC profiles in exhaled air, and to obtain insight in intra- and interindividual variations. Methods and results: Three human interventions are performed. In the first, 12 males consume a high-fat drink on three study days. In the second, 12 males receive a high- and a low-fat drink on 6 days. In the third, three volunteers consume the high-fat drink again for tentative compound identification. Participants are asked to exhale, for 5 h postprandial with 15–20 min intervals, into a proton-transfer-reaction mass spectrometer, and VOCs in exhaled air are measured. Consumption of a drink alters the VOC profile, with considerable interindividual variation and quantitative intraindividual differences between days. Consumption of two different drinks results in a distinct VOC profile, caused by several specific m/z values. Most of these compounds are identified as being related to ketone body formation and lipid oxidation, showing an increase in high- versus low-fat drink. Conclusion: Exhaled VOCs have the potential to assess differences in metabolic responses induced by nutrition, especially when day-to-day variation can be minimized.

    Human Milk Short-Chain Fatty Acid Composition is Associated with Adiposity Outcomes in Infants
    Prentice, Philippa M. ; Schoemaker, Marieke H. ; Vervoort, Jacques ; Hettinga, Kasper ; Lambers, Tim T. ; Tol, Eric A.F. van; Acerini, Carlo L. ; Olga, Laurentya ; Petry, Clive J. ; Hughes, Ieuan A. ; Koulman, Albert ; Ong, Ken K. ; Dunger, David B. - \ 2019
    The Journal of Nutrition 149 (2019)5. - ISSN 0022-3166 - p. 716 - 722.
    breast milk - growth - lipids - nutrition - short chain fatty acids - weight

    BACKGROUND: Presumed benefits of human milk (HM) in avoiding rapid infancy weight gain and later obesity could relate to its nutrient composition. However, data on breast milk composition and its relation with growth are sparse. OBJECTIVE: We investigated whether short-chain fatty acids (SCFAs), known to be present in HM and linked to energy metabolism, are associated with infancy anthropometrics. METHODS: In a prospective birth cohort, HM hindmilk samples were collected from 619 lactating mothers at 4-8 wk postnatally [median (IQR) age: 33.9 (31.3-36.5) y, body mass index (BMI) (kg/m2): 22.8 (20.9-25.2)]. Their offspring, born at 40.1 (39.1-41.0) wk gestation with weight 3.56 (3.22-3.87) kg and 51% male, were assessed with measurement of weight, length, and skinfold thickness at ages 3, 12, and 24 mo, and transformed to age- and sex-adjusted z scores. HM SCFAs were measured by 1H-nuclear magnetic resonance spectroscopy (NMR) and GC-MS. Multivariable linear regression models were conducted to analyze the relations between NMR HM SCFAs and infancy growth parameters with adjustment for potential confounders. RESULTS: NMR peaks for HM butyrate, acetate, and formic acid, but not propionate, were detected. Butyrate peaks were 17.8% higher in HM from exclusively breastfeeding mothers than mixed-feeding mothers (P = 0.003). HM butyrate peak values were negatively associated with changes in infant weight (standardized B = -0.10, P = 0.019) and BMI (B = -0.10, P = 0.018) between 3 and 12 mo, and negatively associated with BMI (B = -0.10, P = 0.018) and mean skinfold thickness (B = -0.10, P = 0.049) at age 12 mo. HM formic acid peak values showed a consistent negative association with infant BMI at all time points (B < = -0.10, P < = 0.014), whereas HM acetate was negatively associated with skinfold thickness at 3 mo (B = -0.10, P = 0.028) and 24 mo (B = -0.10, P = 0.036). CONCLUSIONS: These results suggest that HM SCFAs play a beneficial role in weight gain and adiposity during infancy. Further knowledge of HM SCFA function may inform future strategies to support healthy growth.

    Photosynthetic efficiency in microalgal lipid production
    Remmers, Ilse M. - \ 2017
    Wageningen University. Promotor(en): R.H. Wijffels, co-promotor(en): P.P. Lamers. - Wageningen : Wageningen University - ISBN 9789463434607 - 200
    algae - biofuels - light - triacylglycerols - lipids - metabolism - algae culture - cultural methods - algen - biobrandstoffen - licht - triacylglycerolen - lipiden - metabolisme - algenteelt - cultuurmethoden

    Microalgae can contain large amounts of lipids which make them a promising feedstock for sustainable production of food, feed, fuels and chemicals. Various studies, including pilot-scale, have been performed and the knowledge on microalgal processes has advanced quickly. Unfortunately, current production costs for cultivation are still too high for bulk lipid production from microalgae.

    One of the major causes for the high costs of bulk lipid production is the reduced solar-to-lipid conversion efficiency. Current research, however, does not provide sufficient insight to identify optimization targets. Therefore, in this thesis we have studied the lipid production in microalgae in depth.

    Different TAG-accumulation strategies were investigated from a process engineering and metabolic point of view. The combination of all findings were used in the general discussion to thoroughly evaluate the microalgal lipid accumulation strategies. Current phototrophic microalgal lipid yields are still 10 times lower than the theoretical maximum. There is, however, still an enormous potential for further improvements. Future research should focus on (genetically) improved strains and advanced cultivation strategies, including adaptation to fluctuating outdoor weather conditions.

