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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    Towards microalgal triglycerides in the commodity markets
    Benvenuti, Giulia ; Ruiz, Jesús ; Lamers, Packo P. ; Bosma, Rouke ; Wijffels, René H. ; Barbosa, Maria J. - \ 2017
    Biotechnology for Biofuels 10 (2017)1. - ISSN 1754-6834
    Microalgae - Production costs - Techno-economic analysis - Triglyceride production
    Background: Microalgal triglycerides (TAGs) hold great promise as sustainable feedstock for commodity industries. However, to determine research priorities and support business decisions, solid techno-economic studies are essential. Here, we present a techno-economic analysis of two-step TAG production (growth reactors are operated in continuous mode such that multiple batch-operated stress reactors are inoculated and harvested sequentially) for a 100-ha plant in southern Spain using vertically stacked tubular photobioreactors. The base case is established with outdoor pilot-scale data and based on current process technology. Results: For the base case, production costs of 6.7 € per kg of biomass containing 24% TAG (w/w) were found. Several scenarios with reduced production costs were then presented based on the latest biological and technological advances. For instance, much effort should focus on increasing the photosynthetic efficiency during the stress and growth phases, as this is the most influential parameter on production costs (30 and 14% cost reduction from base case). Next, biological and technological solutions should be implemented for a reduction in cooling requirements (10 and 4.5% cost reduction from base case when active cooling is avoided and cooling setpoint is increased, respectively). When implementing all the suggested improvements, production costs can be decreased to 3.3 € per kg of biomass containing 60% TAG (w/w) within the next 8 years. Conclusions: With our techno-economic analysis, we indicated a roadmap for a substantial cost reduction. However, microalgal TAGs are not yet cost efficient when compared to their present market value. Cost-competiveness strictly relies on the valorization of the whole biomass components and on cheaper PBR designs (e.g. plastic film flat panels). In particular, further research should focus on the development and commercialization of PBRs where active cooling is avoided and stable operating temperatures are maintained by the water basin in which the reactor is placed.
    Batch and semi-continuous microalgal TAG production in lab-scale and outdoor photobioreactors
    Benvenuti, Giulia ; Bosma, Rouke ; Ji, Fang ; Lamers, Packo ; Barbosa, Maria J. ; Wijffels, René H. - \ 2016
    Journal of Applied Phycology 28 (2016)6. - ISSN 0921-8971 - 11 p.
    Batch - Microalgae - Outdoor - Semi-continuous - TAG production

    Microalgal triglycerides (TAGs) represent a sustainable feedstock for food, chemical and biofuel industries. The operational strategy (batch, semi-continuous, continuous cultivations) has an impact on the TAG productivity. In this study, semi-continuous (i.e. with fixed harvesting frequency) and batch cultivations were compared on TAG production both at lab-scale and in outdoor cultivations. At lab-scale, the semi-continuous TAG productivity was highest for a cycle time of 2 days (SC1; 0.21 g L−1 day−1) and similar to the maximum obtained with the batch (optimal harvest time; 0.23 g L−1 day−1). Although TAG content was lower for SC1 (22 %) than for the batch (35 %), higher biomass productivities were obtained with SC1. Outdoors, semi-continuous cultivations were subjected to a lower degree of stress (i.e. higher amount of nitrogen present in the system relative to the given irradiance) compared to lab-scale. This yielded low and similar TAG contents (10–13 %) in the different semi-continuous runs that were outdone by the batch on both TAG content (15–25 %) and productivity (batch, 0.97–2.46 g m−2 day−1; semi-continuous, 0.35–0.85 g m−2 day−1). The lab-scale experiments showed that semi-continuous strategies, besides leading to similar TAG productivities compared to the batch, could make TAG production cost effective by valorising also non-TAG compounds. However, optimization of outdoor semi-continuous cultivations is still required. For instance, the nitrogen supply and the harvest frequency should be adjusted on the total irradiance. Additionally, future research should focus on recovery metabolism upon nitrogen resupply.

