Sustainable Production of Aromatic Chemicals from Lignin using Enzymes and Engineered Microbes

Abstract

Lignin is an aromatic biopolymer found in plant cell walls, that is the must abundant source of renewable aromatic carbon in the biosphere. Hence there is considerable interest in the conversion of lignin , either from agricultural waste, or as a bi-product of pulp/paper manufacture, into high-value chemicals. Although lignin is rather inert, due to the presence of ether C-O and C-C linkages, several microbes are able to degrade lignin. This article will introduce these microbes and the enzymes that they use to attack lignin, and will describe recent metabolic engineering studies that can generate high-value chemicals from lignin bioconversion. Catabolic pathways for degradation of lignin fragments will be introduced, and case studies described where these pathways have been engineered by gene knockout/insertion to generate bioproducts that are of interest as monomers for bioplastic synthesis, or aroma chemicals. Life cycle analysis of lignin bioconversion processes is discussed.