    This thesis was performed within the EU FP7 FUEL4ME project under grand agreement No 308938. Objective of this program is to develop a sustainable and scalable process for biofuels from microalgae and to valorize the by-products.

    In vivo 1H NMR methods to study dynamics of chloroplast water and thylakoid membrane lipids in leaves and in photosynthetic microorganisms
    Pagadala, Shanthi - \ 2017
    Wageningen University. Promotor(en): H. van Amerongen, co-promotor(en): H. van As. - Wageningen : Wageningen University - ISBN 9789463431569 - 130
    cell membranes - membranes - chloroplasts - thylakoids - photosynthesis - in vivo experimentation - stress conditions - stress - proteins - lipids - mobility - dynamics - celmembranen - membranen - chloroplasten - thylakoïden - fotosynthese - in vivo experimenten - stress omstandigheden - stress - eiwitten - lipiden - mobiliteit - dynamica

    Dynamics of thylakoid membranes and mobility of pigment-protein complexes therein are essential for survival of photosynthetic organisms under changing environmental conditions. The published approaches to probe mobility of the thylakoid membrane lipids and protein complexes are either dependent on the use of external labels or are used only for in vitro studies. Here, we present non-invasive 1H NMR methods (DOSY and DRCOSY) to study dynamics of water in chloroplasts, lipids in oil bodies and in thylakoid membranes and pigment-protein complexes under complete in vivo conditions in leaf disks of F. benjamina and A. platanoides and in suspensions of the green alga Chlamydomonas reinhardtii and blue-green alga Synechocystissp.PCC 6803.

    In leaf disks of Ficus benjamina and Acer platanoides, water in chloroplasts could be clearly discriminated from other pools. Both water in chloroplasts, and water in vacuoles of palisade and spongy cells showed resonances in the high field part of the spectra (with respect to pure water), in contrast to what has been reported in literature. Subepidermal cells (present only in F. benjamina but not in A. platanoides) may act as a water storage, buffer pool during drought. This pool prevented the fast loss of water from the chloroplasts. Nutrient stress and excess salt stress resulted in accumulated lipid bodies and in striking differences in the dynamics and spectra/composition of the different components. T2 values of the different components are compared with those observed in suspensions of Synechocystissp.PCC 6803. The differences in membrane composition (ratio of the different membrane lipids) were clearly observed in the DANS of the oil bodies and the (thylakoid) membranes, but the diffusion coefficients were quite comparable. Also the DANS of the component that is assigned to the pigment-protein complexes are quite different, reflecting the differed composition. The diffusion coefficients of this component in isolated spinach thylakoids and in C. reinhardtii are very comparable, but about a factor of 10 lower with respect to that of Synechocystis at short diffusion times. The dynamics of these complexes in these systems are thus quite different.

    The fatter the better : selecting microalgae cells for outdoor lipid production
    Dominguez Teles, I. - \ 2016
    Wageningen University. Promotor(en): Rene Wijffels, co-promotor(en): Maria Barbosa; Dorinde Kleinegris. - Wageningen : Wageningen University - ISBN 9789462578821 - 164
    algae - chlorococcum - lipids - lipogenesis - fat - production - phenotypes - inoculum - diameter - cells - sorting - algen - chlorococcum - lipiden - lipogenese - vet - productie - fenotypen - entstof - diameter - cellen - sorteren

    In chapter 1 we introduce microalgae, photosynthetic microorganisms with potential to replace commodities (such as food, feed, chemicals and fuels). Production costs are still high, reason why microalgae are still only economically feasible for niche markets. We suggest to borrow the concept of plant domestication to select industrial microalgae cells. Two approaches can be successfully used to domesticate microalgae: adaptive laboratory evolution (ALE) and fluorescence assisted cell sorting (FACS). ALE takes advantage of the natural adaptability of microorganisms to different environments, while FACS actually select cells with specific phenotypes. This thesis aimed to select cells of Chlorococcum littorale with improved phenotypes, assuming that these cells could establish new populations with increased industrial performance.

