Understanding how physicochemical features from steam exploded wood affect enzymatic saccharification efficiency for bioethanol production†

Abstract

Lignocellulosic biomass is a widely available renewable feedstock that can be used as an alternative to fossil resources to produce bioproducts. Due to cellulose, hemicellulose and lignin entanglement, the complex structure of lignocellulosic biomass is responsible for its recalcitrance towards the enzymatically catalyzed biological fractionation of the constituents mentioned above: a pretreatment step is thus required to optimize the hydrolysis yields of polysaccharides. Multimodal characterization of steam-exploded wood (oak, poplar and spruce) was carried out to investigate the impact of structural and morphological modifications on fermentable sugar release. Physicochemical properties were interpreted using statistical analyses and correlations to establish the structure–property relationships. Some features such as particle size, chemical composition and lignin modifications were found to be related to the increase of saccharification yields, while others such as cellulose crystallinity and hydrophobicity had a negative impact during enzymatic saccharification. Importantly, even if the impact of these features is dependent on biomass species, the existence of a specific threshold regarding pretreatment severity conditions has been highlighted. This demonstrates the necessity of pinpointing the chemical, structural and morphological features that critically affect enzymatic saccharification in order to select the biomass feedstock and pretreatment conditions depending on the expected product yield.