Decolorization of synthetic dyes by free and immobilized laccases from newly isolated strain Brevibacterium halotolerans N11 (KY883983)

Green synthesis of NiO NPs for metagenome-derived laccase stabilization: Detoxifying pollutants and wastes

Laccases play a crucial role in neutralizing environmental pollutants, including antibiotics and phenolic compounds, by converting them into less harmful substances via a unique oxidation process. This study introduces an environmentally sustainable remediation technique, utilizing NiO nanoparticles (NPs) synthesized through green chemistry to immobilize a metagenome-derived laccase, PersiLac1, enhancing its application in pollutant detoxification. Salvadora persica leaf extract was used for the synthesis of NiO nanoparticles, utilizing its phytochemical constituents as reducing and capping agents, followed by characterization through different analyses. Characterization of NiO nanoparticles revealed distinctive FTIR absorption peaks indicating the nanoparticulate structure, while FESEM showed structured NiO with robust interconnections and dimensionality of about 50nm, confirmed by EDX analysis to have a consistent distribution of Ni and O. The immobilized PersiLac1 demonstrated enhanced thermal stability, with 85.55 % activity at 80 °C and reduced enzyme leaching, retaining 67.93 % activity across 15 biocatalytic cycles. It efficiently reduced rice straw (RS) phenol by 67.97 % within 210 min and degraded 70-78 % of tetracycline (TC) across a wide pH range (4.0-8.0), showing superior performance over the free enzyme. Immobilized laccase achieved up to 71 % TC removal at 40-80 °C, significantly outperforming the free enzyme. Notably, 54 % efficiency was achieved at 500 mg/L TC by immobilized laccase at 120 min. This research showed the potential of green-synthesized NiO nanoparticles to effectively immobilize laccase, presenting an eco-friendly approach to purify pollutants such as phenols and antibiotics. The durability and reusability of the immobilized enzyme, coupled with its ability to reduce pollutants, indicates a viable method for cleaning the environment. Nonetheless, the production costs and scalability of NiO nanoparticles for widespread industrial applications pose significant challenges. Future studies should focus on implementation at an industrial level and examine a wider range of pollutants to fully leverage the environmental clean-up capabilities of this innovative technology.

Exploring laccase: a sustainable enzymatic solution for the paper recycling domain

The global advocacy of resource conservation and waste management emphasizes the significance of sustainable practices, particularly in sectors such as paper manufacturing and recycling. Currently, conventional chemical methods are predominant for paper production, necessitating the use of substantial amount of toxic chemicals. This chemical-intensive approach compromises the recycled fiber quality, generates hazardous effluent causing serious ecological threats which triggers regulatory complexities for the mills. To address these challenges modern research suggests adopting sustainable eco-friendly practices such as employing enzymes. This review aims to explore the applicability of 'laccase' enzyme for paper recycling, investigating its properties and contribution to improved recycling practices. By delving into the potential application of laccase integration into the papermaking process, this article sheds light on the limitations inherent in traditional methods surmounted within both research and translational landscapes. Culture and process optimization studies, supporting the technological improvements and the future prospects have been documented.

Harnessing the power of bacterial laccases for xenobiotic degradation in water: A 10-year overview

Industrialization and population growth are leading to the production of significant amounts of sewage containing hazardous xenobiotic compounds. These compounds pose a threat to human and animal health, as well as the overall ecosystem. To combat this issue, chemical, physical, and biological techniques have been used to remove these contaminants from water bodies affected by human activity. Biotechnological methods have proven effective in utilizing microorganisms and enzymes, particularly laccases, to address this problem. Laccases possess versatile enzymatic characteristics and have shown promise in degrading different xenobiotic compounds found in municipal, industrial, and medical wastewater. Both free enzymes and crude enzyme extracts have demonstrated success in the biotransformation of these compounds. Despite these advancements, the widespread use of laccases for bioremediation and wastewater treatment faces challenges due to the complex composition, high salt concentration, and extreme pH often present in contaminated media. These factors negatively impact protein stability, recovery, and recycling processes, hindering their large-scale application. These issues can be addressed by focusing on large-scale production, resolving operation problems, and utilizing cutting-edge genetic and protein engineering techniques. Additionally, finding novel sources of laccases, understanding their biochemical properties, enhancing their catalytic activity and thermostability, and improving their production processes are crucial steps towards overcoming these limitations. By doing so, enzyme-based biological degradation processes can be improved, resulting in more efficient removal of xenobiotics from water systems. This review summarizes the latest research on bacterial laccases over the past decade. It covers the advancements in identifying their structures, characterizing their biochemical properties, exploring their modes of action, and discovering their potential applications in the biotransformation and bioremediation of xenobiotic pollutants commonly present in water sources.

