Microbiome-mediated improvement of industrial Chlorella biomass production

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The osteogenic and mineralogenic potential of the microalgae Skeletonema costatum and Tetraselmis striata CTP4 in fish models

Publication . Carletti, Alessio; Rosa, Joana; Pes, Katia; Borges, Inês; Santos, Tamara; Barreira, Luísa; Varela, João; Pereira, Hugo; Cancela, M. Leonor; J. Gavaia, Paulo; Laizé, Vincent

Skeletal disorders are problematic aspects for the aquaculture industry as skeletal deformities, which affect most species of farmed fish, increase production costs and affect fish welfare. Following recent findings that show the presence of osteoactive compounds in marine organisms, we evaluated the osteogenic and mineralogenic potential of commercially available microalgae strains Skeletonema costatum and Tetraselmis striata CTP4 in several fish systems. Ethanolic extracts increased extracellular matrix mineralization in gilthead seabream (Sparus aurata) bone-derived cell cultures and promoted osteoblastic differentiation in zebrafish (Danio rerio) larvae. Long-term dietary exposure to both extracts increased bone mineralization in zebrafish and upregulated the expression of genes involved in bone formation (sp7, col1a1a, oc1, and oc2), bone remodeling (acp5a), and antioxidant defenses (cat, sod1). Extracts also improved the skeletal status of zebrafish juveniles by reducing the incidence of skeletal anomalies. Our results indicate that both strains of microalgae contain osteogenic and mineralogenic compounds, and that ethanolic extracts have the potential for an application in the aquaculture sector as dietary supplements to support fish bone health. Future studies should also identify osteoactive compounds and establish whether they can be used in human health to broaden the therapeutic options for bone erosive disorders such as osteoporosis.

2023-10Journal article

Open access

Dunaliella viridis TAV01: A halotolerant, Protein-Rich Microalga from the Algarve Coast

Publication . Bombo, Gabriel; Cristofoli, N. L.; Santos, Tamara; Schüler, Lisa M.; Maia, Inês Beatriz; Pereira, Hugo; Barreira, Luísa; Varela, João

Tolerance to harsh environmental conditions, high growth rates and an amino acid profile adequate for human consumption are beneficial features observed in Dunaliella viridis TAV01, a novel strain isolated from a salt pond in the Algarve, Portugal. TAV01 was identified down to the species level by maximum likelihood and Bayesian phylogenetic analyses of the ribosomal internal transcribed spacers one and two regions (ITS1 and ITS-2) and was supported by ITS2 secondary structure analysis. The biochemical profile revealed high protein (35.7 g 100 g−1 DW; 65% higher than the minimum recommended by the World Health Organization) and lipid contents (21.3 g 100 g−1 DW), a relatively higher proportion of the polyunsaturated fatty acids (PUFAs), α-linolenic (26.3% of total fatty acids (TFA)) and linoleic acids (22.8% of TFA), compared to those of other Dunaliella strains, and a balanced essential amino acids profile containing significant levels of leucine, phenylalanine, valine, and threonine. The major carotenoid was lutein, making up over 85% of total carotenoids. The presence of high-quality natural products in D. viridis TAV01 offers the possibility of using this new strain as a valuable biological resource for novel feed or food products as ingredients or supplements.

2023-02-07Journal article

Open access

Improved production of lutein and β-carotene by thermal and light intensity upshifts in the marine microalga Tetraselmis sp. CTP4

Publication . Schüler, Lisa Maylin; Santos, Tamara; Pereira, Hugo; Duarte, Paulo; Katkam, Dr. Gangadhar N.; Florindo, Claudia; Schulze, Peter S.C.; Barreira, Luísa; Varela, João

The 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.

2020Journal article

Open access

Enhancement of heat tolerance by salt stress in Tetraselmis striata CTP4: impacts on HSP gene expression, pigments, and proximal composition

Publication . Santos, Tamara; Pereira, Hugo; Maia, Inês Beatriz; Jacinto, Rita; Bombo, Gabriel; Ribeiro Pinheiro, Filipa Maria; Barreira, Luísa; Varela, João

As the world average temperature is on the rise and heat waves are becoming more prevalent, microalgal producers have been facing significant challenges regarding the time periods during which they are able to grow less thermotolerant microalgae in outdoor production facilities. Therefore, it is urgent to explore how microalgae cope with thermal stress and under which growth conditions tolerance to temperatures close to or higher than their maximum thermal threshold is induced. For this purpose, Tetraselmis striata CTP4, a euryhaline microalga known for its thermotolerance, was selected. Tetraselmis striata belongs to the Chlorodendrophyceae, a clade that branched off early from other "core chlorophyte" clades, usually comprised of microalgae able to colonise freshwater habitats. Here, we present compelling evidence that the ability of this microalga to withstand otherwise lethal thermal upshifts to 40 degrees C is induced by exposure to higher salinity (35 ppt). In contrast, this response is abrogated at lower salinities. Concomitantly, the expression of genes encoding HSP70 and HSP100, two heat shock proteins known to mediate thermotolerance and tolerance to other stresses (e.g., salt stress) in fungi, animals and plants, was enhanced when exposed to both heat stress and higher salinities. This suggests that cross-protective mechanisms against abiotic stress appeared early during the evolution of the core chlorophytes and of Archaeplastida in general. This knowledge can be used to select novel strains and growth conditions that promote thermotolerance in microalgae that are grown in outdoor industrial production facilities in environments where heat waves are expected.

2024-11-12Journal article

Open access