Two-stage acid saccharification of fractionated Gelidium amansii minimizing the sugar decomposition

► This study conducted two stage acid hydrolysis on the residual cellulose derived from Red Algae (Gelidium amansii). ► This study conformed that G. amansii is a very promising advance biomass for ethanol production. ► This study investigated the biphasic characteristic of cellulose, namely it is composed of easy reacting and resistant reacting cellulose. ► This study established the operation conditions leading to the maximum yield of glucose for 1st and 2nd acid hydrolysis, respectively. ► This study got the competitive glucose yield with enzymatic saccharification of cellulose derived from G. amansii.