Immobilization of laccase-ABTS system for the development of a continuous flow packed bed bioreactor for decolorization of textile effluent

Silk Industry Waste Protein-Derived Sericin Hybrid Nanoflowers for Antibiotics Remediation via Circular Economy

Hybrid protein-copper nanoflowers have emerged as promising materials with diverse applications in biocatalysis, biosensing, and bioremediation. Sericin, a waste biopolymer from the textile industry, has shown potential for fabricating such nanoflowers. However, the influence of the molecular weight of sericin on nanoflower morphology and peroxidase-like activity remains unexplored. This work focused on the self-assembly of nanoflowers using high- and low-molecular-weight (HMW and LMW) silk sericin combined with copper(II) as an inorganic moiety. The peroxidase-like activity of the resulting nanoflowers was evaluated using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydrogen peroxide (H2O2). The findings revealed that high-molecular-weight sericin hybrid nanoflowers (HMW-ShNFs) exhibited significantly higher peroxidase-like activity than low-molecular-weight sericin hybrid nanoflowers (LMW-ShNFs). Furthermore, HMW-ShNFs demonstrated superior reusability and storage stability, thereby enhancing their potential for practical use. This study also explored the application of HMW-ShNF for ciprofloxacin degradation to address the environmental and health hazards posed by this antibiotic in water. The results indicated that HMW-ShNFs facilitated the degradation of ciprofloxacin, achieving a maximum degradation of 33.2 ± 1% at pH 8 and 35 °C after 72 h. Overall, the enhanced peroxidase-like activity and successful application in ciprofloxacin degradation underscore the potential of HMW-ShNFs for a sustainable and ecofriendly remediation process. These findings open avenues for the further exploration and utilization of hybrid nanoflowers in various environmental applications.

Recent Advances in Applications of Oxidases and Peroxidases Polymer-Based Enzyme Biocatalysts in Sensing and Wastewater Treatment: A Review

Oxidase and peroxidase enzymes have attracted attention in various biotechnological industries due to their ease of synthesis, wide range of applications, and operation under mild conditions. Their applicability, however, is limited by their poor stability in harsher conditions and their non-reusability. As a result, several approaches such as enzyme engineering, medium engineering, and enzyme immobilization have been used to improve the enzyme properties. Several materials have been used as supports for these enzymes to increase their stability and reusability. This review focusses on the immobilization of oxidase and peroxidase enzymes on metal and metal oxide nanoparticle-polymer composite supports and the different methods used to achieve the immobilization. The application of the enzyme-metal/metal oxide-polymer biocatalysts in biosensing of hydrogen peroxide, glucose, pesticides, and herbicides as well as blood components such as cholesterol, urea, dopamine, and xanthine have been extensively reviewed. The application of the biocatalysts in wastewater treatment through degradation of dyes, pesticides, and other organic compounds has also been discussed.

Optimization of heterologous production of Bacillus ligniniphilus L1 laccase in Escherichia coli through statistical design of experiments

Laccases are powerful multi-copper oxidoreductases that have wide applicability as "green" biocatalysts in biotechnological, bioremediation, and industrial applications. Sustainable production of large amounts of functional laccases from original sources is limited by low yields, difficulties in purification, slow growth of the organisms, and high cost of production. Harnessing the full potential of these versatile biocatalysts will require the development of efficient heterologous systems that allow high-yield, scalable, and cost-effective production. We previously cloned a temperature- and pH-stable laccase from Bacillus ligniniphilus L1 (L1-lacc) that demonstrated remarkable activity in the oxidation of lignin and delignification for bioethanol production. However, L1-lacc is limited by low enzyme yields in both the source organism and heterologous systems. Here, to improve production yields and lower the cost of production, we optimized the recombinant E. coli BL21 strain for high-level production of L1-lacc. Several culture medium components and fermentation parameters were optimized using one-factor-at-a-time (OFAT) and Plackett-Burman design (PBD) to screen for important factors that were then optimized using response surface methodology (RSM) and an orthogonal design. The optimized medium composition had compound nitrogen (15.6 g/L), glucose (21.5 g/L), K₂HPO₄ (0.15 g/L), MgSO₄ (1 g/L), and NaCl (7.5 g/L), which allowed a 3.3-fold yield improvement while subsequent optimization of eight fermentation parameters achieved further improvements to a final volumetric activity titer of 5.94 U/mL in 24 h. This represents a 7-fold yield increase compared to the initial medium and fermentation conditions. This work presents statistically guided optimization strategies for improving heterologous production of a bacterial laccase that resulted in a high-yielding, cost-efficient production system for an enzyme with promising applications in lignin valorization, biomass processing, and generation of novel composite thermoplastics.