    In Chapter 2 we wanted to know what happened during time to biomass and lipid productivities of Chlorococcum littorale repeatedly subjected to N-starvation. We tested 2 different cycles of N-starvation, short (6 days) and long (12 days). Short cycles didn’t affect lipid productivity, highlighting the potential of C. littorale to be produced in semi-continuous cultivation. Repeated cycles of N-starvation could have caused adaptations of the strain. Hence, we also discussed the implications of using repeated N-starvation for adaptive laboratory evolution (ALE) experiments. Chapter 3 introduces a method to detect and to select microalgae cells with increased lipid content. The method requires only the fluorescence dye Bodipy505/515 dissolved in ethanol, and the method was designed to maintain cellular viability so the cells could be used to produce new inoculum. In chapter 4 we evaluated a question that emerged while deciding which criteria to use to sort lipid-rich cells: does cellular size affects lipid productivity of C. littorale? We hypothesized that cells with different diameters have different division rates, which could affect lipid productivity. Therefore, we assessed the influence of cell diameter, as a sorting parameter, on both biomass and lipid productivity of Chlorococcum littorale (comparing populations before and after sorting, based on different diameters). Results showed that the size of vegetative cells doesn’t affect the lipid productivity of C. littorale. In chapter 5 we present a strategy to sort cells of C. littorale with increased TAG productivity using the method developed at chapter 3. Both the original and the sorted population with the highest lipid productivity (namely, S5) were compared under simulated Dutch summer conditions. The results confirmed our data from experiments done under continuous light: S5 showed a double TAG productivity. Our results showed also that the selected phenotype was stable (1.5 year after sorting) and with potential to be used under industrial conditions. In chapter 6 we extrapolated our results (indoor and outdoor) to other climate conditions. We ran simulations changing the light conditions to four different locations worldwide (the Netherlands, Norway, Brazil and Spain) to estimate both biomass and TAG productivities. Results indicated that biomass yields were reduced at locations with higher light intensities (Brazil/Spain) when compared with locations with lower light intensities (Norway/Netherlands). Hence, the choice of location should not be based on light intensity, but on how stable irradiation is. Chapter 7 is the general discussion of the thesis, demonstrating that both ALE and FACS are effective approaches to select industrial microalgae cells. We also present our view on how ALE and FACS could further improve microalgae strains for industry.

    Lipid bilayer stability in relation to oxide nanoparticles
    Pera, H. - \ 2015
    Wageningen University. Promotor(en): Frans Leermakers, co-promotor(en): Mieke Kleijn. - Wageningen : Wageningen University - ISBN 9789462574670 - 144
    lipids - membranes - stability - nanotechnology - particles - analytical methods - models - modeling - lipiden - membranen - stabiliteit - nanotechnologie - deeltjes - analytische methoden - modellen - modelleren
    Lipid bilayer stability in relation to oxide nanoparticles

    All living organisms are composed of cells that are filled with a thick molecular soup. These molecules constitute a complex machinery that brings these cells to life. To contain these molecules, and to protect them from the hostile outer environment, a phospholipid bilayer envelopes the cell. It is essential that this lipid bilayer, also known as the cell membrane, should remain intact and form a perfect barrier at all times. Industrially manufactured nanoparticles are suspect to be able to penetrate this barrier, and thus endanger living organisms in the environment. This thesis deals with some aspects of the structural integrity of lipid bilayers, and especially how this integrity is affected by the interaction with nanoparticles.

    Experiments were performed with silica and titanium dioxide nanoparticles, interacting with lipid bilayers, using a variety of experimental techniques. In addition, a theoretical model was applied that is based on the Scheutjens-Fleer Self Consistent Field (SCF) theory. This model delivered detailed structural and thermodynamic information about the lipid bilayer. The modelling work helped us to improve our understanding of lipid bilayer stability, and showed the effect of the interaction with the nanoparticles on the phospholipid bilayer. These latter results could be related directly to our experiments.

    Let us first experimentally regard the interaction of lipid bilayers with synthetic oxide nanoparticles. We developed a protocol for high-throughput screening of the nanoparticle-bilayer interaction using a fluorescence technique. Results from this method were combined with reflectometry measurements and atomic force microscopy (AFM). The combination of these methods allowed us to relate lipid bilayer integrity to its interaction with nanoparticles and their adsorption onto the bilayer. In addition, the AFM results yielded detailed structural information at the nano-scale. We found that the interaction strongly depends on both lipid bilayer and nanoparticle charge. However, the specific interaction that depends on the nanoparticle type, starts to play a role when the charges are low. When the total interaction strength is regarded, a regime was found at which interaction is strong enough for the nanoparticles to adsorb onto the bilayer, but too weak to disrupt the bilayer. If, however, the bilayer is disrupted by the nanoparticles, the particle may steal away some lipid molecules from the bilayer, and leave again to disrupt the bilayer elsewhere.

    Let us now go into more detail on the SCF modelling. Bilayers are composed of phospholipids, which consist of a hydrophilic head group, and a hydrophobic tail. These bilayers were modelled using a single lipid molecule type, of which the head group structure and lipid tail length could be varied. We thus obtained bilayers that varied in their thickness, and the space that a single lipid takes within the bilayer. Changes in bilayer composition affect the bilayer mechanical properties, such as those constants that describe bilayer stretching or bending. This thesis shows how vesicles, which are bilayers in a globular shape, may become unstable if the bilayer lipid composition is changed. Under certain conditions, a vesicle would prefer to fall apart into many smaller vesicles, which is when highly charged head groups start to repel each other. Or the bilayer may form continuous cubic phases, which might occur if lipids with uncharged head groups but with very long tails are used to form the bilayer. Under very specific and finely tuned conditions, a lipid bilayer may become unstable to form stable pores in the membrane, or to fall apart into tiny lipid discs.

