Different extraction procedures and analysis of protein from Ulva sp. in Brittany, France

Seaweeds are well recognized as a potential protein source. The edible green seaweed, Ulva sp., is abundant in the Brittany Coast, France. This study examined the extraction of proteins and glycoproteins from this seaweed. Four different extraction procedures (Procedure 1: deionized water, DW; Procedure 2: lysis solution 1 (LS1) containing 8 M urea, 2% Tween 20, 2% Triton X-100, 30 mM dithiothreitol, and 1% polyvinylpyrolidine; Procedure 3: lysis solution 2 (LS2) containing 50 mM Tris-HCl buffer pH 8, 10 mM EDTA, 2 mM Na₂S₂O₅, and 1% Triton X-100; Procedure 4: 50 mM Tris-HCl buffer, pH 8) were applied to extract proteins from Ulva sp. in Brittany. The protein contents (%, dry basis) in the above extracts from Procedures 1–4 were 4.36 ± 0.21, 11.88 ± 0.23, 10.34 ± 0.35, and 3.58 ± 0.48, respectively. Moreover, electrophoresis (SDS-PAGE) revealed that the protein profile varies with season. Three glycoprotein-rich fractions, namely, GP-1 (from Procedure GP1), GP-2-DA, and GP-2-DS (from Procedure GP2), were extracted from Ulva sp. GP-1 and GP-2-DA fractions have a higher protein content than neutral sugars, while GP-2-DS contains a higher amount of neutral sugars than proteins. Matrix-assisted laser desorption ionization-time of flight/mass spectrometry (MALDI-TOF/MS) technique was applied to further proteomic analysis of each glycoprotein-rich fraction. GP-2-DS was hydrolyzed with protease enzyme to confirm the availability of proteins, and interestingly, the particular hydrolysate shows no original peaks in the MALDI-TOF/MS analysis. All three glycoprotein-rich fractions show no cytotoxicity in Vero cells at the tested concentration (500 mg dw mL⁻¹). Collectively, these results revealed that the extractable protein content and protein profile of Ulva sp. differ according to the extraction liquid system and the season. The utilization and value addition of proliferative Ulva sp. in Brittany as a protein source is promising but needs to consider the seasonal change of the protein profile.