The Isolation, Identification and Immobilization Method of Three Novel Enzymes with Diosgenin-Producing Activity Derived from an Aspergillus flavus

Diosgenin is an important raw material used in the synthesis of steroid drugs, and it is widely used in the pharmaceutical industry. The traditional method of producing diosgenin is through using raw materials provided via the plant Dioscorea zingiberensis C. H. Wright (DZW), which is subsequently industrially hydrolyzed using a high quantity of hydrochloric and sulfuric acids at temperatures ranging from 70 °C to 175 °C. This process results in a significant amount of unmanageable wastewater, creates issues of severe environmental pollution and consumes high quantities of energy. As an alternative, the enzymolysis of DZW to produce diosgenin is an environmentally and friendly method with wide-ranging prospects for its application. However, there are still only a few enzymes that are suitable for production on an industrial scale. In this study, three new key enzymes, E1, E2, and E3, with a high conversion stability of diosgenin, were isolated and identified using an enzyme-linked-substrate autography strategy. HPLC-MS/MS identification showed that E1, a 134.45 kDa protein with 1019 amino acids (AAs), is a zinc-dependent protein similar to the M16 family. E2, a 97.89 kDa protein with 910 AAs, is a type of endo-β-1,3-glucanase. E3, a 51.6 kDa protein with 476 AAs, is a type of Xaa-Pro aminopeptidase. In addition, the method to immobilize these proteins was optimized, and stability was achieved. The results show that the optimal immobilization parameters are 3.5% sodium alginate, 3.45% calcium chloride concentration, 1.4 h fixed time, and pH 8.8; and the recovery rate of enzyme activity can reach 43.98%. A level of 70.3% relative enzyme activity can be obtained after employing six cycles of the optimized technology. Compared with free enzymes, immobilized enzymes have improved stability, acid and alkaline resistance and reusability, which are conducive to large-scale industrial production.

Immobilized laccase: an effective biocatalyst for industrial dye degradation from wastewater

Environmental concerns due to the release of industrial wastewater contaminated with dyes are becoming more and more intense with the increasing industrialization. Decolorization of industrial effluents has become the top priority due to the continuous demand for color-free discharge into the receiving water bodies. Different dye removal techniques have been developed, among which biodegradation by laccase enzyme is competitive. Laccase, as a green catalyst, has a high catalytic activity, generates less toxic by-products, and has been extensively researched in the field of remediation of dyes. However, laccase's significant catalytic activity could only be achieved after an effective immobilization step. Immobilization helps strengthen and stabilize the protein structure of laccase, thus enhancing its functional properties. Additionally, the reusability of immobilized laccase makes it an attractive alternative to traditional dye degradation technologies and in the realistic applications of water treatment, compared with free laccase. This review has elucidated different methods and the carriers used to immobilize laccase. Furthermore, the role of immobilized laccase in dye remediation and the prospects have been discussed.

Heterogeneous biocatalytic system for effective decolorization of textile dye effluent

The current physicochemical methods for decolorizing toxic synthetic dyes are not sustainable to halt the environmental damage as they are expensive and often produce concentrated sludge, which may lead to secondary disposal problems. Biocatalysis (microbes and/or their enzymes) is a cost-effective, versatile, energy-saving and clean alternative. The most common enzymes involved in dye degradation are laccases, azoreductases and peroxidases. Toxic dyes could be converted into less harmful byproducts through the combined action of many enzymes or the utilization of whole cells. The action of whole cells to treat dye effluents is either by biosorption or degradation (aerobic or anaerobic). Using immobilized cells or enzymes will offer advantages such as superior stability, persistence against harsh environmental conditions, reusability and longer half-lives. This review envisages the recent strategies of immobilization and bioreactor considerations with the immobilized system as the effective treatment of textile dye effluents. Packed bed reactors are the most popular heterogeneous biocatalytic reactors for dye decolorization due to their efficiency and cost-effectiveness.