    Effect of dietary protein on lipid and glucose metabolism: implications for metabolic health
    Rietman, A. - \ 2015
    Wageningen University. Promotor(en): Frans Kok; D. Tomé, co-promotor(en): Marco Mensink. - Wageningen : Wageningen University - ISBN 9789462573482 - 160
    voeding en gezondheid - stofwisselingsstoornissen - eiwitinname - dieet - metabolisme - lipiden - glucose - macronutriënten - nutrition and health - metabolic disorders - protein intake - diet - metabolism - lipids - glucose - macronutrients


    Background: Diet is an important factor in the development of the Metabolic Syndrome (Mets) and type 2 Diabetes Mellitus. Accumulation of intra hepatic lipid (IHL) can result in non-alcoholic fatty liver disease (NAFLD), which is sometimes considered the hepatic manifestation of Mets. Manipulation of the dietary macronutrient composition – altering either fat or simple carbohydrates – has the potential to change lipid storage in the liver. Protein also has this ability, however human data is scarce. Moreover, high dietary protein intake is linked with an increased type 2 Diabetes risk. Therefore, it is essential to study the metabolic consequences of changes in macronutrient composition focussing on altering dietary protein quantity.

    Objective: In this thesis the effects of dietary protein on metabolic health focusing on lipid and glucose metabolism were investigated in both observational studies as well as in a human dietary intervention trial.

    Methods: In an observational study (n=1283), Fatty Liver Index (FLI) was calculated and related to macronutrient consumption from dietary assessment data. In a controlled dietary intervention, participants (n=27) were assigned to either a control-diet for 4 weeks, or a high-fat, hypercaloric diet, with either a high-protein or a normal-protein content for two weeks, and vice versa. Measurements of IHL (1H-MRS) and blood plasma glucose and lipid concentrations were performed, both in the fasting state and following a meal.

    Results: In the observational study, the prevalence of fatty liver as indicated by an FLI>60, was 22.0%. Compared to persons with a normal FLI score of <30, protein intake was positively related with high FLI score >60 (OR: 1.26 per 1 en%, 95%CI 1.16-1.37). This was in particular the case for protein intake from animal sources. In the dietary intervention study, the high-protein diet compared to the normal-protein diet resulted in lower IHL and plasma TG concentrations (IHL: 0.35 ± 0.04 % vs. 0.51 ± 0.08 %; p=0.08; TG: 0.65 ± 0.03 vs. 0.77 ± 0.05 mmol/L; p=0.07). Furthermore, after the meal challenge the free fatty acids (FFA) response was significant different between all three intervention diets (p=0.03). Moreover, the postprandial glucose response was significantly lower after adaptation to NP compared with HP (p=0.03), without differences in the postprandial insulin responses (p=0.37).

    Conclusions: From data of the intervention study and observational studies reported in this thesis, it can be concluded that dietary protein intake is associated with alterations in metabolic profile, with both favourable and potential unfavorable health outcomes. On the short term increasing dietary protein in healthy subjects improved lipid metabolism, as seen by lower TG and IHL levels, but not glucose metabolism. On the long term, however, a high-protein intake was related to a fatty liver, and associated to insulin resistance.

    Pre- and post-treatment enhance the protein enrichment from milling and air classification of legumes
    Pelgrom, P.J.M. ; Wang, J. ; Boom, R.M. ; Schutyser, M.A.I. - \ 2015
    Journal of Food Engineering 155 (2015). - ISSN 0260-8774 - p. 53 - 61.
    seed moisture-content - product characteristics - flour - pea - separation - fractions - starch - extraction - storage - lipids
    Air classification is a milder and more sustainable method to obtain protein-enriched fractions than commonly used wet fractionation. The protein content of air-classified fractions is generally lower than obtained with wet methods, therefore we applied pre- and post-treatments to increase the protein purity. A starch-rich legume, pea, and an oil-rich legume, lupine, were pre-treated by varying the moisture content, defatting, soaking or freezing cycles. Higher moisture contents and defatting of lupine increased the protein purity, but lower moisture contents increased the protein yield. Soaking and freezing cycles lowered the particle density, which impaired the separation. Electrostatic separation is based on electrostatic charging behaviour and was successfully applied to enrich air-classified fractions by separating protein and fibre into oppositely charged fractions. The results showed that pre- and post-treatments yielded protein fractions that are significantly purer than those obtained in single-step milling and air classification.
    Lipoxygenase : a game-changing enzyme
    Heshof, R. - \ 2015
    Wageningen University. Promotor(en): Willem de Vos; Vitor Martins dos Santos, co-promotor(en): Leo de Graaff. - Wageningen : Wageningen University - ISBN 9789462571761 - 160
    lipoxygenase - aminozuursequenties - lipiden - schimmels - bio-informatica - kaliumjodide - industriële toepassingen - biobased economy - lipoxygenase - amino acid sequences - lipids - fungi - bioinformatics - potassium iodide - industrial applications - biobased economy

