Evaluation of Lignin-Modifying Enzyme Activity of Trametes spp. (Agaricomycetes) Isolated from Georgian Forests with an Emphasis on T. multicolor Biosynthetic Potential.

Abstract

In this study, a wide diversity in lignin-modifying enzyme (LME) secretion by 11 Trametes spp. strains isolated from the forests of Georgia was revealed in their submerged cultivation in both synthetic and lignocellulose-based media. Among them, T. multicolor BCC 511 was distinguished by simultaneous production of laccase, manganese peroxidase (MnP), and lignin peroxidase (LiP) in the presence of high carbon and nitrogen concentrations. Mannitol at the concentration of 15 g/L provided an accumulation of 23.7 U/mL laccase and 0.56 U/mL MnP. Significant modulation of LME activity by lignocellulosic substrates, metals, aromatic compounds, and their concentrations was established. Mandarin peels manifold increased the fungus laccase and LiP activities, while the ethanol production residue and banana peels activated manganese-oxidizing and Phenol Red-oxidizing manganese peroxidases, respectively. The addition of 2 mM of copper sulfate to the control medium induced the laccase production 28-fold and did not significantly affect the MnP and LiP activities. Fe2+ at a concentration of 0.1 mM enhanced the fungus volumetric and specific laccase activities almost 8-fold; at a concentration of 0.25-0.5 mM, there was a 2-fold increase in the MnP activity. Mn2+ appeared to be an effective inducer of the Mn-oxidizing MnP, increasing specific activity of the enzyme 14-fold. Supplementation of the copper-containing medium with 1 mM veratryl alcohol or guaiacol favored laccase and MnP production. The high yields of laccase (110 U/mL), MnP (0.62 U/mL), and LiP (0.71 U/mL) obtained in a laboratory fermenter make T. multicolor 511 useful for industrial and environmental applications.