Effects of preservation on protein extraction in four seaweed species

Abstract

Using either freshly pulped or preserved seaweed biomass for the extraction of protein can have a great effect on the amount of protein that can be extracted. In this study, the effect of four preservation techniques (frozen, freeze-dried, and air-dried at 40 and 70 °C) on the protein extractability, measured as Kjeldahl nitrogen, of four seaweed species, Chondrus crispus (Rhodophyceae), Ascophyllum nodosum, Saccharina latissima (both Phaeophyceae) and Ulva lactuca (Chlorophyceae), was tested and compared with extracting freshly pulped biomass. The effect of preservation is species dependent: in all four seaweed species, a different treatment resulted in the highest protein extractability. The pellet (i.e., the non-dissolved biomass after extraction) was also analyzed as in most cases the largest part of the initial protein ended up in the pellet and not in the supernatant. Of the four species tested, freeze-dried A. nodosum yielded the highest overall protein extractability of 59.6% with a significantly increased protein content compared with the sample before extraction. For C. crispus extracting biomass air-dried at 40 °C gave the best results with a protein extractability of 50.4%. Preservation had little effect on the protein extraction for S. latissima; only air-drying at 70 °C decreased the yield significantly. Over 70% of the initial protein ended up in the pellet for all U. lactuca extractions while increasing the protein content significantly. Extracting freshly pulped U. lactuca resulted in a 78% increase in protein content in the pellet while still containing 84.5% of the total initial total protein. These results show the importance of the right choice when selecting a preservation method and seaweed species for protein extraction. Besides the extracted protein fraction, the remaining pellet also has the potential as a source with an increased protein content.

Identification of Bioactive Peptides from Nannochloropsis oculata Using a Combination of Enzymatic Treatment, in Silico Analysis and Chemical Synthesis

“…Protein is extracted by re-suspending the pellet in an alkaline solution (normally ammonium sulphate) and further separation of the supernatant and pellet, and subsequently combining the two supernatants as one final extract that contains the protein. However, there are several reports of protein yield variabilities with this method with some authors suggesting that preservation methods for seaweeds also have an impact on protein yields [ 32 ]. In this work, we used a combination of the Galland-Irmouli method [ 22 ] and xylanase treatment to add value to the resulting protein extract.…”

Seaweeds as a Source of Functional Proteins

“…The amount of protein that can be extracted from seaweeds depends on various factors, such as the species, seasonal variation, pre-treatment, the combination of extraction methods, preservation method, extraction method, and its processing parameters, such as extraction temperature, time, and pH [3,71,96]. The most influencing factor in seaweed protein extraction is the complex rigid cell wall, and its composition varies with species.…”

“…Seaweeds are seasonal, and fresh seaweeds can deteriorate quickly after harvest. Therefore, seaweeds are preserved by freezing or freeze-, sun-, vacuum-, or airdrying at different temperatures to ensure year-round availability [3]. The methods used for protein extraction and the processing parameters also have an effect on the amino acid profile [74,98].…”

“…2 Sulfur amino acids (methionine + cysteine). 3 Aromatic amino acids (phenylalanine + tyrosine). NEAA, non-essential amino acids.…”

“…Seaweeds are emerging as one of the alternative protein sources with several benefits over traditional high-protein crops in relation to nutritional value, productivity, protein yield per unit area, and the need for arable land, freshwater, and artificial fertilizer [3]. Algae are aquatic organisms categorized as microalgae and macroalgae based on their size.…”