Disparate roles of solvent extractable lignin and residual bulk lignin in enzymatic hydrolysis of pretreated sweetgum

Abstract

The roles of solvent extractable lignin and residual bulk lignin in enzymatic hydrolysis of Avicel and lignocellulosic biomass were distinguished in this study. Solvent extractable lignin removal reduced the 72 h hydrolysis yields of dilute acid pretreated sweetgum (DASG) and organosolv pretreated sweetgum (OPSG) from 38.1% to 31.8% and from 69.9 to 49.3%, respectively. On the contrary, residual bulk lignin removal enhanced the 72 h hydrolysis yields of DASG and OPSG to 91.7% and 90.5%, respectively. The isolated lignins were added into enzymatic hydrolysis of Avicel, which revealed the positive effect of extractable lignin and the negative effect of residual bulk lignin on enzymatic hydrolysis. The cellulase distribution during the hydrolysis and cellulase adsorption indicated that the extractable lignin could counter the negative effect of residual bulk lignin by reducing the non-productive binding between cellulase and bulk lignin.