(191f) Systems Biology-Guided Biodesign of Consolidated Lignin Conversion

Lignin is the second most abundant biopolymer on the earth. However, due to the recalcitrant nature of the complex polyphenolic structure, the conversion of lignin remains a major challenge for sustainable biorefineries. We hereby elucidated the lignin degradation mechanisms and carbon utilization pattern in a unique lignin-utilizing Pseudomonas putida strain (A514) with comparative genomics and systems biology. The mechanistic study further guided the design of three functional modules to validate the molecular mechanisms and enable a consolidated lignin bioconversion route. First, P. putida A514 coordinately up-regulated a dye peroxidase-based enzymatic system for lignin depolymerization. The augmentation of this system by production and secretion of a heterologous, highly active dye peroxidase significantly improved the cell growth on Kraft lignin. Together with the NMR analysis of lignin structure, the study established the role of bacterial peroxidase in effective degradation of lignin, instead of model compounds, to promote cell growth. Second, the lignin substrate induced production of a network of enzymes and pathways for aromatic compound degradation, which can be enhanced by over-expressing genes encoding key enzymes. Third, the β-oxidation of fatty acid was up-regulated when A514 was grown on lignin and vanillic acid. Based on the carbon utilization pattern, the functional module for PHA production was designed to channel β-oxidation products for increasing PHA yield. The integration of the three functional modules enabled the direct production of PHA from lignin polymer, elucidated the lignin conversion mechanisms in bacteria, and laid out the concept for designing a consolidated lignin conversion route.