Thermostable Bacterial Laccase: Catalytic Properties and Its Application in Biotransformation of Emerging Pollutants

Abstract

Laccases have been predominantly reported in fungi, and primarily, fungal laccases are currently exploited in industrial applications. However, extremophilic bacterial laccases possess immense potential, as they can withstand extreme temperatures, pH, and salt concentrations. In addition, unlike fungal laccases, the production of bacterial laccases is cost-effective. Therefore, bacterial laccases are gaining significant attention for their large-scale applications. Previously, we reported a novel thermostable laccase (LacT) from Brevibacillus agri . Herein, we have confirmed that LacT shares a high sequence similarity with CotA laccase from Bacillus amyloliquefaciens . Peptide mass fingerprinting of LacT was conducted via matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF/MS-MS). Inductively coupled plasma-optical emission spectroscopic (ICP-OES) analysis revealed the presence of ∼3.95 copper ions per protein molecule. Moreover, the secondary and tertiary structure of LacT was studied using circular dichroism (CD) and fluorescence spectroscopy. The absence of notable shifts in CD and fluorescence spectra with an increase in temperature established that LacT remains intact even at elevated temperatures. Analysis of the thermal denaturation profile of LacT by thermogravimetric analysis (TGA) also confirmed its temperature stability. Thereafter, we exploited LacT in its application for the bioremediation of phenolic endocrine disruptors, namely, triclosan, 4,4′-dihydroxybiphenyl, and dienestrol. LacT oxidizes 4,4′-dihydroxybiphenyl and triclosan but no LacT activity was detected with dienestrol. The rate of biotransformation of 4,4′-dihydroxybiphenyl and triclosan increased in the presence of CuSO 4 and a redox mediator, ABTS. Transformation of dienestrol was observed only with LacT in the presence of ABTS. This study establishes the application of LacT for the bioremediation of phenolic compounds.

Extremozyme-Based Biosensors for Environmental Pollution Monitoring: Recent Developments

“…To conclude, the combination of mesophilic enzymes with nanomaterials lead to stable and sensitive biosensors for the detection of phenols. Extremozymes, including, e.g., a recently reported thermostable laccase [ 242 ] might bring additional advantages in terms of selectivity and operational stability. Efficient immobilization strategies proven with mesophilic enzymes such as, e.g., attachment of Trametes versicolor laccase on sulfur-doped titania nanoparticles [ 243 ] or the electrospray deposition of the same enzyme [ 108 ], might find applications also with new bioreceptors from extremophilic strains leading to surface immobilized biocatalysts with high activity and stability.…”

Optical Properties of Laccases and Their Use for Phenolic Compound Detection and Quantification: A Brief Review

“…Fluorescence spectroscopy has been successfully adopted by several authors for characterizing different aspects of laccases [33,70,71]. In recent years, interest in the application of this technique has particularly been addressed to fungal and bacterial laccases [72,73].…”

Computational Insights into Enzyme‐Substrate Binding Interplay Exhibit Variable Binding Attributes: A Framework for Implementing Oxidoreductase‐Based Applications

“…[24,25] Nevertheless, fungal laccases have many disadvantages, including low enzyme yield, inability to operate under severe pH levels, temperature, and high concentrations of salts, metals, and organic solvents. [24] These limitations render them unsuitable for commercial applications. [24] The structural attributes of LACs differ based on their bacterial or fungal origin.…”

“…[24] These limitations render them unsuitable for commercial applications. [24] The structural attributes of LACs differ based on their bacterial or fungal origin. For instance, bacterial origin LAC (Thermus thermophilus HB27) with a PDB: 6W9X consists of a single chain with a sequence length of 440 amino acids.…”

“…Laccase‐like enzymes from bacterial cultures resemble fungal laccases however feature distinct activity [23] . Fungal LACs have been widely studied owing to their high redox potential [24,25] . Nevertheless, fungal laccases have many disadvantages, including low enzyme yield, inability to operate under severe pH levels, temperature, and high concentrations of salts, metals, and organic solvents [24] .…”