Application of enzymes for an eco-friendly approach to textile processing

Textile industry is one of the oldest industries existing from several centuries. Major concern of the industry is to design, produce, and distribute yarn, cloth, and clothing. Diverse physical and chemical operations are required in order to achieve this. Environmental concerns related to textile industry have attained attention all around the world as it is generating large amounts of effluents having various toxic agents and chemicals. Enzymes have been suggested as the best possible alternative to replace or reduce these hazardous and toxic chemicals. Enzymes like amylase, cellulase, catalase, protease, pectinase, laccase, and lipase have widely been used in textile manufacturing processes. Use of enzymatic approach is very promising as they are eco-friendly, produce high-quality products, and lead to the reduction of energy, water, and time. This review highlights the significance of different enzymes employed in the textile industry at various stages along with the conventional textile processing.

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.

Assessment of biodegradation kinetics and mass transfer aspects in attached growth bioreactor for effective treatment of Brilliant green dye from wastewater

In this study, Bacillus licheniformis immobilized with low-density polyethylene (LDPE) was employed to degrade Brilliant Green (BG) dye from wastewater in a packed bed bioreactor (PBBR). Bacterial growth and extracellular polymeric substance (EPS) secretion were also assessed under different concentrations of BG dye. The impacts of external mass transfer resistance on BG biodegradation were also evaluated at different flow rates (0.3 - 1.2 L/h). A new mass transfer correlation [Formula: see text] was proposed to study the mass transfer aspects in attached-growth bioreactor. The intermediates, namely 3- dimethylamino phenol, benzoic acid, 1-4 benzenediol, and acetaldehyde were identified during the biodegradation of BG and, subsequently degradation pathway was proposed. Han - Levenspiel kinetics parameters μ_max and K_s were found to be 0.185 per day and 115 mg/L, respectively. The new insight into mass transfer and kinetics support the design of efficiently attached growth bioreactor to treat a wide range of pollutants.

Enzyme Immobilization Technologies and Industrial Applications

Enzymes play vital roles in diverse industrial sectors and are essential components of many industrial products. Immobilized enzymes possess higher resistance to environmental changes and can be recovered/recycled easily when compared to the free forms. The primary benefit of immobilization is protecting the enzymes from the harsh environmental conditions (e.g., elevated temperatures, extreme pH values, etc.). The immobilized enzymes can be utilized in various large-scale industries, e.g., medical, food, detergent, textile, and pharmaceutical industries, besides being used in water treatment plants. According to the required application, a suitable enzyme immobilization technique and suitable carrier materials are chosen. Enzyme immobilization techniques involve covalent binding, encapsulation, entrapment, adsorption, etc. This review mainly covers enzyme immobilization by various techniques and their usage in different industrial applications starting from 1992 until 2022. It also focuses on the multiscale operation of immobilized enzymes to maximize yields of certain products. Lastly, the severe consequence of the COVID-19 pandemic on global enzyme production is briefly discussed.

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.

A pilot study for enhanced transformation of a metabolite 3,5-dichloroaniline derived from dicarboximide fungicides through immobilized laccase mediator system

This pilot investigation aimed to evaluate the removal efficiency and the underlying biocatalytic pathways of immobilized fungal laccase during the oxidative biotransformation of a non-phenolic metabolite, 3,5-dichloroaniline (3,5-DCA) derived from dicarboximide fungicides. The maximum loading of laccase on the microporous support surfaces could reach 36.4 mg/g. The immobilized laccase on the microporous support surfaces exhibited excellent thermal stability, pH adaptability, storage stability, and reusability compared to free laccase. The ILMS assay indicated that the immobilized laccase efficiently removed studied 3,5-DCA (99-100%) in the aqueous medium, within 72 h in the presence of catechol. In this study, we identified three coupling reaction products during the removal of 3,5-DCA through an ILMS assay. Based on the identified coupling reaction products, we proposed the reaction pathway for the biotransformation of 3,5-DCA by immobilized laccase, which was shown to be potentially useful in the sustainable environmental remediation of aniline metabolite (i.e., 3,5-DCA) derived from dicarboximide fungicides.

