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

Abstract

Production of added value compounds from waste materials is of utmost importance for the development of a sustainable society especially regarding their use as catalysts in industrially relevant synthetic reactions. Herein, we show the production of laccases from four white-rot fungi, which were grown on agricultural residues, specifically Trametes versicolor 11269, Pleurotus ostreatus 1020, Panus tigrinus 707 and Lentinula edodes SC-495. The produced laccases were tested on biphasic laccase-mediator system (LMS) for the biocatalytic oxidation of the model substrate benzyl alcohol into benzaldehyde. The biphasic LMS was carried out in the presence both of tetrahydrofuran as co-solvent and of the mediator 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) due to its high redox potential and its ability to perform the oxidation. Tolerance studies showed that the dialyzed solutions were able to tolerate 1% of co-solvent, while a concentration of 10% v/v negatively affected their activity. Performances in the biocatalytic oxidation of laccase solutions from different purification steps were compared. Similar conversion was observed for laccase in dialysis and gel filtration product versus commercial T. versicolor laccase. The latter oxidized almost 99% of substrate while the other laccase solutions were able to reach a conversion from 91% for the laccase solution from P. tigrinus 707 after dialysis, to 50% for the laccase solution from P. ostreatus 1020 after gel filtration. This work highlights the potential of unpurified laccase solutions to be used as catalysts in synthetic reactions.

Eco-friendly TEMPO/laccase/O2 biocatalytic system for degradation of Indigo Carmine: operative conditions and laccase inactivation

“…21 Many applications of this system have been proposed over the past twenty years, including bioremediation and detoxication of environmental pollutants, [22][23][24] aerobic oxidation of non-phenolic substrates, 14,19,21,25 selective oxidative modication of cellulose, 18,26 sugars, 27 cellulose nanober production, 28 biocatalyzed organic synthesis, including transformation of biomass into compounds with high added value. [29][30][31][32][33][34][35] The mechanistic details of laccase/TEMPO catalyzed aerobic oxidation of organic compounds is still a matter of discussion. [17][18][19]36,37 According with the proposed ionic mechanism, 17,18,21,36 laccase oxidizes TEMPO with concomitant fourelectron reduction of molecular oxygen to water.…”