Exogenous xylanase expression simultaneously with the indigenous cellulase to increase the cellulose hydrolysis efficiency

Abstract

To eliminate the xylan steric hindrance to lignocellulosic biomass hydrolysis, a xylanase with exoglucanase and endoglucanase activity was expressed simultaneously with the cellulase in Aspergillus niger. The indigenous coding sequence of the endoglucanase in A. niger was replaced by the encoding xylanase sequence by Agrobacterium mediated transformation. The xylanase was transcribed and translated simultaneously with the indigenous exoglucanase and β-glucosidase. The xylanase activity of the reconstructed A. niger was 3.28 U/mL. The activity of the exoglucanase from the constructed strain was increased to 1.95 U/mL from 0.21 U/mL of the original A. niger. The reconstructed A. niger cellulase could hydrolyze wheat straw to release 19.7 g/L of glucose, compared to 12.01 g/L of that released by the cellullase from the original A. niger. More efficient hydrolysis was achieved by the expression of an exogenous xylanase integrated under the expression regulation system of an indigenous endoglucanase in A. niger.