Novel mechanism and degradation kinetics of pesticides mixture using Bacillus sp. strain 3C in contaminated sites

The present study has investigated the potential of Bacillus sp. strain 3C able to degrade mixture of pesticides from the environment. It showed maximum tolerance up to 450 mg·L^-1 for cypermethrin, fipronil, imidacloprid and sulfosulfuron. The strain 3C was able to degrade up to the 94% of mixture of pesticides (20 mg·L^-1) within 15 days of experiment. The Box-Behnken design of Response Surface Methodology (RSM) determined the optimized conditions as; inoculum size 3.0 × 10⁷ CFU·mL^-1, shaking speed 120 rpm, and pesticides concentration 80 mg·L^-1. In soil-based bioremediation with strain 3C after 15 days degradation pattern was; 99, 94, 92, 92 and 7% for the imidacloprid, sulfosulfuron, fipronil, cypermethrin and control respectively. The novel intermediate metabolites for cypermethrin degradation were investigated as decyl isobutyl ester, phthalic acid, cyclopropane carboxylic acid tri dec-2-ynyl ester, 9- octadecanal, tridecane, propanoic acid, cyclohexene, bicyclo[2.2.1] heptan-2-ol, and acetic acid were identified using Gas chromatography Mass Spectrometry (GC-MS) with strain 3C. Moreover, the results of the laccase based enzymatic kinetics suggested that the rate of production was maximum in pesticides stress (94 μg·μL^-1) whereas, in normal condition 51 μg·μL^-1. The K_m value found to be decreased in pesticides stress condition 12.25 and increment in K_m 13.58 mM was observed without stress. Furthermore, aldehyde dehydrogenase (ALDH) and laccase encoding genes were amplified and linked with mixture of pesticides bioremediation. The efficiency of bacterial strain 3C, could be used for bioremediation of mixture of pesticides, and other xenobiotic compounds from the contaminated environments.

Facile mussel-inspired polydopamine-coated 3D-printed bioreactors for continuous flow biocatalysis

Enantiopure alcohol production by a flow system of 3D-printed bioreactor with immobilized Geotrichum candidum acetophenone reductase (GcAPRD).

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.

Biotechnological potential of fungi from a mangrove ecosystem: Enzymes, salt tolerance and decolorization of a real textile effluent

The mangrove is an ecosystem bounded by the line of the largest tide in size that occurs in climatic and subtropical regions. In this environment, microorganisms and their enzymes are involved in a series of transformations and nutrient cycling. To evaluate the biotechnological potential of fungi from a mangrove ecosystem, samples from mangrove trees were collected at the Paranaguá Estuarine Complex in Brazil and 40 fungal isolates were obtained, cultivated, and screened for hydrolytic and ligninolytic enzymes production, adaptation to salinity and genetic diversity. The results showed a predominance of hydrolytic enzymes and fungal tolerance to ≤ 50 g L^-1 sodium chloride (NaCl) concentration, a sign of adaptive halophilia. Through morphological and molecular analyses, the isolates were identified as: Trichoderma atroveride, Microsphaeropsis arundinis, Epicoccum sp., Trichoderma sp., Gliocladium sp., Geotrichum sp. and Cryphonectria sp. The ligninolytic enzymatic potential of the fungi was evaluated in liquid cultures in the presence and absence of seawater and the highest activity of laccase among isolates was observed in the presence of seawater with M. arundinis (LB07), which produced 1,037 U L^-1. Enzymatic extracts of M. arundinis fixed at 100 U L^-1 of laccase partially decolorized a real textile effluent in a reaction without pH adjustment and chemical mediators. Considering that mangrove fungi are still few explored, the results bring an important contribution to the knowledge about these microorganisms, as their ability to adapt to saline conditions, biodegradation of pollutants, and enzymatic potential, which make them promising candidates in biotechnological processes.