    Microalgal TAG production strategies: why batch beats repeated-batch
    Benvenuti, G. ; Lamers, P.P. ; Breuer, G. ; Bosma, R. ; Cerar, Ana ; Wijffels, R.H. ; Barbosa, M.J. - \ 2016
    Biotechnology for Biofuels 9 (2016). - ISSN 1754-6834
    For a commercially feasible microalgal triglyceride (TAG) production, high TAG productivities are required. The operational strategy affects TAG productivity but a systematic comparison between different strategies is lacking. For this, physiological responses of Nannochloropsis sp. to nitrogen (N) starvation and N-rich medium replenishment were studied in lab-scale batch and repeated-batch (part of the culture is periodically harvested and N-rich medium is re-supplied) cultivations under continuous light, and condensed into a mechanistic model.

    The model, which successfully described both strategies, was used to identify potential improvements for both batch and repeated-batch and compare the two strategies on optimized TAG yields on light (amount of TAGs produced per mol of supplied PAR photons). TAG yields on light, for batch, from 0.12 (base case at high light) to 0.49 g mol ph −1 (at low light and with improved strain) and, for repeated-batch, from 0.07 (base case at high light) to 0.39 g mol ph −1 (at low light with improved strain and optimized repeated-batch settings). The base case yields are in line with the yields observed in current state-of-the-art outdoor TAG production.

    For continuous light, an optimized batch process will always result in higher TAG yield on light compared to an optimized repeated-batch process. This is mainly because repeated-batch cycles start with N-starved cells. Their reduced photosynthetic capacity leads to inefficient light use during the regrowth phase which results in lower overall TAG yields compared to a batch process.
    Batch and repeated-batch oil production by microalgae
    Benvenuti, G. - \ 2016
    Wageningen University. Promotor(en): Rene Wijffels, co-promotor(en): Rouke Bosma; Maria Barbosa. - Wageningen : Wageningen University - ISBN 9789462576582 - 149
    algae - chlorella - arthrospira - dunaliella - nostoc - triacylglycerols - light - lipogenesis - photosynthesis - oil products - productivity - biomass conversion - economic analysis - algen - chlorella - arthrospira - dunaliella - nostoc - triacylglycerolen - licht - lipogenese - fotosynthese - olieproducten - productiviteit - biomassaconversie - economische analyse

    Microalgal triglycerides (TAGs) are promising feedstocks for the commodity markets (i.e. food, chemical and biofuel). Nevertheless, microalgal TAGs are not yet economically feasible due to the high production costs. To reduce these costs, TAG productivity needs to be maximized.

    The aim of this thesis was to increase microalgal TAG productivity by investigating the effects of biological and engineering parameters (i.e. production strain and operational strategy).

    We first screened seven marine species on their TAG productivity under nitrogen (N) starvation. Nannochloropsis sp. was identified as the most suitable species as it retained its photosynthetic activity while accumulating large amounts of TAGs ensuring the highest TAG productivity. Therefore, Nannochloropsis sp. was used in all following studies.

    Next, we aimed at optimizing TAG productivity by investigating the effect of initial-biomass-specific (IBS) light availability (i.e. ratio of light impinging on reactor ground area divided by initial biomass concentration per ground area) in batch outdoor cultivations carried out in horizontal and vertically stacked tubular reactors at different initial biomass concentrations at the start of the TAG accumulation phase, over different seasons. Based on the observed trends of TAG productivity for the Dutch climate, optimal initial biomass concentrations were suggested to achieve high areal TAG productivities for each reactor configuration and season.

    Subsequently, repeated-batch processes were investigated to further increase TAG productivity compared to batch processes. For this, repeated-batch cultivations were tested and compared to batch cultivations both at lab-scale under day/night cycles and in two identical, simultaneously operated, outdoor vertically stacked tubular reactors over different seasons. Although at lab-scale, batch and repeated-batch cultivations led to similar TAG productivities, outdoor repeated-batch processes were always outcompeted by the batch. It was concluded that repeated-batch processes require further optimization.

