Functional characterization of a yellow laccase from Leucoagaricus gongylophorus

Wheat bran as an efficient agro-process waste for enhanced yellow laccase production by Lentinus tigrinus SSB_W2 and its application in anthraquinone dye degradation

Lentinus tigrinus SSB_W2, isolated from Mahabaleshwar in the Western Ghats of Maharashtra, India, was employed to enhance laccase production in solid-state fermentation (SSF). The spectral analysis indicated that the laccase produced by L. tigrinus is a typical yellow laccase, exhibiting no absorption at 600 nm. Notably, this yellow laccase demonstrated exceptional catalytic activity, as confirmed by electrochemical analysis. Four agricultural processing wastes were evaluated as substrates for SSF, and the results showed that L. tigrinus effectively utilized wheat bran. Initial testing by one-factor-at-a-time method showed 3.79-fold increase in yellow laccase production, which subsequently increased to 6.51-fold after Plackett-Burman design. Moreover, employing response surface methodology resulted in 11.87-fold increase (108,472 IU gds-1) in laccase production. The utilization of yellow laccase for the biotransformation of various textile dyes was investigated, and it exhibited the highest degradation efficiency toward Reactive blue 4, a recalcitrant anthraquinone dye, with a rate of 18.36 mg L-1 h-1, for an initial concentration of 1000 mg L-1.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03881-9.

Endophytic, extremophilic and entomophilic fungi strains biodegrade anthracene showing potential for bioremediation

Anthropogenic activities have been increasing Polycyclic Aromatic Hydrocarbons (PAHs) release, promoting an urgent need for decontamination methods. Therefore, anthracene biodegradation by endophytic, extremophilic, and entomophilic fungi was studied. Moreover, a salting-out extraction methodology with the renewable solvent ethanol and the innocuous salt K₂HPO₄ was employed. Nine of the ten employed strains biodegraded anthracene in liquid medium (19-56% biodegradation) after 14 days at 30 °C, 130 rpm, and 100 mg L^-1. The most efficient strain Didymellaceae sp. LaBioMMi 155, an entomophilic strain, was employed for optimized biodegradation, aiming at a better understanding of how factors like pollutant initial concentration, pH, and temperature affected this process. Biodegradation reached 90 ± 11% at 22 °C, pH 9.0, and 50 mg L^-1. Futhermore, 8 different PAHs were biodegraded and metabolites were identified. Then, experiments with anthracene in soil ex situ were performed and bioaugmentation with Didymellaceae sp. LaBioMMi 155 presented better results than natural attenuation by the native microbiome and biostimulation by the addition of liquid nutrient medium into soil. Therefore, an expanded knowledge about PAHs biodegradation processes was achieved with emphasis to the action of Didymellaceae sp. LaBioMMi 155, which can be further employed for in situ biodegradation (after strain security test), or for enzyme identification and isolation aiming at oxygenases with optimal activity under alkaline conditions.

Production and characterization of a novel thermostable laccase from Bacillus licheniformis VNQ and its application in synthesis of bioactive 1,4-naphthoquinones

Bacterial laccases have proven to be a potential biocatalyst for various industrial applications due to their remarkable catalytic and stability properties. In this study, a novel thermostable laccase was produced from the bacterium Bacillus licheniformis VNQ by submerged fermentation. The specific activity of crude and purified laccase was found to be 13.17 U mg^-1 and 83.47 U mg^-1, respectively. The enzyme possessed a molecular mass of ∼48 kDa when characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The optimum temperature and pH for enzyme activity was determined to be 55°C and 5.0, respectively. The enzyme was considered to be thermo-tolerant as it possessed a half-life of 4 h at 70°C. The enzyme was utilized for the oxidative biotransformation of in situ synthesized p-quinones to biologically active compounds, 1,4-naphthoquinone and its derivative. The obtained products were characterized using nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) analysis. A high yield of naphthoquinones (74.93 ± 1.2%) with 1,4-naphthoquinone (60.61 ± 1.0%), and its derivative 2-hydroxy-1,4-naphthoquinone (14.32 ± 0.2%) was obtained at the optimized reaction conditions.

"Yellow" laccase from Sclerotinia sclerotiorum is a blue laccase that enhances its substrate affinity by forming a reversible tyrosyl-product adduct

Yellow laccases lack the typical blue type 1 Cu absorption band around 600 nm; however, multi-copper oxidases with laccase properties have been reported. We provide the first evidence that the yellow laccase isolated from Sclerotinia sclerotiorum is obtained from a blue form by covalent, but nevertheless reversible modification with a phenolic product. After separating the phenolics from the extracellular medium, a typical blue laccase is obtained. With ABTS as model substrate for this blue enzyme, a non-natural purple adduct is formed with a spectrum nearly identical to that of the 1:1 adduct of an ABTS radical and Tyr. This modification significantly increases the stability and substrate affinity of the enzyme, not by acting primarily as bound mediator, but by structural changes that also alters the type 1 Cu site. The HPLC-MS analyses of the ABTS adduct trypsin digests revealed a distinct tyrosine within a unique loop as site involved in the modification of the blue laccase form. Thus, S. sclerotiorum yellow laccase seems to be an intrinsically blue multi-copper oxidase that boosts its activity and stability with a radical-forming aromatic substrate. This particular case could, at least in part, explain the enigma of the yellow laccases.