Differential proteomic analysis under pesticides stress and normal conditions in Bacillus cereus 2D

A potential pesticide degrading bacterial isolate (2D), showing maximum tolerance (450 mg∙L^-1) for cypermethrin, fipronil, imidacloprid and sulfosulfuron was recovered from a pesticide contaminated agricultural field. The isolate degraded cypermethrin, imidacloprid, fipronil and sulfosulfuron in minimal salt medium with 94, 91, 89 and 86% respectively as revealed by high performance liquid chromatography (HPLC) and gas chromatography (GC) analysis after 15 days of incubation. Presence of cyclobutane, pyrrolidine, chloroacetic acid, formic acid and decyl ester as major intermediate metabolites of cypermethrin biodegradation was observed in gas chromatography mass spectrometry (GC-MS) analysis. Results based on 16S rDNA sequencing, and phylogenetic analysis showed maximum similarity of 2D with Bacillus cereus (Accession ID: MH341691). Stress responsive and catabolic/pesticide degrading proteins were over expressed in the presence of cypermethrin in bacteria. Enzymatic kinetics of laccase was deduced in the test isolate under normal and pesticide stress conditions which suggested that the production of enzyme was induced significantly in pesticide stress (163 μg.μL^-1) as compare to normal conditions(29 μg.μL^-1) while the K_m value was decreased in pesticides stress condition (K_m = 10.57 mM) and increases in normal condition (K_m = 14.33 mM).Amplification of laccase gene showed a major band of 1200bp. The present study highlights on the potential of 2D bacterial strain i.e., high tolerance level of pesticide, effective biodegradation rate, and presence of laccase gene in bacterial strain 2D, could become a potential biological agent for large-scale treatment of mixture of pesticide (cypermethrin, fipronil, imidacloprid and sulfosulfuron) in natural environment (soil and water).

Exploring current tendencies in techniques and materials for immobilization of laccases - A review

Nanotechnology has transformed the science behind many biotechnological sectors, and applied bio-catalysis is not the exception. In 2017, the enzyme industry was valued at more than 7 billion USD and projected to 10.5 billion by 2024. The laccase enzyme is an oxidoreductase capable of oxidizing phenolic and non-phenolic compounds that have been considered an essential tool in the fields currently known as white biotechnology and green chemistry. Laccase is one of the most robust biocatalysts due to its wide applications in different environmental processes such as detecting and treating chemical pollutants and dyes and pharmaceutical removal. However, these biocatalytic processes are usually limited by the lack of stability of the enzyme, the half-life time, and the application feasibility at an industrial scale. Physical or chemical approaches have performed different laccase's immobilization methods to improve its catalytic properties and reuse. Emerging technologies have been proven to reduce the manufacturing process cost and increase application feasibility while looking for ecological and economical materials that can be used as support. Therefore, this review discusses the trends of enzyme immobilization recently studied, analyzing biomaterials and agro-industrial waste used for that intention, their advantages, and disadvantages. Finally, the work also highlights the performance obtained with these materials and current challenges and potential alternatives.

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.

Co-immobilization of laccase and ABTS onto amino-functionalized ionic liquid-modified magnetic chitosan nanoparticles for pollutants removal

This work aims to achieve the co-immobilization of laccase and 2,2-binamine-di-3-ethylbenzothiazolin-6-sulfonic acid (ABTS) to improve removal capability of the biocatalyst for pollutants while avoiding potential pollution caused by ABTS. The laccase was immobilized on magnetic chitosan nanoparticles modified with amino-functionalized ionic liquid containing ABTS (MACS-NIL) based on Cu ion chelation (MACS-NIL-Cu-lac). The carrier was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, x-ray diffraction and etc., and electron paramagnetic resonance confirmed the mediator molecule ABTS on the carrier could also play the role of electron transmission. MACS-NIL-Cu-lac presented relatively high immobilization capacity, enhanced activity (1.7-fold that of free laccase), improved pH and temperature adaptability, and increased thermal and storage stability. The removal performance assay found that MACS-NIL-Cu-lac had a good removal efficiency with 100.0 % for 2,4-dichlorophenol in water at 25 °C, even when the concentration reached 50 mg/L. Reusability study showed that after six catalytic runs, the removal efficiency of 2,4-dichlorophenol by MACS-NIL-Cu-lac could still reach 93.2 %. Additionally, MACS-NIL-Cu-lac exhibited higher catalytic efficiencies with 100.0 %, 70.5 % and 93.3 % for bisphenol A, indole, and anthracene, respectively. The high catalytic performance in pure water system obtained by the novel biocatalyst co-immobilizing laccase and electron mediator ABTS showed greater practical application value.

