Biomass structure and its contributions to recalcitrance during consolidated bioprocessing with clostridium thermocellum

Abstract

Clostridium thermocellum, a thermophilic bacterium, inherently generates cellulosic ethanol from a process known as consolidated bioprocessing (CBP). Unlike conventional cellulosic ethanol production schemes, CBP employs microorganisms that produce their own enzymes for biomass deconstruction, hydrolyze several plant cell wall polymers, and ferment certain hydrolysis products. Because cost has deterred industrial-scale cellulosic ethanol production, CBP offers a promising production scheme that addresses several issues that have previously driven up costs. Despite the benefits associated with CBP, the microorganisms employed experience difficulties breaking down the plant cell wall architecture. In particular, lignin has presented the greatest challenges to traditional ethanol production, and previous studies suggest that it also hinders CBP. Accordingly, the investigations in this work used polymeric characterization tools to confirm and detail lignin's restrictive effect towards CBP. Ultimately, chromatographic and spectroscopic techniques identified several restrictive features of lignin towards CBP, confirming that it remains a hindrance to ethanol production.