45 research outputs found

    Microalgae production cost in aquaculture hatcheries

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    Microalgae are a crucial part in many aquaculture feed applications processes, mainly in hatcheries. Many aquaculture hatcheries maintain a small scale microalgae production facility in-house for the production of live feed. Microalgae are usually grown in non-automated bubble-column systems at unknown production costs. Other reactor systems or scenarios utilizing artificial light or sunlight and at different scales could result in a more cost efficient production processes. To determine the cost-price and cost-distribution of microalgae production facilities in Dutch aquaculture industry and identify the most efficient cost reducing strategies a techno-economic analysis for small scale microalgae production facilities (25-1500 m2) was developed. Commercially available reactors commonly used in aquaculture were compared; tubular photobioreactors (TPBR) and bubble-columns (BC) in two placement possibilities; using artificial light in an indoor facility (AL) and utilizing sunlight in a greenhouse (GH) under Dutch climate conditions. Data from commercial microalgae facilities in the Netherlands are used to model reference scenarios describing the cost price of microalgae production with state of the art technology in aquaculture for a biomass production capacity of 125 kg year−1. The reference cost price for algae biomass (on the basis of dry matter) is calculated at €290,- kg−1 and € 329 kg−1 for tubular reactors under artificial light and a greenhouse, respectively and €587,- kg−1 and €573 kg−1 for bubble-columns under artificial light and a greenhouse, respectively. The addition of more artificial light will significantly reduce production costs (by 33%) in all small-scale systems modelled. Biomass yield on light (Yx,ph) showed the largest effect on cost price when not considering a different scale of the production process. Process parameters like temperature control should be aimed at optimizing Yx,ph rather than other forms of cost reduction. The scale of a microalgae production facility has a very large impact on the cost price. With state of the art technologies a cost price reduction of 92% could be achieved by changing the scale from 25m2 to 1500m2, resulting in a cost price of €43,- kg−1, producing 3992 kg year−1 for tubular reactors in a greenhouse. The presented techno-economic model gives valuable insights in the cost price distribution of microalgae production in aquaculture. This allows to focus research efforts towards the most promising cost reduction methods and to optimize existing production facilities in aquaculture companies to achieve economically sustainable microalgae production for live feed in hatcheries.publishedVersionPaid Open Acces

    Optimization of Rhodomonas sp. under continuous cultivation for industrial applications in aquaculture

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    The microalgae species Rhodomonas sp. is commonly used in aquaculture for its high nutritional value due to the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content. Understanding the effect of cultivation parameters on biomass production rate and composition is presently limited, however essential in further commercialization of this strain. Under nutrient replete conditions, light intensity and temperature are the main factors determining biomass growth and composition. Therefore, the combined effect of light and temperature on the biomass production rate and biomass composition of Rhodomonas sp. was studied using a statistical Design of Experiment approach. Rhodomonas sp. was cultivated under continuous (turbidostat) conditions in lab-scale reactor systems (1.8 l) under different temperature (15–20–25–30 °C) and light conditions (60–195–330–465–600 ÎŒmol m−2 s−1). Stable biomass production was observed under all conditions except experiments performed at 30 °C, which led to cell death. Under optimized growth conditions, high growth rates (>1.0d−1) and high biomass production rates, up to 1.5 g l−1 d−1, were obtained in this study. The biomass production rate reported here is >10-fold higher than values reported in literature on Rhodomonas sp. The optimal temperature for maximal growth was found at T = 22–24 °C under all light conditions. The maximum biomass yield on light (Yx,ph – 0.87 g mol−1) was found at light levels between 110 and 220 ÎŒmol m−2 s−1. The fatty acid profile was only significantly influenced by temperature, with higher EPA and DHA contents at lower temperatures (15 °C). A total fatty acid (TFA) content of 8–10% of the total dry-weight was found for all tested conditions. The EPA content fluctuated between 9 and 16% of TFA and DHA content between 6 and 9% of TFA, only affected by temperature. A maximum EPA + DHA production rate of 114 mg l‐−1 d−1 was obtained at 20 °C and high light (600 ÎŒmol m−2 s−1) conditions.publishedVersionPaid Open Acces

