Copyright © 2022 Foshan MBRT Nanofiberlabs Technology Co., Ltd All rights reserved.Site Map
Professor Cui Baokai & Professor Si Jing (Beijing Forestry University): Green Biocatalyst Fabricated by Immobilizing Ganoderma lingzhi Laccase on Nanofibrous Composites for Phenolic Compound Removal
With modern industrial development, phenolic compounds are widely present in wastewater from metallurgy, pesticide/dye manufacturing, chemical synthesis, and pharmaceuticals. These substances exhibit high biotoxicity and pathogenicity, posing significant threats to ecosystems and health. Immobilized laccase can effectively remove phenolics without toxic byproducts, serving as an eco-friendly catalyst. However, selecting suitable carrier materials to enhance laccase stability and removal efficiency remains challenging.
Recently, Professors Cui Baokai and Si Jing from Beijing Forestry University published their latest research titled "A green biocatalyst fabricated by fungal laccase immobilized onto Fe3O4@polyaniline-chitosan nanofibrous composites for the removal of phenolic compounds" in Chemical Engineering Journal.
The researchers successfully isolated and purified free laccase Gllacc-II from wild Ganoderma lingzhi. Using electrospinning technology, they prepared Fe3O4 magnetic polyaniline-chitosan nanofiber composite particles (Fe3O4@PANI-Chit), and then created immobilized laccase Fe3O4@PANI-Chit-Gllacc-II using glutaraldehyde as a cross-linking agent. Compared to free laccase, the immobilized version demonstrated significantly enhanced stability and higher removal efficiency for phenol, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol.
Figure 1: Purification and immobilization of wild Ganoderma lingzhi laccase Gllacc-II and its biological removal of phenolic compounds.
Through fermentation of wild G. lingzhi followed by salt precipitation, anion exchange chromatography, and dextran gel chromatography, the team obtained a novel monomeric laccase protein Gllacc-II with molecular weight of 51 kDa, specific activity of 25.712 U/mg, purification fold of 26.452, and activity recovery of 73.39%. Enzymatic characterization revealed Gllacc-II's optimal pH at 7, optimal temperature at 50°C, and notable tolerance to metal ions, protein inhibitors, surfactants, and organic solvents.
Figure 2: Detailed immobilization process of wild Ganoderma lingzhi laccase Gllacc-II.
The Fe3O4@PANI-Chit-Gllacc-II showed immobilization efficiency of 87.475% and retained 84.607% activity. Various characterization techniques (SEM, XRD, FTIR, XPS, VSM, TGA, water contact angle) confirmed successful laccase immobilization.
Figure 3: Effects of pH, temperature, and time on the removal of phenolic compounds by immobilized laccase Fe3O4@PANI-Chit-Gllacc-II.
The immobilized laccase exhibited significantly improved phenolic compound removal across broader pH and temperature ranges, achieving removal rates of 95.97%, 80.71%, 96.75%, and 97.33% for phenol, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol respectively at pH 7.0 and 50°C within 24 hours, compared to free laccase's 55.97%, 53.62%, 56.09%, and 63.34%.
Figure 4: Degradation mechanism (a) and toxicity changes (b) of phenolic compounds by immobilized laccase Fe3O4@PANI-Chit-Gllacc-II.
Reaction mechanism studies (Figure 4a) revealed the removal process involves dehydrogenation, active radical intermediates, oligomer/polymer formation, self-coupling, dehalogenation, and ring-opening reactions, producing more separable and degradable intermediates. Toxicity tests (Figure 4b) showed significant reduction in intermediate product toxicity compared to parent compounds.
Figure 5: Storage stability and reusability of the laccase.
The immobilized laccase demonstrated excellent storage stability and reusability, retaining 66.59% activity after 30-day storage and 60.01% after 14 reuse cycles, potentially greatly reducing operational costs. These superior properties suggest tremendous potential for industrial and environmental applications of Fe3O4@PANI-Chit-Gllacc-II.
