The results show that thermal /chemical pretreatment (dilute acid) hydrolyzed most part of xylan in the biomass. At the same time, lignin is also somewhat depolymerized and becomes less entrained with the cell wall matrix. It is clear that most of the lignin remains coalesced and trapped in the residual solids (85-95%). However, as the native lignin is hydrolyzed, smaller molecular weight fractions seem to migrate from their original location to the point where a small population (5-15%) makes its way into the aqueous phase of the flowing pretreatment liquor. A small portion of the lignin is redeposited on the cooled cell wall surface. The results give an understanding of the effects of lignin mobility due to pretreatment on enzymatic digestibility with application to further process development of commercial bioethanol plants.
This work was supported by the U.S. Department of Energy under contract number DE-AC36-99GO10337 with the National Renewable Energy Laboratory.