Applications and immobilization strategies of the copper-centred laccase enzyme; a review

Laccase is a multi-copper enzyme widely expressed in fungi, higher plants, and bacteria which facilitates the direct reduction of molecular oxygen to water (without hydrogen peroxide production) accompanied by the oxidation of an electron donor. Laccase has attracted attention in biotechnological applications due to its non-specificity and use of molecular oxygen as secondary substrate. This review discusses different applications of laccase in various sectors of food, paper and pulp, waste water treatment, pharmaceuticals, sensors, and fuel cells. Despite the many advantages of laccase, challenges such as high cost due to its non-reusability, instability in harsh environmental conditions, and proteolysis are often encountered in its application. One of the approaches used to minimize these challenges is immobilization. The various methods used to immobilize laccase and the different supports used are further extensively discussed in this review.

Four Decades of Laccase Research for Wastewater Treatment: Insights from Bibliometric Analysis

Increasing trends of environmental pollution and emerging contaminants from anthropogenic activities have urged researchers to develop innovative strategies in wastewater management, including those using the biocatalyst laccase (EC 1.10.3.2). Laccase works effectively against a variety of substrates ranging from phenolic to non-phenolic compounds which only require molecular oxygen to be later reduced to H2O as the final product. In this study, we performed a bibliometric analysis on the metadata of literature acquired through the Scopus database (24 October 2022) with keyword combination "Laccase" AND "Pollutant" OR "Wastewater". The included publications were filtered based on year of publication (1978-2022), types of articles (original research articles and review articles) and language (English). The metadata was then exported in a CSV (.csv) file and visualized on VosViewer software. A total of 1865 publications were identified, 90.9% of which were original research articles and the remaining 9.1% were review articles. Most of the authors were from China (n = 416; 22.3%) and India (n = 276; 14.79%). In the case of subject area, 'Environmental Science' emerged with the highest published documents (n = 1053; 56.46%). The identified papers mostly cover laccase activity in degrading pollutants, and chitosan, which can be exploited for the immobilization. We encourage more research on laccase-assisted wastewater treatment, especially in terms of collaborations among organizations.

Laccase production from Bacillus aestuarii KSK using Borassus flabellifer empty fruit bunch waste as a substrate and assessing their malachite green dye degradation

AIMS

The lignocellulosic waste, Borassus flabellifer empty fruit bunch waste (BFEFBW), was employed to produce laccase using Bacillus aestuarii KSK under solid-state fermentation (SSF) conditions and to assess the efficiency of malachite green (MG) dye decolourization.

METHODS AND RESULTS

Abiotic factors such as pH (5.0-9.0), temperature (25-45°C) and incubation time (24-96 h) were optimized using Response surface methodology-Box-Behenan Design (RSM-BBD) to exploit the laccase production. The anticipated model revealed that the highest laccase activity of 437 U/ml shows after 60 h of incubation at 35°C at pH 7.0. The bacterial laccase was used to remove 89% of the MG dye in less time.

CONCLUSION

The laccase from B. aestuarii KSK decolorizes the MG and thereby making it a suitable choice for wastewater treatment from industrial effluents.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first report on the production of laccase from B. flabellifer empty fruit bunch waste as a substrate. Bacillus aestuarii KSK was isolated from the soil sample and used to produce laccase under SSF conditions. The bacterial laccase has the potential for industrial application in textile waste dye treatment.

Laccases as green and versatile biocatalysts: from lab to enzyme market-an overview

Laccases are multi-copper oxidase enzymes that catalyze the oxidation of different compounds (phenolics and non-phenolics). The scientific literature on laccases is quite extensive, including many basic and applied research about the structure, functions, mechanism of action and a variety of biotechnological applications of these versatile enzymes. Laccases can be used in various industries/sectors, from the environmental field to the cosmetics industry, including food processing and the textile industry (dyes biodegradation and synthesis). Known as eco-friendly or green enzymes, the application of laccases in biocatalytic processes represents a promising sustainable alternative to conventional methods. Due to the advantages granted by enzyme immobilization, publications on immobilized laccases increased substantially in recent years. Many patents related to the use of laccases are available, however, the real industrial or environmental use of laccases is still challenged by cost-benefit, especially concerning the feasibility of producing this enzyme on a large scale. Although this is a compelling point and the enzyme market is heated, articles on the production and application of laccases usually neglect the economic assessment of the processes. In this review, we present a description of laccases structure and mechanisms of action including the different sources (fungi, bacteria, and plants) for laccases production and tools for laccases evolution and prediction of potential substrates. In addition, we both compare approaches for scaling-up processes with an emphasis on cost reduction and productivity and critically review several immobilization methods for laccases. Following the critical view on production and immobilization, we provide a set of applications for free and immobilized laccases based on articles published within the last five years and patents which may guide future strategies for laccase use and commercialization.

