Comparison of a solvent mixture assisted dilute acid and alkali pretreatment in sugar production from hybrid Pennisetum

The effects of an acetone-butanol-ethanol (ABE) mixture on dilute H2SO4 and NaOH pretreatment for enzymatic saccharification of hybrid Pennisettmt (HP) were investigated. The results showed that ABE assisted the removal of xylan and lignin during H2SO4 and NaOH pretreatment, respectively. The glucose yield of HP increased from 33.6% to 52.9% with the assistance of a relatively higher concentration of ABE mixture (ABE4) during H2SO4 pretreatment, and during NaOH pretreatment, a lower concentration of ABE (ABE2) increased the glucose yield from 64.6% to 80.2%. The hydrolysis yield increases were related to the compositional change and surface characteristics of the pretreated materials. As observed by X-ray photoelectron spectroscopy, ABE4 resulted in a greater lignin content on the surface of materials than that produced by ABE2 during NaOH pretreatment, which possibly increased the non-productive adsorption of cellulase, thus decreasing the hydrolysis yield. The results suggested that an ABE mixture could be used as an auxiliary agent for further increasing of the digestibility of acid- and alkali-pretreated lignocellulosic materials. However, the digestibility was different depending on the concentrations of ABE during acid and alkali pretreatments.