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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    Protein drink from beer industry waste products
    Safi, Carl - \ 2020
    Effects of soil fertilization on terpenoids and other carbon-based secondary metabolites in rosmarinus officinalis plants : A comparative study
    Bustamante, Maria Ángeles ; Michelozzi, Marco ; Caracciolo, Anna Barra ; Grenni, Paola ; Verbokkem, Janine ; Geerdink, Peter ; Safi, Carl ; Nogues, Isabel - \ 2020
    Plants 9 (2020)7. - ISSN 2223-7747 - p. 1 - 19.
    Compost - Flavonoids - Leaf nitrogen - Leaf phosphorus - Monoterpenes - Phenolic compounds - Sesquiterpenes - Structural carbohydrates

    Rosmarinus officinalis is an evergreen aromatic plant with important commercial interest as it contains numerous essential oils (composed of terpenoid compounds) and phenolic constituents (natural antioxidant compounds). This work aims at evaluating the concomitant effects of different inorganic and organic fertilization treatments and the subsequent increases in soil nutrient availability on terpenoids and other carbon-based secondary metabolites, e.g., flavonoids and phenolic compounds, in Rosmarinus officinalis leaves. The results showed that, as expected, the structural carbohydrate content (lignocellulosic compounds) in stems was higher in fertilized plants than in controls. Additionally, positive correlations were observed of the absolute amounts of total terpenoids and some single terpenoid compounds with N or P contents in leaves. On the contrary, the phenolic and flavonoid concentrations in all the rosemary plant parts were lower with the fertilization treatments. Indeed, negative correlations between the phenolic compounds (and flavonoids) and N in rosemary leaves were also found. Overall, the results suggest that the terpenoid production’s response to fertilization was due to N, which is essential for protein synthesis and terpene synthase activity, and to P, which is necessary for the synthesis of both terpenoid precursors and ATP and NADPH, also needed for terpenoid synthesis. On the other hand, the basis for the fertilization’s effects on the production of phenolic compounds is the direct nitrogen trade-off between growth and the shikimic acid pathway by which phenolics compounds are synthesized.

    Effect of growth conditions on the efficiency of cell disruption of Neochloris oleoabundans
    Safi, C. ; Olivieri, G. ; Engelen-Smit, N. ; Spekking, W. ; Veloo, R. ; Broek, L.A.M. van den; Sijtsma, L. - \ 2020
    Bioresource Technology 300 (2020). - ISSN 0960-8524
    Cell disintegration - Enzymes - High-pressure homogenization - Nitrogen deplete - Nitrogen replete

    The impact of four different growth conditions on the cell disruption efficiency of Neochloris oleoabundans was investigated. A mechanical and biological cell disruption methods were evaluated separately and combined. It has been established that microalgae grown in marine water under nitrogen deprivation were the most resistant against cell disruption methods and released the lowest amount of proteins. The release of lipids, however, followed the “hindered molecule diffusion phenomenon” because it did not follow the same release pattern as proteins. The enzymatic treatment was efficient enough to release the majority of the proteins without combining it with high-pressure homogenization. Regarding energy input, Neochloris oleoabundans grown in marine water under nitrogen deprivation required the highest energy input to release proteins (Ep = 13.76−1) and to break the cells by high-pressure homogenization (Ex – HPH = 1.14−1) or by the combination of enzymes and High-pressure homogenization (Ex – ENZ = 2.79−1).

    Blue Bioeconomy Forum : Highlights: Summary of the roadmap and a selection of viable and innovative projects
    Ligtvoet, A. ; Maier, F. ; Sijtsma, L. ; Broek, L.A.M. van den; Safi, Carl ; Doranova, A. ; Eaton, D. ; Guznajeva, T. ; Kals, J. ; Gallou, M. Le; Poelman, M. ; Saes, L. ; Zhechkov, R. - \ 2019
    Brussels : European Commission (Blue Bioeconomy Forum Newsletter ) - ISBN 9789292027308 - 42 p.
    Current Bottlenecks and Challenges of the Microalgal Biorefinery
    Gifuni, Imma ; Pollio, Antonino ; Safi, Carl ; Marzocchella, Antonio ; Olivieri, Giuseppe - \ 2019
    Trends in Biotechnology 37 (2019)3. - ISSN 0167-7799 - p. 242 - 252.
    biorefinery - cascade extraction - co-accumulation - microalgae - thin photobioreactors

    Microalgae are increasingly considered as sources of renewable feedstocks for industrial production, and microalgae production now focuses on the multiproduct microalgal biorefinery. However, such a biorefinery presents several bottlenecks that are mainly associated with downstream processes. This reduced downstream efficiency results from unsolved problems related to the culture strategy for the accumulation of different products – the protein versus lipid dilemma – and the dilute nature of the microalgal culture. We identify new trends and propose promising solutions for realizing microalgal biorefineries at industrial scale. New perspectives and challenges are identified in protein properties and in the integration and cooptimization of culture and downstream processes.

