Synergistic Effect of Moderate Steam Explosion Pretreatment and Bovine Serum Albumin Addition for Enhancing Enzymatic Hydrolysis of Poplar

Abstract

Steam explosion (SE) pretreatment is a widely adopted method for enhancing enzymatic hydrolysis of lignocellulosic biomass in biorefinery. In this work, moderate SE pretreatment was employed to overcome the recalcitrance of cell wall through systematically assessing physicochemical and structural modifications. The hydrolysis yield of pretreated poplar by SE pretreatment (up to 69.7%) was higher than untreated poplar (26.8%). With increasing SE severity from 3.5 to 4.5, the contents of hemicellulose and lignin were reduced from 15.7 to 5.3% and 25.4 to 20.7%, respectively. Furthermore, it was observed that the cell wall structure became rough and collapsed. Meanwhile, channels emerged in the internal cell wall primarily due to the removal of hemicellulose and lignin along with the migration of lignin from inside to the out surface of cell wall. These results induced more exposure of cellulose to enzyme attacking, thus improved accessibility to cellulolytic enzymes. Addition of bovine serum albumin (BSA) obtained equal hydrolysis efficiency of 70.1% with a 33% reduction of enzyme loading, which was advantageous for enzyme costs effective.