Abstract
BackgroundLytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass. LPMO-driven cellulose oxidation can be enhanced considerably through photobiocatalysis using chlorophyll derivatives and light. Water soluble chlorophyll binding proteins (WSCPs) make it is possible to stabilize and solubilize chlorophyll in aqueous solution, allowing for in vitro studies on photostability and ROS production. Here we aim to apply WSCP–Chl a as a photosensitizing complex for photobiocatalysis with the LPMO, TtAA9.ResultsWe have in this study demonstrated how WSCP reconstituted with chlorophyll a (WSCP–Chl a) can create a stable photosensitizing complex which produces controlled amounts of H2O2 in the presence of ascorbic acid and light. WSCP–Chl a is highly reactive and allows for tightly controlled formation of H2O2 by regulating light intensity. TtAA9 together with WSCP–Chl a shows increased cellulose oxidation under low light conditions, and the WSCP–Chl a complex remains stable after 24 h of light exposure. Additionally, the WSCP–Chl a complex demonstrates stability over a range of temperatures and pH conditions relevant for enzyme activity in industrial settings.ConclusionWith WSCP–Chl a as the photosensitizer, the need to replenish Chl is greatly reduced, enhancing the catalytic lifetime of light-driven LPMOs and increasing the efficiency of cellulose depolymerization. WSCP–Chl a allows for stable photobiocatalysis providing a sustainable solution for biomass processing.
Highlights
Lytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass
The photostability of free Chl a and Chl a bound to the Water-soluble chlorophyll protein (WSCP) (WSCP–Chl a) was measured over time in an LPMO light-driven system which includes LPMO from Thielavia terrestris (TtAA9) and a reductant
We observed that, in the light-driven LPMO system, the WSCP–Chl a complex is more stable than free Chl a in all conditions (Fig. 1a)
Summary
Lytic polysaccharide monooxygenases (LPMOs) are indispensable redox enzymes used in industry for the saccharification of plant biomass. LPMOs are soluble copper enzymes, found in fungi, bacteria and insects, among others, that aid in the natural decomposition and recycling of biomass [11] Their copper active site is solvent exposed and coordinated by. The flat binding surface and aromatic residues flanking the active site allow LPMOs to bind and cleave recalcitrant substrates such as chitin and cellulose [13, 14]. These enzymes are, used in current industrial enzyme cocktails to increase saccharification efficiency and glucose release [15]. LPMOs have proven useful at higher substrate loadings by synergistically enhancing the hydrolytic activity of cellulases [16, 17]
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