    Quantification of proteins in seaweeds
    Safi, Carl ; Leeuwen, J.J.A. van; Telleman, Yvette ; Engelen-Smit, N.P.E. ; Broek, L.A.M. van den; Harmsen, P.F.H. - \ 2018
    In: Protocols for Macroalgae Research / Charrier, B., Wichard, T., Reddy, C.R.K., Boca Raton : CRC Press, Taylor & Francis - ISBN 9781498796422 - p. 211 - 224.
    The protein quality and the amino acid composition are key elements for the valorization of seaweeds. Proteins represent a significant part of the primary composition of seaweeds. In this chapter, we describe several protocols for the characterization and quantification of proteins in seaweeds and in the crude extracts. The protocols described are hydrolysis methods, colorimetric methods, amino acid determination, and the determination of the nitrogen to protein conversion factor.
    Selective and energy efficient extraction of functional proteins from microalgae for food applications
    Suarez Garcia, E. ; Leeuwen, J. van; Safi, C. ; Sijtsma, L. ; Eppink, M.H.M. ; Wijffels, R.H. ; Berg, C. van den - \ 2018
    Bioresource Technology 268 (2018). - ISSN 0960-8524 - p. 197 - 203.
    Bead milling - Energy efficient - Functional protein - Gelation - Surface activity

    The use of a single controlled bead milling step of the microalga Tetraselmis suecica resulted in a soluble fraction, rich in functional proteins. This was achieved by fine-tuning the processing time, thereby exploiting the difference in rates of protein and carbohydrate release during milling. Soluble proteins were extracted under mild conditions -room temperature, no addition of chemicals, pH 6.5-, with a yield of 22.5% and a specific energy consumption of 0.6 kWh kgDW −1, which is within the recommended minimum energy for an extraction step in a biorefinery process. The resulting protein extract contained 50.4% (DW) of proteins and 26.4% carbohydrates, showed light green color and displayed superior surface activity and gelation behavior compared to whey protein isolate. The proposed process is simple (only one bead milling step), scalable, and allows the mild extraction of functional proteins, making it interesting for industrial applications in the food industry.

    Techno-Functional Properties of Crude Extracts from the Green Microalga Tetraselmis suecica
    SuarezGarcia, E. ; Leeuwen, J.J.A. Van; Safi, C. ; Sijtsma, L. ; Broek, L.A.M. van den; Eppink, M.H.M. ; Wijffels, R.H. ; Berg, C. van den - \ 2018
    Journal of Agricultural and Food Chemistry 66 (2018)29. - ISSN 0021-8561 - p. 7831 - 7838.
    bead milling - crude extract - filtration - gelation - surface activity

    A mild fractionation process to extract functional biomolecules from green microalgae was implemented. The process includes bead milling, centrifugation, and filtration with several membrane cut-offs. For each fraction, the corresponding composition was measured, and the surface activity and gelation behavior were determined. A maximum protein yield of 12% was obtained in the supernatant after bead milling and between 3.2 and 11.7% after filtration. Compared to whey protein isolate, most of the algae fractions exhibited comparable or enhanced functionality. Surface activity for air-water and oil-water interfaces and gelation activities were notably superior for the retentate fractions compared to the permeates. It is proposed that such functionality in the retentates is due to the presence of hydrophobic compounds and molecular complexes exhibiting a similar behavior as Pickering particles. We demonstrated that excellent functionality can be obtained with crude fractions, requiring minimum processing and, thus, constituting an interesting option for commercial applications.

    LPCAT1 controls phosphate homeostasis in a zinc-dependent manner
    Kisko, Mushtak ; Bouain, Nadia ; Safi, Alaeddine ; Medici, Anna ; Akkers, Robert C. ; Secco, David ; Fouret, Gilles ; Krouk, Gabriel ; Aarts, Mark G.M. ; Busch, Wolfgang ; Rouached, Hatem - \ 2018
    eLife 7 (2018). - ISSN 2050-084X

