Fig. 1From: Consolidated bioprocessing of Populus using Clostridium (Ruminiclostridium) thermocellum: a case study on the impact of lignin composition and structure Top The three primary monolignols (from left to right) that form H, G, and S lignin units (respectively) and the most common linkage in the lignin polymer, the β-O-4 ether bond (right-most); Bottom highly resistant 5-5 (left) and β-5 (right) lignin linkages facilitated by the G unitBack to article page