Enzymatic characterization, molecular dynamics simulation, and application of a novel Bacillus licheniformis laccase

A new laccase gene from newly isolated Bacillus licheniformis TCCC 111219 was actively expressed in Escherichia coli. This recombinant laccase (rLAC) exhibited a high stability towards a wide pH range and high temperatures. 170% of the initial activity was detected at pH 10.0 after 10-d incubation, and 60% of the initial activity was even kept after 2-h incubation at 70 °C. It indicated that only single type of extreme environment, such as strong alkaline environment (300 K, pH 12) or high temperature (370 K, pH 7), did not show obvious impact on the structural stability of rLAC during molecular dynamics simulation process. But the four loop regions of rLAC where the active site is situated were seriously destroyed when strong alkaline and high temperature environment existed simultaneously (370 K, pH 12) because of the damage of hydrogen bonds and salt bridges. Moreover, this thermo- and alkaline-stable enzyme could efficiently decolorize the structurally differing azo, triphenylmethane, and anthraquinone dyes with appropriate mediator at pH 3.0, 7.0, and 9.0 at 60 °C. These rare characteristics suggested its high potential in industrial applications to decolorize textile dyeing effluent.

Removal of dye using peroxidase-immobilized Buckypaper/polyvinyl alcohol membrane in a multi-stage filtration column via RSM and ANFIS

The feasibility and performance of Jicama peroxidase (JP) immobilized Buckypaper/polyvinyl alcohol (BP/PVA) membrane for methylene blue (MB) dye removal was investigated in a customized multi-stage filtration column under batch recycle mode. The effect of independent variables, such as influent flow rate, ratio of H₂O₂/MB dye concentration, and contact time on the dye removal efficiency, were investigated using response surface methodology (RSM). To capture the inherent characteristics and better predict the removal efficiency, a data-driven adaptive neuro-fuzzy inference system (ANFIS) is implemented. Results indicated that the optimum dye removal efficiency of 99.7% was achieved at a flow rate of 2 mL/min, 75:1 ratio of H₂O₂/dye concentration with contact time of 183 min. The model predictions of ANFIS are significantly good compared with RSM, thus resulting in R² values of 0.9912 and 0.9775, respectively. The enzymatic kinetic parameters, K_m and V_max, were evaluated, which are 1.98 mg/L and 0.0219 mg/L/min, respectively. Results showed that JP-immobilized BP/PVA nanocomposite membrane can be promising and cost-effective biotechnology for the practical application in the treatment of industrial dye effluents.

Biodegradation and biosorption of Reactive Red 120 dye by immobilized Pseudomonas guariconensis: Kinetic and toxicity study

Reactive dyes are pernicious pollutants in textile effluent, which are to be treated passably before discharging into the environment. In the present study, a potential dye degrading bacterial strain Pseudomonas guariconensis was isolated from paddy rhizosphere and was characterized by 16S rRNA gene sequencing. The biodegradation ability of the strain was evaluated by time-based study with immobilized bacterial cells in calcium alginate biocarrier matrix and also with free cells. The results indicated that the strain exhibited maximum degradation of 91% when immobilized in the biocarrier matrix. The enzymatic study revealed the production of oxidoreductase enzymes. The degraded products were identified as 2-amino-3-phenylpropanoic acid and benzoquinone by gas chromatography-mass spectroscopy (GC-MS) analysis, and a degradative pathway was derived based on the enzymatic profile. A packed bed column was designed using P. guariconensis VITSAJ5 immobilized in calcium alginate beads as a biosorbent for the removal of Reactive Red 120. The immobilized bacterial cells exhibited 87% uptake of RR120, whereas the nonimmobilized bacterial cells exhibited a maximum uptake of 37%. The phytotoxicity analysis by seed germination assay revealed an enhanced plumule and radicle length, indicating the nontoxic byproducts after the treatment of Reactive Red 120 by VITSAJ5 compared to the untreated Reactive Red 120 solution. PRACTITIONER POINTS: Current study is the first report on Pseudomonas guariconensis capable of degrading reactive dyes (Reactive Red 120) It was observed that the degradation potential was maximum when cells were immobilized with Ca-Ag biocarrier matrix Breakdown metabolism of Reactive Red 120 was derived through pathway prediction Employing immobilized bacteria in a packed bed column found to possess a prominent biosorption ability on the matrix enhancing the degradation process Toxic reactive dye was converted into nontoxic compounds, evidenced by phytotoxicity studies.

