Toward optimal control of flat plate photobioreactors: the greenhouse analogy?

Abstract: The cultivation of algae in photo-bioreactors shows similarities to crop cultivation in greenhouses, especially when the reactors are driven by sun light. Advanced methodologies for dynamic optimization and optimal control for greenhouses are known from earlier research. The aim here is to extend these methodologies to microalgae cultivated in a flat plate photo-bioreactor. A one-state space model for the algal biomass in the reactor is presented. The growth rate vs. light curve is parameterized on the basis of experimental evidence. Spatial distribution of light and growth rate between the plates is also considered. The control variable is the dilution rate. Dynamic optimal control trajectories are presented for various choices of goal function and external solar irradiation trajectories over a horizon of 3 days. It was found that the algae present in the reactor at final time represent a value for the future. Numerical and theoretical results suggest that the control is bang-(singular-)bang, with a strong dependence on the weather. The optimal biomass also depends on the available light, and achieving it to reach a new optimal steady cycle after a prolonged change in weather may take several days. A preliminary theoretical analysis suggests a control law that maximizes the effective growth rate. The analysis shows that like in the greenhouse case, the co-state of the algal biomass plays a pivot role in developing on-line controllers

Marine Biotechnology: A New Vision and Strategy for Europe

Marine Board-ESF The Marine Board provides a pan-European platform for its member organisations to develop common priorities, to advance marine research, and to bridge the gap between science and policy in order to meet future marine science challenges and opportunities. The Marine Board was established in 1995 to facilitate enhanced cooperation between European marine science organisations (both research institutes and research funding agencies) towards the development of a common vision on the research priorities and strategies for marine science in Europe. In 2010, the Marine Board represents 30 Member Organisations from 19 countries. The Marine Board provides the essential components for transferring knowledge for leadership in marine research in Europe. Adopting a strategic role, the Marine Board serves its Member Organisations by providing a forum within which marine research policy advice to national agencies and to the European Commission is developed, with the objective of promoting the establishment of the European Marine Research Area

Selective extraction of intracellular components from the microalga Chlorella vulgaris by combined pulsed electric field–temperature treatment

Author's accepted version (post-print).Available from 16/12/2017

Biorefinery of the macroalgae Ulva lactuca : extraction of proteins and carbohydrates by mild disintegration

publishedVersionPaid Open Acces

Monitoring of eicosapentaenoic acid (EPA) production in the microalgae Nannochloropsis oceanica

UID/QUI/50006/2019 SFRH/BD/108894/2015With the increase awareness for a healthier food regime and greener environmental processes, microalgae are being looked as a solution for a sustainable production of polyunsaturated fatty acids, such as omega-3 eicosapentaenoic acid (EPA). Nannochloropsis oceanica is an oleaginous microalga, well-known for the ability of EPA accumulation, although higher lipid productivities are still required to make the process competitive. Therefore, three cultivation parameters were tested in the present work (temperature, light cycles and nitrogen supply) in order to study the EPA profile in the polar and neutral fractions of the cells. In addition, an online monitoring tool based on a fluorescence spectroscopy technique was developed with the aim of increasing process knowledge at real time. The results of this work show that nitrogen depletion induces the highest variability in EPA accumulation in the neutral fraction (triacylglycerols). However, to increase the EPA content in the polar fraction a different strategy needs to be implemented, such as decreasing the cultivation temperature or the light available per cell. Chemometric models were developed through PCA (Principal Component Analysis) and PLS (Projection to Latent Structures), using only fluorescence spectra as inputs, enabling the monitoring of EPA in both fractions separately. High explained variance was observed (above 85%) in both fractions, with R2 above 0.81 and slopes above 0.93 for both validation and training data sets. Lower values of cross-validation and prediction errors were observed (between 0.29 and 0.49% g/gDW). The results obtained show that fluorescence spectroscopy is a powerful technique for online monitoring of non-fluorophore molecules, such as EPA, in complex process like microalgae cultivation.authorsversionpublishe

High-frequency oscillatory ventilation in children: a single-center experience of 53 cases

