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Two grams of delignified substrate at 10% (w/v) level was subjected to biphasic dilute acid hydrolysis using phosphoric acid, hydrochloric acid and sulfuric acid separately at 110 °C for 10 min in phase-I and 121 °C for 15 min in phase-II. Combinations of acid concentrations in two phases were varied for maximum holocellulose hydrolysis with release of fewer inhibitors, to select the suitable acid and its concentration. Among three acids, sulfuric acid in combination of 1 & 2% (v/v) hydrolyzed maximum holocellulose of 25.44±0.44% releasing 0.51±0.02 g/L of phenolics and 0.12±0.002 g/L of furans, respectively. Further, hydrolysis of delignified substrate using selected acid by varying reaction time and temperature hydrolyzed 55.58±1.78% of holocellulose releasing 2.11±0.07 g/L and 1.37±0.03 g/L of phenolics and furans, respectively at conditions of 110 °C for 45 min in phase-I & 121 °C for 60 min in phase-II., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Pretreatment is a pre-requisite step in bioethanol production from lignocellulosic biomass required to remove lignin and increase the porosity of the substrate for saccharification. In the present study, chemical pretreatment of Prosopis juliflora was performed using alkali (NaOH, KOH, and NH3), reducing agents (Na2S2O4, Na2SO3) and NaClO2 in different concentration ranges at room temperature (30±2 °C) to remove maximum lignin with minimum sugar loss. Further, biphasic acid hydrolysis of the various pretreated substrates was performed at mild temperatures. Considering the amount of holocellulose hydrolyzed and inhibitors released during hydrolysis, best chemical pretreatment was selected. Among all the chemicals investigated, pretreatment with sodium dithionite at concentration of 2% (w/v) removed maximum lignin (80.46±1.35%) with a minimum sugar loss (2.56±0.021%). Subsequent biphasic acid hydrolysis of the sodium dithionite pretreated substrate hydrolyzed 40.09±1.22% of holocellulose and released minimum amount of phenolics (1.04±0.022 g/L) and furans (0.41±0.012 g/L) in the hydrolysate., (Copyright © 2013 Elsevier Ltd. All rights reserved.)