Glycerol-FeCl₃ pretreatment stabilizes cellulose and enables selective saccharification of sugarcane bagasse

Abstract

Organosolv pretreatment of biomass is a promising strategy for subsequent selective saccharification. This study demonstrates that Glycerol-FeCl3 pretreated bagasse produces a levoglucosan yield of 33.0 wt% in fast pyrolysis, remarkably higher than 4.1 wt% from the untreated sample. In enzymatic hydrolysis, the pretreated bagasse affords 84.4 wt% glucose, compared to 8.6 wt% for the untreated biomass. Quantum chemical calculations show that Fe3+ forms strong coordination bonds with the glycosidic oxygen (binding energy: −40.6 kJ/mol), stabilizing the cellulose structure, whereas its interaction with axyl groups is much weaker (−5.7 kJ/mol). This weak interaction is attributed to the confinement effect imposed by the branched side chains of hemicellulose, which destabilizes and disrupts the hemicellulose structure. Together, these findings show that Glycerol-FeCl₃ pretreatment not only alters biomass composition but also reshapes molecular-level interactions, promoting cellulose preservation while facilitating hemicellulose and lignin removal. This dual function increases levoglucosan yields during fast pyrolysis and enhances enzymatic accessibility for glucose production.