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2018 (English)In: Biotechnology for Biofuels, E-ISSN 1754-6834, Vol. 11, no 1, article id 296Article in journal (Refereed) Published
Abstract [en]
Background
Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that oxidatively cleave recalcitrant lignocellulose in the presence of oxygen or hydrogen peroxide as co-substrate and a reducing agent as electron donor. One of the possible systems that provide electrons to the LPMOs active site and promote the polysaccharide degradation involves the mediation of phenolic agents, such as lignin, low-molecular-weight lignin-derived compounds and other plant phenols. In the present work, the interaction of the bulk insoluble lignin fraction extracted from pretreated biomass with LPMOs and the ability to provide electrons to the active site of the enzymes is studied.
Results
The catalytic efficiency of three LPMOs, namely MtLPMO9 with C1/C4 regioselectivity, PcLPMO9D which is a C1 active LPMO and NcLPMO9C which is a C4 LPMO, was evaluated in the presence of different lignins. It was correlated with the physicochemical and structural properties of lignins, such as the molecular weight and the composition of aromatic and aliphatic hydroxyl groups. Moreover, the redox potential of lignins was determined with the use of large amplitude Fourier Transform alternating current cyclic voltammetry method and compared to the formal potential of the Cu (II) center in the active site of the LPMOs, providing more information about the lignin-LPMO interaction. The results demonstrated the existence of low-molecular weight lignin-derived compounds that are diffused in the reaction medium, which are able to reduce the enzyme active site and subsequently utilize additional electrons from the insoluble lignin fraction to promote the LPMO oxidative activity. Regarding the bulk lignin fractions, those isolated from the organosolv pretreated materials served as the best candidates in supplying electrons to the soluble compounds and, finally, to the enzymes. This difference, based on biomass pretreatment, was also demonstrated by the activity of LPMOs on natural substrates in the presence and absence of ascorbic acid as additional reducing agent.
Conclusions
Lignins can support the action of LPMOs and serve indirectly as electron donors through low-molecular-weight soluble compounds. This ability depends on their physicochemical and structural properties and is related to the biomass source and pretreatment method.
Place, publisher, year, edition, pages
London: BMC, 2018
Keywords
Lytic polysaccharide monooxygenases, Lignin structural properties, Electron donor, Cyclic voltammetry, Redox potential, Forest biomass, Pretreatment
National Category
Bioprocess Technology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-71479 (URN)10.1186/s13068-018-1294-6 (DOI)000448645700001 ()30386433 (PubMedID)2-s2.0-85055687969 (Scopus ID)
Note
Validerad;2018;Nivå 2;2018-11-07 (johcin)
2018-11-072018-11-072024-07-04Bibliographically approved