Lytic Polysaccharide Monooxygenases - Studies of Fungal Secretomes and Enzyme Properties

Laura Nekiunaite

    Research output: Book/ReportPh.D. thesis

    1496 Downloads (Pure)


    Efficient degradation of plant biomass by enzymes is an important step towards a more environmentally friendly and sustainable bioeconomy. However, the complexity and recalcitrant nature of the substrates limit enzyme performance on plant biomass and current enzyme cocktails are not efficient enough to degrade it. The recently discovered lytic polysaccharide monooxygenases (LPMOs) are crucial enzymes employed in biomass breakdown in nature owing to their ability to boost activity of other biomass degrading hydrolases. Filamentous fungi are known to be significant players in plant biomass conversion as they produce a wide diversity of degrading enzymes. In the first part of this PhD thesis, the secretomes of the well-known fungus Aspergillus nidulans grown on cereal and legume starches were analyzed. Secretomics is a powerful tool to unravel secretion patterns of fungi and their response to different substrates at the protein level. It could help to design better enzyme cocktails that increase efficiency of biomass degradation. The secretomes of A. nidulans revealed differences in growth and secretion of enzymes, depending on the type and properties of starches. A common
    characteristic of the fungus secretomes on different starches was that the LPMOs, shown to be active on starch, were highly abundant, together with other oxidative enzymes suggesting an important role for these enzymes in fungal starch degradation. The presence of binding sites for AmyR, a transcriptional regulator for starch degradation, were also identified upstream the LPMO genes, providing evidence for a co-regulatory mechanism of LPMOs and amylolytic hydrolases. The second part of the PhD thesis is focused on understanding the binding properties of LPMOs to starch and starch mimic substrate. It was shown that LPMOs possessing starch binding domain (CBM20) has similar binding affinities as the amylolytic hydrolases containing CBM20. The binding of the LPMO to starch is presumably mediated by the CBM20. In the last part of the PhD thesis, the action of a novel LPMO from the plant pathogenic fungus Fusarium graminearum on cellulose and xyloglucan is demonstrated. Previous studies have shown that some fungal LPMOs are capable to degrade xyloglucan but only by unsubstituted glucose unit in the backbone. This study for the first time showed that LPMO from F. graminearum is able to cleave xyloglucan backbone randomly, including two substituted glucose units. Moreover, a question about a connection between LPMOs and fungi pathogenesis was raised. The novel insight from work done during the PhD study promotes our understanding of unexplored aspects of fungal LPMOs and inspires further research in this realm of glycoscience.
    Original languageEnglish
    PublisherDepartment of Systems Biology, Technical University of Denmark
    Number of pages165
    Publication statusPublished - 2016


    Dive into the research topics of 'Lytic Polysaccharide Monooxygenases - Studies of Fungal Secretomes and Enzyme Properties'. Together they form a unique fingerprint.

    Cite this