Evaluation the efficacy of extrusion pretreatment via enzymatic digestibility and simultaneous saccharification & fermentation with rapeseed straw

• Thermo-mechanical extrusion pretreatment of rape straw has been demonstrated.
• The efficacy of extrusion pretreatment was evaluated via enzymatic hydrolysis and SSF.
• Modified screw configurations facilitated the effective pulverization and longer residence time.
• Many options to be explored in the extrusion process are left to be a commercially feasible pretreatment method.

The efficacy of extrusion pretreatment was evaluated by enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) with straw of rapeseed, Brassica napus, an agricultural residue. An acceptable pretreatment result was obtained at a barrel temperature of 165 °C, acid concentration of 20 g L−1, liquid feeding rate of 13.4 cm3 min−1, solid feeding rate of 1.0 g min−1, screw rotation speed of 6.3 rad s−1, and residence time of 10.2 min, with a yield of xmg, representing the sum of the corresponding hydrolyzed sugars; xylose, mannose and galactose, of 794.3 g kg−1 and a glucose release of 21.0 g kg−1. These were calculated to be 963.0 g kg−1 and 910.3 g kg−1 based on cellulose and hemicellulose recoveries,respectively. The highest enzymatic digestibility of 781.0 g kg−1was higher than that obtained from the batch pretreatment with dilute acid by 1.4-fold. The SSF process afforded an ethanol concentration of 16.0 g L−1, corresponding to an ethanol yield of 790 g kg−1 based on the total available cellulose in the pretreated rapeseed straw.

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