Breaking lignin: blue and yellow laccases for a green chemistry

Lignin is an amorphous polymer with a molecular mass around 10 kDa that presents a three-dimensional structure disordered and branched, insoluble in water and most common solvents. During the industrial processes, lignin must be degraded and effectively removed. Enzymatic hydrolysis could be an environmentally friendly alternative to chemical methods to perform lignin degradation. The identification of enzymes able to efficiently fragmenting lignin, i.e., an "enzymatic tool box", is of utmost importance. On this side, laccase represents an enzymatic class of main relevance. Laccases are attracting great scientific interest because of their very basic requirements and huge catalytic capabilities: this renders it one of the ‘‘greenest’’ enzymes [1]. In order to identify interesting lignin degrading biocatalysts, in this study we evaluated the main biochemical properties of a number of commercial and recombinant laccases under identical experimental conditions. The kinetic properties of laccases has been determined on 3 substrates: ABTS, catechol and 2,6-dimethoxyphenol (2,6-DMP). The microbial Bacillus licheniformis laccase (BALL) showed the highest specific activity and catalytic efficiency on ABTS, while the recombinant OB1 from Basidiomycete PM-1 showed the highest affinity for this compound [2]. The stability on pH, temperature, detergents and DMSO of the different laccases was also assessed. Finally, a change in MW distribution after incubation of lignin with the laccase from Trametes versicolor was observed in gel permeation chromatography. This work was done as part of the ValorPlus project that has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no FP7-KBBE-2013-7-613802. [1] L. Pollegioni, F. Tonin, E. Rosini, FEBS J. 282 (7) (2015) 1190-1213 [2] F. Tonin, R. Melis, A. Cordes, A. Sanchez-Amat, L. Pollegioni, E. Rosini, Submitted