Hyperstabilization of a thermophile bacterial laccase and its application for industrial dyes degradation

In the present study, a novel extracellular laccase isolated from Geobacillus stearothermophilus ATCC 10149 was entrapped in a bionanocomposite matrix consisting of copper alginate (Cu-alginate) supplemented with the nanoclay bentonite. After optimization, this nanobiocatalyst was able to degrade up to 90% of Remazol Brilliant Blue R (RBBR) without the addition of redox mediators and retained 70% of its initial activity for at least 1440 h, equivalent to more than 288 uses. The incorporation of nanoclay allowed alginate beads to be used in alkaline pH and strengthened its mechanical properties. Besides, this thermophilic laccase was able to decolorize other structurally different synthetic dyes such as Methyl Orange, Malachite Green and Indigo Carmine. These preliminary results suggested that the nanobiocatalyst could be a suitable option for dye decolorization and be further developed for large scale bioremediation of toxic dyes.

The heterologous expression, characterization, and application of a novel laccase from Bacillus velezensis

Laccases have a huge potential in numerous environmental and industrial applications due to the ability to oxidized a wide range of substrates. Here, a novel laccase gene from the identified Bacillus velezensis TCCC 111904 was heterologously expressed in Escherichia coli. The optimal temperature and pH for oxidation by recombinant laccase (rLac) were 80 °C and 5.5, respectively, in the case of the substrate 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and 80 °C and 7.0, respectively, in the case of 2,6-dimethoxyphenol (2,6-DMP). rLac exhibited high thermostability and pH stability over a wide range (pH 3.0, 7.0, and 9.0). Additionally, most of the metal ions did not inhibit the activity of rLac significantly. rLac showed great tolerance against high concentration of NaCl, and 50.8% of its initial activity remained in the reaction system containing 500 mM NaCl compared to the control. Moreover, rLac showed a high efficiency in decolorizing different types of dyes including azo, anthraquinonic, and triphenylmethane dyes at a high temperature (60 °C) and over an extensive pH range (pH 5.5, 7.0, and 9.0). These unique characteristics of rLac indicated that it could be a potential candidate for applications in treatment of dye effluents and other industrial processes.

Applications of Microbial Laccases: Patent Review of the Past Decade (2009–2019)

There is a high number of well characterized, commercially available laccases with different redox potentials and low substrate specificity, which in turn makes them attractive for a vast array of biotechnological applications. Laccases operate as batteries, storing electrons from individual substrate oxidation reactions to reduce molecular oxygen, releasing water as the only by-product. Due to society’s increasing environmental awareness and the global intensification of bio-based economies, the biotechnological industry is also expanding. Enzymes such as laccases are seen as a better alternative for use in the wood, paper, textile, and food industries, and they are being applied as biocatalysts, biosensors, and biofuel cells. Almost 140 years from the first description of laccase, industrial implementations of these enzymes still remain scarce in comparison to their potential, which is mostly due to high production costs and the limited control of the enzymatic reaction side product(s). This review summarizes the laccase applications in the last decade, focusing on the published patents during this period.

Naturally-derived biopolymers: Potential platforms for enzyme immobilization

Naturally-derived biopolymers such as alginate, chitosan, cellulose, agarose, guar gum/guaran, agar, carrageenan, gelatin, dextran, xanthan, and pectins, etc. have appealed significant attention over the past several years owing to their natural abundance and availability all over the years, around the globe. In addition, their versatile properties such as non-toxicity, biocompatibility, biodegradability, flexibility, renewability, and the availability of numerous reactive sites offer significant functionalities with multipurpose applications. At present, intensive research efforts have been focused on engineering enzymes using natural biopolymers as novel support/composite materials for diverse applications in biomedical, environmental, pharmaceutical, food and biofuel/energy sectors. Immobilization appears as a straightforward and promising approach to developing biocatalysts with improved catalytic properties as compared to their free counterparts. Biopolymers-assisted enzymes are more stable, robust, and recoverable than that of free forms, and can be employed for continuous biocatalytic reactions. The present review highlights the recent developments and use of biopolymers and their advanced composites as support carriers for the immobilization of a variety of different enzymes to develop biocatalysts with desired catalytic activity and stability characteristics for emerging applications.