Acetylcholinesterases from Leaf-Cutting ant Atta sexdens: Purification, Characterization, and Capillary Reactors for On-Flow Assays

Acetylcholinesterase (AChE) is responsible for catalyzing the hydrolysis of the neurotransmitter acetylcholine (ACh) leading to acetate and choline (Ch) release. The inhibition of AChE produces a generalized synaptic collapse that can lead to insect death. Herein we report for the first time the isolation of two AChEs from Atta sexdens which were purified by sulphate ammonium precipitation followed by ion exchange chromatography. AsAChE-A and AsAChE-B enzymes have optimum pH of 9.5 and 9.0 and higher activities in 30/50°C and 20°C, respectively, using acetylthiocholine (ATCh) as substrate. Immobilized capillary enzyme reactors (ICERs) were obtained for both enzymes (AsAChE-A-ICER and AsAChE-B-ICER) and their activities were measured by LC-MS/MS through hydrolysis product quantification of the natural substrate ACh. The comparison of activities by LC-MS/MS of both AChEs using ACh as substrate showed that AsAChE-B (free or immobilized) had the highest affinity. The inverse result was observed when the colorimetric assay (Elman method) was used for ATCh as substrate. Moreover, by mass spectrometry and phylogenetic studies, AsAChE-A and AsAChE-B were classified as belonging to AChE-2 and AChE-1 classes, respectively.

Biodegradation of anthracene and different PAHs by a yellow laccase from Leucoagaricus gongylophorus

Laccases produced by Leucoagaricus gongylophorus act in lignocellulose degradation and detoxification processes. Therefore, the use of L. gongylophorus laccase (Lac1Lg) was proposed in this work for degradation of anthracene and others polycyclic aromatic hydrocarbons without the use of mediators. Degradation reactions were performed in buffer aqueous solution with 10 ppm of anthracene and other PAHs, Tween-20 in 0.25% v/v and a laccase preparation of 50 U. The optimum condition (pH 6.0 and 30 °C) was determined by response surface methodology with an excellent coefficient of determination (R²) of 0.97 and an adjusted coefficient of determination (R²_adj) of 0.93. In addition, the employment of the mediator ABTS decreased the anthracene biodegradation from 44 ± 1% to 30 ± 1%. This optimum pH of 6.0 suggests that the reaction occurs by a hydrogen atom transfer mechanism. Additionally, in 24 h Lac1Lg biodegraded 72 ± 1% anthracene, 40 ± 3% fluorene and 25 ± 3% phenanthrene. The yellow laccase from L. gongylophorus biodegraded anthracene and produced anthrone and anthraquinone, which are interesting compounds for industrial applications. Moreover, this enzyme also biodegraded the PAHs phenanthrene and fluorene justifying the study of Lac1Lg for bioremediation of these compounds in the environment.

Biodegradation of anthracene and several PAHs by the marine-derived fungus Cladosporium sp. CBMAI 1237

The biodegradation of polycyclic aromatic hydrocarbons (PAHs) by marine-derived fungi was reported in this work. Marine-derived fungi (Trichoderma harzianum CBMAI 1677, Cladosporium sp. CBMAI 1237, Aspergillus sydowii CBMAI 935, Penicillium citrinum CBMAI 1186 and Mucor racemosus CBMAI 847) biodegraded anthracene (14days, 130rpm, 50mgmL^-1 initial concentration in malt 2% medium). Cladosporium sp. CBMAI 1237 was the most efficient strain and biodegraded more anthracene in the presence (42% biodegradation) than in the absence (26%) of artificial seawater, suggesting that the biodegradation of PAHs may be faster in seawater than in non-saline environment. After 21days, Cladosporium sp. CBMAI 1237 biodegraded anthracene (71% biodegradation), anthrone (100%), anthraquinone (32%), acenaphthene (78%), fluorene (70%), phenanthrene (47%), fluoranthene (52%), pyrene (62%) and nitropyrene (64%). Previous undocumented metabolites were identified and, anthraquinone was a common product of different PAHs biodegradation. The marine-derived fungus Cladosporium sp. CBMAI 1237 showed potential for bioremediation of PAHs.