Water-soluble chlorophyll-binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellul
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Biotechnology for Biofuels Open Access
RESEARCH
Water‑soluble chlorophyll‑binding proteins from Brassica oleracea allow for stable photobiocatalytic oxidation of cellulose by a lytic polysaccharide monooxygenase N. Dodge1, D. A. Russo2, B. M. Blossom3, R. K. Singh4, B. van Oort5, R. Croce5, M. J. Bjerrum4 and P. E. Jensen1*
Abstract 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 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. Results: We 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. Conclusion: With 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. Keywords: Cellulose, Light-driven, Monooxygenases, Photobiocatalysis, Chlorophyll-binding protein Background Renewable and sustainable energy resources are necessary to sustain human consumption and decrease our reliance on fossil fuels [1]. Solutions for this can be found in nature where biological pathways exist that can convert sunlight into energy-rich biomass. Plant and algal biomass are renewable and can provide sustainable fuel *Correspondence: [email protected] 1 Department of Food Science, University of Copenhagen, Rolighedsvej 26, 1958 Frederiksberg, Denmark Full list of author information is available at the end of the article
alternatives including bioethanol, biodiesel and biogas [2]. Besides providing biomass, photosynthetic organisms have also inspired the development of photobiocatalysis, a biomimicry tool designed to speed up enzymatic reactions using light [3–5]. Photobiocatalysis has been shown to increase the activity of cytochrome P450s [6], methane monooxygenases (pMMO) [7] and lytic polysaccharide monooxygenases (LPMOs) [8–10]. LPMOs are soluble copper enzymes, found in fungi, bacteria and insects, among others, that
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