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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State-of-the-art global models underestimate impacts from climate extremes
Schewe, Jacob ; Gosling, Simon N. ; Reyer, Christopher ; Zhao, Fang ; Ciais, Philippe ; Elliott, Joshua ; Francois, Louis ; Huber, Veronika ; Lotze, Heike K. ; Seneviratne, Sonia I. ; Vliet, Michelle T.H. Van; Vautard, Robert ; Wada, Yoshihide ; Breuer, Lutz ; Büchner, Matthias ; Carozza, David A. ; Chang, Jinfeng ; Coll, Marta ; Deryng, Delphine ; Wit, Allard De; Eddy, Tyler D. ; Folberth, Christian ; Frieler, Katja ; Friend, Andrew D. ; Gerten, Dieter ; Gudmundsson, Lukas ; Hanasaki, Naota ; Ito, Akihiko ; Khabarov, Nikolay ; Kim, Hyungjun ; Lawrence, Peter ; Morfopoulos, Catherine ; Müller, Christoph ; Müller Schmied, Hannes ; Orth, René ; Ostberg, Sebastian ; Pokhrel, Yadu ; Pugh, Thomas A.M. ; Sakurai, Gen ; Satoh, Yusuke ; Schmid, Erwin ; Stacke, Tobias ; Steenbeek, Jeroen ; Steinkamp, Jörg ; Tang, Qiuhong ; Tian, Hanqin ; Tittensor, Derek P. ; Volkholz, Jan ; Wang, Xuhui ; Warszawski, Lila - \ 2019
Nature Communications 10 (2019). - ISSN 2041-1723
Global impact models represent process-level understanding of how natural and human systems may be affected by climate change. Their projections are used in integrated assessments of climate change. Here we test, for the first time, systematically across many important systems, how well such impact models capture the impacts of extreme climate conditions. Using the 2003 European heat wave and drought as a historical analogue for comparable events in the future, we find that a majority of models underestimate the extremeness of impacts in important sectors such as agriculture, terrestrial ecosystems, and heat-related human mortality, while impacts on water resources and hydropower are overestimated in some river basins; and the spread across models is often large. This has important implications for economic assessments of climate change impacts that rely on these models. It also means that societal risks from future extreme events may be greater than previously thought.
Recent insights on uncertainties present in integrated catchment water quality modelling
Tscheikner-Gratl, Franz ; Bellos, Vasilis ; Schellart, Alma ; Moreno-Rodenas, Antonio ; Muthusamy, Manoranjan ; Langeveld, Jeroen ; Clemens, Francois ; Benedetti, Lorenzo ; Rico-Ramirez, Miguel Angel ; Carvalho, Rita Fernandes de; Breuer, Lutz ; Shucksmith, James ; Heuvelink, Gerard B.M. ; Tait, Simon - \ 2019
Water Research 150 (2019). - ISSN 0043-1354 - p. 368 - 379.
Complexity management - Integrated catchment modelling - Sub-models of integrated modelling - Uncertainty - Water quality

This paper aims to stimulate discussion based on the experiences derived from the QUICS project (Quantifying Uncertainty in Integrated Catchment Studies). First it briefly discusses the current state of knowledge on uncertainties in sub-models of integrated catchment models and the existing frameworks for analysing uncertainty. Furthermore, it compares the relative approaches of both building and calibrating fully integrated models or linking separate sub-models. It also discusses the implications of model linkage on overall uncertainty and how to define an acceptable level of model complexity. This discussion includes, whether we should shift our attention from uncertainties due to linkage, when using linked models, to uncertainties in model structure by necessary simplification or by using more parameters. This discussion attempts to address the question as to whether there is an increase in uncertainty by linking these models or if a compensation effect could take place and that overall uncertainty in key water quality parameters actually decreases. Finally, challenges in the application of uncertainty analysis in integrated catchment water quality modelling, as encountered in this project, are discussed and recommendations for future research areas are highlighted.

