Chapter 10. Using Aerobic Pathways for Aromatic Compound Degradation to Engineer Lignin Metabolism

Remarkable microbial abilities to degrade diverse aromatic compounds present exciting opportunities in biotechnology. Long studied for applications in bioremediation, aerobic pathways for the metabolism of aromatic compounds are receiving renewed attention. Recent studies demonstrate that the, once seemingly daunting, possibility of converting lignin into valuable chemical products is becoming a reality. The achievement of this goal builds on decades of experimental investigation and the development of powerful techniques in metabolic engineering, molecular biology, and synthetic biology. The breakdown of the chemically complex lignin polymer yields a heterogeneous slate of lower molecular weight aromatic compounds, many of which can be utilized by bacteria as carbon and energy sources. This chapter focuses on the biochemistry, regulation, and distribution of these naturally occurring bacterial pathways as well as on their application to lignin valorization. Recent successes and ongoing challenges in the design and implementation of strategies to re-direct metabolic pathways are discussed.