Laccase-Driven Transformation of High Priority Pesticides Without Redox Mediators: Towards Bioremediation of Contaminated Wastewaters

Abstract

In this study, Pleurotus dryinus was grown on municipal biosolids (BS) as the substrate to produce laccase for the removal of pesticides (fungicides, herbicides, and insecticides) from wastewater. Among the various types of BS tested, sterilized biosolids were the most promising substrate for laccase production by P. dryinus with a maximal laccase activity (162.1 ± 21.1 U/g dry substrate), followed by hygenized biosolids (96.7 ± 17.6 U/g dry substrate), unsterilized biosolids (UBS) (31.9 ± 1.2 U/g dry substrate), and alkali-treated biosolids (8.2 ± 0.4 U/g dry substrate). The ultrasound-assisted extraction of this enzyme from fermented UBS was carried out with 0.1 M phosphate buffer at pH 7.0, which increased the enzyme activity of the crude extract by 30%. To test the catalytic potential of the biocatalyst in real matrices, 1 U/ml of recovered crude laccase extract was applied for 24 h for the removal of 29 pesticides (nine fungicides, 10 herbicides, and 10 insecticides) either separately or as a mixture from spiked biologically treated wastewater effluent. When treated with crude enzyme extract, high-priority herbicides metolachlor and atrazine were completely removed, while 93%–97% of the insecticides aldicarb, spinosad, and azinphos-methyl and up to 91% of kresoxim-methyl were removed. Promising results were obtained with BS-derived crude enzyme extract exhibiting improved pesticides removal, which may be due to the mediator effect resulting from the catalytic transformation of other molecules in the cocktail. The results demonstrated a promising integrated bioprocess for the removal of pesticides in wastewater using crude laccase obtained from BS.

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

“…The most effective mediators are N-heterocyclic compounds containing N-OH groups, such as hydroxybenzotriazole (HBT), 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO), N-hydroxyphthaimide (HPI), Nhydroxyacetanilide (NHA) and violuric acid (VLA) [82]. The laccase-mediator system (LMS) has been used in the degradation of a wide range of contaminants as it induces the cleavage of oxidative bonds present in the structure of many types of xenobiotics dissected in this review [186,[255][256][257][258][259][260].…”

“…Worldwide, 80% of untreated industrial wastewater goes directly to water reservoirs [266]. Industries, such as paper and pulp, textile, tanning, chemical, pharmaceutical, cosmetics, food processing and petrochemical, and other manufacturing industries, are major sources of industrial wastewater [256,266,269].…”

“…Laccases produced by various groups of microorganisms are capable of oxidizing ortho-and paradiphenols, aminophenols, polyphenols, polyamines, lignins, aryldiamines and some inorganic ions [65,187,243,256]. In addition to oxidizing phenolic and methoxyphenolic acids, laccases also attack their carboxyl (decarboxylation) and methoxy (demethylation) groups.…”

Recombinant Laccase: A Promising Tool for Industrial Effluent Bioremediation

“…The color molecules are oxidized by laccase, which transforms them into less complex chemicals that microbes can then further break down. An environmentally acceptable alternative to traditional dye degradation techniques that are frequently expensive and result in harmful consequences is laccase-mediated dye degradation (Vaithyanathan et al, 2022). Phenolic compounds are typical wastewater contaminants, and it is crucial to prevent environmental harm by degrading them.…”

“…Recombinant laccase has been demonstrated to efficiently break down a number of pesticides, including atrazine, diazinon, and chlorpyrifos. A promising method for treating contaminated soils and water is a laccase-mediated breakdown of pesticides (Vaithyanathan et al, 2022). Organic chemicals known as PAHs are a persistent category that has the potential to harm the environment.…”