Draft genome sequence of the oleaginous green alga Tetradesmus obliquus UTEX 393
Carreres, B.M. ; Jaeger, L. de; Springer, J. ; Barbosa, M.J. ; Breuer, G. ; End, E.J. van den; Kleinegris, D.M.M. ; Schäffers, I. ; Wolbert, E.J.H. ; Zhang, H. ; Lamers, P.P. ; Martins dos Santos, V.A.P. ; Wijffels, R.H. ; Eggink, G. ; Schaap, P.J. ; Martens, D.E. - \ 2017
Genome Announcements 5 (2017)3. - ISSN 2169-8287

The microalgae Tetradesmus obliquus is able to maintain a high photosynthetic efficiency under nitrogen limitation and is considered a promising green microalgae for sustainable production of diverse compounds, including biofuels. Here, we report the first draft whole-genome shotgun sequencing of T. obliquus. The final assembly comprises 108,715,903 bp with over 1,368 scaffolds.

Food Safety Crisis Management—A Comparison between Germany and the Netherlands
Asselt, E.D. van; Fels, Ine van der; Breuer, O. ; Helsloot, I. - \ 2017
Journal of Food Science 82 (2017)2. - ISSN 0022-1147 - p. 477 - 483.
crisis management - emergency response - food safety incidents
In order to prevent food safety incidents from becoming a crisis, a good crisis management structure is essential. The aim of the current study was to compare and evaluate the national food incident response plans of 2 neighboring EU Member States: Germany and the Netherlands. This revealed that the structure of these plans is comparable, starting with initial alerting, assessment of the problem, upscaling, an execution phase and finally an evaluation of the crisis management. However, the German communication structure is more complex than the Dutch one and cross-border communication between both countries is currently limited. In general, the presence of national response plans does not guarantee a good and swift response to a food safety incident as this is often hampered by difficulties in tracing the source of the problem as well as difficulties in communication between organizations involved in crisis management. A timely detection can be improved through the development of fast screening and detecting systems and through combining various data sources using computer software systems. Mutual cooperation and communication can be improved through joint exercises or projects. This will help to streamline communication toward consumers and trade partners. Such communication should be transparent relaying not only the facts but also the uncertainties in a crisis in order to gain consumer trust and safeguard international trade.
Scenedesmus Obliquus UTEX393 draft genome
Carreres, B.M. ; Jaeger, L. de; Springer, J. ; Barbosa, M.J. ; Breuer, G. ; End, E.J. van den; Kleinegris, D.M.M. ; Schäffers, I. ; Wolbert, E.J.H. ; Zhang, H. ; Lamers, P.P. ; Martins dos Santos, V.A.P. ; Wijffels, R.H. ; Eggink, G. ; Schaap, P.J. ; Martens, D.E. - \ 2016
Wageningen University
PRJEB15865 - ERP017702 - Scenedesmus obliquus - Tetradesmus obliquus - FNXT01000000 - PRJEB15865 - ERP017702 - Scenedesmus obliquus - Tetradesmus obliquus - FNXT01000000
The first draft genome of Scenedesmus obliquus (UTEX 393). The assembly yielded 9191 contigs (min length 200bp) for a total length of 96197736 bp. The scaffolding yielded 1680 sequences for a total of 126848291 bp. We were not able to recover four chromosomes and the two organelle genomes. Few scaffolds were found to cover 99.97% of the reference chloroplast genome. The mitochondrial genome was too fragmented and the scaffolds covered only 46% of UTEX78 and KS3-2.
Impacts of dietary changes on global scale nitrogen losses to air and water
Vries, W. de; Wei, Jia ; Kros, J. ; Windhorst, David ; Breuer, Lutz - \ 2016
A simple fast calculation approach has been developed that gives insight in the overall effects of dietary changes on nitrogen (N) emission to air and water by 2050 for ten identified world regions. The impact of dietary change on N fertilizer and N manure applications and related emissions was based on the consumption of crop and animal commodities, making use of the FAO data from 1961 to 2005 and extrapolating the data towards 2050 in response to five dietary change scenarios. Scenarios included a ‘North American Diet’ (NAD), a ‘Same Diet’ (SD), a ‘Business-as-Usual’ (BAU) diet; a ‘Demitarian Diet’ (DD) and a ‘Vegan Diet’ (VD). The calculated N2O and NH3 emissions and N leaching/runoff for the reference year (i.e. 2005) showed good agreement with various literature estimates. N2O was the most persistent problem, even increasing under the VD scenario, due to the increased use of N fertilizer to cultivate food crops and the assumed high contribution of N fertilizer to N2O emission. NH3 emissions increased three times in the NAD scenario, while it decreased by 13% in the VD scenario. This happens because NH3 emissions mainly follow the N manure trends. In the VD scenario, N leaching/runoff remains equal to 2005, while it increases by 145% in the NAD scenario. Overall, results show that dietary change affects most strongly NH3 emissions, followed by N leaching/runoff and then N2O emissions. Only a severe reduction in meat consumption can substantially reduce N losses with the exception of N2O emissions.
Effects of water diversion and climate change on the Rur and Meuse in low-flow situations
Pyka, Christiane ; Jacobs, Cor ; Breuer, Roman ; Elbers, Jan ; Nacken, Heribert ; Sewilam, Hani ; Timmerman, Jos - \ 2016
Environmental Earth Sciences 75 (2016). - ISSN 1866-6280
Climate change - Low-flow - Water quality - Water temperature

