(459f) Defining the Minimal Set of Microbial Genes Required for Valorization of Lignin Biomass

Lignin is the second-most abundant biopolymer in the world, but substantial previous efforts to break it down into useful carbon-based platform chemicals in a reliable and scalable manner have been largely unsuccessful, rendering lignin substantially underutilized. By contrast, numerous fungi and bacteria readily degrade this exceptionally recalcitrant biopolymer using a milieu of specialized enzymes, and are thus able to metabolize lignocellulose as an energy source. Reconstituting the lignin-degrading machinery of these specialized microbes in a genetically-tractable model organism may therefore enable a route to efficient valorization of lignin biomass. To date, however, no engineered heterologous host has been shown to have degradation activity toward whole lignin biomass. Identification of the minimum necessary set of enzymes required for the conversion of lignin biomass into valuable feedstock chemicals has likewise not yet been realized. This study investigates the co-expression of putative lignin-degrading enzymes in the model host organism Saccharomyces cerevisiae. Specifically, recombinant strains were engineered to drive efficient export of peroxide-generating enzymes as well as ligninase candidates identified through transcriptomic and secretomic data from lignin-degrading fungi. A combinatorial approach was employed to develop an enhanced understanding of the interconnected roles of putative ligninases in degrading lignin biomass.