Revealing key factors influencing enzymatic digestibility of hydrothermally pretreated poplar in comparison with corn stover

Poor enzymatic digestibility of pretreated biomass is recognized as the main technical hindrance toward the biorefining of hardwood, beginning with hydrothermal pretreatment. The key factors influencing enzymatic digestibility of hydrothermally pretreated poplar (HP-PS) were investigated with hydrothermally pretreated corn stover (HP-CS) as comparisons in this study. Results showed a low glucose yield was observed for HP-PS (23.7%) in comparison with HP-CS (63.0%). The effects of lignin content, lignin inhibition mechanism, and lignin distribution on the enzymatic digestibility of HP-PS and HP-CS were compared. It suggested that the high content of lignin, which was in relatively homogenous distribution, mainly affected the bioconversion of HP-PS by impeding cellulase via physical blockage. Additionally, correlations among other factors and glucose yields were also analyzed, revealing the key inhibitory effect of surface lignin content on the bioconversion efficiency of HP-PS. The enzymatic digestibility of poplar was improved to 84.6% as a result of the disruption of lignin-derived physical blocking. These results give insights into developing strategies for the efficient bioconversion of hardwood candidates for biorefinery feedstocks.