Comparison of Enzymatic Hydrolysis of Bamboo Using Steam Explosion and Acid Sulfite, Alkali, and Alkaline Sulfite Pretreatments

Abstract

A combination of steam explosion (SE) and chemical pretreatments, such as acid sulfite (AS), alkali (AL), and alkaline sulfite (ALS), were evaluated using bamboo. Low pressure steam explosion at 1.25 MPa for 4 min was first applied to the bamboo. Then, the pretreated bamboo was delignified using three chemical pretreatments. Enzymatic hydrolysis was also compared among the pretreated bamboo samples. It was found that SE-ALS could be a potential method for bamboo pretreatment, which led to the reduction of lignin from 25.15% to 1.74% at 165 °C for 2 h in 5% (w/v) Na2SO3 and 0.7% (w/v) NaOH; however, little cellulose was solubilized during ALS pretreatment. A maximum glucose yield of 99.35% was achieved during the enzymatic hydrolysis process when combined with the SE-ALS pretreatment. The SE-ALS method resulted in a lower degree of lignin condensation and increased delignification compared to the SE-AS method. In addition, the SE-ALS pretreatment protected carbohydrates from degradation better than the SE-AL methods.

Keywords

• Bamboo
• Glucose
• Combined pretreatment
• Steam explosion
• Sulfonation
• Alkalization