In silico and in vitro assays suggests Congo red dye degradation by a Lentinus sp. laccase enzyme

Abstract

Laccase is a superfamily of ligninolytic enzymes known to degrade a wide variety of xenobiotics, including synthetic dyes. Congo Red (CR) has a diazo dye function, carcinogenic and mutagenic potential, and is currently applied in clinical analysis. The objective of this work was to produce and characterize the crude extract of Lentinus sp. in semi-solid fermentation (FSS) and perform in vitro and in silico studies to assess the potential of the crude extract to discolor the CR dye. Laccase activity was determined using ABTS as substrate and characterized. The in vitro discoloration was carried out using experimental design 2² at room temperature and monitored at 340 nm for 24h. Molecular docking and molecular dynamics simulations were performed between laccase and CR. The maximum laccase activity production was 29.63 U L⁻¹ with six days of FSS. The optimal temperature and pH were 50 °C and 3.0, respectively. Discoloration of the CR dye was obtained only in tests containing CuSO₄. Laccase formed stable complexes with the dye, presenting negative binding energy values ranging from −70.94 to −63.16 kcal mol⁻¹ and the occurrence of seven hydrogen bonds. Molecular dynamics results showed the stability of the system (RMSD ranging from 1.0 to 2.5 Ä) and protein-ligand interaction along simulation. RMSF values pointed residues at the end of chains A (residues 300 to 305, 480 to 500) and B (residues 650 to 655 and 950 to 1000) as the most flexible regions of the laccase. This study highlighted the enzymatic action in the bioremediation of CR in vitro in agreement with the in silico simulations that demonstrate the enzyme potential.

Communicated by Ramaswamy H. Sarma

Keywords:

• Basidiomycete
• bioprocesses
• bioremediation
• ligninolytic enzyme
• molecular docking
• molecular dynamics

Acknowledgements

We thank to Aggeu Magalhães Research Center (Fiocruz/Recife-PE) for providing computational resources for molecular dynamics simulations. We also thank to Professor Gustavo de Miranda Seabra for discussing some results.

Disclosure statement

The authors report there are no competing interests to declare.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.