    Many challenges lie ahead in using LOXs as tools in industrial oleochemistry. One of these challenges is the supply of PUFAs. Although we are moving towards a biobased economy where second and third generation biomass is taking a leading role, it is still faster and cheaper to use first generation biomass. Industrialization of microbial oils is a good alternative to supply the demand of PUFAs. Another challenge is the production of heterologous LOX in sufficient quantities. Since the last decade this problem is being tackled and more research is being done in heterologous expression of LOXs. The LOX with the highest potential so far is the secreted Pseudomonas aeruginosa LOX produced in Escherichia coli. During this thesis research different lox genes were tried for heterologous production of LOX using different Aspergillus niger and Aspergillus nidulans strains as expression hosts. These LOXs were identified as discussed in Chapter 3 and Chapter 6. Unfortunately, heterologous production in sufficient quantities was unsuccessful using these expression hosts as discussed in Chapter 5 and Chapter 6. Since production of Gaeumannomyces graminis LOX was successful in Trichoderma reesei, as discussed in Chapter 4, the production of polymers used for bioplastics could be demonstrated in this ERA-NOEL project anyway. Therefore this thesis shifted its focus on resolving the question of the difficulties in the heterologous expression of LOX in different Aspergillus species. Chapter 5 is the result of a systematic approach to analyze different aspects of G. graminis LOX expression in A. nidulans. Chapter 2 shows that heterologous expression of extracellular fungal LOX can be performed using T. reesei and Pichia pastoris as production hosts, and E. coli can be used for the production of intracellular LOXs of plant, mammal, bacterial, and fungal origin. As shown in Chapter 2, E. coli is not very efficient in the production of heterologous LOX due to the formation of inclusion bodies and low induction temperature necessary for production. The use of Aspergillus oryzae can be exploited further in the heterologous production of LOXs. Due to the choice of using A. niger and A. nidulans as expression hosts, this expression host was not exploited for its potential. The last challenge is to synthetically engineer LOX to broaden its use in industry. In this way more building blocks for chemicals can be synthetically produced and more products based on LOX origin can be made. Therefore, LOX can be a world-wide game-changing enzyme in a biobased economy as its use can decrease the demand for petroleum-based products.

