Water-soluble chlorophyll-binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellulose by a lytic polysaccharide monooxygenase

Abstract

<jats:title>Abstract</jats:title> <jats:p>Background Lytic 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 <jats:italic>in vitro</jats:italic> studies on photostability and ROS production. Here we aim apply a WSCP-Chl <jats:italic>a</jats:italic> as a photosensitizing complex for photobiocatalysis with the LPMO, <jats:italic>Tt</jats:italic>AA9. Results We have in this study demonstrated how WSCP reconstituted with chlorophyll <jats:italic>a</jats:italic> (WSCP-Chl <jats:italic>a</jats:italic>) can create a stable photosensitizing complex which produces controlled amounts of H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> in the presence of ascorbic acid and light. WSCP-Chl <jats:italic>a</jats:italic> is highly reactive and allows for tightly controlled formation of H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> by regulating light intensity. <jats:italic>Tt</jats:italic>AA9 together with WSCP-Chl <jats:italic>a</jats:italic> shows increased cellulose oxidation under low light conditions, and the WSCP-Chl <jats:italic>a</jats:italic> complex remains stable after 24 hours of light exposure. Additionally, the WSCP-Chl <jats:italic>a</jats:italic> complex demonstrates stability over a range of temperatures and pH conditions relevant for enzyme activity in industrial settings. Conclusion With WSCP-Chl <jats:italic>a</jats:italic> 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 <jats:italic>a</jats:italic> allows for stable photobiocatalysis providing a sustainable solution for biomass processing.</jats:p>