The valorisation of lignin is a key aspect in the optimal exploitation of the paradigm of a biorefinery based on lignocellulosic biomass. In this work, the treatment of the technical lignin Indulin AT with a recombinant laccase, or with a combination of this enzyme with the mediator 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), has been carried out at 25 °C in a mildly acidic buffered aqueous medium. The presence of the ionic liquid 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) has also been investigated. Due to the limited solubility of Indulin AT in water, only partial dissolution occurred. In the lignin recovered after the treatments, a preferential diminution of the guaiacyl units was observed. In the analysis of the aqueous phases, a variety of phenolic compounds were identified, deriving from either guaiacyl or p-hydroxyphenyl units, although in moderately low concentrations. The highest assigned concentrations, always achieved when using the laccase-ABTS system (versus the treatment with no mediator), corresponded to different phenolic compounds, depending on whether the ionic liquid was involved or not in the treatment. In general, the overall concentration of phenolic compounds (measured as equivalents of gallic acid) was much greater after treatments involving the ionic liquid.This work was supported by Xunta de Galicia through grant numbers ED431B 2017/023 and ED431E 2018/01 (CRETUS Strategic Partnership), and by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and by LABBELS – Associate Laboratory in Biotechnology, Bioengineering and Microelectromechanical Systems, LA/P/0029/2020. C.A.P. and H.R. are grateful to “Agrupación Europea de Cooperación Territorial – Galicia - Norte de Portugal (GNP-AECT)” for support of stays at the Centre of Biological Engineering of the University of Minho via the Iacobus programme. The use of RIAIDT-USC analytical facilities is also acknowledged.info:eu-repo/semantics/publishedVersio