    For this, the physiological responses of Nannochloropsis sp. to N-starvation and N-replenishment were determined under continuous light in lab-scale batch and repeated-batch cultivations and condensed into a mechanistic model describing both cultivation strategies. Scenarios for improved TAG yields on light were simulated and, based on the optimized yields, a comparison of the two processes was performed. It was concluded that under continuous light, an optimized batch process will always result in higher TAG productivities than an optimized repeated-batch process.

    Finally, a techno-economic analysis for a two-step-continuous TAG production process (i.e. growth reactors are operated in continuous mode such that multiple batch-operated stress reactors are inoculated and sequentially harvested) is performed for a hypothetical 100 ha-scale plant in southern Spain using vertically stacked tubular reactors. Photosynthetic efficiencies based on outdoor pilot data were used as model input. By optimizing both photosynthetic efficiency and process technology, the production cost could be decreased from 7.4 to 3.0 €·kg-1 of TAG-enriched biomass. We believe to be on the right track to achieve an economically feasible TAG production platform provided that photosynthetic efficiency is further improved, the whole biomass is valorized and cheaper reactors are designed.

    The impact of rearing environment on the development of gut microbiota in tilapia larvae
    Giatsis, Christos ; Sipkema, Detmer ; Smidt, Hauke ; Heilig, Hans ; Benvenuti, Giulia ; Verreth, Johan ; Verdegem, Marc - \ 2015
    Scientific Reports 5 (2015). - ISSN 2045-2322 - 15 p.

    This study explores the effect of rearing environment on water bacterial communities (BC) and the association with those present in the gut of Nile tilapia larvae (Oreochromis niloticus, Linnaeus) grown in either recirculating or active suspension systems. 454 pyrosequencing of PCR-Amplified 16S rRNA gene fragments was applied to characterize the composition of water, feed and gut bacteria communities. Observed changes in water BC over time and differences in water BCs between systems were highly correlated with corresponding water physico-chemical properties. Differences in gut bacterial communities during larval development were correlated with differences in water communities between systems. The correlation of feed BC with those in the gut was minor compared to that between gut and water, reflected by the fact that 4 to 43 times more OTUs were shared between water and gut than between gut and feed BC. Shared OTUs between water and gut suggest a successful transfer of microorganisms from water into the gut, and give insight about the niche and ecological adaptability of water microorganisms inside the gut. These findings suggest that steering of gut microbial communities could be possible through water microbial management derived by the design and functionality of the rearing system.

    Microalgal triacylglycerides production in outdoor batch-operated tubular PBRs
    Benvenuti, Giulia ; Bosma, Rouke ; Klok, Anne J. ; Ji, Fang ; Lamers, Packo P. ; Barbosa, Maria J. ; Wijffels, René H. - \ 2015
    Biotechnology for Biofuels 8 (2015). - ISSN 1754-6834 - 9 p.
    chlorella-zofingiensis - lipid-accumulation - growth - light - photobioreactors - cultivation - design

    Background: Microalgal triacylglycerides (TAGs) are a promising sustainable feedstock for the biofuel, chemical and food industry. However, industrial production of microalgal products for commodity markets is not yet economically viable, largely because of low microalgal productivity. The latter is strictly dependent on initial-biomass-specific (IBS) light availability (i.e. ratio of light impinging on reactor ground area divided by initial biomass concentration per ground area). This study investigates the effect of IBS-light availability on batch TAG production for Nannochloropsis sp. cultivated in two outdoor tubular reactors (i.e. vertical and horizontal) at different initial biomass concentrations for the TAG accumulation phase, during two distinct seasons (i.e. high and low light conditions). Results: Increasing IBS-light availability led to both a higher IBS-TAG production rate and TAG content at the end of the batch, whereas biomass yield on light decreased. As a result, an optimum IBS-light availability was determined for the TAG productivity obtained at the end of the batch and several guidelines could be established. The vertical reactor (VR) should be operated at an initial biomass concentration of 1.5 g L-1 to achieve high TAG productivities (1.9 and 3.2 g m-2 day-1 under low and high light, respectively). Instead, the horizontal reactor (HR) should be operated at 2.5 g L-1 under high light (2.6 g m-2 day-1), and at 1.5 g L-1 under low light (1.4 g m-2 day-1). Conclusions: From this study, the great importance of IBS-light availability on TAG production can be deduced. Although maintaining high light availabilities in the reactor is key to reach high TAG contents at the end of the batch, considerable losses in TAG productivity were observed for the two reactors regardless of light condition, when not operated at optimal initial biomass concentrations (15-40% for VR and 30-60% for HR).

