Specialized iNANO Lecture by Dr. Alissa Bleem, Research Scientist at National Renewable Energy Laboratory

Dr. Alissa Bleem
Research Scientist
Synthetic Biology and Bioconversion Center
Renewable Resources and Enabling Sciences Center
National Renewable Energy Laboratory
Golden, Colorado 80401, United States

Combining chemo- and bio-catalysis for conversion of lignin to value-added products

Lignin valorization represents a key opportunity for sustainable production of chemicals, fuels, and materials. The depolymerization of lignin to aromatic monomers is one of the most sought-after contemporary approaches to derive value from lignin, as these monomers can be used as fuel precursors or substrates for biological funneling by bacteria such as Pseudomonas putida. Our group has developed a variety of approaches for reductive catalytic fractionation (RCF), which depolymerizes lignin by cleaving aryl–ether bonds and leaving C–C linkages largely intact. To cleave C–C bonds and maximize the overall yield of aromatic monomers from RCF oil, we implemented technologies for hydrodeoxygenation and autooxidation, which produce a slate of oxygenated aromatic monomers at >85% molar yield. Next, we engineered strains of P. putida to utilize the aromatic mixture for bioconversion to muconic acid or muconolactone, value-added products with applications in polymers and composites. Strain development techniques – including bioinformatics, genome-scale libraries, and adaptive laboratory evolution (ALE) – resulted in P. putida strains with enhanced bioconversion capability, ultimately resulting in >75% molar yield of muconolactone product from RCF oil. Together, these studies demonstrate strategies to enable higher yields of bioavailable aromatic monomers from lignin, paving the way for a lignin-first bioeconomy.