A commercial laccase-mediator system to delignify and improve saccharification of the fast-growing Paulownia fortunei (Seem.) Hemsl.

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It was demonstrated for the first time that a laccase-based enzymatic pretreatment is able to delignify fast-growing paulownia species. The treatment was performed with a commercial low-redox potential laccase isolated from Myceliophthora thermophila (Apinis) Oorschot and methyl syringate (MeS) as a natural phenolic mediator. Up to 24% lignin removal was attained by the laccase-MeS treatment (L/MeS), followed by alkaline peroxide extraction in a multistage sequence. The reduction in lignin content was accompanied by a significant improvement in the subsequent enzymatic saccharification, with increases of up to 38% glucose and 34% xylose yields. The structural modifications of the lignin were analyzed in situ by two dimensional-nuclear magnetic resonance (2D-NMR) spectroscopy. A considerable removal of guaiacyl and syringyl lignin units with respect to the carbohydrate signals was visible as well as the cleavage of β-O-4′, β-5′ and β-β′ linkages leading to elevated amounts of Cα-oxidized guaiacyl and syringyl units. The presence of oxidized lignin compounds in the filtrates of the enzymatic treatments - such as vanillin, vanillic acid, syringaldehyde and syringic acid - conclusively demonstrates the ability of L/MeS treatment to oxidize and depolymerize the lignin in paulownia wood

This study has been funded by the Spanish projects CTQ2014-60764-JIN, AGL2014-53730-R and AGL2017-83036-R (financed by Agencia Estatal de Investigación, AEI, and Fondo Europeo de Desarrollo Regional, FEDER) and the CSIC project 2014-40E-097.

Peer reviewed