    Seasonal Variation of Fatty Acids and Stable Carbon Isotopes in Sponges as Indicators for Nutrition: Biomarkers in Sponges Identified
    Koopmans, M. ; Rijswijk, P. van; Boschker, H.T.S. ; Houtekamer, M. ; Martens, D.E. ; Wijffels, R.H. - \ 2015
    Marine Biotechnology 17 (2015)1. - ISSN 1436-2228 - p. 43 - 54.
    marine organisms - halichondria-panicea - lipids - sea - demospongiae - community - bacteria
    To get a better understanding of sponge feeding biology and efficiencies, the fatty acid (FA) composition and 13C natural abundance of sponges and of suspended particulate matter (SPM) from surrounding seawater was studied in different seasons at three locations. Haliclona oculata and Haliclona xena from the Oosterschelde, the Netherlands, Halichondria panicea and H. xena from Lake Veere, the Netherlands, and Aplysina aerophoba and Dysidea avara from the Mediterranean, Spain, were studied. Several FA biomarkers for different algal groups, bacteria and sponge biomass were identified in all sponges. The FA concentration variation in sponges was related to changes in fatty acid concentration in SPM. Stable carbon isotopic ratios (d13C) in sponge specific FAs showed very limited seasonal variation at all sites. Algal FAs in sponges were mainly acquired from the SPM through active filtration in all seasons. At the two sites in the Netherlands only in May (spring), the sponge specific FAs had similar d13C ratios as algal FAs, suggesting that sponges were mainly growing during spring and probably summer. During autumn and winter, they were still actively filtering, but the food collected during this period had little effect on sponge d13C values suggesting limited incorporation of filtered material into the sponge body. The sponge A. aerophoba relied mostly on the symbiotic bacteria. In conclusion, fatty acid composition in combination with stable carbon isotope analysis can be used to analyze the food source of sponges.
    Colorectal cancer risk and dyslipidemia: a case-cohort study nested in an Italian multicentre cohort
    Agnoli, C. ; Grioni, S. ; Sieri, S. ; Sacerdote, C. ; Vineis, P. ; Tumino, R. ; Giurdanella, M.C. ; Pala, V. ; Mattiello, A. ; Chiodini, P. ; Iacoviello, L. ; Curtis, A. de; Cattaneo, L. ; Duijnhoven, F.J.B. van - \ 2014
    Cancer Epidemiology 38 (2014)2. - ISSN 1877-7821 - p. 144 - 151.
    metabolic syndrome - serum-cholesterol - colon-cancer - lipoprotein levels - blood-cholesterol - glucose - triglyceride - association - nutrition - lipids
    Background: Dyslipidemia is an established risk factor for many diseases, but its effect on colorectal cancer risk is less clear. We investigated the association of colorectal cancer risk with plasma triglycerides, total, HDL, and LDL cholesterol in four Italian EPIC centers. Methods: We conducted a case-cohort study on participants recruited to four Italian EPIC centers (Turin, Varese, Naples, and Ragusa; 34,148 subjects). A random subcohort of 850 subjects was obtained and 286 colorectal cancer cases were diagnosed. Triglycerides, total and HDL cholesterol were determined in plasma samples obtained at baseline and stored at -196 degrees C; LDL cholesterol was calculated. Hazard ratios (HR) with 95% confidence intervals (CI), adjusted for potential confounders, were estimated by Cox regression models using the Prentice method. Results: The highest tertiles of total (HR 1.66, 95% CI 1.12-2.45) and LDL cholesterol (HR 1.87, 95% CI 1.27-2.76) were associated with increased colorectal cancer risk compared to lowest tertiles. Risks were greater for men than women, and for postmenopausal than premenopausal women. Highest tertiles of total and LDL cholesterol were also significantly associated with increased risks of colon cancer, distal colon cancer, and rectal cancer, but not proximal colon cancer. Conclusions: Our findings suggest that high levels of total and LDL cholesterol increase colorectal cancer risk, particularly in men and postmenopausal women. However additional studies are needed to clarify the role of plasma lipids in these cancers, particularly in view of the conflicting findings of previous studies. (C) 2014 Elsevier Ltd. All rights reserved.
    Long-term acclimation of anaerobic sludges for high-rate methanogenesis from LCFA
    Silva, S.A. ; Cavaleiro, A.J. ; Pereira, M.A. ; Stams, A.J.M. ; Alves, M.M. ; Sousa, D.Z. - \ 2014
    Biomass and Bioenergy 67 (2014). - ISSN 0961-9534 - p. 297 - 303.
    chain fatty-acids - oleic-acid - oxidizing bacteria - methane production - waste-water - digestion - lipids - quantification - hybridization - accumulation
    Inhibition of methanogens by long chain fatty acids (LCFA) and the low numbers of LCFA-degrading bacteria are limitations to exploit biogas production from fat-rich wastewaters. Generally reactors fail due to excessive LCFA accumulation onto the sludge. Here, long-term acclimation and bioaugmentation with a LCFA-degrading coculture were hypothesized as strategies to enhance methanogenic conversion of these compounds. Anaerobic sludges previously exposed to LCFA for more than 100 days converted a specific biomass-associated substrate of (3.2 ± 0.1) kg·kg-1 with very short lag phases (
    Response to Hoenselaar from Pedersen et al.: The importance of reducing SFA intake to limit CHD risk
    Pedersen, J.I. ; Norum, K.R. ; James, P.T. ; Brouwer, I.A. ; Katan, M.B. ; Clarke, R. ; Elmadfa, I. ; Kris-Etherton, P.M. ; Kromhout, D. ; Margetts, B.M. ; Mensink, R.P. ; Rayner, M. ; Uusitupa, M. - \ 2012
    The British journal of nutrition 107 (2012)3. - ISSN 0007-1145 - p. 452 - 454.
    cardiovascular-disease - cholesterol - metaanalysis - association - lipids - heart - fat
    Continuous TAG production by the green microalga Neochloris oleoabundans under nitrogen limited conditions
    Klok, Anne - \ 2012
    algae - lipids - productivity - triacylglycerols - biofuels - biobased economy
    The effect of conjugated linoneic acid, a natural trans fat from milk and meat, on human blood pressure: results from a randomized crossover feeding study
    Engberink, M.F. ; Geleijnse, J.M. ; Wanders, A.J. ; Brouwer, I.A. - \ 2012
    Journal of Human Hypertension 26 (2012). - ISSN 0950-9240 - p. 127 - 132.
    body-composition - vaccenic acid - hypertension - rats - esters - lipids - men
    Cis-9, trans-11 conjugated linoleic acid (CLA) is a natural trans fatty acid that is largely restricted to ruminant fats and consumed in foods and supplements. Its role in blood pressure (BP) regulation is still unclear. We examined the effect of cis-9, trans-11 CLA on BP compared with oleic acid. A total of 61 healthy volunteers were sequentially fed each of 3 diets for 3 weeks, in random order, for a total of 9 weeks. The diets were identical except for 7% of energy (18.9¿g in a diet of 10¿MJ¿day–1) that was provided either by oleic acid, by industrial trans fatty acids or by cis-9, trans-11 CLA. We measured BP on two separate days at the end of each intervention period. At baseline, mean BP was 113.8±14.4¿mm¿Hg systolic and 66.3±9.6¿mm¿Hg diastolic. The effect of the CLA diet compared with the oleic acid diet was 0.11¿mm¿Hg (95% confidence interval: -1.27, 1.49) systolic and -0.45¿mm¿Hg (-1.63, 0.73) diastolic. After the industrial trans fatty acid diet, the effect was 1.13¿mm¿Hg (-0.25, 2.51) systolic and -0.44¿mm¿Hg (-1.62, 0.73) diastolic compared with the oleic acid diet. Our study suggests that short-term high intakes of cis-9,trans-11 CLA do not affect BP in healthy volunteers
    Production of fungal lipids : kinetic modeling and process design
    Meeuwse, P. - \ 2011
    Wageningen University. Promotor(en): Hans Tramper, co-promotor(en): Arjen Rinzema. - [S.l.] : S.n. - ISBN 9789461730930 - 239
    mortierella - lipiden - bioproceskunde - afvalhergebruik - biodiesel - mortierella - lipids - bioprocess engineering - waste utilization - biodiesel

    Finding alternatives for fossil fuels is currently urgent. One of the new processes in this field is the production of biodiesel from lipids accumulated by microorganisms. Some yeasts and fungi accumulate lipids when a component needed for growth, usually the N-source, is limiting while the C-source is in excess. These oleaginous yeasts and fungi were previously mainly used for unsaturated fatty acid production, but now also come into view for production of lipids as a source of biodiesel.