    All living organisms require a variety of essential elements for their basic biological functions. While the homeostasis of nutrients is highly intertwined, the molecular and genetic mechanisms of these dependencies remain poorly understood. Here, we report a discovery of a molecular pathway that controls phosphate (Pi) accumulation in plants under Zn deficiency. Using genome-wide association studies, we first identified allelic variation of the Lyso- Phosphatidyl Choline (PC) Acyl Transferase 1 (LPCAT1) gene as the key determinant of shoot Pi accumulation under Zn deficiency. We then show that regulatory variation at the LPCAT1 locus contributes significantly to this natural variation and we further demonstrate that the regulation of LPCAT1 expression involves bZIP23 TF, for which we identified a new binding site sequence. Finally, we show that in Zn deficient conditions loss of function of LPCAT1 increases the phospholipid Lyso-Phosphatidyl Choline/Phosphatidyl Choline ratio, the expression of the Pi transporter PHT1;1, and that this leads to shoot Pi accumulation.

    Energy consumption and water-soluble protein release by cell wall disruption of Nannochloropsis gaditana
    Safi, C. ; Cabas Rodriguez, L. ; Mulder, W.J. ; Engelen-Smit, N. ; Spekking, W. ; Broek, L.A.M. van den; Olivieri, G. ; Sijtsma, L. - \ 2017
    Bioresource Technology 239 (2017). - ISSN 0960-8524 - p. 204 - 210.
    Bead milling - Enzymes - High-pressure homogenization - Pulsed Electric Field - Soluble proteins
    Several cell disruption methods were tested on Nannochloropsis gaditana, to evaluate their efficiency in terms of cell disintegration, energy input and release of soluble proteins. High-pressure homogenization (HPH) and bead milling were the most efficient with >95% cell disintegration, ±50% (w/w) release of total proteins and low energy input (<0.5−1 biomass). Enzymatic treatment required low energy input (<0.34−1 biomass), but it only released ±35% protein (w/w). Pulsed Electric Field (PEF) was neither energy-efficient (10.44−1 biomass) nor successful for protein release (only 10% proteins w/w) and cell disintegration. The release of proteins after applying HPH and bead milling always required less intensive operating conditions for cell disruption. The energy cost per unit of released protein ranged from 0.15–0.25 €.kgProtein −1 in case of HPH, and up to 2–20 €.kgProtein −1 in case of PEF.
    Energy efficient bead milling of microalgae: Effect of bead size on disintegration and release of proteins and carbohydrates
    Postma, P.R. ; Suarez Garcia, E. ; Safi, Carl ; Yonathan, K. ; Olivieri, G. ; Barbosa, M.J. ; Wijffels, R.H. ; Eppink, M.H.M. - \ 2017
    Bioresource Technology 224 (2017). - ISSN 0960-8524 - p. 670 - 679.
    The disintegration of three industry relevant algae (Chlorella vulgaris, Neochloris oleoabundans and Tetraselmis suecica) was studied in a lab scale bead mill at different bead sizes (0.3–1 mm). Cell disintegration, proteins and carbohydrates released into the water phase followed a first order kinetics. The process
    is selective towards proteins over carbohydrates during early stages of milling. In general, smaller beads led to higher kinetic rates, with a minimum specific energy consumption of 60.47 kWh kgDW1 for 0.3 mm beads. After analysis of the stress parameters (stress number and stress intensity), it appears that
    optimal disintegration and energy usage for all strains occurs in the 0.3–0.4 mm range. During the course of bead milling, the native structure of the marker protein Rubisco was retained, confirming the mildness f the disruption process.
    Biorefinery of microalgal soluble proteins by sequential processing and membrane filtration
    Safi, C. ; Olivieri, G. ; Pina Campos, Rui ; Engelen-Smit, N. ; Mulder, W.J. ; Broek, L.A.M. van den; Sijtsma, L. - \ 2017
    Bioresource Technology 225 (2017). - ISSN 0960-8524 - p. 151 - 158.
    Biorefinery - Cell disruption - Fractionation - Proteins - Ultrafiltration

    A mild biorefinery process was investigated on the microalga Nannochloropsis gaditana, to obtain an enriched fraction of water soluble proteins free from chlorophyll. After harvesting, a 100 g.L−1 solution of cells was first subjected to cell disruption by either high-pressure homogenization (HPH) or enzymatic treatment (ENZ). HPH resulted in a larger release of proteins (49%) in the aqueous phase compared to the Alcalase incubation (35%). In both cases, an ultrafiltration/diafiltration (UF/DF) was then performed on the supernatant obtained from cell disruption by testing different membrane cut-off (1000 kDa, 500 kDa and 300 kDa). After optimising the process conditions, the combination of ENZ → UF/DF ended in a larger overall yield of water soluble proteins (24.8%) in the permeate compared to the combination of HPH → UF/DF (17.4%). A gel polarization model was implemented to assess the maximum achievable concentration factor during ultrafiltration and the mass transfer coefficient related to the theoretical permeation flux rate.

