Enhanced enzymatic hydrolysis of olive tree wood by steam explosion and alkaline peroxide delignification

Abstract

Olive tree wood, a renewable low-cost agricultural residue, was submitted to steam explosion pretreatment at 190, 210, 230 and 240 °C for 5 min. To improve enzymatic hydrolysis yields, the water-insoluble fiber was further delignified by an alkaline peroxide treatment. Enzymatic hydrolysis was performed using a commercial cellulolytic complex supplemented with β-glucosidase at 10% (w/v) pretreated material concentration. Delignification did enhance enzymatic hydrolysis yields of steam pretreated olive tree wood. Up to 80% of the lignin in the original wood was solubilized, leaving a cellulose-rich residue that led to a concentrated glucose solution (51.3 g/l after 72 h enzymatic hydrolysis in the best case). The maximum overall process yield, taking into account both sugars present in the liquid from steam pretreatment and glucose from the steamed, delignified and hydrolyzed solid was obtained at the lowest steam pretreatment temperature assayed. As a result, from 100 g of raw material, 28.8 g of sugars were recovered of 54.7 g available (52.6%).