Water scarcity is one of the problems in water management that hinders European rivers in reaching a good ecological status as defined in the European Water Framework Directive. Water scarcity often coincides with high water temperature and low water quality. High water temperatures decrease the oxygen supply and often coincide with low flows that tend to increase the load of various compounds that affect the equilibrium in the ecosystem. The river Meuse regularly encounters situations of low water flow. In these situations, the river Rur, an important tributary of the river Meuse in Germany, contributes significantly to the Meuse discharge. Climate change can lead to more frequent periods of water scarcity. Moreover, plans exist to divert water from the Rur to former brown coal quarries in Germany. This exploratory study examines the relationships between discharge, water temperature and water quality under future climate change and water diversion scenarios in low-flow situations for the rivers Meuse and Rur. The results of the study confirm that rising air temperatures as a result of climate change will lead to higher water temperatures which will negatively impact the water quality of the Meuse in particular. Despite the fact that the contribution of the Rur has a positive impact on the water quality of the Meuse, the results suggest that effects of plans to divert water from the Rur may be small on average. However, the impact of the diversion may be stronger on individual hot summer days with low water levels when the Rur contributes significantly to the discharge of the Meuse.

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
Background
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.

Results
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.

Conclusions
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.
Limited carbon and biodiversity co-benefits for tropical forest mammals and birds
Beaudrot, L. ; Kroetz, K. ; Alvarez-Loayza, P. ; Amaral, I. ; Breuer, T. ; Fletcher, C.D. ; Jansen, P.A. ; Kenfack, D. ; Andelman, S. - \ 2016
Ecological Applications 26 (2016)4. - ISSN 1051-0761 - p. 1098 - 1111.
The conservation of tropical forest carbon stocks offers the opportunity to curb climate change by reducing greenhouse gas emissions from deforestation and simultaneously conserve biodiversity. However, there has been considerable debate about the extent to which carbon storage will provide benefits to biodiversity in part because whether forests that contain high carbon density in their aboveground biomass also contain high animal diversity is unknown. Here, we empirically examined medium to large bodied ground-dwelling mammal and bird (hereafter "ground-dwelling endotherm") diversity and carbon stock levels within the tropics using camera trap and vegetation data from a pantropical network of sites. Specifically, we tested whether tropical forests that stored more carbon contained higher ground-dwelling endotherm species richness, taxonomic diversity and trait diversity. We found that carbon storage was not a significant predictor for any of these three measures of diversity, which suggests that benefits for ground-dwelling endotherm diversity will not be maximized unless endotherm diversity is explicitly taken into account; prioritizing carbon storage alone will not necessarily meet biodiversity conservation goals. We recommend conservation planning that considers both objectives because there is the potential for more terrestrial endotherm diversity and carbon storage to be achieved for the same total budget if both objectives are pursued in tandem rather than independently. Tropical forests with low elevation variability and low tree density supported significantly higher ground-dwelling endotherm diversity. These tropical forest characteristics may provide more affordable proxies of ground-dwelling endotherm diversity for future multi-objective conservation planning when fine scale data on wildlife are lacking.
