Chapter 11: Biological Funneling as a Means of Transforming Lignin-derived Aromatic Compounds into Value-added Chemicals

Bacteria have tremendous potential as biocatalysts to valorize lignin streams. This biocatalytic potential derives from the recent characterization of their lignolytic enzymes and, more importantly, their inherent ability to catabolize a wide variety of aromatic compounds, transforming them into central metabolites through a limited suite of shared intermediates. This convergent catabolism facilitates the engineering of “biological funneling” to transform lignin depolymerization products to commodity chemicals. Indeed, biological funneling has the potential to overcome a major challenge of lignin valorization by converting complex mixtures of compounds into single chemical species in high atom yield. In this chapter, we first highlight newly developed deconstruction technologies and recent advances in our understanding of bacterial lignin catabolism. We then summarize features of this catabolism that are particularly advantageous to biotechnological applications and discuss characteristics of specific strains that make them good chasses for lignin-transforming biocatalysts. Examples of tailoring bacterial strains to transform specific lignin streams into target end-products are provided. Finally, we discuss advances in genome-editing tools, bioprospecting, and metabolic modeling that are essential to developing next generation bacterial biocatalysts for economically viable lignin valorization technologies.