Removal of bisphenol A and its derivatives from aqueous medium through laccase-catalyzed treatment enhanced by addition of polyethylene glycol

Research Progress of Methods for Degradation of Bisphenol A

Bisphenol A (BPA), an endocrine disruptor widely used in industrial production, is found in various environmental sources. Despite numerous reports on BPA degradation and removal, the details remain unclear. This paper aims to address this gap by providing a comprehensive review of BPA degradation methods, focusing on biological, physical, and chemical treatments and the factors that affect the degradation of BPA. Firstly, the paper uses VOSviewer software (version 1.6.15) to map out the literature on BPA degradation published in the past 20 years, which reveals the trends and research focus in this field. Next, the advantages and limitations of different BPA degradation methods are discussed. Overall, this review highlights the importance of BPA degradation to protect the environment and human health. The paper provides significant insights for researchers and policymakers to develop better approaches for BPA degradation and removal.

Bisphenol A contamination in aquatic environments: a review of sources, environmental concerns, and microbial remediation

The production of polycarbonate, a high-performance transparent plastic, employs bisphenol A, which is a prominent endocrine-disrupting compound. Polycarbonates are frequently used in the manufacturing of food, bottles, storage containers for newborns, and beverage packaging materials. Global production of BPA in 2022 was estimated to be in the region of 10 million tonnes. About 65-70% of all bisphenol A is used to make polycarbonate plastics. Bisphenol A leaches from improperly disposed plastic items and enters the environment through wastewater from plastic-producing industries, contaminating, sediments, surface water, and ground water. The concentration BPA in industrial and domestic wastewater ranges from 16 to 1465 ng/L while in surface water it has been detected 170-3113 ng/L. Wastewater treatment can be highly effective at removing BPA, giving reductions of 91-98%. Regardless, the remaining 2-9% of BPA will continue through to the environment, with low levels of BPA commonly observed in surface water and sediment in the USA and Europe. The health effects of BPA have been the subject of prolonged public and scientific debate, with PubMed listing more than 17,000 scientific papers as of 2023. Bisphenol A poses environmental and health hazards in aquatic systems, affecting ecosystems and human health. While several studies have revealed its presence in aqueous streams, environmentally sound technologies should be explored for its removal from the contaminated environment. Concern is mostly related to its estrogen-like activity, although it can interact with other receptor systems as an endocrine-disrupting chemical. Present review article encompasses the updated information on sources, environmental concerns, and sustainable remediation techniques for bisphenol A removal from aquatic ecosystems, discussing gaps, constraints, and future research requirements.

An indirect method for the analysis of bisphenol A, as a Mn(III)-chelate complex, in milk samples by ultrasound assisted-cloud point extraction/flame atomic absorption spectrometry

A method for indirect determination of bisphenol A (BPA), as a Mn(III)-chelate complex, in milk samples by flame atomic absorption spectrometry (FAAS) was developed. The method was based on cloud point extraction with ultrasound assistance (UA-CPE). In the pre-concentration step by UA-CPE, the ternary complex selectively formed between BPA and Mn(III)-oxalate at pH 5.0 was extracted into the mixed micellar phase of ionic and nonionic surfactants, cetyltrimethylammonium bromide (CTABr) and polyethylene glycol tert-octylphenyl ether (Triton X-114) as a sensitivity enhancer and extractant. After phase separation by centrifugation, the separated extract was diluted with acidic methanol and analyzed by FAAS. The reproducibility of the signal in the detection step especially at low concentrations was greatly improved by the use of polyvinyl alcohol (PVA) as a stabilizer. Using indirect Mn-responses by FAAS, the main variables affecting the extraction efficiency were evaluated and optimized. Under optimized conditions, the calibration graph was highly linear in the range of 0.8-130 μg L^-1 with limits of detection and quantification of 0.23 and 0.76 μg L^-1, intra- and inter-day precisions in the range of 2.8-5.2% and 3.8-7.2%, and recovery in the range of 94.2-98.5% (10, 25, 100 μg L^-1, n: 5 and 3 × 5). From pre-concentration of a 35 mL sample by UA-CPE, the pre-concentration factor was found to be 70 with a 41-fold sensitivity improvement. The matrix effect was greatly reduced by deproteinization with trichloroacetic acid (TCA) and 20-fold dilution of milk samples before analysis. The method accuracy was checked by analysis of trace BPA in milk samples via a calibration curve in solvent and a matrix-matched calibration curve prepared from sample extracts. The results were in the range of 2.1-7.3 μg L^-1 and 2.0-7.0 μg L^-1 without any matrix effect. According to the Student's t-test, there is not a statistically significant difference between the results found by using the two calibration curves. Finally, it can be concluded that the method is suitable for detecting BPA in milk based products at concentrations far below the specific migration limit (SML) of 600 μg L^-1.

