Lignin degradation by a novel thermophilic and alkaline yellow laccase from Chitinophaga sp.

Laccases (EC 1.10.3.2) are oxidoreductases that belong to the multicopper oxidase subfamily and are classifiedas yellow/white or blue according to their absorption spectrum. Yellow laccases are more useful for industrial processes since they oxidize nonphenolic compounds in the absence of a redox mediator and stand out for being more stable and functional under extreme conditions. This study aimed to characterize a new laccase that was predicted to be present in the genome of Chitinophaga sp. CB10 - Lac_CB10. Lac_CB10, with a molecular mass of 100.06 kDa, was purifiedand characterized via biochemical assays using guaiacol as a substrate. The enzyme demonstrated extremophilic characteristics, exhibiting relative activity under alkaline conditions (CAPS bufferpH 10.5) and thermophilic conditions (80-90°C), as well as maintaining its activity above 50% for 5 h at 80°C and 90°C. Furthermore, Lac_CB10 presented a spectral profiletypical of yellow laccases, exhibiting only one absorbance peak at 300 nm (at the T2/T3 site) and no peak at 600 nm (at the T1 site). When lignin was degraded using copper as an inducer, 52.27% of the material was degraded within 32 h. These results highlight the potential of this enzyme, which is a novel yellow laccase with thermophilic and alkaline activity and the ability to act on lignin. This enzyme could be a valuable addition to the biorefineryprocess. In addition, this approach has high potential for industrial application and in the bioremediation of contaminated environments since these processes often occur at extreme temperatures and pH values.