Comparison of a fungal and a bacterial laccase for lignosulfonate polymerization

Enzymatic Oxidation of Ca-Lignosulfonate and Kraft Lignin in Different Lignin-Laccase-Mediator-Systems and MDF Production

“…In contrast, as also shown in Table 1, most enzymatic treatments with either asco-laccase MtL or basi-laccase CcLcc5, without or with addition of a mediator, increased significantly the average MW of the technical lignins, similar to that reported in our previous study with Novozym 51003 and lignosulfonate, and either caffeic acid or vanillyl alcohol as mediators (Euring et al, 2016a). The results suggest that both laccases oxidized, directly or indirectly, the lignins and that these secondarily reacted by polymerization via modified phenolic groups, in accordance with earlier observations on different laccases with lignins (Johansson et al, 2014;Ortner et al, 2015;Euring et al, 2016a;Gouveia et al, 2018;Braunschmid et al, 2021) and with mediators and lignins (Ortner et al, 2015;Euring et al, 2016a) where the presence of laccase-oxidized mediators resulted in an additional and enhanced lignin radicalization (Bourbonnais and Paice, 1990;Potthast et al, 1995;Potthast et al, 1999;Rittstieg et al, 2002;Kües et al, 2007;Areskogh et al, 2010;Prasetyo et al, 2010;Euring et al, 2011).…”

“…For further comparison, the well-studied asco-laccase MtL has an optimal pH with syringaldazine as a phenolic substrate at pH 6.5 to 7.0 and with the non-phenolic ABTS at pH 2.7 (Berka et al, 1997;Xu, 1997) and the novel basi-laccase CcLcc5 at pH 7.0 and 5.0 (Rühl, 2010), indicating a good potential for enzymatic activities of CcLcc5 with substrates around the neutral pH. Indeed, pH values in the neutral range are best suited for laccase-catalyzed lignin polymerization reactions (Euring, 2008;Huber et al, 2016a;Ortner et al, 2018), among other things through a more open structure of lignosulfonates at pH 7.0 for better enzymatic access and for Indulin AT the restricted solubilization behavior at low pH (Huber et al, 2016a;Braunschmid et al, 2021;Mayr et al, 2021). These arguments together underline our investigation of the quality of basi-laccase CcLcc5 in experimental tests as an alternative to the asco-laccase MtL as functional enzymes in LLMS for MDF production.…”

“…The first approaches to produce fiberboards were made by applying technical lignins in conjunction with a laccase as a "twocomponent-system," resulting in lignin activation and enhanced self-bonding of wood fibers (Hüttermann et al, 2001;Mai et al, 2004). Incorporation of lignin into the LMS (aka LLMS) (Euring et al, 2016a) and the search for alternative mediators (Kirsch et al, 2015;Kirsch et al, 2016) and alternative laccases that work well within the LMS (Gouveia et al, 2018;Braunschmid et al, 2021;Garajová et al, 2021) are approaches for further process optimization and potential cost reduction. From an economic point of view, a first MDF pilot plant study in LLMS with lignosulfonate and either caffeic acid or vanillyl alcohol as a mediator indicated a good possibility to set the laccase activity lower with still consistently good technical product values as in the work before that used 100 kU Novozym 51003/kg of atro wood fiber and 10 mM of a mediator (Euring et al, 2016a).…”

Screening of Laccase-Mediator Systems by White-Rot Fungi Laccases for Biocatalytic Benzyl Alcohol Oxidation

“…For example, in the food and textile industry, laccases are used to reduce the oxygen content, speci cally in beer production to increase the product shelf-life and for their bleaching activities on denim fabrics, respectively (Mate and Alcalde 2017). Moreover, different studies showed the ability of laccases to produce polymeric structures (Braunschmid et al 2021;Pollard and Bruns 2018).…”

A comparative screening of laccase-mediator systems by white-rot fungi laccases for biocatalytic benzyl alcohol oxidation

“…In the food and textile industry, laccases are used to reduce the oxygen content, specifically in beer production to increase the product shelf-life and for their bleaching activities on denim fabrics, respectively 11 . Moreover, different studies showed the ability of laccases to produce polymeric structures [12][13][14] .…”