Dottorato in SCIENZE DELLA VITA

Titolo della tesi: Novel insights into fungal degradation of lignin: role of a flavoenzyme in assisting laccase-mediated oxidations.

Lignin is the second most abundant biopolymer on earth. It could be a source of aromatic compounds of biotechnological and pharmaceutical interest; however, its heterogeneous and extremely complex chemical structure makes its valorization scarce. Filamentous fungi are efficient degraders of lignin owing to the secretion of a wide arsenal of redox proteins, such as laccase enzymes, which perform an enzymatic combustion. Attempts to reproduce laccase oxidation on lignin-derived compounds in vitro, yielded in repolymerization, resulting in recalcitrant lignin. It has been suggested that oligosaccharide dehydrogense from Pycnoporus cinnabarinus (PcODH), together with other fungal flavoenzymes classified in the “Auxiliary activities” class from the CAZy database, are involved in avoiding repolymerization in vivo. In this thesis, the structural and functional characterization of PcODH, provides new insights into its role as an auxiliary enzyme, supporting laccase during the lignin degradation process.