    Selecting microalgae with high lipid productivity and photosynthetic activity under nitrogen starvation
    Benvenuti, G. ; Bosma, R. ; Cuaresma Franco, M. ; Janssen, M.G.J. ; Barbosa, M.J. ; Wijffels, R.H. - \ 2015
    Journal of Applied Phycology 27 (2015)4. - ISSN 0921-8971 - p. 1425 - 1431.
    neochloris-oleoabundans - parietochloris-incisa - marine-phytoplankton - biodiesel production - nutrient stress - fatty-acids - light - accumulation - efficiency - biofuels
    An economically feasible microalgal lipid industry heavily relies on the selection of suitable strains. Because microalgae lipid content increases under a range of adverse conditions (e.g. nutrient deprivation, high light intensity), photosynthetic activity is usually strongly reduced. As a consequence, lipid productivity rapidly declines overtime, after reaching a maximum within the first days of cultivation. The microalgae Chlorella vulgaris, Chlorococcum littorale, Nannochloropsis oculata, Nannochloropsis sp., Neochloris oleoabundans, Stichococcus bacillaris and Tetraselmis suecica were compared on fatty acid content and productivity, and also on photosynthetic activity under nitrogen (N) starvation. Cultures in N-replete conditions were used as reference. Photosystem II (PSII) maximumefficiency was followed during the experiment, as proxy for the change in photosynthetic activity of the cells. Strains with a high capacity for both lipid accumulation as well as high photosynthetic activity under N starvation exhibited a high lipid productivity over time. Among the tested strains, Nannochloropsis sp. showed highest fatty acid content (45%w/w) and productivity (238 mg L-1 day-1) aswell as PSII maximum efficiency, demonstrating to be the most suitable strain, of those tested, for lipid production. This study highlights that for microalgae, maintaining a high photosynthetic efficiency during stress is the key to maintain high fatty acid productivities overtime and should be considered when selecting strains for microalgal lipid production.
    Selecting microalgae on lipid productivity and photosynthetic efficiency under nitrogen-starvation
    Benvenuti, Giulia - \ 2014
    Innovative products from the sea
    Benvenuti, Giulia - \ 2014
    Microalgal TAG production in batch-operated outdoor PBRs
    Benvenuti, Giulia - \ 2014
    Photosynthetic efficiency and oxygen evolution of Chlamydomonas reinhardtii under continuous and flashing light
    Vejrazka, C. ; Janssen, M. ; Benvenuti, G. ; Streefland, M. ; Wijffels, R.H. - \ 2013
    Applied Microbiology and Biotechnology 97 (2013)4. - ISSN 0175-7598 - p. 1523 - 1532.
    photobioreactors - phytoplankton - cyanobacteria - irradiance - microalgae - growth
    As a result of mixing and light attenuation in a photobioreactor (PBR), microalgae experience light/dark (L/D) cycles that can enhance PBR efficiency. One parameter which characterizes L/D cycles is the duty cycle; it determines the time fraction algae spend in the light. The objective of this study was to determine the influence of different duty cycles on oxygen yield on absorbed light energy and photosynthetic oxygen evolution. Net oxygen evolution of Chlamydomonas reinhardtii was measured for four duty cycles (0.05, 0.1, 0.2, and 0.5) in a biological oxygen monitor (BOM). Oversaturating light flashes were