Laccase production from sucrose by recombinant Yarrowia lipolytica and its application to decolorization of environmental pollutant dyes

Reusable magnetic alginate nanocomposite with immobilized Pseudozyma antarctica yeast cells offers the potential for bioremediation and detoxification of reactive black 5 dye

Azo dyes in wastewater of textile, paper and pulp, cosmetics, and leather tanning industries have toxicity and mutagenicity for all living organisms. The aim of the current research was the study of free and immobilized yeast cells of Pseudozyma antarctica on the beads of magnetic alginate nanocomposite to decolorize and detoxify Reactive Black 5 (RB5) as a representative of azo dyes. This yeast decolorized a high concentration of RB5 (2500 mg/L) with 82.30 % decolorization efficiency. The beads containing immobilized yeast cells were used for decolorization in consecutive cycles, and the decolorization efficiency of the beads after four cycles was more than 67 %. UV-visible and FTIR spectroscopy studies showed that the azo bond in RB5 was removed and destroyed by yeast activity. The azo bond of RB5 is destroyed in the biodegradation mechanism which confirms the decolorization of RB5 by P. antarctica via the biodegradation mechanism. According to the phytotoxicity results, RB5 decolorization by P. antarctica reduced the toxicity of the dye. This is the first study on the decolorizing and detoxifying potentials of P. antarctica and introduces a promising candidate for the treatment of wastewater containing azo dyes. Furthermore, its successful immobilization on magnetic alginate nanocomposite and its convenient consecutive uses make it more attractive for environmental applications.

Effective Decolorization and Detoxification of Single and Mixed Dyes with Crude Laccase Preparation from a White-Rot Fungus Strain Pleurotus eryngii

To fully harness the potential of laccase in the efficient decolorization and detoxification of single and mixed dyes with diverse chemical structures, we carried out a systematic study on the decolorization and detoxification of single and mixed dyes using a crude laccase preparation obtained from a white-rot fungus strain, Pleurotus eryngii. The crude laccase preparation showed efficient decolorization of azo, anthraquinone, triphenylmethane, and indigo dyes, and the reaction rate constants followed the order Remazol Brilliant Blue R > Bromophenol blue > Indigo carmine > New Coccine > Reactive Blue 4 > Reactive Black 5 > Acid Orange 7 > Methyl green. This laccase preparation exhibited notable tolerance to SO42- salts such as MnSO4, MgSO4, ZnSO4, Na2SO4, K2SO4, and CdSO4 during the decolorization of various types of dyes, but was significantly inhibited by Cl- salts. Additionally, this laccase preparation demonstrated strong tolerance to some organic solvents such as glycerol, ethylene glycol, propanediol, and butanediol. The crude laccase preparation demonstrated the efficient decolorization of dye mixtures, including azo + azo, azo + anthraquinone, azo + triphenylmethane, anthraquinone + indigo, anthraquinone + triphenylmethane, and indigo + triphenylmethane dyes. The decolorization kinetics of mixed dyes provided preliminary insight into the interactions between dyes in the decolorization process of mixed dyes, and the underlying reasons and mechanisms were discussed. Importantly, the crude laccase from Pleurotus eryngii showed efficient repeated-batch decolorization of single-, two-, and four-dye mixtures. This crude laccase demonstrated high stability and reusability in repeated-batch decolorization. Furthermore, this crude laccase was efficient in the detoxification of different types of single dyes and mixed dyes containing different types of dyes, and the phytotoxicity of decolorized dyes (single and mixed dyes) was significantly reduced. The crude laccase efficiently eliminated phytotoxicity associated with single and mixed dyes. Consequently, the crude laccase from Pleurotus eryngii offers significant potential for practical applications in the efficient decolorization and management of single and mixed dye pollutants with different chemical structures.