    Production of Rhodomonas sp. at pilot scale under sunlight conditions

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    Rhodomonas sp., is an important microalga for aquaculture feed applications and gained increased research interest over the past few years. While efforts to optimise cultivation of the strain have been studied in detail under laboratory conditions, Rhodomonas sp. has never been grown in photobioreactors at large scale under outdoor light conditions. To study the industrial potential of this strain, we cultivated Rhodomonas sp. in three identical tubular photobioreactors with 200 l working volume each, located in a greenhouse using sunlight conditions only. Growth experiments were performed from February with winter light conditions (−2 d−1) up to high light conditions of summer (>50 mol m−2 d−1) in July, representing all sunlight conditions in the Netherlands. All nutrients were supplied in surplus and temperature and pH were maintained at optimum values for growth of Rhodomonas sp., based on lab data. The total light per reactor was calculated using a ray-tracing analysis to allow calculations based on the light reaching each individual reactor. Rhodomonas sp. grew under all tested light conditions. Biomass yield on light decreased with increasing light conditions from 0.43 ± 0.21 g mol−1 to 0.18 ± 0.04 g mol−1 at 0–10 molph m−2 d−1 to 30–40 molph m−2 d−1. Biomass productivities increased with increasing light from 0.09 ± 0.04 g l−1 d−1 to 0.19 ± 0.06 g l−1 d−1, for 0–10 and 30–40 molph m−2 d−1. We obtained a 2–5 fold increase in biomass productivity compared to previous reports on Rhodomonas sp. cultivation using artificial light at large scale. Our results show that Rhodomonas sp. can be grown at pilot scale using sunlight conditions and further improvements can be reached in the future.</p

    Von der Schule in den Beruf: Wege und Umwege in der nachobligatorischen Ausbildung

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    Array-based technology and recommendations for utilization in medical genetics practice for detection of chromosomal abnormalities

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    Laboratory evaluation of patients with developmental delay/intellectual disability, congenital anomalies, and dysmorphic features has changed significantly in the last several years with the introduction of microarray technologies. Using these techniques, a patient’s genome can be examined for gains or losses of genetic material too small to be detected by standard G-banded chromosome studies. This increased resolution of microarray technology over conventional cytogenetic analysis allows for identification of chromosomal imbalances with greater precision, accuracy, and technical sensitivity. A variety of array-based platforms are now available for use in clinical practice, and utilization strategies are evolving. Thus, a review of the utility and limitations of these techniques and recommendations regarding present and future application in the clinical setting are presented in this study

    Soziale Ungleichheiten im Leistungszuwachs und bei BildungsĂŒbergĂ€ngen

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    Dieser Beitrag beschreibt den lĂ€ngsschnittlichen Lernzuwachs in den FĂ€chern Mathematik und Deutsch wĂ€hrend der obligatorischen Schulzeit. Die Grundlage dafĂŒr bildet eine Zufallsstichprobe von etwa 2000 SchĂŒlerinnen und SchĂŒlern aus dem Kanton ZĂŒrich, die im Sommer 2003 eingeschult worden sind. Neben der Beschreibung der Schulleistungen wird ĂŒberprĂŒft, in welchem Ausmass sich diese durch die soziale Herkunft und die Erstsprache vorhersagen lĂ€sst. Ausserdem wird untersucht, inwieweit soziale Herkunft und Erstsprache die Wahrscheinlichkeit eines Übertritts in ein Langgymnasium ĂŒber die Schulleistungen hinaus erklĂ€ren können. Es zeigt sich, dass die Schulleistungen auf der Primarstufe stark und auf der Sekundarstufe nur noch mĂ€ssig ansteigen. Die Abflachung des Lernzuwachses lĂ€sst sich inbesondere im Fach Mathematik beobachten. WĂ€hrend die soziale Herkunft sehr stark mit den Schulleistungen zusammenhĂ€ngt, zeigt sich, dass die Erstsprache nach Kontrolle der sozialen Herkunft keinen eigenstĂ€ndigen Effekt mehr hat. Die soziale Herkunft hat schliesslich einen grossen Einfluss auf den Übertritt in ein Langgymnasium, und zwar selbst nach Kontrolle der Schulleistungen und der ĂŒbertrittsrelevanten Noten. Es wird geschlussfolgert, dass allfĂ€llige Programme zum Nachteilausgleich der sozialen Herkunft frĂŒh ansetzen mĂŒssen, um die sozialen DisparitĂ€ten in den Lernvoraussetzungen zu reduzieren

    Perceived Mutual Understanding (PMU): development and initial testing of a german short scale for perceptual team cognition

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    Team cognition plays an important role in predicting team processes and outcomes. Thus far, research has focused on structured cognition while paying little attention to perceptual cognition. The lack of research on perceptual team cognition can be attributed to the absence of an appropriate measure. To address this gap, we introduce the construct of perceived mutual understanding (PMU) as a type of perceptual team cognition and describe the development of a respective measure – the PMU-scale. Based on three samples from different team settings (NTotal = 566), our findings show that the scale has good psychometric properties – both at the individual as well as at the teamlevel. Item parameters were improved during a multistage process. Exploratory as well as confirmatory factor analyses indicate that PMU is a one-dimensional construct. The scale demonstrates sufficient internal reliability. Correlational analyses provide initial proof of construct validity. Finally, common indicators for inter-rater reliability and inter-rater agreement suggest that treating PMU as a team-level construct is justified. The PMU-scale represents a convenient and versatile measure that will potentially foster empirical research on perceptual team cognition and thereby contribute to the advancement of team cognition research in general
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