Cassava starch factory residue (CSFR), a low cost solid byproduct of the cassava starch industry, having around 60% unextracted starch and 15% cellulose is a potential candidate for bioethanol production. As the economic feasibility depends on complete degradation of the polysaccharides to fermentable glucose, the comparative hydrolytic potential of four enzymes such as Multifect (R) XL, Optimash (TM) XL, Optimash (TM) BG and Accellerase (TM) 1000 was studied. Whilst the former three enzymes exerted maximum activity at pH 5.0 and 60 degrees C, Accellerase had optimum activity at pH 4.5 and 60 C. The enzyme cocktail, Multifect XL-Optimash XL-Accellerase (5, 15 and 20 g enzyme protein kg (-1) CSFR respectively) was more effective than sequential process with the same enzyme loading. Hydrothermal treatment (HT) of CSFR for 30 min at 100 degrees C enhanced the susceptibility to enzymatic cleavage as compared to HT for 45 and 60 min as well as autoclaving or microwave exposure. Optimash BG was the most effective on HT CSFR and approximately 704.8 g glucose was released kg (1) CSFR. The high yield of glucose indicates the potential use of hydrothermally treated CSFR as a cheap substrate for ethanol production. (C) 2010 Elsevier Ltd. All rights reserved.