High BPA removal by immobilized crude laccase in a batch fluidized bed bioreactor

A novel univariate interpolation and bivariate regression hybrid method application to biodegradation of bisphenol A diglycidyl ether using laccases from Geobacillus stearothermophilus and Geobacillus thermoparafinivorans strains

Bisphenol A diglycidyl ether (BADGE), a derivative of the well-known endocrine disruptor Bisphenol A (BPA), is a potential threat to long-term environmental health due to its prevalence as a micropollutant. This study addresses the previously unexplored area of BADGE toxicity and removal. We investigated, for the first time, the biodegradation potential of laccase isolated from Geobacillus thermophilic bacteria against BADGE. The laccase-mediated degradation process was optimized using a combination of response surface methodology (RSM) and machine learning models. Degradation of BADGE was analyzed by various techniques, including UV-Vis spectrophotometry, high-performance liquid chromatography (HPLC), Fourier transform infrared (FTIR) spectroscopy, and gas chromatography-mass spectrometry (GC-MS). Laccase from Geobacillus stearothermophilus strain MB600 achieved a degradation rate of 93.28% within 30 min, while laccase from Geobacillus thermoparafinivorans strain MB606 reached 94% degradation within 90 min. RSM analysis predicted the optimal degradation conditions to be 60 min reaction time, 80°C temperature, and pH 4.5. Furthermore, CB-Dock simulations revealed good binding interactions between laccase enzymes and BADGE, with an initial binding mode selected for a cavity size of 263 and a Vina score of -5.5, which confirmed the observed biodegradation potential of laccase. These findings highlight the biocatalytic potential of laccases derived from thermophilic Geobacillus strains, notably MB600, for enzymatic decontamination of BADGE-contaminated environments.

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.

Immobilized-laccase bioreactors for wastewater treatment

Laccases have shown to be efficient biocatalysts for the removal of recalcitrant pollutants from wastewater. Thus, they catalyze the oxidation of a wide variety of organic compounds by reducing molecular oxygen to water. However, the use of free laccases holds several drawbacks such as poor reusability, high cost, low stability and sensitivity to different denaturing agents that may occur in wastewater. Such drawbacks can be circumvented by immobilizing laccase enzymes in/on solid carriers. Hence, during the last decades different approaches considering various techniques and solid carriers to immobilize laccase enzymes have been developed and tested for the removal of pollutants from wastewater. To scale up wastewater treatment bioprocesses, immobilized laccases are placed in different reactor configurations.

Metal-organic frameworks for enzyme immobilization and nanozymes: A laccase-focused review

Laccases are natural catalysts with remarkable catalytic activity. However, their application is limited by their lack of stability. Metal-organic frameworks (MOFs) have emerged as a promising alternative for enzyme immobilization. Enzymes can be immobilized in MOFs via two approaches: postsynthetic immobilization and in situ immobilization. In postsynthetic immobilization, an enzyme is embedded after MOF formation by covalent interactions or adsorption. In contrast, in in situ immobilization, a MOF is formed in the presence of an enzyme. Additionally, MOFs have exhibited intrinsic enzyme-like activity. These materials, known as nanozymes when they have the ability to replace enzymes in certain catalytic processes, have multiple key advantages, such as low cost, easy preparation, and large surface areas. This review presents a general overview of the most recent advances in both enzyme@MOF biocatalysts and MOF-based nanozymes in different applications, with a focus on laccase, which is one of the most widely investigated enzymes with excellent industrial potential.

Physico-chemical and biological remediation techniques for the elimination of endocrine-disrupting hazardous chemicals

Due to their widespread occurrence and detrimental effects on human health and the environment, endocrine-disrupting hazardous chemicals (EDHCs) have become a significant concern. Therefore, numerous physicochemical and biological remediation techniques have been developed to eliminate EDHCs from various environmental matrices. This review paper aims to provide a comprehensive overview of the state-of-the-art remediation techniques for eliminating EDHCs. The physicochemical methods include adsorption, membrane filtration, photocatalysis, and advanced oxidation processes. The biological methods include biodegradation, phytoremediation, and microbial fuel cells. Each technique's effectiveness, advantages, limitations, and factors affecting their performance are discussed. The review also highlights recent developments and future perspectives in EDHCs remediation. This review provides valuable insights into selecting and optimizing remediation techniques for EDHCs in different environmental matrices.

