Aqueous ammonia pretreatment of sugar beet pulp for enhanced enzymatic hydrolysis

Aqueous ammonia pretreatment under various temperatures was applied to enhance enzymatic hydrolysis of sugar beet pulp (SBP), and the mechanism of pretreatment was evaluated in terms of the enzymatic hydrolysis, chemical composition, pore size distribution, crystallinity index, and microstructure. The results showed that aqueous ammonia played a vital role in degrading of neutral detergent soluble fraction as well as softening and partly exposing of cellulose under moderate temperatures. Apertures of various sizes in the SBP tissues were formed, specific surface area was increased, and the fiber became rougher after pretreatment. The highest reducing sugar yield reached 448.52 mg/g when the SBP was pretreated by aqueous ammonia at 80 °C for 6 h, which was 2.42 times higher than that of the raw SBP. The aqueous ammonia pretreatment improved the enzymatic digestibility of SBP, which was a promising method that might be explored in ethanol production from SBP.