Laccase-mediated delignification and detoxification of lignocellulosic biomass: removing obstacles in energy generation

The rising global population and worldwide industrialization have led to unprecedented energy demand that is causing fast depletion of fossil reserves. This has led to search for alternative energy sources that are renewable and environment friendly. Use of lignocellulosic biomass for energy generation is considered a promising approach as it does not compete with food supply. However, the lignin component of the biomass acts as a natural barrier that prevents its efficient utilization. In order to remove the lignin and increase the amount of fermentable sugars, the lignocellulosic biomass is pretreated using physical and chemical methods which are costly and hazardous for environment. Moreover, during the traditional pretreatment process, numerous inhibitory compounds are generated that adversely affect the growth of fermentative microbes. Alternatively, biological methods that use microbes and their enzymes disrupt lignin polymers and increase the accessibility of the carbohydrates for the sugar generation. Microbial laccases have been considered as an efficient biocatalyst for delignification and detoxification offering a green initiative for energy generation process. The present review aims to bring together recent studies in bioenergy generation using laccase biocatalyst in the pretreatment processes. The work provides an overview of the sustainable and eco-friendly approach of biological delignification and detoxification through whole-cell and enzymatic methods, use of laccase-mediator system, and immobilized laccases for this purpose. It also summarizes the advantages, associated challenges, and potential prospects to overcome the limitations.

Evaluation of a Trametes pubescens laccase concentrated extract on allura red AC decolorization without the addition of synthetic mediators

Synthetic dye bioremediation is a topic of great importance since these pollutants possess toxic effects, and huge quantities of them are being discharged into water bodies. Ligninolytic enzyme treatment stands out for being a cost-effective methodology, capable of obtaining high decolorization levels. In this work, a laccase enzyme treatment was evaluated to effectively perform a cycle of dye bioremediation. Furthermore, a dye decolorization improvement was also assessed through laccase immobilization. Particularly, a Trametes pubescens enzyme extract was concentrated, immobilized onto calcium alginate beads, and characterized to assess its dye decolorization potential. Ammonium sulfate precipitation and vacuum evaporation were evaluated to concentrate the crude extract and to decolorize allura red AC. Both treatments reached a high enzyme yield recovery (>90%), but only the vacuum-evaporated extract achieved a high allura red AC decolorization level after 16 h of contact time. This suggested that essential compounds for allura red AC decolorization were present in the crude extract, implying that neither a complete laccase purification process nor an addition of synthetic mediators are necessary. Under optimized immobilization conditions, 94.6% immobilization efficiency and 49.8% activity recovery were obtained with 0:1 alginate:enzyme (v/v), 100 mM CaCl₂, and 5.0% w/v sodium alginate. Furthermore, by immobilizing the laccase concentrated extract, both the pH and temperature stabilities were improved. The decolorization of allura red AC by free and immobilized laccase was 68.4% and 4.6%, respectively, showing that although the enzyme stability was improved, dye decolorization was negatively affected. Thus, an efficient allura red AC decolorization was obtained with concentrated-free laccase by a feasible and low-cost methodology.

Recent environmental applications of and development prospects for immobilized laccase: a review

