What is it about?

We describe a new and unusual pathway for bacterial degradation of aromatic compounds, including acetovanillone. This pathway is unusual in that it involves phosphorylation and carboxylation before conversion to the intermediate, vanillate, which is degraded via the β-ketoadipate pathway. Acetovanillone is a major product from the pretreatment of lignin. We show that this pathway can potentially be used in conjunction with other pathways to transform the lignin component of biomass to valuable chemicals.

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Why is it important?

Upgrading lignin, an underutilized component of biomass, is essential for sustainable biorefining. Biocatalysis has considerable potential for upgrading lignin, but our lack of knowledge of the necessary enzymes and pathways has limited its application. We describe a microbial pathway that catabolizes acetovanillone, a major component of several industrial lignin streams. Importantly, this pathway enables bacterial growth on softwood lignin pretreated by oxidative catalytic fractionation. Overall, these insights greatly facilitate the engineering of bacteria to biocatalytically upgrade lignin.

Perspectives

Much of my career has involved investigating the diversity of microbial metabolism. The acetovanillone degradation pathway that we describe is interesting to me, because it involves unusual mechanisms and may be a case where bacteria have recruited enzymes from an anaerobic metabolic pathway for the aerobic biodegradation of a chemical. Humans may now be able to recruit this pathway to develop an environmentally and economically sustainable process to transform biomass to useful chemicals.

William Mohn
University of British Columbia

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This page is a summary of: Bacterial catabolism of acetovanillone, a lignin-derived compound, Proceedings of the National Academy of Sciences, October 2022, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2213450119.
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