Bacterial Laccases as Biocatalysts for the Remediation of Environmental Toxic Pollutants: A Green and Eco-Friendly Approach—A Review

Abstract

Biological treatment methods for the biodegradation of anthropogenic toxic pollutants are eco-friendly in nature and are powered by a variety of microbial enzymes. Green chemistry and enzymes play a crucial role in catalyzing the biodegradation of organic and inorganic pollutants including azo dyes; polyaromatic hydrocarbons; lead; organic cyanides; aromatic amines; mono-, di-, and polyphenols; polymers; and mercury. Laccases form a prospective group of multifunctional oxidoreductase enzymes with great potential for oxidizing different categories of organic and inorganic pollutants and their diversified functions, such as pigment formation, lignin degradation, and detoxification of industrial wastes including xenobiotics mainly from the pharmaceutical, paper textile, and petrochemical industries. Therefore, it is very important to study laccases as green and environmentally friendly alternatives for the degradation of xenobiotics. This review article will cover comprehensive information about the functions and properties of bacterial laccases for a deep understanding of their scope and applications for effective bioremediation of recalcitrant xenobiotics.

Biochemical Characteristics of Laccases and their Practical Application in the Removal of Xenobiotics from Waters

“…Intracellular laccases are responsible for neutralizing toxic by-products released in biochemical reactions. Under natural conditions, bacterial laccases are also involved in pigmentation, morphogenesis, toxin oxidation and protection from UV light and the cross-linking of envelope proteins in bacterial spores, among others [18,[35][36][37][38][39][40].…”

“…Temperature optima, depending on the bacterial species, range from 25 to 85 • C. A similar trend is observed for pH optimum values. Bacterial laccases have been known to be active in acidic environments as well as in neutral and alkaline environments [18,21]. For example, A. lipoferum laccase shows the highest activity for syringaldazine at 70 at pH 6.0 [56], while B. subtilis ≤ pH 3.0 at pH 7.0 for ABTS [60].…”

“…For example, A. lipoferum laccase shows the highest activity for syringaldazine at 70 at pH 6.0 [56], while B. subtilis ≤ pH 3.0 at pH 7.0 for ABTS [60]. Under laboratory conditions, bacterial laccase shows activity against many substrates, including 2,4 dimethoxy phenol (B. licheniformis LS04), azinobis(3ethylbenzthiazoline-6-sulfonic acid, ABTS) (Pseudomonas aeruginosa), guiacol (B. subtilis), syringaldazine (Stenotrophomonas maltophilia) and hydroquinone (P. desmolyticum) [18,58,61,62].…”

“…Enzymes enable microorganisms to use organic and inorganic substances, such as carbon and energy sources, by catalyzing the degradation of specific substances [17], which was used in the biodegradation of environmental xenobiotics. Laccases are currently being intensively researched for potential use in the biodegradation of xenobiotic compounds, such as pharmaceuticals, dyes or plasticizers [18]. The costs of the industrial production of enzymes and their sensitivity to unfavorable conditions, such as temperature, pH or the presence of inhibitors in wastewater, are a problem.…”

Improvement of aflatoxin B1 degradation ability by Bacillus licheniformis CotA-laccase Q441A mutant

“…In fungi, laccases are related to plant pathogenesis and lignin degradation [ 13 ]. In bacteria, laccases are involved in melanin production and copper detoxification [ 14 ].…”