applied in a square-wave fashion with four flash frequencies (5, 10, 50, and 100 Hz). Algae were precultivated in a turbidostat and acclimated to a low photon flux density (PFD). A photosynthesis-irradiance (PI) curve was measured under continuous illumination and used to calculate the net oxygen yield, which was maximal between a PFD of 100 and 200 µmol m(-2)¿s(-1). Net oxygen yield under flashing light was duty cycle-dependent: the highest yield was observed at a duty cycle of 0.1 (i.e., time-averaged PFD of 115 µmol m(-2)¿s(-1)). At lower duty cycles, maintenance respiration reduced net oxygen yield. At higher duty cycles, photon absorption rate exceeded the maximal photon utilization rate, and, as a result, surplus light energy was dissipated which led to a reduction in net oxygen yield. This behavior was identical with the observation under continuous light. Based on these data, the optimal balance between oxygen yield and production rate can be determined to maximize PBR productivity.
    Latte vivo. Il lungo vaggio dell latte dai campi alla tavola. Prospettive dopo il Parmacrack
    Ploeg, J.D. van der; Benvenuti, B. ; Bussi, E. ; Pignagnoli, C. - \ 2004
    Reggio Emiglia, Italia : Diabasis - ISBN 9788881033218 - 178 p.
    De dialectiek van autonomie en systeemintegratie in de landbouw. Naar een synthese van structuralisme en actor-oriëntatie in de rurale sociologie
    Benvenuti, B. ; Frouws, J. - \ 1999
    Tijdschrift voor sociaalwetenschappelijk onderzoek van de landbouw 13 (1999)4. - ISSN 0921-481X - p. 212 - 220.
    Design methods for endogenous rural development: a synthetic overview.
    Ploeg, J.D. van der; Broekhuizen, R. van; Sevilla Guzmán, E. ; Nikolaidis, A. ; Cristóvâo, A. ; Portela, J. ; Benvenuti, B. ; Saccomandi, V. - \ 1995
    In: Design methods for endogenous rural development Wageningen : Circle for Rural European Studies - p. 123 - 128.
    Il modello agricolo Olandese in crisi.
    Ploeg, J.D. van der; Mansholt, S. ; Benvenuti, B. ; Saccomandi, V. - \ 1995
    Assisi, Italië : CESAR - 85 p.
    Geschriften over landbouw, structuur en technologie; ingeleid, bewerkt en vertaald door Jan Douwe van der Ploeg.
    Ploeg, J.D. van der; Benvenuti, B. - \ 1991
    Wageningen : Landbouwuniversiteit Wageningen (Wageningse sociologische studies 29) - ISBN 9789067541886 - 140 p.
    sociology - rural communities - rural sociology - agricultural situation - economic situation
    Analisi dei fattori condizionanti l'adozione da parte dei destinari dei provvedimenti di politica economica.
    Ploeg, J.D. van der; Benvenuti, B. - \ 1990
    Bologna, Italy : IRFATA - 119 p.
    Produttore agricolo e potere, modernizzazione delle relazione sociali ed economiche e fattori determinanti dell'imprenditorialità agricola.
    Ploeg, J.D. van der; Benvenuti, B. ; Antonello, S. ; Roest, C. de; Sauda, E. - \ 1989
    Rome : AIPA/Coldiretti - 223 p.
    Guastalla Due, ricerca sui effetti.
    Ploeg, J.D. van der; Benvenuti, B. ; Sauda, E. ; Antonello, S. ; Roest, C. de - \ 1988
    Unknown Publisher - 320 p.
    Technologia lavoro e bilancio energetico nella agricoltura italiana. Rapport geschreven op verzoek van IPRA/CNR.
    Ploeg, J.D. van der; Roest, C. de; Sauda, E. ; Benvenuti, B. - \ 1986
    Unknown Publisher - 53 p.
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