The effect of aqueous ammonia soaking on enzymatic hydrolysis of wheat straw

Abstract

Enzymatic hydrolysis of wheat straw was performed following aqueous-ammonia soaking. The effects of various operating variables including pretreatment temperature (30, 50, and 70 °C), pretreatment time (15, 30, and 45 h), and ammonia concentration (10% and 30%) on the enzymatic digestibility were investigated. Enzymatic hydrolysis were performed at 5% (w/w) solid loading, 50 °C, and 150 rpm for 96 h, using Accellerase 1500 (30 FPU/g dry biomass). The best reaction conditions observed (50 °C, 45 h, and 30% ammonia) resulted in enzymatic hydrolysis yields of 76% for glucose and 81% for xylose. Total reducing sugars released during hydrolysis experiments were also determined. As the severity of the pretreatment was increased, higher reducing sugar release was observed. It was also found that total reducing sugars vary exponentially with the reciprocal of the pretreatment temperature. An empirical model was developed, which relates reducing sugar concentrations to pretreatment time and temperature.