INTRODUCTION: The present article reports our experience with high-frequency oscillatory ventilation (HFOV) in pediatric patients who deteriorated on conventional mechanical ventilation. METHODS: The chart records of 53 consecutively HFOV-treated patients from 1 January 1998 to 1 April 2004 were retrospectively analyzed. The parameters of demographic data, cause of respiratory insufficiency, Pediatric Index of Mortality score, oxygenation index and PaCO(2 )were recorded and calculated at various time points before and after the start of HFOV, along with patient outcome and cause of death. RESULTS: The overall survival rate was 64%. We observed remarkable differences in outcome depending on the cause of respiratory insufficiency; survival was 56% in patients with diffuse alveolar disease (DAD) and was 88% in patients with small airway disease (SAD). The oxygenation index was significantly higher before and during HFOV in DAD patients than in SAD patients. The PaCO(2 )prior to HFOV was higher in SAD patients compared with DAD patients and returned to normal values after the initiation of HFOV. CONCLUSION: HFOV rescue therapy was associated with a high survival percentage in a selected group of children. Patients with DAD primarily had oxygenation failure. Future studies are necessary to evaluate whether the outcome in this group of patients may be improved if HFOV is applied earlier in the course of disease. Patients with SAD primarily had severe hypercapnia and HFOV therapy was very effective in achieving adequate ventilation

Perspectives of fluorescence spectroscopy for online monitoring in microalgae industry

OSR‐2016‐CPF‐2907‐05 UIDB/50006/2020 UIDP/50006/2020 SFRH/BD/108894/2015Microalgae industrial production is viewed as a solution for alternative production of nutraceuticals, cosmetics, biofertilizers, and biopolymers. Throughout the years, several technological advances have been implemented, increasing the competitiveness of microalgae industry. However, online monitoring and real-time process control of a microalgae production factory still require further development. In this mini-review, non-destructive tools for online monitoring of cellular agriculture applications are described. Still, the focus is on the use of fluorescence spectroscopy to monitor several parameters (cell concentration, pigments, and lipids) in the microalgae industry. The development presented makes it the most promising solution for monitoring up-and downstream processes, different biological parameters simultaneously, and different microalgae species. The improvements needed for industrial application of this technology are also discussed.publishersversioninpres

The role of starch as transient energy buffer in synchronized microalgal growth in Acutodesmus obliquus

publishedVersionPaid Open Acces

Unabated bottom water warming and freshening in the south Pacific Ocean.

Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124(3), (2019): 1778-1794, doi:10.1029/2018JC014775.Abyssal ocean warming contributed substantially to anthropogenic ocean heat uptake and global sea level rise between 1990 and 2010. In the 2010s, several hydrographic sections crossing the South Pacific Ocean were occupied for a third or fourth time since the 1990s, allowing for an assessment of the decadal variability in the local abyssal ocean properties among the 1990s, 2000s, and 2010s. These observations from three decades reveal steady to accelerated bottom water warming since the 1990s. Strong abyssal (z > 4,000 m) warming of 3.5 (±1.4) m°C/year (m°C = 10−3 °C) is observed in the Ross Sea, directly downstream from bottom water formation sites, with warming rates of 2.5 (±0.4) m°C/year to the east in the Amundsen‐Bellingshausen Basin and 1.3 (±0.2) m°C/year to the north in the Southwest Pacific Basin, all associated with a bottom‐intensified descent of the deepest isotherms. Warming is consistently found across all sections and their occupations within each basin, demonstrating that the abyssal warming is monotonic, basin‐wide, and multidecadal. In addition, bottom water freshening was strongest in the Ross Sea, with smaller amplitude in the Amundsen‐Bellingshausen Basin in the 2000s, but is discernible in portions of the Southwest Pacific Basin by the 2010s. These results indicate that bottom water freshening, stemming from strong freshening of Ross Shelf Waters, is being advected along deep isopycnals and mixed into deep basins, albeit on longer timescales than the dynamically driven, wave‐propagated warming signal. We quantify the contribution of the warming to local sea level and heat budgets.S. G. P. was supported by a U.S. GO‐SHIP postdoctoral fellowship through NSF grant OCE‐1437015, which also supported L. D. T. and S. M. and collection of U.S. GO‐SHIP data since 2014 on P06, S4P, P16, and P18. G. C. J. is supported by the Global Ocean Monitoring and Observation Program, National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce and NOAA Research. B. M. S and S. E. W. were supported by the Australian Government Department of the Environment and CSIRO through the Australian Climate Change Science Programme and by the National Environmental Science Program. We are grateful for the hard work of the science parties, officers, and crew of all the research cruises on which these CTD data were collected. We also thank the two anonymous reviewers for their helpful comments that improve the manuscript. This is PMEL contribution 4870. All CTD data sets used in this analysis are publicly available at the website (https://cchdo.ucsd.edu).2019-08-2