Advances from conventional to biochar enhanced biotreatment of dyeing wastewater: A critical review

DW (Dyeing wastewater) contains a large amount of dye organic compounds. A considerable proportion of dye itself or its intermediate products generated during wastewater treatment process exhibits CMR (Carcinogenic/Mutagenic/Toxic to Reproduction) toxicity. Compared with physicochemical methods, biological treatment is advantageous in terms of operating costs and greenhouse gas emissions, and has become the indispensable mainstream technology for DW treatment. This article reviews the adsorption and degradation mechanisms of dye organic compounds in wastewater and analyzed different biological processes, ranging from traditional methods to processes enhanced by biochar (BC). For traditional biological processes, microbial characteristics and communities were discussed, as well as the removal efficiency of different bioreactors. BC has adsorption and redox electron mediated effects, and coupling with biological treatment can further enhance the process of biosorption and degradation. Although BC coupled biological treatment shows promising dye removal, further research is still needed to optimize the treatment process, especially in terms of technical and economic competitiveness.

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.

Synthetic Saccharomyces cerevisiae tolerate and degrade highly pollutant complex hydrocarbon mixture

Fungal laccase (Lac) has become a very useful biocatalyst in different industries, bio-refineries and, most importantly, bioremediation. Many reports have also linked hydrocarbon tolerance and degradation by various microorganisms with Lac secretion. In this study, Trametes trogii Lac (Ttlcc1) was engineered into Saccharomyces cerevisiae strain CEN.PK2-1 C under the constitutive GPD promoter (pGPD) for multi-fold synthesis with efficient hydrocarbon tolerance and degradation. Protein expression in heterologous hosts is strictly strain-specific, it can also be influenced by the synthetic design and culture conditions. We compared synthetic designs with different shuttle vectors for the yeast strains and investigated the best culture conditions by varying the pH, temperature, carbon, nitrogen sources, and CuSO₄ amount. Two S. cerevisiae strains were built in this study: byMM935 and byMM938. They carry the transcription unit pGPD-Ttlcc1-CYC1t either inside the pRSII406 integrative plasmid (byMM935) or the pRSII426 multicopy plasmid (byMM938). The performance of these two synthetic strains were studied by comparing them to the wild-type strain (byMM584). Both byMM935 and byMM938 showed significant response to different carbon sources (glucose, galactose, lactose, maltose, and sucrose), nitrogen sources (NH₄Cl, NH₄NO₃, KNO₃, malt extract, peptone, and yeast extract), and solid state fermentation of different plant biomasses (bagasse, banana peels, corn cob, mandarin peels, and peanut shells). They performed best in optimized growth conditions with specific carbon and nitrogen sources, and a preferred pH in the range 3.5-4.5, temperature between 30 and 40 ⁰C, and 1 mM CuSO_4. In optimized yeast-growth medium, strain byMM935 showed the highest laccase activities of 1.621 ± 0.063 U/mL at 64 h, whereas byMM938 gave its highest activity (1.417 ± 0.055 U/mL) at 48 h. In this work, we established, by using Bushnell Hass synthetic medium, that the new Ttlcc1-yeast strains tolerated extreme pH and complex hydrocarbon mixture (CHM) toxicity. They degraded 60-90% of the key components in CHM within 48 h, including poly-cyclic aromatic hydrocarbons, alkyl indenes, alkyl tetralines, alkyl benzenes, alkyl biphenyls, and BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes). This is the first report on the hydrocarbon degradation potential of a Ttlcc1-yeast. Compared to the native organism, such synthetic strains are better suited for meeting growing demands and have potentials for application in large-scale in situ bioremediation of hydrocarbon-polluted sites.

Microbial approaches for sustainable remediation of dye-contaminated wastewater: a review

The coloured effluents produced from different industries, such as textile, plastics, printing, cosmetics, leather and paper, are extremely toxic and a tremendous threat to the aquatic organisms and human beings. The removal of coloured dye pollutants from the aqueous environment is a great challenge and a pressing task. The growing demand for low-cost and efficient treatment approaches has given rise to alternative and eco-friendly methods, such as biodegradation and microbial remediation. This work summarizes the overview and current research on the remediation of dye pollutants from the aqueous environment by microbial bio-sorbents, such as bacteria, fungi, algae, and yeast. In addition, dye degradation capabilities of microbial enzymes have been highlighted and discussed. Further, the influence of various experimental parameters, such as temperature, pH, and concentrations of nutrients, and dye, has been summarized. The proposed mechanism for dye removal by microorganisms is also discussed. The object of this review is to provide a state-of-the-art of microbial remediation technologies in eliminating dye pollutants from water resources.