Elimination of tetracyclines in seawater by laccase-mediator system

Long-term exposure of antibiotics at low level leads to the accumulation of antibiotics in environmental media and organisms, inducing the formation of antibiotic resistance genes. Seawater is an important sink for many contaminants. Here, laccase from Aspergillus sp. And mediators that follow different oxidation mechanisms were combined to degrade tetracyclines (TCs) at environmentally relevant levels (ng·L^-1-μg·L^-1) in coastal seawater. The high salinity and alkaline of seawater changed the enzymatic structure of laccase, resulting in a reduced affinity of laccase to the substrate in seawater (K_m of 0.0556 mmol L^-1) than that in buffer (K_m of 0.0181 mmol L^-1). Although the stability and activity of the laccase decreased in seawater, laccase at a concentration of 200 U·L^-1 with a laccase/syringaldehyde (SA) ratio of 1 U: 1 μmol could completely degrade TCs in seawater at initial concentrations of less than 2 μg L^-1 in 2 h. Molecular docking simulation showed that the interaction between TCs and laccase mainly includes hydrogen bond interaction and hydrophobic interaction. TCs were degraded into small molecular products through a series of reactions: demethylation, deamination, deamidation, dehydration, hydroxylation, oxidation, and ring-opening. Prediction of the toxicity of intermediates showed that the majority of TCs can be degraded into low-toxic or non-toxic, small-molecule products within 1 h, indicating that the degradation process of TCs by a laccase-SA system has good ecological safety. The successful removal of TCs by the laccase-SA system demonstrates its potential for the elimination of pollutants in marine environment.

A novel PEI-grafted N-doping magnetic hydrochar for enhanced scavenging of BPA and Cr(VI) from aqueous phase

Herein, polyethyleneimine (PEI)-grafted nitrogen-doping magnetic hydrochar (PEI_MW@MNHC) was synthesized for hexavalent chromium (Cr(VI)) and bisphenol A (BPA) elimination from water. Characterizations exhibited that abundant amino functional groups, intramolecular heterocyclic N, azo and Fe-N_X structures were successfully introduced into the inherent structure of hydrochar. The obtained PEI_MW@MNHC presented maximum uptake of 205.37 and 180.79 mg/g for Cr(VI) and BPA, respectively, and was highly tolerant to various co-existing ions. Mechanism investigation revealed that the protonated amino, intramolecular heterocyclic N and Fe(II) participated in Cr(VI) reduction, and the N/O-containing groups and Fe(III) fixed Cr(III) onto PEI_MW@MNHC by the formation of complexes and precipitates. On the other hand, azo, Fe-N_X and graphitic N structures contributed to the removal of BPA via pore filling, hydrogen bonding and π-π interactions. Additionally, PEI_MW@MNHC maintained over 85.0% removal efficiency for Cr(VI) and BPA after four cycles, manifesting that PEI_MW@MNHC was an ideal adsorbent with outstanding practical application potential.

Laccase: A potential biocatalyst for pollutant degradation

In the continual march to a predominantly urbanized civilization, anthropogenic activities have increased scrupulously, industrialization have occurred, economic growth has increased, and natural resources are being exploited, causing huge waste management problems, disposal issues, and the evolution of several pollutants. In order to have a sustainable environment, these pollutants need to be removed and degraded. Bioremediation employing microorganisms or enzymes can be used to treat the pollutants by degrading and/or transforming the pollutants into different form which is less or non-toxic to the environment. Laccase is a diverse enzyme/biocatalyst belonging to the oxidoreductase group of enzymes produced by microorganisms. Due to its low substrate specificity and monoelectronic oxidation of substrates in a wide range of complexes, it is most commonly used to degrade chemical pollutants. For degradation of emerging pollutants, laccase can be efficiently employed; however, large-scale application needs reusability, thermostability, and operational stability which necessitated strategies like immobilization and engineering of robust laccase possessing desirable properties. Immobilization of laccase for bioremediation, and treatment of wastewater for degrading emerging pollutants have been focussed for sustainable development. Challenges of employing biocatalysts for these applications as well as engineering robust laccase have been highlighted in this study.

Immobilization of Biomass Materials for Removal of Refractory Organic Pollutants from Wastewater

In the field of environmental science and engineering, microorganisms, enzymes and algae are promising biomass materials that can effectively degrade pollutants. However, problems such as poor environmental adaptability, recycling difficulties, and secondary pollution exist in the practical application of non-immobilized biomass materials. Biomass immobilization is a novel environmental remediation technology that can effectively solve these problems. Compared with non-immobilized biomass, immobilized biomass materials have the advantages of reusability and stability in terms of pH, temperature, handling, and storage. Many researchers have studied immobilization technology (i.e., methods, carriers, and biomass types) and its applications for removing refractory organic pollutants. Based on this, this paper reviews biomass immobilization technology, outlines the mechanisms and factors affecting the removal of refractory organic pollutants, and introduces the application of immobilized biomass materials as fillers for reactors in water purification. This review provides some practical references for the preparation and application of immobilized biomass materials and promotes further research and development to expand the application range of this material for water purification.