Ecklonia maxima

2.3 Extraction of sodium alginate from E. maxima

Sodium alginate was extracted according to a modified extraction process described by Lorbeer et al. (2015). Ground seaweed was depigmented in ethanol for 2 h with 99 % ethanol (1:2, solid:liquid) with gentle shaking; the process was repeated. The depigmented ground seaweed was dried at room temperature for 24 h, thereafter submerged in deionised water, and the pH adjusted to 1.0 using 2 M HCl in a solid-to-liquid ratio of 1:30 (w/v). This was left for 2 h at room temperature with a magnetic stirrer at 100 rpm on a magnetic stirrer plate. Thereafter, the supernatant and the residual biomass were separated through a cheesecloth, and the residual biomass was resuspended into a 0.5 M sodium carbonate solution at a solid-to-liquid ratio of 1:50. This solution was left overnight at a room temperature of 22 °C with a constant stirring with a magnetic stirrer at 100 rpm. The biomass was then sieved using a cheesecloth to separate it from the liquid containing the dissolved sodium alginate. This supernatant was made to a final ethanol concentration of 70 % (v/v) by adding 99 % ethanol and left for 1 h at room temperature to precipitate the sodium alginate. A sieve was used to separate the precipitated sodium alginate from the supernatant, which was washed with methanol and acetone (50 mL each) and then dried at room temperature of 22 °C overnight. The dried sodium alginate was stored in a closed container at room temperature until further use.