    This thesis takes the first steps in the development of a new process to produce lipids with an oleaginous fungus in solid-state fermentation on agro-industrial waste. Solid-state fermentation is the cultivation on solid substrate particles without (free) flowing water, and has several advantages over submerged fermentation such as less waste water production, less energy use for oxygen transfer and lower production costs. In this thesis, we focused on growth and lipid production kinetics in submerged as well as solid-state fermentation. The models developed for these systems provide insight in the lipid production mechanism, needed to develop the new process based on solid-state fermentation.

    The thesis starts with the selection of a model strain (Chapter 2). With this strain, the kinetics of growth and lipid accumulation were studied and modeled. We started with a steady-state model (Chapter 3 and 4) in submerged chemostat culture, and extended this to a dynamic model for submerged batch culture (Chapter 5). As the next step towards solid-state fermentation, we developed a model for growth and lipid accumulation on κ-carrageenan plates with monomers (Chapter 6). These three models were finally used to calculate potential lipid yield and energy use in a biodiesel production system (Chapter 7).

    For the system we want to develop, we need a fungus that can utilize different substrates and can produce lipids. For this purpose, we tested two oleaginous fungi: Mortierella alpina and Umbelopsis isabellina, which is described in Chapter 2. We cultivated both fungi on agar plates containing glucose, xylose, starch, cellulose or pectin, and on sugar beet pulp in a packed bed. M. alpina did not utilize xylose, cellulose and pectin, utilized starch much slower than glucose and only consumed approximately 40% of the sugar beet pulp in 20 days. This shows that M. alpina is not a suitable organism for our production system. U. isabellina utilized pectin and xylose with the same rate as glucose, but used starch slower and (crystalline) cellulose not at all. It consumed approximately 75% of the sugar beet pulp after 8 days and approximately 100% after 20 days. Also, it accumulated some lipids (3% of remaining dry mass) in the culture on sugar beet pulp; optimization of this process by addition of enzymes increased the lipid content to 9% of remaining dry mass. This shows that U. isabellina is a promising strain for lipid production from agro-industrial waste, and is therefore a good strain to use in our research.

    The lipid concentrations found in SSF culture were quite low; we therefore decided to look in more depth into the kinetics of lipid production in different model systems. The first model system was a submerged chemostat culture, because the substrate supply rates can be varied in this system by varying the dilution rate as well as the concentrations in the feed. Chapter 3 describes the development of a mathematical model that includes growth, lipid accumulation and substrate consumption of oleaginous fungi in submerged chemostat cultures. Key points of the model are: (1) If the C-source supply rate is limited, maintenance has a higher priority than growth, which has a higher priority than lipid production; (2) the maximum specific lipid production rate of the fungus is independent of the actual specific growth rate. This model was validated with chemostat cultures of U. isabellina grown on mineral media with glucose and NH4+. Because of practical problems at low dilution rates, the model could only be validated for D>0.04 h‑1. For further validation, published data sets for chemostat cultures of oleaginous yeasts and a published data set for a poly-hydroxyalkanoate accumulating bacterial species were used, which is described in Chapter 4. All data sets could be described well by the model. Analysis of all data showed that the maximum specific lipid production rate is in most cases very close to the specific production rate of membrane and other functional lipids for cells growing at their maximum specific growth rate. The limiting factor suggested by Ykema et al.(1986, Antonie van Leeuwenhoek 52: 491-506), i.e. the maximum glucose uptake rate, did not give good predictions of the maximum lipid production rate. The model shows that both the C/N-ratio of the feed as well as the dilution rate has a large influence on the lipid production rate. When these data are translated to SSF, it means that a low substrate supply rate can prevent lipid production, even when the C/N-ratio of the substrate is high.

    The next step towards understanding lipid accumulation was a model that also describes changes in time. Therefore, we developed a model for growth, lipid production and lipid turnover in submerged batch fermentation, which is shown in Chapter 5. This model describes three subsequent phases: exponential growth when both a C-source and an N-source are available, carbohydrate and lipid production when the N-source is exhausted, and turnover of accumulated lipids when the C-source is exhausted. The model was validated with submerged batch cultures of U. isabellina with two different initial C/N-ratios. In batch culture, the specific lipid production rate was almost four times higher than in chemostat cultures and it decreased exponentially in time. This indicates that different mechanisms for lipid production are active in batch and chemostat cultures. The model could also describe several data sets from literature very well. Furthermore, the model shows that local limitation of C-source in SSF can cause lipid turnover before the average C-source concentration in the substrate is zero.

    The next step towards an SSF system is the inclusion of diffusion in the batch model. We did this by developing a model that describes growth, lipid production and lipid turnover in a culture on κ-carrageenan plates containing the monomers glucose and alanine as C-source and N-source, respectively. This is described in Chapter 6. The model includes reaction kinetics and diffusion of glucose, alanine and oxygen. It was validated with U. isabellina and describes the different phases of the culture very well: exponential growth, linear growth because of oxygen limitation, accumulation of lipids and carbohydrates after local N-depletion and turnover of lipids after local C-depletion. Extending the model with an unidentified extracellular product improved the fit of the model to the data. The model shows that oxygen limitation is extremely important in solid-state cultures using monomers. Together with the low specific lipid production rate found in SSF, it explains the difference in production rate with submerged cultures.

