Expression and characterization of lytic polysaccharide monooxygenases from Myriococcum thermophilum

Abstract

In the field of biomass utilization, better enzyme technologies need to be developed for more efficient production of biofuels, materials and chemicals. In this regard, the study of the novel oxidative carbohydrate degrading enzymes lytic polysaccharide monooxygenases (LPMOs) are important. In this master thesis three LPMOs from the filamentous fungi Myriococcum thermophilum, a cellulose degrading organism with a genome containing over 20 possible LPMOs, are characterized.

One of these three enzymes, together with its truncated version, was successfully cloned and expressed in the yeast Pichia pastoris. All three enzymes were characterized using bioinformatics, chromatography, mass spectrometry and colorimetric analysis. Important structural elements and activities were investigated and the three enzymes were compared to each other and to previously characterized LPMOs from other fungi.

By using bioinformatic tools the enzymes were found to most likely belong to three different subclasses of LPMOs. These classes differ in their structures and sequences and use slightly different mechanisms for cellulose degradation, forming different oxidized products. The enzymes showed activity on different substrates and yielded different products, and these results confirmed affiliation to the three subclasses. It is interesting and probably important for cellulose degradation in nature that a wide diversity of these enzymes are found in certain microorganisms. This study adds new information to the as of now quite limited knowledge base that exists for this interesting, newly discovered class of enzymes.