Recombinant production and regioselectivity study of lytic polysaccharide monooxygenases

Our dependence of the oil industry is one of today’s major concerns worldwide. Plant biomass has the potential to replace a large fraction of fossil resources for the production of fuels, chemicals and materials. Lignocellulose is, however, very recalcitrant towards enzymatic degradation, representing one of the biggest hurdles to cost-effective bio-refining. In this regard, a major breakthrough came with the discovery of lytic polysaccharide monooxygenases (LPMOs). These enzymes oxidatively cleave and disrupt the ordered structure of cellulose, making it better accessible for classical cellulases. Therefore, these enzymes are currently attracting much scientific attention. Although they all have a relatively similar active site, the target of their oxidative activity is known to differ amongst LPMOs. In this thesis, an extensive mutagenesis study was performed to better understand the determinants of this oxidative regioselectivity. For this, four fungal and two bacterial LPMO representatives were produced in Pichia pastoris and Escherichia coli, respectively. Carefully studying the mixture of products released from cellulose by these enzymes and their mutants, showed that a complex matrix of interactions on the enzyme’s substrate binding surface is not only responsible for binding cellulose, but also for accurately directing the oxidative force towards the C1 and/or C4 carbon