Residual seaweed after fucoidan extraction was suspended in 15 mL 0.1 M Na2CO3 solution and put into the 35 mL reactor for microwave irradiation at 100 C for 10 min. After irradiation, the suspension was centrifuged to separate the residual alga, which was washed prior to further hydrolysis.
Aqueous solution of sodium alginate obtained in the extraction step was directly precipitated, under stirring, by addition of ethanol until reaching a proportion 1:1 in volume.
The ethanol-precipitated polysaccharides were recovered by centrifugation, then washed and dried at
40 C.
The supernatant after alginate precipitation was concentrated to 5 ml and neutralized for HPAEC analysis