Delignification overmatches hemicellulose removal for improving hydrolysis of wheat straw using the enzyme cocktail from Aspergillus niger

Abstract

Based on a general understanding that hemicellulose removal is more efficient than delignification for biomass deconstruction, an Aspergillus niger strain producing high xylanase activity was screened out from seventeen strains by clear halo experiments. Low-cost enzyme cocktail with high xylanase activity was produced from wheat straw medium fermented by the Gyx086 strain. The enzyme cocktail with high xylanase activity could more effectively hydrolyze wheat straw than other biomasses. However, only 30% of total carbohydrates could be hydrolyzed to reducing sugar in untreated wheat straw. Further enzymatic hydrolysis and pretreated trials were carried out, the results indicated that hemicellulose removal was less effective than delignification for de-recalcitrance of wheat straw and the crystallinity is little interference with the hydrolysis process. Delignified wheat straw was near-completely hydrolyzed by the enzyme cocktail in 60 h. This study advanced the knowledge in promoting wheat straw as feedstock for bio-based industry.

Keywords: Aspergillus niger; Delignification; Enzymatic hydrolysis; Hemicellulose removal; Wheat straw; Xylanase.