Bioethanol production from the macroalgae Sargassum spp.

Macroalgae, an abundant and carbon-neutral renewable resource, with several species rich in carbohydrates are suitable for bioethanol production. This study focused on the pretreatment, enzyme saccharification and fermentation of Sargassum spp., a brown macroalgae for bioethanol production. The optimal acid pretreatment condition achieved in terms of glucose and reducing sugar yields was 3.4-4.6% (w/v) H₂SO₄ concentration, 115°C and 1.50h. The pretreated biomass was hydrolyzed with cellulase enzyme system supplemented with β-glucosidase. After fermentation by Saccharomyces cerevisiae at 40°C, pH of 4.5 for 48h, the ethanol conversion rate of the enzyme hydrolysate reached 89%, which was markedly higher than the theoretical yield of 51% based on glucose as substrate. Since all the glucose was consumed during fermentation, other sugar sources might be present in the hydrolysate. The macroalgae, Sargassum spp., showed significant potential as a renewable feedstock for the production of bioethanol.