Fabrication and Catalytic Characterization of Laccase-Loaded Calcium-Alginate Beads for Enhanced Degradation of Dye-Contaminated Aqueous Solutions

From nature to applications: Laccase immobilization onto bio-based materials for eco-conscious environmental remediation

Biodegradable and sustainable materials utilized for laccase immobilization have garnered substantial scholarly interest owing to their capacity to enhance enzyme stability and reusability, which are paramount for effective bioremediation methodologies. Laccase, a versatile oxidase, possesses the ability to degrade a broad spectrum of environmental contaminants, thus rendering it an invaluable asset in bioremediation endeavours. The immobilization of laccase onto biodegradable substrates not only augments its operational stability but also resonates with sustainable environmental strategies. This article systematically investigates recent advancements in sustainable and eco-conscious methodologies aimed at immobilizing laccase. By integrating biodegradable and non-toxic components, we elucidated how these materials not only proficiently enhanced the operational stability of laccases, but also improved their biodegradation effectiveness. A comprehensive analysis revealed that these sustainable materials facilitate immobilized laccase-mediated efficient removal of hazardous chemicals. Furthermore, we highlight the challenges that persist despite the encouraging characteristics of sustainable and eco-friendly approaches to laccase immobilization and pollutant elimination, and engage in discourse regarding potential pathways for their broader application and scalable solutions. This review highlights the significance of incorporating green technologies into environmental remediation efforts, thereby fostering the development of more effective and ecologically sound solutions for sustainable laccase immobilization to mitigate environmental contaminants efficiently.

Computational and biochemical characterization of the immobilized esterase of Salinicoccus roseus for pesticide degradation

The continuous exposure of chemical pesticides in agriculture, their contamination in soil and water pose serious threat to the environment. Current study used an approach to evaluate various pesticides like Hexaconazole, Mancozeb, Pretilachlor, Organophosphate and λ-cyhalothrin degradation capability of esterase. The enzyme was isolated from Salinicoccus roseus. Genome analysis unveiled the carboxylesterase genes underlying the degradation of pesticides, and was located between 2070Mbp to 2080Mbp region. Herein, partially purified esterase was immobilized into beads by mixing with an equal volume (1:1) of sodium alginate solution [2.5% (w/v)].Scanning electron microscopy (SEM) of the beads showed the microspheres for enhanced enzyme-substrate reaction, wide peak at 3316, 1635 and 696 cm- 1 in Fourier-transform infrared spectroscopy (FTIR) represented intermolecular hydrogen bonding, and thermogravimetric analysis (TGA) reaffirmed the binding of esterase entrapped into the beads. Maximum degradation rate (after 4 days) for free enzyme accounted 83.2% in Hexaconazole. Degradation rate moderately increased 4% in the presence of immobilized esterase. Degradation products were detected by liquid chromatography-mass spectrometry (LC-MS). Cytotoxicity test (root length and mitotic index) revealed differences in various treatments. Enzyme kinetics parameters, Michaëlis-Menten constant (KM) 6.61 mM and maximum velocity (Vmax) 1.89 µmol/min/mg increased after immobilization. Further, molecular docking results validated that esterase contributed to pesticide degradation by catalytic triad of Ser93-His222-Phe24, ligand interactions, and specific binding pockets. Additionally, molecular dynamics (MD) simulations confirmed the protein-ligand conformational stability. Hence, present study highlighted an effective method for improving the catalytic properties of esterase, and also potential candidate for bioremediation of pesticides.

Immobilization of laccases on mechanically ground silk fibroin nanofibers for enhanced stability

Azo dyes in textile industry effluents pose significant health and environmental risks. Laccase is an enzyme capable of degrading azo dyes, offering an environmentally friendly solution for treating textile wastewater. However, laccases need to be immobilized on specific carriers to enable effective reuse in batch reactors and continuous operation in flow-through reactors. This study employed silk fibroin nanofibers (SFNFs) obtained by mechanically grinding degummed silkworm silk as sustainable carriers to immobilize laccases through carbodiimide-mediated crosslinking. The immobilized laccases (SFNF-laccases) exhibited improved pH tolerance in the range of pH 3.0-8.0 with a smaller reduction in activity compared to free laccases (SFNF-laccases: 32.9 %, free laccases: 50.4 %). The thermal stability of immobilized laccases was also improved, showing 19, 13, and 9 % higher activities than those of free laccases at 40, 50, and 60 °C, respectively. After 8 days of storage, the activity of SFNF-laccases was 79 % of their activity immediately after immobilization, whereas free laccases retained only 29 % of their initial activity. In addition, SFNF-laccases maintained 73 % of their original operational activity in a flow-through reactor after 8 days. These results demonstrate the great potential of mechanically ground SFNFs as carriers of laccase and the resulting SFNF-laccases in industrial wastewater treatment.

