Bioethanol production from the acid hydrolysate of the carrageenophyte Kappaphycus alvarezii (cottonii)

Seaweed resources can be used as raw materials to produce bioethanol, a renewable biofuel, to overcome fossil fuel depletion and environmental problems. Red seaweeds possess high amount of bioethanol-producible carbohydrates. Among 55 species tested, the carrageenophyte Kappaphycus alvarezii (also known as cottonii) was selected as the best resource for bioethanol production. This species is one of the most abundant and easily cultured red seaweeds. The main components of carrageenan are d-galactose-4-sulfate and 3,6-anhydro-d-galactose-2-sulfate, which are potentially fermentable d-typed carbohydrates. The seaweed powder was hydrolyzed with 0.2 M sulfuric acid and fermented with brewer's yeast. The ethanol yield from the K. alvarezii hydrolysate was 0.21 g g(-1)-galactose, which corresponded to a 41% theoretical yield. It revealed a relative ethanol production of 66% comparing to that of pure galactose.