The aim of this research was to produce high reduction sugar component of bioethanol fermentation substrate using E. cottonii seaweed. The dried E. cottonii was taken from Buton district, South East Sulawesi. The seaweed was hydrolyzed using cellulose for 24 hours with various enzyme concentrations (19, 36, and 52 AU) and temperatures (40 and 50 °C). The reduction sugar was analyzed by Nelson-…