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Depolymerisation of Kraft Lignin by Tailor-Made Alkaliphilic Fungal Laccases

Lignins released in the black liquors of kraft pulp mills are an underutilised source of aromatics. Due to their phenol oxidase activity, laccases from ligninolytic fungi are suitable biocatalysts to depolymerise kraft lignins, which are characterised by their elevated phenolic content. However, the...

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Autores principales: Rodríguez-Escribano, David, de Salas, Felipe, Pliego, Rocío, Marques, Gisela, Levée, Thomas, Suonpää, Anu, Gutiérrez, Ana, Martínez, Ángel T., Ihalainen, Petri, Rencoret, Jorge, Camarero, Susana
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2023
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Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10675753/
https://www.ncbi.nlm.nih.gov/pubmed/38006155
http://dx.doi.org/10.3390/polym15224433
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author Rodríguez-Escribano, David
de Salas, Felipe
Pliego, Rocío
Marques, Gisela
Levée, Thomas
Suonpää, Anu
Gutiérrez, Ana
Martínez, Ángel T.
Ihalainen, Petri
Rencoret, Jorge
Camarero, Susana
author_facet Rodríguez-Escribano, David
de Salas, Felipe
Pliego, Rocío
Marques, Gisela
Levée, Thomas
Suonpää, Anu
Gutiérrez, Ana
Martínez, Ángel T.
Ihalainen, Petri
Rencoret, Jorge
Camarero, Susana
author_sort Rodríguez-Escribano, David
collection PubMed
description Lignins released in the black liquors of kraft pulp mills are an underutilised source of aromatics. Due to their phenol oxidase activity, laccases from ligninolytic fungi are suitable biocatalysts to depolymerise kraft lignins, which are characterised by their elevated phenolic content. However, the alkaline conditions necessary to solubilise kraft lignins make it difficult to use fungal laccases whose activity is inherently acidic. We recently developed through enzyme-directed evolution high-redox potential laccases active and stable at pH 10. Here, the ability of these tailor-made alkaliphilic fungal laccases to oxidise, demethylate, and depolymerise eucalyptus kraft lignin at pH 10 is evidenced by the increment in the content of phenolic hydroxyl and carbonyl groups, the methanol released, and the appearance of lower molecular weight moieties after laccase treatment. Nonetheless, in a second assay carried out with higher enzyme and lignin concentrations, these changes were accompanied by a strong increase in the molecular weight and content of β–O–4 and β–5 linkages of the main lignin fraction, indicating that repolymerisation of the oxidised products prevails in one-pot reactions. To prevent it, we finally conducted the enzymatic reaction in a bench-scale reactor coupled to a membrane separation system and were able to prove the depolymerisation of kraft lignin by high-redox alkaliphilic laccase.
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spelling pubmed-106757532023-11-16 Depolymerisation of Kraft Lignin by Tailor-Made Alkaliphilic Fungal Laccases Rodríguez-Escribano, David de Salas, Felipe Pliego, Rocío Marques, Gisela Levée, Thomas Suonpää, Anu Gutiérrez, Ana Martínez, Ángel T. Ihalainen, Petri Rencoret, Jorge Camarero, Susana Polymers (Basel) Article Lignins released in the black liquors of kraft pulp mills are an underutilised source of aromatics. Due to their phenol oxidase activity, laccases from ligninolytic fungi are suitable biocatalysts to depolymerise kraft lignins, which are characterised by their elevated phenolic content. However, the alkaline conditions necessary to solubilise kraft lignins make it difficult to use fungal laccases whose activity is inherently acidic. We recently developed through enzyme-directed evolution high-redox potential laccases active and stable at pH 10. Here, the ability of these tailor-made alkaliphilic fungal laccases to oxidise, demethylate, and depolymerise eucalyptus kraft lignin at pH 10 is evidenced by the increment in the content of phenolic hydroxyl and carbonyl groups, the methanol released, and the appearance of lower molecular weight moieties after laccase treatment. Nonetheless, in a second assay carried out with higher enzyme and lignin concentrations, these changes were accompanied by a strong increase in the molecular weight and content of β–O–4 and β–5 linkages of the main lignin fraction, indicating that repolymerisation of the oxidised products prevails in one-pot reactions. To prevent it, we finally conducted the enzymatic reaction in a bench-scale reactor coupled to a membrane separation system and were able to prove the depolymerisation of kraft lignin by high-redox alkaliphilic laccase. MDPI 2023-11-16 /pmc/articles/PMC10675753/ /pubmed/38006155 http://dx.doi.org/10.3390/polym15224433 Text en © 2023 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Rodríguez-Escribano, David
de Salas, Felipe
Pliego, Rocío
Marques, Gisela
Levée, Thomas
Suonpää, Anu
Gutiérrez, Ana
Martínez, Ángel T.
Ihalainen, Petri
Rencoret, Jorge
Camarero, Susana
Depolymerisation of Kraft Lignin by Tailor-Made Alkaliphilic Fungal Laccases
title Depolymerisation of Kraft Lignin by Tailor-Made Alkaliphilic Fungal Laccases
title_full Depolymerisation of Kraft Lignin by Tailor-Made Alkaliphilic Fungal Laccases
title_fullStr Depolymerisation of Kraft Lignin by Tailor-Made Alkaliphilic Fungal Laccases
title_full_unstemmed Depolymerisation of Kraft Lignin by Tailor-Made Alkaliphilic Fungal Laccases
title_short Depolymerisation of Kraft Lignin by Tailor-Made Alkaliphilic Fungal Laccases
title_sort depolymerisation of kraft lignin by tailor-made alkaliphilic fungal laccases
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10675753/
https://www.ncbi.nlm.nih.gov/pubmed/38006155
http://dx.doi.org/10.3390/polym15224433
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