Strategies for extraction and recovery of the protein fraction from the macroalga Gelidium sesquipedale

January 25, 2021

The red seaweed Gelidium sesquipedale is commercially explored and harvested for extraction of agar, leaving a large biomass share needing valorization. From a biorefinery concept perspective, implementing a cascading valorization of both protein and agar represents a step closer to a “no waste” agar extraction process. Sun dried and milled G. sesquipedale from the coast of Portugal, composed of 92.3 ± 0.2% of total solids, and 7.7 ± 0.2% of moisture, (in dry weight: 62.4 ± 3.5% total carbohydrates, with 9.5 ± 2.0% cellulose and 52.9 ± 1.2% agar, 14.8 ± 0.2% total protein, and 19.6 ± 1.0% ash content), was used in the screening of 15 protein multi-steps extraction procedures by means of aqueous, alkaline, and acidic solutions, ultrasound-assisted, and enzyme-assisted extractions. Consecutive aqueous and alkaline extractions allowed recovering 14.7 ± 2.3% protein content. Sequential implementation of two enzyme-assisted extractions (Celluclast, followed by Alcalase) and two sequential alkaline extractions, resulted in a protein recovery of 45.5 ± 2.8%. Scaling up of this procedure (with and without the Alcalase step) led to recovery yields of 38.5 ± 3.5% and 15.8 ± 0.6%, respectively. Extraction residues revealed a loss of ~30% of the carbohydrate fraction, although agar levels were still high (~40% dw). Protein precipitation with 85% ammonium sulfate and subsequent diafiltration and concentration using a centrifugal ultrafiltration (3 kDa MWCO) yielded overall recoveries of 14.4% and 11.8%, respectively.

Authors in the community:

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  M

  Mariana Duarte Gordalina

  ist425093

Supervisors of this institution:

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  M

  Maria Teresa Ferreira Cesário Smolders

  ist129469

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  M

  Marília Clemente Velez Mateus

  ist12931

industrial-biotechnology - Industrial Biotechnology

eng - English

Instituto Superior Técnico