Applications of Biocatalysts for Sustainable Oxidation of Phenolic Pollutants: A Review

Phenol and its derivatives are hazardous, teratogenic and mutagenic, and have gained significant attention in recent years due to their high toxicity even at low concentrations. Phenolic compounds appear in petroleum refinery wastewater from several sources, such as the neutralized spent caustic waste streams, the tank water drain, the desalter effluent and the production unit. Therefore, effective treatments of such wastewaters are crucial. Conventional techniques used to treat these wastewaters pose several drawbacks, such as incomplete or low efficient removal of phenols. Recently, biocatalysts have attracted much attention for the sustainable and effective removal of toxic chemicals like phenols from wastewaters. The advantages of biocatalytic processes over the conventional treatment methods are their ability to operate over a wide range of operating conditions, low consumption of oxidants, simpler process control, and no delays or shock loading effects associated with the start-up/shutdown of the plant. Among different biocatalysts, oxidoreductases (i.e., tyrosinase, laccase and horseradish peroxidase) are known as green catalysts with massive potentialities to sustainably tackle phenolic contaminants of high concerns. Such enzymes mainly catalyze the o-hydroxylation of a broad spectrum of environmentally related contaminants into their corresponding o-diphenols. This review covers the latest advancement regarding the exploitation of these enzymes for sustainable oxidation of phenolic compounds in wastewater, and suggests a way forward.

Succinic anhydride-based chemical modification making laccase@Cu3(PO4)2 hybrid nanoflowers robust in removing bisphenol A in wastewater

To prepare a robust biocatalyst and enhance the removal of bisphenol A in wastewater, succinic anhydride was reacted with laccase to obtain succinic anhydride-modified laccase (SA-laccase) and then co-crystallized with Cu₃(PO₄)₂ to form SA-laccase@Cu₃(PO₄)₂ hybrid nanoflowers (hNFs). The activity of SA-laccase@Cu₃(PO₄)₂ reached 5.27 U/mg, 1.86-, 2.88- and 2.15-fold those of bare laccase@Cu₃(PO₄)₂, laccase@Ca₃(PO₄)₂ and laccase@epoxy resin, respectively. Compared with free laccase, the obtained hNFs present enhanced activity and tolerance to pH and high temperature in the removal of BPA. Under the optimum conditions of pH 6.0 and 35 °C, BPA removal reached 93.2% using SA-laccase@Cu₃(PO₄)₂ hNFs, which was 1.21-fold of that using free laccase. In addition, the obtained SA-laccase@Cu₃(PO₄)₂ hNFs retained nearly 90% of their initial catalytic activity for BPA removal after 8 consecutive batch cycles. This efficient method for preparing immobilized laccase can also be further developed and improved to acquire green biocatalysts for removing persistent organic pollutants in wastewater.

