Chemical and structural analysis of alkali pretreated pinewood for efficient ethanol production
Improvement of enzymatic hydrolysis and ethanol production from softwood pine was conducted by pretreatment with 8% (w/v) NaOH at different temperatures of 0, 25, and 80 °C for 2 h. Compared with the untreated wood, the lowest temperature resulted in the highest improvement of 271.1 and 218.2% in glucose and ethanol production yields, respectively. In addition to the pretreatment, Tween-20 as a non-ionic surfactant was used to enhance the enzymatic hydrolysis and fermentation yields by decreasing the ineffective adsorption of cellulases to the substrate. Addition of Tween-20 modified the glucose and ethanol yields from 10.9 and 10.4% for untreated wood to 39.2 and 47.8%, respectively. Structural analyses, including SEM and FTIR along with swelling and buffering capacity measurements, indicated that alkaline pretreatment modified the structure of pinewood by decreasing cellulose crystallinity and lignin content as well as increasing water absorbance and resistance to pH.