    In Chapter 7, we used the models from Chapter 3, 5 and 6 together with basic engineering principles to calculate lipid yield and energy use in the modeled systems. We evaluated a process including pretreatment, cultivation and down-stream processing with sugar beet pulp and wheat straw as substrate, described different reactor types, and considered both a yeast and a fungus as microorganisms. According to the models, lipid yields on substrate were between 5% w/w and 19% w/w, depending on the culture system. With the same models, improvement of the yield to 25-30% w/w was shown to be possible, for example by genetic modification of the microorganism. The net energy ratio of the non-optimized systems varied between 0.8 and 2.5 MJ produced per MJ used; energy use for pretreatment and for oxygen transfer were most important. For the optimized systems, the net energy ratio increased to 2.9 – 5.5 MJ produced per MJ used, which can compete very well with other biofuels such as bioethanol or algal biodiesel. So although there is still quite some work to be done, microbial lipids have the potential to be tomorrow’s source of biodiesel.

    Mitofood conference : bioactive food components, energy metabolism and human health, 13-15 April 2011, Wageningen, The Netherlands : celebrating 90 years of human and animal physiology at Wageningen University : final conference of COST Action FA0602: bioactive food components, mitochondrial function and health
    Keijer, J. - \ 2011
    [Wageningen] : Wageningen UR - 87
    voedselsamenstelling - bioactieve verbindingen - voedingsstoffen - energiemetabolisme - gezondheid - polyfenolen - lipiden - vitaminen - hormonen - verouderen - bio-energetica - mitochondria - voeding - food composition - bioactive compounds - nutrients - energy metabolism - health - polyphenols - lipids - vitamins - hormones - aging - bioenergetics - nutrition
    Carbon conversion and metabolic rate in two marine sponges
    Koopmans, M. ; Rijswijk, P. van; Martens, D.E. ; Egorova-Zachernyuk, T.A. ; Middelburg, J.J. ; Wijffels, R.H. - \ 2011
    Marine Biology 158 (2011)1. - ISSN 0025-3162 - p. 9 - 20.
    fatty-acids - stable-isotopes - organic-carbon - demospongiae - growth - lipids - invertebrates - regeneration - biomarkers - porifera
    The carbon metabolism of two marine sponges, Haliclona oculata and Dysidea avara, has been studied using a 13C isotope pulse-chase approach. The sponges were fed 13C-labeled diatoms (Skeletonema costatum) for 8 h and they took up between 75 and 85%. At different times, sponges were sampled for total 13C enrichment, and fatty acid (FA) composition and 13C enrichment. Algal biomarkers present in the sponges were highly labeled after feeding but their labeling levels decreased until none was left 10 days after enrichment. The sponge-specific FAs incorporated 13C label already during the first day and the amount of 13C label inside these FAs kept increasing until 3 weeks after labeling. The algal-derived carbon captured by the sponges during the 8-h feeding period was thus partly respired and partly metabolized during the weeks following. Apparently, sponges are able to capture enough food during short periods to sustain longer-term metabolism. The change of carbon metabolic rate of fatty acid synthesis due to mechanical damage of sponge tissue was studied by feeding sponges with 13C isotope–labeled diatom (Pheaodactylum tricornutum) either after or before damaging and tracing back the 13C content in the damaged and healthy tissue. The filtration and respiration in both sponges responded quickly to damage. The rate of respiration in H. oculata reduced immediately after damage, but returned to its initial level after 6 h. The 13C data revealed that H. oculata has a higher metabolic rate in the tips where growth occurs compared to the rest of the tissue and that the metabolic rate is increased after damage of the tissue. For D. avara, no differences were found between damaged and non-damaged tissue. However, the filtration rate decreased directly after damage.
    Aquatic worms grown on biosolids: Biomass composition and potential applications
    Elissen, H.J.H. ; Mulder, W.J. ; Hendrickx, T.L.G. ; Elbersen, H.W. ; Beelen, M.J.C. ; Temmink, B.G. ; Buisman, C.J.N. - \ 2010
    Bioresource Technology 101 (2010)2. - ISSN 0960-8524 - p. 804 - 811.
    lumbriculus-variegatus oligochaeta - biodiesel production - sewage-sludge - earthworms - bioaccumulation - toxicity - sediment - cadmium - lipids - diet
    The increasing production of biological waste sludge from wastewater treatment plants is a problem, because stricter legislation inhibits the use of traditional disposal methods. The use of the aquatic worm Lumbriculus variegatus can minimise sludge production. Because the worms can feed and grow on this waste sludge, valuable compounds that are present in the sludge can be recovered by the worms. This paper describes a systematic approach for finding possible applications of the produced biomass. The worm biomass mainly consists of protein and smaller fractions of fat, sugar and ash. It also contains low concentrations of heavy metals. The potential produced amount is relatively small, compared to other waste streams, and is produced decentrally. Therefore, the most promising applications are specific components of the biomass, for example specific amino acids or fatty acids. However, until the process is optimized and there is a stable supply of worms, the focus should be on simple applications, later on followed by specific applications, depending on the market demand. Worm biomass grown on clean sludges has a broader application potential, for example as consumption fish feed.
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