Effects of LED lighting on Nannochloropsis oceanica grown in outdoor raceway ponds

Growth in most microalgal mass cultivation systems is light-limited, particularly in raceway ponds (RWP) where the light path is higher. Artificial lighting can be a promising solution to diminishing dark zones and enhance microalgal productivity. Therefore, our goal was to prevent the cell shift from photosynthesis to a respiration-only stage by resorting to LED illumination. Nannochloropsis oceanica cultures were accordingly grown out-doors in a preliminary small-scaleexperiment, followed by pilot-scale trials. In the former, three 3.0-m(2) RWP were set up under three distinct conditions: 1) without LEDs (control); 2) LEDs turned on during the night; and 3) LEDs turned on for 24 h. In the pilot-scale trial, one of two 28.9-m(2) pilot-scale RWPs was coupled to the best LED setup - determined in the small-scale preliminary experiment - using the same light intensity (normal mode) and half of the intensity (economy mode), with the second RWP serving as a control. In the preliminary experiment, the use of LEDs for 24 h was deemed as not helpful during daytime, before the culture reached asymptotic to 0.5 g DW L-1 - when dark zones appeared during the day due to sunlight attenuation in the 0.1 m-deep cultures. Overall, use of LEDs increased biomass growth chiefly by increasing nighttime productivities - materialized in higher chlorophyll, protein, and carbohydrate productivities in LED-lit cultures. A higher impact of LED lighting was observed under lower sunlight irradiances. A preliminary economic analysis indicates that use of LEDs in RWPs outdoors should be considered for high-value metabolites only.info:eu-repo/semantics/publishedVersio

Control of predators in industrial scale microalgae cultures with Pulsed Electric Fields.

This work describes the utilization of Pulsed Electric Fields to control the protozoan contamination of a microalgae culture, in an industrial 2.7m3 microalgae photobioreactor. The contaminated culture was treated with Pulsed Electric Fields, PEF, for 6h with an average of 900V/cm, 65μs pulses of 50Hz. Working with recirculation, all the culture was uniformly exposed to the PEF throughout the assay. The development of the microalgae and protozoan populations was followed and the results showed that PEF is effective on the selective elimination of protozoa from microalgae cultures, inflicting on the protozoa growth halt, death or cell rupture, without affecting microalgae productivity. Specifically, the results show a reduction of the active protozoan population of 87% after 6h treatment and 100% after few days of normal cultivation regime. At the same time, microalgae growth rate remained unaffected. © 2014 Elsevier B.V

Numerical Simulation of Heat Removal from a Window Slab Partition of a Radiative Coil Coating Oven

In this work, fluid flow and heat transfer performance of a radiative coil coating oven is numerically investigated. In the coil coating oven concept under consideration, porous radiant burners provide the required energy to evaporate the volatile species (solvents) from the applied coating and to promote curing reactions. To avoid the mixing between burners flue gas (with a non-negligible oxygen content) and evaporated (combustible) solvents in the oven (which could lead to a catastrophic oven failure), a semi-transparent window in between both atmospheres is applied. To ensure the window thermal stability during the oven operation, window cooling by wall jets is considered. Different turbulence models were compared against available wall jet heat transfer correlations to select the most suitable for three-dimensional (3D) numerical simulations. Convective heat transfer correlations purposefully developed were embedded in a one-dimensional (1D) window energy model for fast performance characterization, analysing the most influencing parameters—window radiative properties, thickness, inlet temperature and velocity of wall jets, and cooling strategy. The 1D window thermal performance is compared with literature and 3D results considering the full coil coating oven, providing satisfactory confidence on the developed strategy. The 1D model is used for an optimisation study to find the minimum energy consumption while ensuring the safety requirements (maximum window temperature and thermal gradient) are met

Cultivo mixotrófico da microalga Spirulina platensis em batelada alimentada Mixotrophic growth of Spirulina platensis in fed-batch mode

A Spirulina platensis tem sido estudada devido a seu alto valor protéico, digestibilidade e por apresentar quantidades significativas de ácidos graxos poliinsaturados, vitaminas, fenólicos e ficocianina, podendo ser utilizada na alimentação humana. A utilização de nutrientes de baixo custo é um fator importante na produção da cianobactéria por possibilitar a redução de custos de processo. Objetivou-se com este trabalho estudar o cultivo mixotrófico da S. platensis por meio da adição de uma fonte orgânica de carbono (glicose) em modo bateladaalimentada. Foi utilizado um Planejamento Fatorial Completo 2³ para o cultivo e as variáveis de estudo foram a concentração de glicose (0,5 gL-1 e 1,0 gL-1), a diluição do meio Zarrouk (50% e 75%) e a iluminância (1800 lux e 3000 lux). A concentração celular máxima obtida foi de 5,38 gL-1 com uma velocidade específica máxima de crescimento de 0,0063 h-1, nas condições de 0,5 gL-1 de glicose, diluição do meio de 75% e iluminância de 3000 lux.<br>The cyanobacterium Spirulina platensis has been studied due to its high content (~65%) of highly digestible protein as well as significant amounts of polyunsaturated fatty acids, phenolics, vitamins, minerals and phycocyanin which could be useful in the human nutrition. The use of nutrients of low costs in the cyanobacterium growth could reduce the costs of production. We studied the fed-batch mixotrophic growth of the S. platensis in Zarrouk's medium with glucose (0.5 gL-1 and 1.0 gL-1) as carbon source and also investigated the effects of dilution (50% and 75%, with water) and illumination (1,800 lux and 3,000 lux) using a 2³ factorial design. The maximum celular concentration of 5.38 gL-1 and maximum specific growth rate of 0.0063 h-1 were obtained with a glucose concentration of 0.5 gL-1, 50% dilution and 1800 lux of illuminance