Response surface based optimization of laccase production from Bacillus sp. MSK-01 using fruit juice waste as an effective substrate

Laccases are multicopper oxidases containing four copper atoms per monomer distributed in three redox sites. Because of its tremendous applications in different areas, isolation of new laccases with wide range of industrial implementation. The present study focuses on the optimization of laccase production from Bacillus sp. MSK-01 under solid state fermentation conditions using fruit juice waste as the substrate. MSKLAC was produced extracellularly by the bacteria. This laccase was able to oxidize ABTS and syringaldazine. Various nutritional and environmental factors were utilized for increasing the enzyme yield. Plackett Burman was used to study the influence of input parameters on laccase yield. Tween-80, initial moisture ratio and magnesium sulphate were the major influencing factor affecting laccase yield. Central composite design of RSM was used for the modelling of experiment. Desirability approach was used to optimize laccase yield. Maximum laccase yield of 1645 IUg⁻¹ was obtained when 0.55% of tween -80, 1:2.34 initial moisture ratio and 300μM magnesium sulphate was used. A 470 fold increase in the yield of laccase from unoptimized condition was obtained.

Decolorization and detoxification of textile wastewaters by recombinant Myceliophthora thermophila and Trametes trogii laccases

Laccases are multi-copper oxidoreductases with broad biotechnological applications. Here, we report detailed biochemical characterization of purified recombinant laccases originating from Myceliophthora thermophila (MtL) and Trametes trogii (TtL). We identified optimal conditions for decolorization of commercial dyes and textile wastewater samples. We also tested the toxicity of decolorized wastewater samples using human peripheral blood mononuclear cells. MtL and TtL were expressed in Saccharomyces cerevisiae, and secreted enzymes were purified by consecutive hydrophobic and gel chromatography. The molecular masses of TtL (~ 65 kDa) and MtL (> 100 kDa) suggested glycosylation of the recombinant enzymes. Deglycosylation of MtL and TtL led to 25% and 10% decreases in activity, respectively. In a thermal stability assay, TtL retained 61% and MtL 86% of the initial activity at 40 °C. While TtL retained roughly 50% activity at 60 °C, MtL lost stability at temperatures higher than 40 °C. MtL and TtL preferred syringaldazine as a substrate, and the catalytic efficiencies for ABTS oxidation were 7.5 times lower than for syringaldazine oxidation. In the presence of the mediator HBT, purified TtL almost completely decolorized dyes within 30 min and substantially decolorized wastewater samples from a textile factory (up to 74%) within 20 h. However, products of TtL-catalyzed decolorization were more toxic than MtL-decolorized products, which were almost completely detoxified.

Decolourization and detoxification of monoazo dyes by laccase from the white-rot fungus Trametes versicolor

The decolourization and detoxification of azo dyes (Orange 2, Acid Orange 6) by fungal laccase from Trametes versicolor were evaluated. For laccase catalysed reaction, the azonaphthol Orange 2, with 72.8% decolourization, was degraded more rapidly than the azobenzene Acid Orange 6, with 45.3%. The presence of hydroxyl group at o-position to azo bond in the structure of Orange 2 was more preferable than the presence of two hydroxyl groups at o- and p-positions to azo bond in Acid Orange 6. Although the laccase treatment was more effective for the Orange 2 decolourization, the toxicity of both monoazo dye solutions became less toxic for the prokaryote growth. The phytotoxicity of Orange 2 and Acid Orange 6 solutions after laccase treatment was decreased in the range of 41.2-64.3 %. Also, the photoxicity, as measured by the production of chlorophylls a and b by Chlorella vulgaris and Microcystis aeruginosa, was decreased by laccase treatment of selected monoazo dyes. Our results show that different dyes can be decolorized and detoxified by laccase from T. versicolor in a single step.