Jatropha curcas shells were extracted with water in a pilot-scale reactor and then pretreated with dilute sulphuric acid. The pretreatment was initially investigated with a Box-Behnken experimental design in the range of 110-180 degrees C, 0.1-1.5\% H2SO4 and 20-60 min, and then with complementary experiments at 190 degrees C. The glucan recovery was above 87\% in all the experimental runs. Xylan solubilisation was 13-20\% in the milder pretreatments and up to 45\% in the most severe runs. Around 70\% cellulose enzymatic conversion, evaluated with commercial cellulases during 72-h hydrolysis, was achieved for the pretreatments at 180 degrees C, and a region with maximal conversion was predicted for around 190 degrees C. For confirming that estimation, a 2(2)-experiment augmented by one central point and parallel pretreatments of pre-extracted and non-extracted shells were performed. The highest cellulose conversion, reached at the central point, was 16.5\% higher for the pre-extracted and pretreated material than for the directly pretreated one. The low cellulose crystallinity index (0.79) of the pre-extracted and pretreated shells correlated well with their better enzymatic convertibility. (C) 2014 Elsevier B.V. All rights reserved.