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Exploring the Bioactive Potential of Gracilaria gracilis: An Extraction Optimization Study Using Response Surface Methodology
1, 2 , 2 , 2 , * 2 , 3 , 2 , 1, 4 , 2
1  Ciências Químicas e das Biomoléculas/CISA, Escola Superior de Saúde—Instituto Politécnico do Porto, Rua Doutor António Bernardino de Almeida 400, 4200-072 Porto, Portugal
2  REQUIMTE/LAQV, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Rua Dr. António Bernardino de Almeida 431, 4249-015, Porto, Portugal
3  REQUIMTE/LAQV, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Rua Dr. António Bernardino de Almeida 431, 4249-015 Porto, Portugal
4  TBIO, Center for Translational Health and Medical Biotechnology, R. Dr. António Bernardino de Almeida 400, 4200-072 Porto
Academic Editor: Antonello Santini


The extraction of bioactive compounds from the seaweed Gracilaria gracilis for food applications was optimized using a Response Surface Methodology (RSM) approach. Employing two experimental designs - a Central Composite Face-centered Design (CCFD) and a Box-Behnken Design (BBD), the effects of extraction time (1 to 5 h), temperature (25 to 75°C), and seaweed biomass: solvent ratio (1:25 to 1:75) on the yield of compounds were evaluated [1]. Using a solid-liquid extraction method, water was chosen as the solvent for the intended use of the extracts in food products, and the extraction yield was measured by the extracts' Total Phenolic Content (TPC) [2]. For the BBD model, the best fit was the Reduced Quadratic with an R2 = 0.9356. It predicted a TPC value of 3.336 mg GAE/L at 74°C for 1.4 hours with a 1:75 seaweed:solvent ratio. For the CCFD model, the best fit was the Reduced Cubic with an R2 = 0.9091. It predicted a TPC value 4.278 mg GAE/L at 46°C for 1.1 hours with the same 1:75 ratio. Actual TPC values at these conditions were 4.35 mg GAE/L for BBD and 4.25 mg GAE/L for CCFD. This work emphasizes the customization of extraction parameters considering the structural attributes of G. gracilis and the impact of the chosen conditions. The research also reveals the antioxidant properties of the extracted compounds, demonstrating the potential of this seaweed species in the food sector. The extraction process is cost-effective, scalable, and environmentally friendly, adhering to the principles of green chemistry. While this investigation has highlighted the potential of G. gracilis, further research is needed to fully understand its limits and broader applications as an untapped resource.


This work has been developed within the scope of "BLUE BIOECONOMY INNOVATION PACT" (Project Nº. C644915664-00000026) financed by NextGenerationEU, under the incentive line “Agendas for Business Innovation” of the Recovery and Resilience Plan (PRR). This work was supported by projects REQUIMTE/LAQV—UIDB/50006/2020, UIDP/50006/2020, and financed by FCT/Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) through national funds.


[1] Heckert, N., et al., Handbook 151: NIST/SEMATECH e-Handbook of Statistical Methods, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, 2002. (Accessed June 19, 2023)

[2] C. Soares, et al., Processes, 2021, 9, 893.

Keywords: Seaweeds; Functional Food; Bioactivity