The application of microbes to valorize aromatic compounds derived from the abundant plant biopolymer lignin is a rapidly developing area of research that may ultimately enable viable conversion of this recalcitrant and heterogeneous resource to valuable bio-based chemical products. Starting from the three canonical lignin building blocks, which differ in the extent of aromatic ring methoxylation, several common classes of enzymatic reaction occur in the upper pathways of aromatic catabolism to prepare aromatic compounds for assimilation into central carbon metabolism, including aromatic O-demethylation, hydroxylation and decarboxylation. These critical enzymatic steps can often be rate-limiting for efficient biological funnelling of aromatic compounds. Here we review the known enzymatic mechanisms for these reactions that are relevant for aerobic aromatic catabolism of lignin-related monomers, highlighting opportunities at the intersection of biochemistry, enzyme engineering and metabolic engineering for applications in the expanding field of microbial lignin valorization.

应用微生物来评估源自丰富植物生物聚合物木质素的芳香族化合物的价值是一个快速发展的研究领域，它最终可能使这种顽固和异质的资源可行地转化为有价值的生物基化学产品。从芳环甲氧基化程度不同的三个典型木质素构件开始，在芳族分解代谢的上游途径中发生了几种常见的酶促反应，以制备用于同化到中心碳代谢的芳族化合物，包括芳族O-去甲基化、羟基化和脱羧。这些关键的酶促步骤通常会限制芳香族化合物的有效生物漏斗的速率。在这里，我们回顾了与木质素相关单体的有氧芳香分解代谢相关的这些反应的已知酶促机制，突出了生物化学、酶工程和代谢工程在微生物木质素增值领域的应用的机会。