Experiments were conducted for various pretreated substrates to investigate the impact of lignin content on cellulase adsorption and substrate digestibility. Compared with other treatments

2% (mass) NaOH pretreated solids with the highest level of lignin removal (85%) exhibited the highest accessibility to cellulase [4.7 mg protein·(g glucan) -1] and enzymatic digestibility (18.9%). The obtained maximum adsorption capacity (Wmax) and equilibrium constant (K) derived from fitting the Langmuir adsorption isotherm for different delignified substrates indicated that the removal of lignin benefited cellulase adsorption. The relationship between cellulase adsorption capacities and enzymatic digestibility for raw and pretreated solids correlated well (R2>0.8)

supporting the hypothesis that carbohydrate conversion was primarily dominated by enhancing substrate accessibility owing to lignin removal. Nevertheless

further delignification by NaOH with concentrations of 3% (mass) and 4% (mass) was unfavorable to improving substrate accessibility to cellulase and enhancing carbohydrates conversion to monosaccharide. It appeared that the appropriate delignification to some degree was a significant pretreatment factor to be taken into consideration to achieve more effectively enzymatic digestibility.