Opportunities to improve the areal oil productivity of microalgae
Breuer, G. ; Lamers, P.P. ; Janssen, M.G.J. ; Wijffels, R.H. ; Martens, D.E. - \ 2015
Bioresource Technology 186 (2015). - ISSN 0960-8524 - p. 294 - 302.
triacylglycerol tag accumulation - nitrogen starvation - scenedesmus-obliquus - starchless mutants - photosynthesis - light - photobioreactors - temperature - metabolism - simulation
Microalgae are often considered as a promising alternative source of vegetable oils. These oils can be used for food and biofuel applications. Productivities that are projected for large-scale microalgal oil production are, however, often poorly supported by scientific evidence and based on too optimistic assumptions. To facilitate the inclusion of the microalgal physiology in these projections, existing knowledge and novel scientific insights were condensed into a mechanistic model that describes photosynthesis and carbon partitioning during nitrogen starvation. The model is validated using experimental data from both wild-type and a starchless mutant of Scenedesmus obliquus. The model is subsequently used to quantify how reactor design, process design, and strain improvement can improve the oil productivity from 2.1 to up to 10.9 g m-2 day-1. These projected productivities are used to reflect on commonly assumed oil productivities and it is concluded that the microalgal oil productivity is often overestimated several folds.
Photosynthetic efficiency and carbon partitioning in nitrogen-starved Scenedesmus obliquus
Breuer, G. ; Martens, D.E. ; Draaisma, R.B. ; Wijffels, R.H. ; Lamers, P.P. - \ 2015
Algal Research 9 (2015). - ISSN 2211-9264 - p. 254 - 262.
triacylglycerol tag accumulation - lipid-accumulation - chlamydomonas-reinhardtii - nannochloropsis-oculata - starchless mutants - oil accumulation - light-intensity - microalgae - irradiance - starvation
This work investigates how the photoacclimated state at the onset of nitrogen starvation and the light intensity during nitrogen starvation influence carbon partitioning and photosynthetic efficiency in nitrogen-starved Scenedesmus obliquus. Nitrogen-depleted batch cultivations were performed at an incident light intensity of 200 and 1000 µmol m- 2 s- 1. These nitrogen-depleted batch cultivations were started with biomass that was photoacclimated to an incident light intensity of either 200 or 1000 µmol m- 2 s- 1 under nitrogen replete conditions. During initial nitrogen starvation, fatty acids and starch were produced in a 1:4 ratio. This ratio progressively increased towards only fatty acid synthesis. Hereafter, the initially accumulated starch was degraded and likely used as a substrate for fatty acid synthesis. The ratio between starch and fatty acid synthesis correlated strongly to the biomass nitrogen content. Slightly more carbon was partitioned to starch synthesis at high light intensities. Carbon partitioning was not affected by the photoacclimated state at the onset of nitrogen starvation. The photosynthetic efficiency decreased 2-fold at high versus low light intensities but was not affected by photoacclimation. Likely, the observed carbon partitioning is caused by competition between fatty acid and starch synthesis for a common carbon pre-cursor.
The dynamics of oil accumulation in Scenedesmus obliquus
Breuer, G. - \ 2015
Wageningen University. Promotor(en): Rene Wijffels, co-promotor(en): Dirk Martens; Packo Lamers. - Wageningen : Wageningen University - ISBN 9789462572348 - 268
algen - stikstof - uithongering - triacylglycerolen - productiviteit - fotosynthese - koolstof - tussenmuren - oliën - algae - nitrogen - starvation - triacylglycerols - productivity - photosynthesis - carbon - partitions - oils

