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- Isolation of a euryhaline microalgal strain, Tetraselmis sp CTP4, as a robust feedstock for biodiesel productionPublication . Pereira, Hugo; Gangadhar, Katkam N.; Schulze, Peter S.C.; Santos, Tamara; de Sousa, Carolina Bruno; Schueler, Lisa; Custódio, Luísa; Malcata, F. Xavier; Gouveia, Luísa; Varela, J.; Barreira, LuísaBioprospecting for novel microalgal strains is key to improving the feasibility of microalgae-derived biodiesel production. Tetraselmis sp. CTP4 (Chlorophyta, Chlorodendrophyceae) was isolated using fluorescence activated cell sorting (FACS) in order to screen novel lipid-rich microalgae. CTP4 is a robust, euryhaline strain able to grow in seawater growth medium as well as in non-sterile urban wastewater. Because of its large cell size (9-22 mu m), CTP4 settles down after a six-hour sedimentation step. This leads to a medium removal efficiency of 80%, allowing a significant decrease of biomass dewatering costs. Using a two-stage system, a 3-fold increase in lipid content (up to 33% of DW) and a 2-fold enhancement in lipid productivity (up to 52.1 mg L-1 d(-1)) were observed upon exposure to nutrient depletion for 7 days. The biodiesel synthesized from the lipids of CTP4 contained high levels of oleic acid (25.67% of total fatty acids content) and minor amounts of polyunsaturated fatty acids with >= 4 double bonds (< 1%). As a result, this biofuel complies with most of the European (EN14214) and American (ASTM D6751) specifications, which commonly used microalgal feedstocks are usually unable to meet. In conclusion, Tetraselmis sp. CTP4 displays promising features as feedstock with lower downstream processing costs for biomass dewatering and biodiesel refining.
- Effects of LED lighting on Nannochloropsis oceanica grown in outdoor raceway pondsPublication . Carneiro, M.; Maia, Inês Beatriz; Cunha, P.; Guerra, I.; Magina, T.; Santos, Tamara; Schulze, Peter S.C.; Pereira, H.; Malcata, F. X.; Navalho, J.; Silva, J.; Otero, A.; Varela, JoãoGrowth 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.
- Improved production of lutein and β-carotene by thermal and light intensity upshifts in the marine microalga Tetraselmis sp. CTP4Publication . Schüler, Lisa Maylin; Santos, Tamara; Pereira, Hugo; Duarte, Paulo; Katkam, Dr. Gangadhar N.; Florindo, Claudia; Schulze, Peter S.C.; Barreira, Luísa; Varela, JoãoThe industrial microalga Tetraselmis sp. CTP4 is a promising candidate for aquaculture feed, novel food, cosmeceutical and nutraceutical due to its balanced biochemical profile. To further upgrade its biomass value, carotenogenesis was investigated by testing four environmental factors, namely temperature, light intensity, salinity and nutrient availability over different growth stages. The most important factor for carotenoid induction in this species is a sufficient supply of nitrates leading to an exponential growth of the cells. Furthermore, high temperatures of over 30 degrees C compared to lower temperatures (10 and 20 degrees C) induced the accumulation of carotenoids in this species. Remarkably, the two different branches of carotenoid synthesis were regulated depending on different light intensities. Contents of beta-carotene were 3-fold higher under low light intensities (33 mu mol m(-2) s(-1)) while lutein contents increased 1.5-fold under higher light intensities (170 and 280 mu mol m(-2) s(-1)). Nevertheless, highest contents of carotenoids (8.48 +/- 0.47 mg g(-1) DW) were found upon a thermal upshift from 20 degrees C to 35 degrees C after only two days at a light intensity of 170 mu mol m(-2) s(-1). Under these conditions, high contents of both lutein and beta-carotene were reached accounting for 3.17 +/- 0.18 and 3.21 +/- 0.18 mg g(-1) DW, respectively. This study indicates that Tetraselmis sp. CTP4 could be a sustainable source of lutein and beta-carotene at locations where a robust, euryhaline, thermotolerant microalgal strain is required.
