The Effect of Severity Factor on the Release of Xylose and Phenolics from Rice Husk and Rice Straw

Abstract

The objective of this work was to compare the effects of dilute acid hydrolysis on two major residues of rice crop cultivation, namely, rice straw and rice husk and to find the optimum hydrolysis parameters for both residues. The hydrolysis conditions were expressed by a severity factor (SF) in the range of −0.2 to 2.01. The xylose release reached maximum at SF of 1.96 for rice straw and 1.88 for rice husk hydrolysates. The glucose release and by-products productions were higher in the rice straw hydrolysate than rice husk hydrolysate over the entire range of SF. Response surface methodology was used for the optimization of the hydrolysis process. The optimum reaction temperature, reaction time, and acid concentration were 122 °C, 60 min and 2.95 % of acid concentration, respectively, for rice straw; the corresponding values for rice husk were 127 °C, 60 min and 2.6 % of acid concentration. Under these conditions, 88.1 % of xylose yield and 1.98 g/g of selectivity for rice straw and 87.7 % of xylose yield and 11.8 g/g of selectivity for rice husk were achieved.