.Abstract long

Global demands for food and biofuels increase rapidly, together with an increase of concerns for depleting fossil resources and climate change. New sustainable sources of vegetable oil, from now on referred to as triacylglycerol (TAG), are therefore highly desired. Arable land to produce these TAGs is however limited. Microalgae have the potential to achieve much higher TAG productivities than commonly used terrestrial plants and can be cultivated on non-arable land. Microalgae are therefore often considered as a promising alternative natural-source of TAGs. Microalgae can accumulate up to 50% of their weight as TAGs, but only do so in response to nitrogen starvation. At the same time, nitrogen starvation also affects many other cellular processes, including photosynthesis. At the start of the work presented in this thesis, little was known about the quantitative aspects of photosynthesis and TAG production during nitrogen starvation. This contributed to a large uncertainty in what could be expected from microalgae. This thesis therefore provides a quantitative understanding of the microalgal response to nitrogen starvation, that can be used to understand and optimize TAG production.

The differences between microalgae species in their response to nitrogen starvation are characterized. It was found that the difference in the response to nitrogen starvation between microalgae could be characterized in 1) how long the species could retain their photosynthetic efficiency during nitrogen starvation, 2) how much the species could in increase in biomass concentration in the absence of a nitrogen source, and 3) which fraction of the newly made biomass constitutes of TAG. The microalga species S. obliquus was chosen as the most suitable species for TAG production and used in all further studies.

It is quantified how process conditions, such as the light intensity, pH, and temperature, influence TAG production during nitrogen starvation in S. obliquus. It was found that TAG could be produced in the ranges pH 5-9, temperature of 20-35°C, and incident light intensity of 200-1500 µmol m-2 s-1. The light intensity did not affect the maximum TAG content. The light intensity did, however, have a major effect on the photosynthetic efficiency. Suboptimal pH values and temperatures resulted in both a reduction in photosynthetic efficiency and reduction in maximum TAG content.

It was found that during nitrogen starvation, at best approximately half of the biomass produced during nitrogen starvation is TAG. Large amounts of starch were produced simultaneously. This simultaneous starch and TAG production was therefore investigated in more detail. It was investigated how the carbon partitioning ratio (the ratio between fatty acid and starch synthesis rates), and the photosynthetic efficiency during nitrogen starvation, are influenced by the light intensity during nitrogen starvation and by the photoacclimated state at the onset of nitrogen starvation. It was found that the ratio between starch and fatty acid synthesis strongly correlated to the extent of nitrogen starvation, quantified as the biomass nitrogen content. Immediately after nitrogen depletion, mostly starch was made, but when nitrogen starvation progressed, this ratio shifted in favour of fatty acid synthesis. When nitrogen starvation progressed further, only fatty acids were made. Hereafter, the initially accumulated starch was degraded while fatty acid synthesis continued. The effects caused by the photoacclimated state persisted during nitrogen starvation. This did however not affect the photosynthetic efficiency or the carbon partitioning ratio during nitrogen starvation. The light intensity during nitrogen starvation had a major impact on the photosynthetic efficiency, but only a minor impact on the carbon partitioning ratio.

Because large amounts of starch are produced during nitrogen starvation in wild-type S. obliquus, it is investigated how starchless mutants of S. obliquus can be used to improve TAG production. The carbon-partitioning of the wild-type and the slm1 starchless mutant of S. obliquus are therefore compared. It was found that the starchless mutant diverted all photosynthetic capacity, that was used for starch synthesis in the wild-type, towards TAG synthesis. This resulted in much higher TAG accumulation rates during initial nitrogen starvation. Furthermore, it was found that the efficiency of photosynthesis was not negatively affected in this starchless mutant. Altogether, the TAG yield on light increased by 51%.

Using these insights, a mechanistic model was developed that describes photosynthesis and carbon partitioning during nitrogen starvation. The model was validated using experimental data from both the wild-type and starchless mutant of S. obliquus. This model was used to investigate how TAG production could be improved by advances in reactor design and strain improvement. Projections are made for productivities that seem feasible when various technologies are implemented in the microalgal cultivation process, using S. obliquus as a case-study.