- Urban wastewater treatment by Tetraselmis sp CTP4 (Chlorophyta)Publication . Schulze, Peter S.C.; Carvalho, Carolina F. M.; H., Pereira; Gangadhar, Katkam N.; Lisa Schueler, Lisa M. Schueler; Santos, Tamara; Varela, J.; Barreira, LuísaThe ability of a recent isolate, Tetraselmis sp. CTP4, for nutrient removal from sewage effluents before and after the nitrification process under batch and continuous cultivation was studied. Biomass productivities in both wastewaters were similar under continuous conditions ( 0.343 +/- 0.053 g L-1 d(-1)) and nutrient uptake rates were maximal 31.4 +/- 0.4 mg N L-1 d(-1) and 6.66 +/- 1.57 mg P-PO43 L- 1 d(-1) in WW before nitrification when cultivated in batch. Among batch treatments, cellular protein, carbohydrate and lipid levels shifted with aging cultures from 71.7 +/- 6.3 to 29.2 +/- 1.2%, 17.4 +/- 7.2 to 57.2 +/- 3.9% and 10.9 +/- 1.7 to 13.7 +/- 4.7%, respectively. In contrast, CTP4 cultivated continuously in Algal medium (control) showed lower biomass productivities ( 0.282 g VSS L-1 d(-1)) although improved lipid content (up to 20% lipids) in batch cultivation. Overall, Tetraselmis sp. CTP4 is promising for WW treatment as a replacement of the costly nitrification process, fixating more nutrients and providing a protein and carbohydrate-rich biomass as by-product. (C) 2016 Elsevier Ltd. All rights reserved.
- Carotenoid biosynthetic gene expression, pigment and n-3 fatty acid contents in carotenoid-rich Tetraselmis striata CTP4 strains under heat stress combined with high lightPublication . Schüler, Lisa Maylin; Bombo, Gabriel; Duarte, Paulo; Santos, Tamara; Maia, Inês Beatriz; Pinheiro, Filipa; Marques, José; Jacinto, Rita; Schulze, Peter S.C.; Pereira, Hugo; Barreira, Luísa; Varela, JoãoIn this study, two carotenoid-rich strains of the euryhaline microalga Tetraselmis striata CTP4 were isolated by random mutagenesis combined with selection via fluorescence activated cell sorting and growth on norflurazon. Both strains, ED5 and B11, showed an up to 1.5-fold increase in carotenoid contents as compared with the wildtype, independent of the growth conditions. More specifically, violaxanthin, beta-carotene and lutein contents reached as high as 1.63, 4.20 and 3.81 mg g-1 DW, respectively. Genes coding for phytoene synthase, phytoene desaturase, lycopene-beta-cyclase and epsilon-ring hydroxylase involved in carotenoid biosynthesis were found to be upregulated in ED5 and B11 cells as compared to the wildtype. Both strains showed higher contents of eicosapentaenoic acid as compared with those of the wildtype, reaching up to 4.41 and 2.88 mg g-1 DW, respectively. Overall, these results highlight the complexity of changes in carotenoid biosynthesis regulation that are required to improve pigment contents in microalgae.
- Effect of light quality supplied by light emitting diodes (LEDs) on growth and biochemical profiles of Nannochloropsis oculata and Tetraselmis chuiiPublication . Schulze, Peter S.C.; Pereira, Hugo; Schueler, Lisa; Guerra, Rui Manuel Farinha das Neves; Barreira, Luísa; Perales, Jose A.; Varela, João; Santos, TamaraBiochemical components obtained by microalgal biomass can be induced by specific wavelengths and processed to high value food/feed supplements or pharma- and nutraceuticals. Two biotechnologically relevant microalgae, Nannochloropsis oculata and Tetraselmis chuii, were exposed to non-tailored LEDs light sources emitting either mono- or multichromatic light with low red but significant blue (<450 nm) photon content, or tailored light sources with high blue or high red photon emissions: fluorescent light (FL), di- or multichromatic LED mixes. Growth of N. oculata and T. chuii under tailored light resulted in a approximate to 24% increase of the average biomass productivity as compared to cultures lit by non-tailored light sources. FL induced the highest C:N ratios in both algae (N. oculata: 7.91 +/- 0.09 and T. chuii: 11.29 +/- 0.03), highest total lipid (48.37 +/- 1.07%) in N. oculata and carbohydrate (55.31 +/- 1.02%) in T. chuii biomass. Among non-tailored light sources, monochromatic LEDs with emission peaks 465, 630 and 660 nm induced a approximate to 29% increase of carbohydrates and a approximate to 20% decrease of protein levels as compared to LEDs peaking at 405 nm and cool-and warm white LEDs. In conclusion, as FL have low photon conversion efficiencies (PCE), particularly within the red wavelength range, LEDs emitting at the 390-450 and 630-690 nm wavebands should be combined for optimal carbon fixation, nitrogen and phosphate uptake. (C) 2016 Elsevier B.V. All rights reserved.