Biodegradation of bisphenol A by the immobilized laccase on some synthesized and modified forms of zeolite Y

Bisphenol A (BPA) is an environmental pollutant with adverse effects on different ecosystems. In this study, immobilized laccase enzymes onto inorganic supports were used to remove BPA. Laccase was successfully immobilized on sodium zeolite Y (NaY) and its modified desilicated (DSY) and dealuminated (DAY) forms. NaY-based supports were instrumentally characterized. The immobilized laccase on NaY (laccase@NaY), desilicated (laccase@DSY), and dealuminated (laccase@DAY) forms showed significant improvement on immobilization yield (IY%) and efficiency (IE%). Laccase@DSY and laccase@NaY showed IY% = 73.18 ± 3.33 % and 46.23 ± 1.81 % and IE% = 94.50 ± 1.86 %, and 74.39 ± 1.41 %, respectively, whereas IY% and IE% for laccase@DAY were achieved as 81.12 ± 1.32 % and 98.56 ± 2.93 %, respectively. The supports also increased the enzyme characteristics such as pH-temperature range, catalytic stability, and reusability. K_m values were 0.73 ± 0.05, 0.26 ± 0.09, 0.31 ± 0.5, and 1.01 ± 0.03 mM for laccase@NaY, laccase@DAY, laccase@DSY, and the free enzyme, respectively. The enzyme demonstrated higher biodegradation ability of bisphenol A upon immobilization on the supports compared to that of the soluble enzyme. A bio-removal yield of 86.7 % was obtained considering three parameters including amount of laccase@DAY (8 U mg^-1), concentration of BPA (0.5 mM), and treatment time (1 h) based on response surface methodology (RSM). Biodegradation metabolites (49 ± 5.8 %) and unconverted BPA (14 ± 5.2 %) were analyzed by gas chromatography-mass spectrometry.

Development of a Surfactant-Containing Process to Improve the Removal Efficiency of Phenol and Control the Molecular Weight of Synthetic Phenolic Polymers Using Horseradish Peroxidase in an Aqueous System

To reduce phenolic pollutants in the environment, many countries have imposed firm restrictions on industrial wastewater discharge. In addition, the current industrial process of phenolic resin production uses phenol and formaldehyde as the reactants to perform a polycondensation reaction. Due to the toxicity of formaldehyde and phenolic pollutants, the main purpose of this research was to design a green process using horseradish peroxidase (HRP) enzymatic polymerization to remove phenols and to produce formaldehyde-free phenolic polymers. In this study, the optimal reaction conditions, such as reaction temperature, pH, initial phenol concentration and initial ratio of phenol, and H₂O₂, were examined. Then, the parameters of the enzyme kinetics were determined. To solve the restriction of enzyme inactivation, several nonionic surfactants were selected to improve the phenol removal efficiency, and the optimal operation conditions in a surfactant-containing system were also confirmed. Importantly, the molecular weight of the synthetic phenolic polymers could be controlled by adjusting the ratio of phenol and H₂O_2. The content of biphenols in the products was almost undetectable. Collectively, a green chemistry process was proposed in this study and would benefit the treatment of phenol-containing wastewater and the production of formaldehyde-free phenolic resin in the future.

Multi-Functional Laccase Immobilized Hydrogel Microparticles for Efficient Removal of Bisphenol A

Hghly stable, reusable, and multi-functional biocatalytic microparticles with Laccase (Lac) enzyme (Lac/particles) were synthesized for bisphenol A (BPA) removal from aqueous solution. The Lac/particles were prepared by encapsulating Lac enzymes into poly ethylene glycol (PEG) hydrogel via the UV assisted emulsion polymerization method followed by cross linking with glutaraldehyde (GA). The obtained Lac/particles were spherical and micron sized (137⁻535 μm), presenting high enzyme entrapment efficiency of 100%, high activity recovery of 18.9%, and great stability at various pHs (3⁻7) than the free Lac. The Lac/particles could adsorb the BPA into the catalytic particles in a short time, promoting contact between BPA and enzyme, and further enzymatically degrade them without the shaking process and independent surrounding buffer solution. The Lac/particles could be reused for another round BPA adsorption and biotranformation by maintaining over 90% of BPA removal efficiency after seven times reuse. The synergistic effects of adsorption and biocatalytical reaction of Lac/particles have significant values in high efficient and cost-effective BPA removal.