(717f) Lignin Bioconversion: Valorization from Heterogeneous Stream to High-Value Target Compound

The heterogeneity of lignin is one of the major challenges for the efficient utilization and commercial valorization of lignocellulosic biomass. Without fully utilization, many lignin streams were burned or even discharged directly, which not only causes waste of resource, but also causes many serious environment problems. The produced aromatic compounds were often heterogeneous streams, for the intrinsic heterogeneity of lignin, which in turn present significant technical challenges when attempting to produce lignin-derived chemicals where purity is often a concern. To overcome this challenge, a microbial bioconversion system will be established by fully using the capacity of the microbe in aromatic compounds catabolism in a funneling-like approach. With the tools of synthetic biology and metabolic engineering, a lignin bioconversion system to produce target compound was synthesized in the bacteria by integrating the lignin depolymerization module and target compound biosynthesis module. A laccase and versatile peroxidase co-secretive expression system was introduced to the bacteria for lignin depolymerization to release aromatic monomers. Chemical structure characterization and bioinformatic analysis were carried out to understand the mechanism of lignin degradation in the bacteria, and further guide the biodesign and optimization of product biosynthesis module. Multiple strategies were applied to optimize the target compound biosynthesis pathway, including replacing with efficient enzyme, promoter or RBS to relieve the bottleneck step, and knocking out the critical genes to block the competitive inhibition pathways. Overall, the study will enable an efficient lignin conversion to target compound with a “one step” microbial fermentation. The outcomes of this study will provide valuable fundamental information for lignin bioconversion to produce high-value aromatic compounds, as well as for the other chemicals production, and thus will promote the developing of industrial valorization of lignocellulosic biomass.