Removal of bisphenol A in aqueous solution using magnetic cross-linked laccase aggregates from Trametes hirsuta

https://doi.org/10.1016/j.biortech.2020.123169Get rights and content

Highlights

  • Magnetic nanoparticles synthesis and amino-functionalization.

  • Preparation of magnetic cross-linked laccase aggregates from Trametes hirsuta.

  • Easy recycling of magnetic cross-linked laccase aggregates.

  • Disability of laccase immobilization by cross-linked enzyme aggregates method.

  • Successful bisphenol A removal using magnetic cross-linked laccase aggregates.

Abstract

Enzymatic removal of Bisphenol A (BPA), acknowledged as an environmentally friendly approach, is a promising method to deal with hard degradable contaminants. However, the application of “enzymatic treatment” has been limited due to lower operational stability and practical difficulties associated with recovery and recycling. Enzyme immobilization is an innovative approach which circumvents these drawbacks. In this study, laccase from Trametes hirsuta was used for BPA removal. Amino-functionalized magnetic Fe3O4 nanoparticles were synthesized via the co-precipitation method followed by surface modification with (3-aminopropyl)trimethoxysilane (APTMS). The as-prepared nanoparticles were utilized for the immobilization of laccase with the magnetic cross-linked enzyme aggregates method (MCLEAs). Activity recovery of 27% was achieved, while no immobilized laccase was observed in the cross-linked enzyme aggregates method. The performance of immobilized laccase was measured by analyzing the degradation of BPA pollutant. The maximum removal efficiency of 87.3% was attained with an initial concentration of 60 ppm throughout 11 h.

Introduction

Among the endocrine-disrupting chemicals, bisphenol A is produced in large amounts due to its vast consumption in industries producing polycarbonate and epoxy resins (Lassouane et al., 2019, Staples et al., 2018). All over the world, the surveys reporte different levels of BPA concentration. The river waters and coastal waters in China had BPA lower than 1 µg/L (Huang et al., 2012). A study in Nigeria reported BPA concentration in the range of 96.5–170 µg/L in different effluents, and 915–1415 µg/L in stored water in different plastic and metal containers (Makinwa & Uadia, 2015). The landfill leachates usually have a BPA concentration of more than 17 mg/L (Pedro-Cedillo et al., 2019). Different clinical studies have proved the occurrence of sexual misbehaviors in animals in contact with BPA, while fewer cases have been reported concerning humans. Studies have revealed that the men who were in contact with BPA have rates of sexual dysfunction four times higher than those who were not (Collica et al., 2018). Moreover, BPA shows similar behavior to estrogen, and it can disturb hormone function, which may result in breast and prostate cancer (Lassouane et al., 2019). Since BPA is used extensively throughout the global market, it seems impossible to avoid its production. Therefore, effective treatment of wastewaters contaminated with BPA should be carried out to prevent the harmful effects produced when BPA is released in the environment. It is noteworthy that BPA removal is challenging due to the disability of conventional biological methods in the treatment of hard-biodegradable materials. Also, chemical oxidation processes, such as advanced oxidation methods (AOP), could potentially generate harmful products (Lin et al., 2016).

Enzymatic removal of bisphenol A has become a particular focus of attention in recent years. Enzymes as biocatalysts have good accordance with green chemistry (Sheldon, 2010). Enzymes are produced from renewable resources such as fungi and bacteria. Furthermore, enzymes possess biocompatible and biodegradable properties, which are considered advantageous and categorize them as environmentally friendly processes for the removal of harmful industrial chemicals. (Sheldon, 2007).

Together with other enzymes such as Manganese peroxidase, Horseradish peroxidase, and Versatile peroxidase, laccase is one of the main enzymes produced in white-rot fungi. Unlike Manganese peroxidase, Horseradish peroxidase, and Versatile peroxidase that need hydrogen peroxide as a co-substrate to oxidize the substrate, laccase needs only dissolved oxygen. Moreover, laccase has a low specificity property, which lets laccase oxidize a broad range of substrates. All these characteristics make laccase an exciting option for the bioremediation of pollutants (Ba et al., 2013, Kadam et al., 2017).

Utilizing enzymes such as laccase for eliminating various micro-pollutants such as BPA has shown great potential. BPA degradation by laccase forms insoluble polymers, which could be easily removed from the aqueous phase, and the biodegradation products do not exhibit the estrogenic activity of the original BPA (Cabana et al., 2007, Hou et al., 2014).

