Purification and Characterization of a White Laccase with Pronounced Dye Decolorizing Ability and HIV-1 Reverse Transcriptase Inhibitory Activity from Lepista nuda

Purification and biochemical characterization of a new thermostable laccase from Enterococcus faecium A2 by a three-phase partitioning method and investigation of its decolorization potential

Three-phase partitioning (TPP) is a simple, fast, cost-effective, and highly efficient process that can be used in the purification of laccases. In this study, microorganisms with laccase activity were isolated from water samples collected from the Agri-Diyadin hot spring. The isolate with the highest laccase activity was found to be the A2 strain. As a result of molecular (16S rRNA sequence) and conventional (morphological, biochemical, and physiological) analyses, it was determined that the A2 isolate was 99% similar to Enterococcus faecium (Genbank number: MH424896). The laccase was purified to 4.9-fold with 110% recovery using the TPP. The molecular mass of the enzyme was found by SDS-PAGE to be 50.11 kDa. Optimum pH 6.0 and optimum temperature for laccase were determined as 80 °C. The laccase exhibited pH stability over a wide range (pH 3.0-9.0) and a high thermostability, retaining over 90% of its activity after 1 h of incubation at 20-90 °C. The laccase exhibited high thermostability, with a heat inactivation half-life of approximately 24 h at 80 °C. The enzyme remained highly stable in the presence of surfactants and increased its activity in the presence of organic solvents, Cr²⁺, Cu²⁺, and Ag⁺ metal ions. The K_m, V_max, k_cat, and k_cat/K_m values of laccase for 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) substrate were 0.68 mM, 5.29 μmol mL^-1 min^-1, 110.2 s^-1, and 162.1 s^-1 mM^-1, respectively.

A New Laccase of Lac 2 from the White Rot Fungus Cerrena unicolor 6884 and Lac 2-Mediated Degradation of Aflatoxin B1

Aflatoxin B₁ (AFB₁) is a known toxic human carcinogen and can be detoxified by laccases, which are multicopper oxidases that convert several environmental pollutants and toxins. In this study, a new laccase that could catalyze AFB₁ degradation was purified and identified from the white-rot fungus Cerrena unicolor 6884. The laccase was purified using (NH₄)₂SO₄ precipitation and anion exchange chromatography, and then identified as Lac 2 through zymogram and UHPLC-MS/MS based on the Illumina transcriptome analysis of C. unicolor 6884. Six putative laccase protein sequences were obtained via functional annotation. The lac 2 cDNA encoding a full-length protein of 512 amino acids was cloned and sequenced to expand the fungus laccase gene library for AFB₁ detoxification. AFB₁ degradation by Lac 2 was conducted in vitro at pH 7.0 and 45 °C for 24 h. The half-life of AFB₁ degradation catalyzed by Lac 2 was 5.16 h. Acetosyringone (AS), Syrinagaldehyde (SA) and [2,2' -azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS) at 1 mM concentration seemed to be similar mediators for strongly enhancing AFB₁ degradation by Lac 2. The product of AFB₁ degradation catalyzed by Lac 2 was traced and identified to be Aflatoxin Q₁ (AFQ₁) based on mass spectrometry data. These findings are promising for a possible application of Lac 2 as a new aflatoxin oxidase in degrading AFB₁ present in food and feeds.

Aptitude of Oxidative Enzymes for Treatment of Wastewater Pollutants: A Laccase Perspective

Natural water sources are very often contaminated by municipal wastewater discharges which contain either of xenobiotic pollutants and their sometimes more toxic degradation products, or both, which frustrates the universal millenium development goal of provision of the relatively scarce pristine freshwater to water-scarce and -stressed communities, in order to augment their socioeconomic well-being. Seeing that both regulatory measures, as regards the discharge limits of wastewater, and the query for efficient treatment methods remain unanswered, partially, the prospects of enzymatic treatment of wastewater is advisable. Therefore, a reconsideration was assigned to the possible capacity of oxidative enzymes and the respective challenges encountered during their applications in wastewater treatment, and ultimately, the prospects of laccase, a polyphenol oxidase that oxidizes aromatic and inorganic substrates with electron-donating groups in treatment aromatic contaminants of wastewater, in real wastewater situations, since it is assumed to be a vehicle for a greener community. Furthermore, the importance of laccase-driven catalysis toward maintaining mass-energy balance, hence minimizing environmental waste, was comprehensibly elucidated, as well the strategic positioning of laccase in a model wastewater treatment facility for effective treatment of wastewater contaminants.

Purification and characterization of a fungal laccase from the ascomycete Thielavia sp. and its role in the decolorization of a recalcitrant dye

A laccase-producing ascomycete was isolated from arid soil in Tunisia. This fungus was identified as Thielavia sp. using the phylogenetic analysis of rDNA internal transcribed spacers. The extracellular laccase produced by the fungus was purified to electrophoretic homogeneity, showing a molecular mass around 70 kDa. The enzyme had an optimum pH of 5.0 and 6.0 for ABTS and 2,6‑DMP, respectively and it showed remarkable high thermal stability, showing its optimal temperature at 70 °C (against 2,6‑DMP). It presented slight inhibiting effect by EDTA, SDS and l‑cyst although this effect was more marked by sodium azide (0.1 mM). On the other hand, it showed tolerance to up to 300 mM NaCl, retaining around 50% of its activity at 900 mM. Among the metal ions tested on TaLac1, Mn²⁺ showed an activating effect. Their kinetic parameters K_m and k_cat were 23.7 μM and 4.14 s^-1 for ABTS, and 24.3 μM and 3.46 s^-1 towards 2,6‑DMP. The purified enzyme displayed greater efficiency in Remazol Brilliant Blue R decolorization (90%) in absence of redox mediator, an important property for biotechnological applications.