Improved performance of immobilized laccase for catalytic degradation of synthetic dyes using redox mediators

Laccase is an important biodegradation agent as the catalytic degradation could be enhanced in the presence of redox mediators. This work aims to improve removal performance of the immobilized laccase...

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.

Yarrowia lipolytica Bioprocess Development: From Flask to Bioreactor

Yarrowia lipolytica produces a range of valuable biotechnological products from natural metabolites and enzymes to heterologous proteins. The production of these products is affected by medium composition and various environmental factors. Here we describe bioprocess development for a recombinant laccase production by Y. lipolytica. At first, response surface methodology (RSM), as a statistical technique for design of experiment (DOE), is used for the optimization of medium composition in flask level. Then, results of RSM are applied to increase laccase production in controlled conditions of the bioreactor.

Modulation of laccase catalysed oxidations at the surface of magnetic nanoparticles

We explored the coupling of laccases to magnetic nanoparticles (MNPs) with different surface chemical coating. Two laccase variants offering two opposite and precise orientations of the substrate oxidation site were immobilised onto core-shell MNPs presenting either aliphatic aldehyde, aromatic aldehyde or azide functional groups at the particles surface. Oxidation capabilities of the six-resulting laccase-MNP hybrids were compared on ABTS and coniferyl alcohol. Herein, we show that the original interfaces created differ substantially in their reactivities with an amplitude from 1 to > 4 folds depending on the nature of the substrate. Taking enzyme orientation into account in the design of surface modification represents a way to introduce selectivity in laccase catalysed reactions.

Design of experiments and design space approaches in the pharmaceutical bioprocess optimization

The optimization of pharmaceutical bioprocesses suffers from several challenges like complexity, upscaling costs, regulatory approval, leading to the risk of delivering substandard drugs to patients. Bioprocess is very complex and requires the evaluation of multiple components that need to be monitored and controlled in order to attain the desired state when the process ends. Statistical design of experiments (DoE) is a powerful tool for optimizing bioprocesses because it plays a critical role in the quality by design strategy as it is useful in exploring the experimental domain and providing statistics of interest that enable scientists to understand the impact of critical process parameters on the critical quality attributes. This review summarizes selected publications in which DoE methodology was used to optimize bioprocess. The main objective of the critical review was to clearly demonstrate potential benefits of using the DoE and design space methodologies in bioprocess optimization.

Degradation of aflatoxin B1 by a recombinant laccase from Trametes sp. C30 expressed in Saccharomyces cerevisiae: A mechanism assessment study in vitro and in vivo

Aflatoxin B₁ (AFB₁) is the most harmful mycotoxin and presents risks to human health. Utilization of enzyme to degrade AFB1 is a promising strategy to overcome this problem. In this study, we evaluated the effect of recombinant laccase expressed in Saccharomyces cerevisiae on the degradation of AFB₁. It was found that AFB₁ could be degraded effectively by laccase up to 91%.The results of ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS) showed that there were four main degradation products of AFB₁ including C₁₆H₂₂O₄, C₁₄H₁₆N₂O₂, C₇H₁₂N₆O and C₂₄H₃₀O₆. Two possible degradation pathways were proposed: 1) AFB₁ lost -CO continuously, and then double bonds of furan ring were broken after reactions with H₂O, H⁺, and -NH₂; 2) AFB₁ occurred decarbonylation reaction after losing -CO and double bonds were broken by additional reaction with H⁺. Two toxicological activity sites in AFB₁, including a double bond of furo-furan ring and lactone ring in the coumarin in moiety, were destroyed. The toxicity of AFB₁ degradation products was evaluated on HepG2 cells and in vivo tests, and the results indicated a decrease in hepatocytes apoptosis, liver and kidney histopathological lesions, oxidative stress, and inflammation as compared to non-laccase degraded AFB_1. Moreover, the AFB₁ degradation products significantly decreased the cytotoxicity and hepatotoxicity. This investigation provides innovative evidence on the effectiveness of laccase expressed in Saccharomyces cerevisiae in detoxifying AFB₁.