Laccases have enormous potential as promising 'green' biocatalysts in environmental applications including wastewater treatment and polluted soil bioremediation. The catalytic oxidation reaction they perform uses only molecular oxygen without other cofactors, and the only product after the reaction is water. The immobilization of laccase offers several improvements such as protected activity and enhanced stability over free laccase. In addition, the reusability of immobilized laccase is adistinct advantage for future applications. This review covers the sources of and progress in laccase research, and discusses the different methodologies of laccase immobilization that have emerged in the recent 5-10 years, as well as its applications to environmental fields, and evaluates these emerging technologies. Abbreviations: (2,4,6-TCP): 2,4,6-trichlorophenol; (2,4-DCP): 2,4-dichlorophenol; (ABTS), 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid); (ACE), acetaminophen; (BC-AS), almond shell; (BC-PM), pig manure; (BC-PW), pine wood; (BPA), bisphenol A; (BPA), bisphenol A; (BPF), bisphenol F; (BPS), bisphenol S; (C₆₀), fullerene; (Ca-AIL), calcium-alginate immobilized laccase; (CBZ), carbamazepine; (CETY), cetirizine; (CHT-PGMA-PEI-Cu (II) NPs), Cu (II)-chelated chitosan nanoparticles; (CLEAs), cross-linked enzyme aggregates; (CMMC), carbon-based mesoporous magnetic composites; (COD), chemical oxygen demand; (CPH), ciprofloxacin hydrochloride; (CS), chitosan; (CTC), chlortetracycline; (Cu-AIL), copper-alginate immobilized laccase; (DBR K-4BL), Drimarene brilliant red K-4BL; (DCF), diclofenac; (E1),estrone; (E2), 17 β-estradiol; (EDC), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride; (EDCs), endocrine disrupting chemicals; (EE2), 17α-ethinylestradiol; (EFMs), electrospun fibrous membranes; (FL), free laccase; (fsMP), fumed silica microparticles; (GA-CBs), GLU-crosslinked chitosan beads; (GA-CBs), glutaraldehyde-crosslinked chitosan beads; (GA-Zr-MOF), graphene aerogel-zirconium-metal organic framework; (GLU), glutaraldehyde; (GO), graphene oxide; (HMCs), hollow mesoporous carbon spheres; (HPEI/PES), hyperbranched polyethyleneimine/polyether sulfone; (IC), indigo carmine; (IL), immobilized laccase; (k_cat), catalytic constant; (K_m), Michealis constant; (M-CLEAs), Magnetic cross-linked enzyme aggregates; (MMSNPs-CPTS-IDA-Cu²⁺), Cu²⁺-chelated magnetic mesoporous silica nanoparticles; (MSS), magnetic mesoporous silica spheres; (MWNTs), multi-walled carbon nanotubes; (MWNTs), multi-walled carbon nanotubes; (NHS), N-hydroxy succinimide; (O-MWNTs), oxidized-MWNTs; (P(AAm-NIPA)), poly(acrylamide-N-isopropylacrylamide); (p(GMA)), poly(glycidyl methacrylate); (p(HEMA)), poly(hydroxyethyl methacrylate); (p(HEMA-g-GMA)-NH₂, poly(glycidyl methacrylate) brush grafted poly(hydroxyethyl methacrylate); (PA6/CHIT), polyamide 6/chitosan; (PAC), powdered active carbon; (PAHs), polycyclic aromatic hydrocarbons; (PAM-CTS), chitosan grafted polyacrylamide hydrogel; (PAN/MMT/GO), polyacrylonitrile/montmorillonite/graphene oxide; (PAN/PVdF), polyacrylonitrile/polyvinylidene fluoride; (PEG), poly ethylene glycol; (PEI), Poly(ethyleneimine); (poly(4-VP)), poly(4-vinyl pyridine); (poly(GMA-MAA)), poly(glycidyl methacrylate-methacrylic acid); (PVA), polyvinyl alcohol; (RBBR), Remazol Brilliant Blue R; (SDE), simulated dye effluent; (semi-IPNs), semi-interpenetrating polymer networks; (TC), tetracycline; (TCH), tetracycline hydrochloride; (TCS), triclosan; (Vmax), maximum activity; (Zr-MOF, MMU), micro-mesoporous Zr-metal organic framework.

Synergistic Degradation of Dye Wastewaters Using Binary or Ternary Oxide Systems with Immobilized Laccase

In recent years, groundwater contamination caused by dyes has become an important problem. They enter into wastewater as a result of the textile, automotive, or cosmetics industries. For this reason, new methods are being sought, which would aid at the removal of dye impurities with high efficiency and also would be relatively cheap. In the presented study synthesized TiO2-ZrO2 (with TiO2:ZrO2 molar ratio of 8:2) and TiO2-ZrO2-SiO2 (with TiO2:ZrO2:SiO2 molar ratio of 8:1:1) oxide materials were used as supports for enzyme immobilization. Effective synthesis of the carriers was confirmed by results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), low-temperature nitrogen sorption and Fourier transform infrared spectroscopy (FTIR). The materials achieve high immobilization efficiency of the laccases from Trametes versicolor (83% and 96% for TiO2-ZrO2-laccase and TiO2-ZrO2-SiO2-laccase, respectively). The effect of selected dye concentrations, pH, temperature, and reusability were also tested. The obtained results showed that after removal of textile dyes, such as Alizarin Red S (ARS), Remazol Brilliant Blue R (RBBR), and Reactive Black 5 (RB5), under optimal process conditions, which were pH 5 and 25 °C, from dye solution of 5 mg/L degradation efficiency reached 100%, 91%, and 77%, respectively, suggesting synergistic mechanism of degradation by simultaneous sorption and catalytic action. Finally, reduction of chemical oxygen demand (COD) of the solution after treatment indicated lower mixture toxicity and effective dye degradation.