Comparison of Six Lytic Polysaccharide Monooxygenases from <i>Thermothielavioides terrestris</i> Shows That Functional Variation Underlies the Multiplicity of LPMO Genes in Filamentous Fungi
Monika Tõlgo, Olav A. Hegnar, Heidi Østby, Anikó Várnai, Francisco Vilaplana, Vincent G. H. Eijsink, Lisbeth Olsson
Abstract
The discovery of LPMOs in 2010 has revolutionized the industrial biotechnology field, mainly by increasing the efficiency of cellulolytic enzyme cocktails. Nonetheless, the biological purpose of the multiplicity of LPMO-encoding genes in filamentous fungi has remained an open question. Here, we address this point by showing that six AA9 LPMOs from a single fungal strain have various substrate preferences and activities on tested cellulosic and hemicellulosic substrates, including several native xylan substrates. Importantly, several of these activities could only be detected when using copolymeric substrates that likely resemble plant cell walls more than single fractionated polysaccharides do. Our results suggest that LPMOs have evolved to contribute to the degradation of different complex structures in plant cell walls where different biomass polymers are closely associated. This knowledge together with the elucidated novel xylanolytic activities could aid in further optimization of enzymatic cocktails for efficient degradation of lignocellulosic substrates and more.