Combination of water extraction with dilute-sulphuric acid pretreatment for enhancing the enzymatic hydrolysis of jatropha curcas shells

• 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.

Nyckelord

Jatropha curcas shells

Dilute-acid pretreatment

Water extraction

Enzymatic hydrolysis

gnocellulosic materials

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