Bacterial catabolism of lignin derived-molecules
Upgrading lignin, an under-utilized component of biomass, is essential for the sustainability of biorefineries. Biocatalysis has considerable potential for upgrading lignin, but our lack of knowledge of relevant enzymes and pathways has limited its application. Bacteria of the genus Rhodococcus are particularly attractive chassis for lignin-transforming biocatalysts due to: (i) their exceptional ability to catabolize aromatic compounds; (ii) the ease with which they can be genetically manipulated; and (iii) their high natural resistance to toxic compounds that can occur in lignin streams. Further, the modular nature of their catabolism makes it relatively easy to expand the diversity of compounds degraded by adding a small number of catabolic activities. Since performing the first genomic analysis of a Rhodococcus in 2006, the Eltis lab has characterized a large number of enzymes and pathways responsible for catabolizing aromatic compounds in this genus. Most recently, we identified a pathway responsible for the catabolism of alkylphenols and alkylguaiacols produced by the reductive catalytic fractionation (RCF) of lignin (Levy-Booth et al. 2019; Fetherolf et al. 2020). As part of this, we were the first to demonstrate the bacterial degradation of RCF lignin. These advances greatly facilitate the engineering of enzymes and bacteria to biocatalytically upgrade lignin. This research benefits from a rich collaboration with the Mohn lab.