1 4 butanediol diglycidyl ether bdde

1,4-Butanediol diglycidyl ether (BDDE, ≥95%) was obtained from Sigma-Aldrich (Darmstadt, Germany). Alkaline processed gelatin (pH 3.8–7.6) was purchased from AppliChem (Darmstadt, Germany). Specimens of the green alga Ulva rigida were collected in the island of Evoia, Greece. The algal specimens were cleaned from epiphytes, rinsed with seawater and fresh water, and dried in continuous air flow. The dried alga was then cut in 1–5 mm pieces with a mill and stored at room temperature until used in paper bags in a dry, dark place. In order to obtain ulvan, 500 g of the air-dried alga were suspended in 10 L of dH₂O and heated in an autoclave at 121 °C for 30 min. The hot aqueous solution was filtrated through cotton cloth and the filtrate was allowed to cool at room temperature. The extracted polysaccharide was then precipitated by the addition of 40 L ethanol (EtOH, 96% v/v). The resulting suspension was left at 4 °C overnight and the precipitate was filtered through cotton cloth, washed three times with EtOH, sonicated for 1 h in an ultrasonic bath, vacuum-filtered, and finally freeze-dried overnight to afford ulvan as an off-white powder. The chemical analyses of ulvan were performed as previously described [41 (link)].