Production and characterization of protein rich extracts from the red macroalga Gelidium sesquipedale and its residues after industrial agar extraction

Rita Isabel Paixão Mão de Ferro

Key information

Authors:

Rita Isabel Paixão Mão de Ferro (Rita Isabel Paixão Mão de Ferro)

Supervisors:

Marília Clemente Velez Mateus (Marília Clemente Velez Mateus); Maria Teresa Ferreira Cesário Smolders (Maria Teresa Ferreira Cesário Smolders)

Published in

11/19/2021

Abstract

The red macroalga Gelidium sesquipedale is a commercially exploited species for agar extraction. Implementing a cascade process, which enables the valorisation of protein and agar fractions and contributes to a “zero waste” process, would be of enormous importance in the context of a biorefinery and circular economy. This work aims to produce protein-rich extracts from the crude alga and alga residues from the industrial agar extraction process and characterize the protein extracts obtained. The sequential implementation of two aqueous extractions followed by two alkaline extractions resulted in the recovery of 12.0 ± 1.2% and 15.4 ± 0.9% of the total protein content from the crude alga and the industrial residues, respectively. Two sequential extractions assisted by the enzymes Celluclast® and Alcalase® followed by two alkaline extractions recovered 52.1 ± 1.7% and 36.5 ± 1.3% of the protein from the crude alga and the industrial residues, respectively. In vitro bioaccessibility assays showed significantly higher values in the protein extracts compared to the original biomass. The protein products revealed a high content of carbohydrates (~30%). Different protein precipitation methods were assessed – ammonium sulfate precipitation, pH-shift method, and ethanol precipitation. The pH-shift method is shown to be a simple, fast and low reagent consumption method. The anion exchange chromatography technique was used to fractionate proteins for further isolation and purification, showing promising results.