In this work, to evaluate the efficacy of marine macro-algae Enteromorpha intestinalis as a potential bioenergy resource, the effects of reaction conditions (solid-to-liquid ratio, reaction temperature, and reaction time) on sugars produced by a combined process of hydrothermal and enzymatic hydrolysis were investigated. As a result of the hydrothermal hydrolysis, a 7.3 g/L (8% yield) total reducing sugar was obtained under conditions including solid-to-liquid ratio of 1:10, reaction temperature of 170 degrees C, and reaction time of 60 min. By subsequent (post-hydrothermal) enzymatic hydrolysis of samples treated at 170 degrees C for 30 min, a 20.1 g/L (22% yield) was achieved. (C) 2014 Elsevier Ltd. All rights reserved.