Improved performance of immobilized laccase on Fe3O4@C-Cu2+ nanoparticles and its application for biodegradation of dyes

An effective strategy for enhancement of catalytic activity and stability of immobilized laccase via metal affinity adsorption on Fe₃O₄@C-Cu²⁺ nanoparticles was developed, which involved the fabrication of hydroxyl and carboxyl functionalized Fe₃O₄@C nanoparticles via a simple hydrothermal process and the subsequent chelation with Cu²⁺ for the immobilization of laccase under a mild condition. Our results revealed that the Fe₃O₄@C-Cu²⁺ nanoparticles possess a high loading amount of bovine serum albumin (BSA, 436 mg/g support) and laccase activity recovery of 82.3 % after immobilization. Laccase activity assays indicated that thermal and pH stabilities, and resistances to organic solvents and metal ions of the immobilized laccase were relatively higher than those of the free enzyme. The immobilized laccase maintained more than 61 % of its original activity after 10 consecutive reuses. Most importantly, the immobilized laccase possessed excellent degradation of diverse synthetic dyes. The degradation rates of malachite green (MG), brilliant green (BG), crystal violet (CV), azophloxine, Procion red MX-5B, and reactive blue 19 (RB19) was approximately 99, 93, 79, 88, 75 and 81 (%) in the first cycle. Even after 10 consecutive reuses, the removal efficiencies of the six dyes were found to be 94, 80, 71, 78, 60, and 65 (%), respectively.

Migration of heavy metals and migration-degradation of phenanthrene in soil using electro kinetic-laccase combined remediation system

In order to solve the problem of heavy metal-organic compound soil pollution, in this paper, we developed a highly efficient electro kinetic-laccase combined remediation (EKLCR) system. The results showed that the EKLCR system had an obvious migration effect on heavy metals (copper and cadmium) and good migration-degradation effect on phenanthrene. The migration rates of copper and cadmium were 48.3% and 40.3%, respectively. Especially, with the presence of laccase, the removal rate of phenanthrene on Cu²⁺-contaminated soil was higher than that of Cd²⁺-contaminated soil due to the significant effect of heavy metals on the enzymatic activity of laccase. The average migration-degradation rate of phenanthrene by EKLCR system was 45.4%. Finally, gas chromatography-mass spectrometry (GC/MS) was used to analyze the degradation intermediates of phenanthrene in the soil, which included 9,10-Phenanthrenequinone, phthalic acid, and 2,2-Biphenyldicarboxylic Acid. In addition, we give the possible degradation pathways of phenanthrene, 2,2-Biphenyldicarboxylic Acid is further degraded to produce phthalic acid. The products of the phthalic acid metabolic pathway are protocatechuic acid, pyruvic acid or succinic acid, the final products of these organic acids are carbon dioxide and water.

Advances in thermostable laccase and its current application in lignin-first biorefinery: A review

As the most abundant aromatic polymers on the Earth, lignin has great potential to produce biofuels and aromatic chemicals due to their high carbon content and low oxygen content. Lignin-first biorefinery methods have attracted increasing attention recently for their high-value of aromatic chemicals, and high biofuels productivity from lignocellulosic wastes. Thermostable laccase has proven to be an excellent alternative catalyst in degrading lignin for its versatile catalytic abilities under industrial conditions and pollution-free by-products. Thermostable laccases can be found in native extreme environments or modified by biologically based technologies such as gene recombination expression and enzyme direct evolution. This review demonstrated thermostable laccases and their application in lignin degradation. Future research should focus more on the investigation of the reaction of thermostable laccases with lignin substrates.