    Select-and-fill-in concept maps as an evaluation tool in science classrooms
    Hatami, Javad ; Farrokhnia, Mohammadreza ; Hassanzadeh, Mohammad - \ 2016
    In: Innovating with Concept Mapping - 7th International Conference on Concept Mapping, CMC 2016, Proceedings. - Springer Verlag (Communications in Computer and Information Science ) - ISBN 9783319455006 - p. 169 - 180.
    Conceptual mapping - Evaluation tool - Science classroom

    Much research has been done on the application of concept maps as means for learning assessment. Similarly, different types of Concept-Map Based Assessments (CMBA) and their validity have been examined as well in many studies, but to a far less extent. The present study uses a descriptive quantitative method and mainly aims to put forward the idea that the select-and-fill-in (SAFI) concept maps could be used as a valid instrument to assess the conceptual understanding of science among thermodynamics students. For this purpose, the concurrent validity of the SAFI concept map was evaluated according to the last version of the Thermodynamic Concept Survey (TCS) in order to develop a standard conceptual survey in thermodynamics. The TCS has a total KR-20 of approximately 0.78, an acceptable value, which could be employed as a valid test to assess teacher-made SAFI concept maps. The study population includes 60 students from two physics classes. An evaluation of the conceptual understandings of thermodynamics students were made concurrently using two assessment tools. Based on the study findings, there is a moderate to strong correlation (0.6) between the Teacher-made SAFI concept map and TCS. This leads us to the conclusion that SAFI concept maps are valid tools, at least, for evaluating conceptual understanding in thermodynamics. Moreover, the results of this study are confirmed a significant relationship between a student’s ability to read and comprehend a given question and his/her ability to solve it.

    La technologie des microalgues: quel potentiel?
    Safi, Carl - \ 2016

    Algae biorefinery: proteins for technical applications
    Safi, Carl ; Broek, L.A.M. van den; Sijtsma, L. - \ 2016
    The concept of biorefiney was mainly inspired from the petroleum refinery concept. It reflects a process to fractionate and valorise the biomass in order to enhance the value derived from each component present in the biomass and to maximise profitability. Microalgae are an excellent source of commodities like proteins, polysaccharides, lipids and pigments. Therefore, it is worthwhile endeavour to extract and fractionate these microalgal components in the framework of a biorefinery that respects the integrity of the components of interest.
    Algae biorefinery for non-food applications
    Broek, L.A.M. van den; Safi, Carl ; Leeuwen, J.J.A. van; Mulder, W.J. ; Sijtsma, L. - \ 2016
    Microalgae are among the most promising raw materials for chemicals.
    Their biomass is an excellent source of proteins, polysaccharides, lipids and
    pigments. These fractions can be used, apart from food and feed, for nonfood
    applications such as binders in coating and adhesives, surface-active
    agents, green chemicals, bioplastics, plants fertilizer, and in the cosmetic
    and pharmaceutical industries.
    Summerschool, Microalgae Biorefinery
    Safi, Carl - \ 2016
    Filtration Techniques
    Identifying the Research Needs of Four Large High-Technology Companies
    Aksit, M. ; Tekinerdogan, B. ; Sozer, H. ; Faruk Safi, Hakan ; Ayas, M. - \ 2016
    In: Proceedings of the Fourth International Conference on Advances in Computing, Control and Networking - ACCN 2016. - - p. 21 - 24.
    Software excellence is defined as the adoption of advanced software techniques and methods to cope with the complexity and the needs of modern software systems. To accomplish this objective, the companies that develop software intensive systems must be able to follow and adopt the state-of-the-art developments in computer science and technology. In general, this implies carrying out research activities with the relevant universities. This paper presents an overview of a pilot implementation of the approach termed as “Describe, Search and Acquire the Required Capability” (DESARC), which aims at establishing a more effective identification of research projects, allocation of these research projects to research groups and the cooperation between universities and industry. In our previous publication [1], we have presented the initial results of the method. Currently, we have extended this study and applied it in total to four large high-technology companies. This paper can be useful for the strategic developers who are interested in setting up university-industry cooperation and for the researchers who want to have an industrial view of the trends on computer science and software engineering.
    The DESARC Method: An Effective Approach for University-Industry Cooperation
    Aksit, M. ; Tekinerdogan, B. ; Sozer, H. ; Safi, H.F. ; Ayas, M. - \ 2015
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