High performance removal of chlorophenols from an aqueous solution using an enzymatic membrane bioreactor

Organochlorides and particularly chlorophenols are environmental pollutants that deserve special attention. Enzymatic membrane bioreactors may be alternatives for efficiently removing such hazardous organochlorides from aqueous solutions. We propose here a novel enzymatic membrane bioreactor comprising an ultrafiltration membrane GR81PP, electrospun fibers made of cellulose acetate, and laccase immobilized using an incubation and a fouling approach. Configurations of this biosystem exhibiting the highest catalytic activity were selected for removal of 2-chlorophenol and 4-chlorophenol from aqueous solution in an enzymatic membrane bioreactor under various process conditions. The highest removal of chlorophenols, at 88% and 74% for 2-chlorophenol and 4-chlorophenol, respectively, occurred at pH 5 and 30 °C in the GR81PP/cellulose acetate/laccase biosystem with enzyme immobilized by the fouling method. Furthermore, the GR81PP/cellulose acetate/laccase biosystem with enzyme immobilized by the fouling method exhibited significant reusability and storage stability compared with the biosystem with laccase immobilized by the incubation method. The mechanism of enzyme immobilization is based on pore blocking and cake-layer formation, while the mechanism of chlorophenols removal was identified as a synergistic combination of membrane separation and enzymatic conversion. The importance of the conducted research is due to efficient removal of hazardous organochlorides using a novel enzymatic membrane bioreactor. The study demonstrates the biosystem's high catalytic activity, reusability, and stability, offering a promising solution for environmental pollution control.

Prevention of Swelling Phenomenon of Alginate Beads To Improve the Stability and Recyclability of Encapsulated Horse Liver Alcohol Dehydrogenase

Horse Liver Alcohol Dehydrogenase (HLADH) has been immobilized on calcium-alginate beads and used for both oxidation and reduction reactions. To avoid swelling of the beads and their subsequent breakage, calcium ions were added to both reaction and storage solutions, allowing the beads to maintain the initial structural features. The techniques used for this purpose revealed that 2 mM Ca2+ is the optimal concentration, which does not significantly change the weight of the beads, the amount of water in them, and their external and internal structure. The optimized experimental procedure has been used to verify the properties of the enzyme in terms of reusability, storage, and thermal stability. The addition of calcium ions allows the enzyme to retain more than 80 % of its initial activity for fourteen cycles and approximately 50 % at the twentieth cycle. Moreover, when the biocatalyst has been stored in a buffer solution containing 2 mM Ca2+ , the retention of enzyme activity after 30 days was 100 %, compared to that measured before incubation. The encapsulated enzyme exhibits greater thermal stability than free HLADH up to at least 60 °C, preventing dimer dissociation into the two subunits.

Ecotoxicological impacts of industrial effluents on irrigation water quality, animal health and the role of calcium alginate in effluents treatment

The effluents discharged from Mansoura Company for Resins and Chemicals Industry were evaluated for drinking and irrigation purposes. Calcium-alginate beads were used for effluents treatment in this study. Young male rats were also allowed to drink effluents at different concentrations (10%, 50%, 100%) and treated 100% effluents with calcium-alginate for 11 weeks. Results indicated high concentrations of some physicochemical parameters and Cd, Co, Fe, Mn, Ni, Pb, and Zn in effluents that exceeded the permissible limits for drinking and irrigation purposes. Treatment by calcium-alginate alleviate heavy metals concentration but did not affect the physicochemical parameters. Depending on effluents concentration, the liver of young male rats showed high accumulation of Fe, Mn, Zn, Pb, Cd, Co, Cu, Cr, and Ni compared to the control group. Serum levels of liver enzymes, total bilirubin significantly increased while total protein, and albumin contents decreased in effluent groups. Liver concentrations of malondialdehyde and protein carbonyl significantly elevated along with significant decrease in superoxide dismutase, catalase, glutathione-S-transferase activities, and glutathione content. Moreover, growth and thyroid hormones were significantly reduced along with significant elevation in thyroid stimulating hormone. This was accompanied by significant decrease in the body weight, especially with 100% effluents concentration compared to control group. Also, histological investigations of both liver and thyroid gland using hematoxylin and eosin showed distortion in the structure of both organs especially with 50% and 100% effluent groups. However, treatment of effluents by calcium-alginate improved these changes. The study revealed that calcium-alginate are effective biosorbents for heavy metals and consequently decrease animal and human health hazards, but further studies are needed to alleviate physicochemical characteristics.