Finally, the findings of this thesis are used to evaluate the outcomes of techno-economic and life cycle analysis (LCA) studies that investigated the cost-price and net energy ratio of microalgal products, mostly biodiesel. It was found that the biomass productivity and biochemical composition associated with the cultivation of microalgae are large uncertainties in the input values for these studies. Several scenarios for microalgal cultivation are therefore presented based on the findings of this thesis. For each scenario, productivities, biochemical compositions, and nutrient requirements are provided that can be used as more realistic input values for techno-economic and LCA studies. It was concluded that the TAG productivity is commonly overestimated by 3 to 6-fold. According to these studies, approximately half of the costs and energy are used in the cultivation step. It was therefore concluded that these techno-economic and LCA studies underestimate the cost-price and energy consumption by 2 to 3.5-fold. The future improvements in productivity that might seem feasible according to the model simulations, could potentially improve the productivity such that it approaches the productivity that is commonly assumed as the base-case in current techno-economic and LCA studies. These advances in productivity can help to reduce the cost-price and specific energy consumption, but in addition, a reduction in costs and energy consumption of photobioreactors is needed before microalgal TAG production can be commercialized.

Superior triacylglycerol (TAG) accumulation in starchless mutants of Scenedesmus obliquus: (II) evaluation of TAG yield and productivity in controlled photobioreactors
Breuer, G. ; Jaeger, L. de; Artus, V.P.G. ; Martens, D.E. ; Springer, J. ; Draaisma, R.B. ; Eggink, G. ; Wijffels, R.H. ; Lamers, P.P. - \ 2014
Biotechnology for Biofuels 7 (2014). - ISSN 1754-6834 - 11 p.
chlamydomonas-reinhardtii - nitrogen starvation - photosynthetic apparatus - biomass composition - biofuel production - oil accumulation - lipid production - microalgae - metabolism - growth
Background Many microalgae accumulate carbohydrates simultaneously with triacylglycerol (TAG) upon nitrogen starvation, and these products compete for photosynthetic products and metabolites from the central carbon metabolism. As shown for starchless mutants of the non-oleaginous model alga Chlamydomonas reinhardtii, reduced carbohydrate synthesis can enhance TAG production. However, these mutants still have a lower TAG productivity than wild-type oleaginous microalgae. Recently, several starchless mutants of the oleaginous microalga Scenedesmus obliquus were obtained which showed improved TAG content and productivity. Results The most promising mutant, slm1, is compared in detail to wild-type S. obliquus in controlled photobioreactors. In the slm1 mutant, the maximum TAG content increased to 57¿±¿0.2% of dry weight versus 45¿±¿1% in the wild type. In the wild type, TAG and starch were accumulated simultaneously during initial nitrogen starvation, and starch was subsequently degraded and likely converted into TAG. The starchless mutant did not produce starch and the liberated photosynthetic capacity was directed towards TAG synthesis. This increased the maximum yield of TAG on light by 51%, from 0.144¿±¿0.004 in the wild type to 0.217¿±¿0.011 g TAG/mol photon in the slm1 mutant. No differences in photosynthetic efficiency between the slm1 mutant and the wild type were observed, indicating that the mutation specifically altered carbon partitioning while leaving the photosynthetic capacity unaffected. Conclusions The yield of TAG on light can be improved by 51% by using the slm1 starchless mutant of S. obliquus, and a similar improvement seems realistic for the areal productivity in outdoor cultivation. The photosynthetic performance is not negatively affected in the slm1 and the main difference with the wild type is an improved carbon partitioning towards TAG.
Data from: Stable isotope labeled n-alkanes to assess digesta passage kinetics through the digestive tract of ruminants
Warner, D. ; Ferreira, L.M.M. ; Breuer, M.J.H. ; Dijkstra, J. ; Pellikaan, W.F. - \ 2013
digesta passage - hydrocarbons - herbivores - ruminants
