Research conducted at NREL has shown that lignin undergoes a phase transition during thermochemical pretreatments conducted above its glass transition temperature.  The lignin coalesces within the plant cell wall and appears as microscopic droplets on cell surfaces.  It is clear that pretreatment causes significant changes in lignin distribution in pretreatments at all scales from small laboratory reactors to pilot scale reactors.  A method for selectively extracting lignin droplets from the surfaces of pretreated cell walls has allowed us to characterize the chemical nature and molecular weight distribution of this fraction.  The effect of lignin redistribution on the digestibility of pretreated solids has also been tested.  It is clear that removal of the droplets increases the digestibility of pretreated corn stover.  The improved digestibility could be due to decreased non-specific binding of enzymes to lignin in the droplets, or because the droplets no longer block access to cellulose.

Redistribution of lignin caused by dilute acid pretreatment of biomass

243rd National Meeting (2012)

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