Despite all these advantages, the industrial application of enzymatic treatment of wastewaters and utilization of enzymes such as laccase has been hampered due to low stability and very challenging recovery, which leads to limitations in reuse and high costs. Enzyme immobilization is a practical solution to overcome the mentioned obstacles (Sheldon & van Pelt, 2013). One of the most feasible and valuable methods in enzyme immobilization is the Cross-linked Enzyme Aggregates (CLEAs) method. CLEAs is a carrier-free method that leads to higher productivity through the elimination of carrier, besides it provides multi-layer immobilization of enzyme. Moreover, the CLEAs procedure can be considered a combination of purification and immobilization of the enzyme. Therefore, the crude enzyme could be used for direct immobilization in the CLEAs process (Wang et al., 2017). Despite all the advantages of CLEAs, their utilization has some limitations. The presence of Lys residues on the surface of the enzyme is crucial for a cross-linking procedure in CLEAs. Therefore, the CLEAs method can be inappropriate for enzymes with a low number of Lys groups due to insufficient cross-linking, which leads to enzyme leaching (Nadar and Rathod, 2016, Shaarani et al., 2016). Centrifugation and filtration required for recycling CLEAs are energy-consuming and also affect enzyme structure due to their soft textures (Sheldon & van Pelt, 2013). This challenging issue makes the recovery of CLEAs difficult, especially on a large scale (Kumar & Cabana, 2016). To tackle this challenge, the utilization of Bovine Serum Albumin (BSA), polylysine, and polyethyleneimine are promising possibilities (Tudorache et al., 2013). A creative solution to deal with this drawback is the immobilization of CLEAs on magnetic nanoparticles with the NH2 terminal, which was proposed by Talekar et al. (Talekar et al., 2012). The applying Magnetic Amino-functionalized Nanoparticle either provides NH2 groups for sufficient cross-linking or eliminates the need for centrifugation and filtration. This creativity has led to the Magnetic cross-linked enzyme aggregates method (MCLEAs).

To the best of our knowledge, laccase from Trametes hirsuta has not been immobilized with the MCLEAs method and also has not been implemented for BPA removal. Therefore, in the present research, the immobilization of laccase from Trametes hirsuta has been studied by the MCLEAs and CLEAs methods. Eventually, the resulting nano-biocatalysts have been applied for BPA removal.

Section snippets

Chemicals

Commercial laccase from Trametes hirsuta was prepared from Novozym Company. Ammonium Hydroxide 25%, FeCl3·6H2O, FeCl2·4H2O, absolute Toluene, 4-aminoantipyrine (4-AAP) were purchased from Merck. Bisphenol A, (3-aminopropyl)trimethoxysilane 97% (APTMS), Guaiacol, Potassium ferricyanide were purchased from Sigma Aldrich. Glutaraldehyde 25% was purchased from Daejung Company.

Magnetic nanoparticles synthesis

Fe3O4 nanoparticles were synthesized by the co-precipitation method with particular modifications. Briefly, a 5 mL HCl

Characterization of nanoparticles and MCLEAs

The XRD analysis of magnetic nanoparticles, synthesized through the co-precipitation method, was carried out to determine their phase structure. Using Xpert HighScore Plus V 3.0e, the magnetic nanoparticles were identified as Fe3O4 (Magnetite) according to the reference code 96-900-5842.

The presence of amino-functional groups on the Fe3O4 NPs surface was confirmed by FTIR analysis. In the spectrum of bare Fe3O4 nanoparticles, the observed absorption at 564.86 (1/cm) is related to the bending

Conclusion

In this study, Fe3O4 nanoparticles were synthesized using the co-precipitation method followed by surface amino-functionalization with APTMS. Laccase from Trametes hirsuta was successfully immobilized on the surface-modified Fe3O4 nanoparticles by the glutaraldehyde cross-linking method. The activity recovery of 27% was achieved, and the resultant magnetic cross-linked laccase aggregates could save more than 30% of their initial activity after six consecutive cycles. MCLEAs were used in

CRediT authorship contribution statement

Sadegh Sadeghzadeh: Writing - original draft, Methodology, Investigation. Zahra Ghobadi Nejad: Supervision, Methodology, Conceptualization, Investigation. Shahnaz Ghasemi: Writing - review & editing, Validation. Mona Khafaji: Methodology. Seyed Mehdi Borghei: Supervision, Project administration, Funding acquisition.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

The authors gratefully acknowledge the Biochemical and Bioenvironmental Research Center, Sharif University of Technology, for providing needed apparatuses and chemicals.

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