We describe the use of carbon stable isotope (13C) labeled n-alkanes as a potential internal tracer to assess passage kinetics of ingested nutrients in ruminants. Plant cuticular n-alkanes originating from intrinsically 13C labeled ryegrass plants were pulse dosed intraruminally in four rumen-cannulated lactating dairy cows receiving four contrasting ryegrass silage treatments that differed in nitrogen fertilization level (45 or 90 kg nitrogen ha−1) and maturity (early or late). Passage kinetics through the gastrointestinal tract were derived from the δ13C (i.e. the ratio 13C:12C) in apparently undigested fecal material. Isotopic enrichment was observed in a wide range of long-chain n-alkanes (C27–C36) and passage kinetics were determined for the most abundant C29, C31 and C33 n-alkanes, for which a sufficiently high response signal was detected by combustion isotope ratio mass spectrometry. Basal diet treatment and carbon chain length of n-alkanes did not affect fractional passage rates from the rumen (K1) among individual n-alkanes (3.71–3.95%/h). Peak concentration time and transit time showed a quantitatively small, significant (p≤0.002) increase with carbon chain length. K1 estimates were comparable to those of the 13C labeled digestible dry matter fraction (3.38%/h; r = 0.61 to 0.71; p≤0.012). A literature review has shown that n-alkanes are not fermented by microorganisms in the rumen and affirms no preferential depletion of 13C versus 12C. Our results suggest that 13C labeled n-alkanes can be used as nutrient passage tracers and support the reliability of the δ13C signature of digestible feed nutrients as a tool to measure nutrient-specific passage kinetics.
Optimalization of TAG production in microalgae
Breuer, Guido - \ 2013
Stable isotope labeled n-alkanes to assess digesta passage kinetics through the digestive tract of ruminants
Warner, D. ; Ferreira, L.M.M. ; Breuer, M.J.H. ; Dijkstra, J. ; Pellikaan, W.F. - \ 2013
PLoS ONE 8 (2013)10. - ISSN 1932-6203 - 9 p.
marker excretion patterns - carbon-isotope - dairy-cows - enrichments delta-c-13 - botanical composition - particle-size - in-vitro - rumen - herbivores - cattle
We describe the use of carbon stable isotope (13C) labeled n-alkanes as a potential internal tracer to assess passage kinetics of ingested nutrients in ruminants. Plant cuticular n-alkanes originating from intrinsically 13C labeled ryegrass plants were pulse dosed intraruminally in four rumen-cannulated lactating dairy cows receiving four contrasting ryegrass silage treatments that differed in nitrogen fertilization level (45 or 90 kg nitrogen ha-1) and maturity (early or late). Passage kinetics through the gastrointestinal tract were derived from the d13C (i.e. the ratio 13C:12C) in apparently undigested fecal material. Isotopic enrichment was observed in a wide range of long-chain n-alkanes (C27–C36) and passage kinetics were determined for the most abundant C29, C31 and C33 n-alkanes, for which a sufficiently high response signal was detected by combustion isotope ratio mass spectrometry. Basal diet treatment and carbon chain length of n-alkanes did not affect fractional passage rates from the rumen (K1) among individual n-alkanes (3.71–3.95%/h). Peak concentration time and transit time showed a quantitatively small, significant (p=0.002) increase with carbon chain length. K1 estimates were comparable to those of the 13C labeled digestible dry matter fraction (3.38%/h; r = 0.61 to 0.71; p=0.012). A literature review has shown that n-alkanes are not fermented by microorganisms in the rumen and affirms no preferential depletion of 13C versus 12C. Our results suggest that 13C labeled n-alkanes can be used as nutrient passage tracers and support the reliability of the d13C signature of digestible feed nutrients as a tool to measure nutrient-specific passage kinetics.
Effect of light intensity, pH, and temperature on triacylglycerol (TAG) accumulation induced by nitrogen starvation in Scenedesmus obliquus
Breuer, G. ; Lamers, P.P. ; Martens, D.E. ; Draaisma, R.B. ; Wijffels, R.H. - \ 2013
Bioresource Technology 143 (2013). - ISSN 0960-8524 - p. 1 - 9.
fatty-acid-composition - neochloris-oleoabundans - nannochloropsis sp - microalgae - growth - photosynthesis - biodiesel - cultures
