(424f) Visualization of Miscanthus x Giganteus Cell Wall Deconstruction Subjected to Dilute Acid Pretreatment for Enhanced Enzymatic Digestibility

Natural recalcitrance that arises from the complicated cell wall structure and heterogeneous components distribution impedes the deconstruction of lignocellulosic plant cell walls to fermentable sugars. Dilute acid pretreatment (DAP) is an attractive method to overcome the ultrastructural and chemical barriers for rendering enzymatic conversion of polysaccharides. In this study, Miscanthus x giganteusinternodes serving as a model bioenergy crop was subjected to DAP with increasing severity to obtain a range of samples with altered structure and chemistry. 

DAP of M. x giganteus resulted in solubilization of arabinoxylan and cross-linking hydroxycinnamic acid in a temperature dependent manner. The optimized pretreatment at 170 ^oC, 1% H₂SO₄for 30 min enabled a significant enhancement in sugar release efficiency of the treated samples in 72 h compared to untreated samples (51.2% yield compared to 11.8%, an increase of 4.4-fold). This remarkable improvement was favored by a sequence of changes that occur in plant cell walls during pretreatment-induced deconstruction, namely, the loss of matrix between neighboring cell walls, selective removal of hemicelluloses, redistribution of phenolic polymers, and increased exposure of cellulose. In addition, changes in cell wall structure including opening up the cell wall, increase of porosity and decreasing mechanical resistance were also found to enhance enzyme access to cellulose and further sugar yield.

Dilute Acid Pretreatment is an effective approach that enhancesthe bioconversion of cellulose to glucose by breaking down the macroscopic rigidity and microscopic resistance of cell walls.