Lytic Polysaccharide MonoOxygenases; their role for lignocellulose depolymerization and production of (functional) biobased compounds

Increased environmental concerns over petroleum-based products triggered the quest to find a sustainable alternative for fuels, chemicals etc. Lignocellulose biomass, due to its abundance, is considered as one of the most promising sustainable sources for the production of fuels and chemicals, while replacing the traditional petroleum resources. In a biorefinery, by choosing a greener biochemical conversion process with cellulolytic enzymes, cellulose from biomass is depolymerized into monomeric sugars and residual fibers; which can be later converted into a spectra of value added products. Lytic polysaccharide monooxygenases (LPMOs) are one of the essential groups of enzymes in the bioconversion of lignocellulose. They are copper active enzymes that are produced by different polysaccharide degrading organisms in nature, such as lignocellulolytic fungi. In lignocellulose degradation, they are different from the traditional hydrolytic cellulolytic enzymes with their unique way of oxidative breakage of cellulose, in the presence of a co-substrate such as oxygen, and a reducing agent like lignin in the biomass. Their ability to enhance the action of traditional cellulases in cellulose depolymerization make them an integral part of today’s commercial cellulosic cocktails. Primary goals of biorefinery research include efficient liquefaction of lignocellulose in order to increase the release of monomeric sugars towards the production of various chemicals and fuels, together with the potential use of residual fibers for the production of value-added products; all by minimizing the release of undesired by-products and the environmental impact of the process. LPMOs, along with other cellulases, have been shown to be very much beneficial in this. This thesis comprises the study of LPMOs from different fungal origin, in their depolymerization ability on various substrates, including both model substrates and natural biomass samples. The evaluation was done based on their ability to release neutral and oxidized sugars, as well as their capability to promote liquefaction. Effect of various pretreatment methods of lignocellulose on the action of LPMOs was studied, together with their capability to use lignin present in the wood as a reducing agent, which gives a better understanding about their function in nature. Lastly, their role in producing value added materials such as nanocellulose, the prebiotic disaccharide cellobiose, from lignocellulose was also evaluated.