Microalgae-derived lipids in the form of triacylglycerols (TAGs) are considered an alternative resource for the production of biofuels and food commodities. Large scale production of microalgal TAGs is currently uneconomical. The cost price could be reduced by improving the areal and volumetric TAG productivity. The economic value could be increased by enhancing the TAG quality. To improve these characteristics, the impact of light intensity, and the combined impact of pH and temperature on TAG accumulation were studied for Scenedesmus obliquus UTEX 393 under nitrogen starved conditions. The maximum TAG content was independent of light intensity, but varied between 18% and 40% of dry weight for different combinations of pH and temperature. The highest yield of fatty acids on light (0.263 g/mol photon) was achieved at the lowest light intensity, pH 7 and 27.5 C.
Analysis of Fatty Acid Content and Composition in Microalgae
Breuer, G. ; Evers, W.A.C. ; Vree, J.H. de; Kleinegris, D.M.M. ; Martens, D.E. ; Wijffels, R.H. ; Lamers, P.P. - \ 2013
Journal of Visualized Experiments (2013)80. - ISSN 1940-087X - 9 p.
A method to determine the content and composition of total fatty acids present in microalgae is described. Fatty acids are a major constituent of microalgal biomass. These fatty acids can be present in different acyl-lipid classes. Especially the fatty acids present in triacylglycerol (TAG) are of commercial interest, because they can be used for production of transportation fuels, bulk chemicals, nutraceuticals (¿-3 fatty acids), and food commodities. To develop commercial applications, reliable analytical methods for quantification of fatty acid content and composition are needed. Microalgae are single cells surrounded by a rigid cell wall. A fatty acid analysis method should provide sufficient cell disruption to liberate all acyl lipids and the extraction procedure used should be able to extract all acyl lipid classes. With the method presented here all fatty acids present in microalgae can be accurately and reproducibly identified and quantified using small amounts of sample (5 mg) independent of their chain length, degree of unsaturation, or the lipid class they are part of. This method does not provide information about the relative abundance of different lipid classes, but can be extended to separate lipid classes from each other. The method is based on a sequence of mechanical cell disruption, solvent based lipid extraction, transesterification of fatty acids to fatty acid methyl esters (FAMEs), and quantification and identification of FAMEs using gas chromatography (GC-FID). A TAG internal standard (tripentadecanoin) is added prior to the analytical procedure to correct for losses during extraction and incomplete transesterification.
Triacylglycerol (TAG) accumulation in microalgae
Breuer, Guido - \ 2012
triacylglycerols - biochemistry - algae - biobased chemicals - biobased economy
The impact of nitrogen starvation on the dynamics of triacylglycerol accumulation in nine microalgae strains
Breuer, G. ; Lamers, P.P. ; Martens, D.E. ; Draaisma, R.B. ; Wijffels, R.H. - \ 2012
Bioresource Technology 124 (2012). - ISSN 0960-8524 - p. 217 - 226.
triglyceride accumulation - neochloris-oleoabundans - lipid production - light - growth - oil - photobioreactor - cultivation - biodiesel - biofuels
Microalgae-derived lipids are an alternative to vegetable and fossil oils, but lipid content and quality vary among microalgae strains. Selection of a suitable strain for lipid production is therefore of paramount importance. Based on published results for 96 species, nine strains were selected to study their biomass, total fatty acid, and triacylglycerol (TAG) production under nitrogen-sufficient and deficient cultivation conditions. Under nitrogen-deficient conditions, Chlorella vulgaris, Chlorella zofingiensis, Neochloris oleoabundans,and Scenedesmus obliquus, accumulated more than 35% of their dry weight as TAGs. Palmitic and oleic acid were the major fatty acids produced. The main difference between these strains was the amount of biomass that was produced (3.0–7.8-fold increase in dry weight) and the duration that the biomass productivity was retained (2–7 days) after nitrogen depletion. S. obliquus (UTEX 393) and C. zofingiensis (UTEX B32) showed the highest average TAG productivity (322 and 243 mg 1 day 1).
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