Decolorization and detoxication of malachite green by engineered Saccharomyces cerevisiae expressing novel thermostable laccase from Trametes trogii

Influence of mutations at different distances from the active center on the activity and stability of laccase 13B22

Laccases with high catalytic efficiency and high thermostability can drive a broader application scope. However, the structural distribution of key amino acids capable of significantly influencing the performance of laccases has not been explored in depth. Thirty laccase 13B22 mutants with changes in amino acids at distances of 5 Å (first shell), 5-8 Å (second shell), and 8-12 Å (third shell) from the active center were validated experimentally with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as substrate. Twelve of these mutants (first shell, 1; second shell, 4; third shell, 7) showed higher catalytic efficiency than the wild-type enzyme. Mutants D511E and I88L-D511E showed 5.36- and 10.58-fold increases in kcat/Km, respectively, with increases in optimal temperature of 15 °C and optimal pH from 7.0 to 8.0. Furthermore, both mutants exhibited greater thermostability compared to the wild-type, with increases of 3.33 °C and 5.06 °C in Tm and decreases of 0.39 J and 0.59 J in total structure energy, respectively. The D511E mutation resides in the third shell, while I88L is in the second shell, and their performance enhancements were attributed to alterations in the rigidity or flexibility of specific protein structural domains. Both mutants showed enhanced degradation efficiency for benzo[a]pyrene and zearalenone. These findings highlight the importance of the residues located far from the active center in the function of laccase (second shell and third shell), suggesting broader implications for enzyme optimization and biotechnological applications.

Identification of Novel Laccase from Ganoderma lucidum and Application in Biotransformation to Bio-based Fragrances Using Alkaline Lignin as Raw Material

A novel laccase, Lac3, was purified from Ganoderma lucidum fermentation broth by salting out, gel filtration chromatography, and Native-PAGE protein recovery. The molecular mass of Lac3 was 58.4 kDa as estimated by SDS-PAGE and exhibited catalytic properties with 2,2'-Biazobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) as substrate. The specific enzyme activity of Lac3 was determined to be 313.69 U/mg. The laccase was stable at temperatures < 65 °C and at pH of 2.5-4.5. The pH, temperature optima, Km and Vmax of the enzyme for ABTS oxidation were 3.0, 55 °C, 0.077 mM, and 2.98 mM/min, respectively. The metal ions and anions showed inhibitory effects on Lac3 activity except Cu2+ (1 mM). GC-MS analysis showed that various aroma products were generated by Lac3 treatment of alkaline lignin. The Lac3 and lignin model compounds had negative binding energy and hydrogen bonding. The analysis of docking suggested that Asp207, Asn256, and His459 play a key role in substrate binding and catalysis.

Production optimization, characterization, and application of a novel thermo- and pH-stable laccase from Bacillus drentensis 2E for bioremediation of industrial dyes

Environmental pollution driven by rapid industrialization and urbanization, has become serious concern due to adverse health effects. Among various bioremediation strategies, laccase, an oxidoreductase enzyme with wide substrate range and high redox-potential (0.4-0.8 V) has garnered significant attention due to its ability to oxidize various organic pollutants into non-toxic products. However, its practical application is often limited due to susceptibility to extreme pH and inhibitory compounds present in wastewater. To overcome this challenge, bacterial laccase, also known as versatile laccases, offer superior stability under harsh environmental conditions making them ideal for bioremediation. Furthermore, isolating native bacterium from contaminated sites enhances their potential, as these organisms are naturally adapted to pollutant-rich environments with intrinsic degradation ability. In this study, Bacillus drentensis 2E was isolated from dye-effluent release site. Laccase production was systematically optimized by One-Factor-at-a-Time, Plackett-Burman Design, and Central Composite Design, yielding a 2.45-fold increase in activity compared to unoptimized condition. Optimized media composition is as follows (g/L): KNO3-5.034,Glucose-3, KH2PO4-0.3,MgSO4-0.3, NaCl-0.55, CaCl2-0.55, CuSO4-0.178 mM, inoculum volume-3.54 %. The enzyme was further characterized for kinetic properties against ABTS, guaiacol and syringaldazine. It demonstrated exceptional stability across a wide temperature (20 ± 1 °C-70 ± 1 °C) and pH range (3.0 ± 0.01-8.0 ± 0.01) with heavy metal tolerance to Ca2+, Mn2+, Mg2+,Zn2+,Cu2+,Co2+,Ni2+. Also, BDLaccase effectively degraded Acid Red-27 (99.76 ± 2.27 %) and Direct Blue-6 (67.43 ± 2.31 %) within 5 h, as confirmed using UV-Vis spectroscopy, FT-IR, and LC-MS. These findings suggests that, BDLaccase is a robust biocatalyst for bioremediation especially in treatment of dyes due to its broad stability and efficiency.

Efficient Biological Decolorization of Malachite Green by Deinococcus wulumuqiensis R12: Process Optimization and Degradation Pathway Analysis

Malachite green (MG) is a toxic triphenylmethane dye widely used in industry, as well as a controversial antimicrobial in aquaculture, leading to environmental concerns. In this study, the conditions for the decolorization of MG by Deinococcus wulumuqiensis R12 were optimized. Under the optimized conditions, a degradation efficiency of 99.30% was achieved for 200 mg/L MG within 30 min, with an initial biomass concentration of 5.5 g/L at 32 °C and pH 5.0. When the initial concentration of MG was increased to 1 g/L, the degradation efficiency surpassed 97% after 2.5 h. Analytical techniques, including UV-VIS, FTIR, GC-MS, and LC-MS analyses revealed that the degradation products included desmethyl-malachite green, di-desmethyl-malachite green, 4-(dimethylamino)benzophenone, and 4-(methylamino)benzophenone, indicating that the MG degradation mechanism of R12 was based on oxidation and demethylation processes. Furthermore, microbial assays confirmed that the byproducts of MG degradation by R12 are much less toxic than the parent compound, indicating the potential of Deinococcus wulumuqiensis R12 as an effective bioremediation agent for MG-contaminated environments.