Laccases: structure, function, and potential application in water bioremediation

The global rise in urbanization and industrial activity has led to the production and incorporation of foreign contaminant molecules into ecosystems, distorting them and impacting human and animal health. Physical, chemical, and biological strategies have been adopted to eliminate these contaminants from water bodies under anthropogenic stress. Biotechnological processes involving microorganisms and enzymes have been used for this purpose; specifically, laccases, which are broad spectrum biocatalysts, have been used to degrade several compounds, such as those that can be found in the effluents from industries and hospitals. Laccases have shown high potential in the biotransformation of diverse pollutants using crude enzyme extracts or free enzymes. However, their application in bioremediation and water treatment at a large scale is limited by the complex composition and high salt concentration and pH values of contaminated media that affect protein stability, recovery and recycling. These issues are also associated with operational problems and the necessity of large-scale production of laccase. Hence, more knowledge on the molecular characteristics of water bodies is required to identify and develop new laccases that can be used under complex conditions and to develop novel strategies and processes to achieve their efficient application in treating contaminated water. Recently, stability, efficiency, separation and reuse issues have been overcome by the immobilization of enzymes and development of novel biocatalytic materials. This review provides recent information on laccases from different sources, their structures and biochemical properties, mechanisms of action, and application in the bioremediation and biotransformation of contaminant molecules in water. Moreover, we discuss a series of improvements that have been attempted for better organic solvent tolerance, thermo-tolerance, and operational stability of laccases, as per process requirements.

Optimum removal conditions of aniline compounds in simulated wastewater by laccase from white-rot fungi

BACKGROUND

Aniline compounds are widely applied as important chemical raw materials. However, they are so toxic and harmful to humans and environment that they need to be removed by an effective and economic approach, such as enzymatic reaction, which is in line with contemporary green development concepts.

METHODS

The effects of major factors, such as temperature, reaction time, concentration of laccase and the initial concentration of substrate on the removal of substrate were investigated by OFAT approach. After simulated wastewater is treated with enzymes, aniline concentration was determined by N-(1-Naphthyl)ethylene-diamine dihydrochloride spectrophotometric method. Concentration of o-phenylenediamine was determined by ferric ammonium alum spectrophotometric method.

RESULTS

For the removal of aniline, the optimum conditions were as follows: 50 °C, initial aniline concentration of 80 mg/L and laccase concentration of 1 g/L. In this case, the total removal of aniline reached 97.1% after 8 h, this also involves the volatilization of aniline itself. The optimum conditions of o-phenylenediamine were as follows: 50 °C, initial concentration of 100 mg/L and laccase concentration of 1 g/L. Under the above condition, the o-phenylenediamine could be removed completely after 60 min.

CONCLUSION

The results show that the removal of aniline compounds by laccase from white-rot fungi has good effect and potential application prospect.

Bioreactor-Scale Strategies for the Production of Recombinant Protein in the Yeast Yarrowia lipolytica

Recombinant protein production represents a multibillion-dollar market. Therefore, it constitutes an important research field both in academia and industry. The use of yeast as a cell factory presents several advantages such as ease of genetic manipulation, growth at high cell density, and the possibility of post-translational modifications. Yarrowia lipolytica is considered as one of the most attractive hosts due to its ability to metabolize raw substrate, to express genes at a high level, and to secrete protein in large amounts. In recent years, several reviews have been dedicated to genetic tools developed for this purpose. Though the construction of efficient cell factories for recombinant protein synthesis is important, the development of an efficient process for recombinant protein production in a bioreactor constitutes an equally vital aspect. Indeed, a sports car cannot drive fast on a gravel road. The aim of this review is to provide a comprehensive snapshot of process tools to consider for recombinant protein production in bioreactor using Y. lipolytica as a cell factory, in order to facilitate the decision-making for future strain and process engineering.