Elucidating the Structural Changes to Populus Lignin during Consolidated Bioprocessing with Clostridium thermocellum

During consolidated bioprocessing (CBP), Clostridium thermocellum hydrolyzes several plant cell wall components. Cellulose hydrolysis, specifically, liberates sugars for fermentation, which generates ethanol, acetate, hydrogen, and other products. While several studies indicate that C. thermocellum hydrolyzes carbohydrates in biomass, the structural changes to lignin during CBP remain unclear. In this study, the whole plant cell walls of untreated and C. thermocellum-treated Populus trichocarpa were characterized using NMR and FTIR The results suggest that C. thermocellum reduces the beta-O-4 linkage content and increases the lignin S/G ratio. This investigation indicates that C. thermocellum not only modifies lignin in order to access cellulose but also leaves behind a suitable lignin substrate for value-added applications in the cellulosic ethanol production scheme.