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Background The presence of a wide range of bioactive organic pollutants in wastewater and municipal water sources is raising concerns about their potential effects on humans. Not surprisingly, various approaches are being explored that can efficiently degrade these persistent organic pollutants. Use of peroxidases has recently been recognized as a novel remediation approach that may have potential advantages over conventional degradation techniques. However, testing the abilities of different peroxidases to degrade diverse emerging pollutants is tedious and cumbersome. Results In the present study, we present a rapid and robust approach to easily test the degradability of 21 different emerging pollutants by five different peroxidases (soybean peroxidase, chloroperoxidase, lactoperoxidase, manganese peroxidase, and horseradish peroxidase) using an LC-MSMS approach. Furthermore, this approach was also used to examine the role of a redox mediator in these enzymatic degradation assays. Our results show that some of the organic pollutants can be easily degraded by all five of the peroxidases tested, whereas others are only degraded by a specific peroxidase (or when a redox mediator was present) and there are some that are completely resistant to degradation by any of the peroxidases tested (even in the presence of a redox mediator). The degradation of furosemide and trimethoprim by soybean peroxidase and chloroperoxidase, respectively, was investigated in detail by examining the transformation products generated during their degradation. Some of the products generated during enzymatic breakdown of these pollutants have been previously reported by others, however, we report many new transformation products. Conclusions LC-MSMS approaches, like the one described here, can be used to rapidly evaluate the potential of different peroxidases (and redox requirements) to be used as bioremediation agents. Our preliminary result shows peroxidases hold tremendous potential for being used in a final wastewater treatment step.

Development of efficient methods for the degradation of emerging pollutants such as pharmaceuticals and pesticides are being recognized as a research priority as more and more of these organic pollutants are being detected in our water bodies. In this work, the degradation of the emerging pollutant sulfamethoxazole (SMX) was carried out using a soybean peroxidase (SBP) enzyme system and an advanced oxidation process (UV + H2O2). The optimized conditions for sulfamethoxazole degradation by the peroxidase enzyme showed an absolute requirement for a redox mediator (1-hydroxybenzotriazole) and low pH. The other conditions for an efficient degradation were as follows: [H2O2] = 56 μM, [SBP] = 78 nM and [SMX] = 5 ppm. The degradation of the pollutant was followed using UV–Vis spectrophotometry and liquid chromatography–mass spectroscopy (LC–MS). The formed products were identified using liquid chromatography–tandem mass spectrometry. The two remediation methods, an enzymatic approach using SBP + H2O2, and the photolytic technique using UV + H2O2, generated diverse sets of intermediates, suggesting that different degradation routes were at work in the two systems. Phytotoxicity studies carried out using Lactuca sativa (lettuce) showed different levels of detoxification of the SMX pollutant after the two different remediation treatments.

Different classes of artificial pollutants, collectively called emerging pollutants, are detected in various water bodies, including lakes, rivers, and seas. Multiple studies have shown the devastating effects these emerging pollutants can have on human and aquatic life. The main reason for these emerging pollutants in the aquatic environment is their incomplete removal in the existing wastewater treatment plants (WWTPs). Several additional treatments that could potentially supplement existing WWTPs to eliminate these pollutants include a range of physicochemical and biological methods. The use of enzymes, specifically, oxidoreductases, are increasingly being studied for their ability to degrade different classes of organic compounds. These enzymes have been immobilized on different supports to promote their adoption as a cost-effective and recyclable remediation approach. Unfortunately, some of these techniques have shown a negative effect on the enzyme, including denaturation and loss of catalytic activity. This review focuses on the major challenges facing researchers working on the immobilization of peroxidases and the recent progress that has been made in this area. It focuses on four major areas: (1) stability of enzymes upon immobilization, enzyme engineering, and evolution; (2) recyclability and reusability, including immobilization on membranes and solid supports; (3) cost associated with enzyme-based remediation; and (4) scaling-up and bioreactors.

In the present study, soybean peroxidase (SBP) was covalently immobilized onto two functionalized photocatalytic supports (TiO2 and ZnO) to create novel hybrid biocatalysts (TiO2-SBP and ZnO-SBP). Immobilization caused a slight shift in the pH optima of SBP activity (pH 5.0 to 4.0), whereas the free and TiO2-immobilized SBP showed similar thermal stability profiles. The newly developed hybrid biocatalysts were used for the degradation of 21 emerging pollutants in the presence and absence of 1-hydroxy benzotriazole (HOBT) as a redox mediator. Notably, all the tested pollutants were not equally degraded by the SBP treatment and some of the tested pollutants were either partially degraded or appeared to be recalcitrant to enzymatic degradation. The presence of HOBT enhanced the degradation of the pollutants, while it also inhibited the degradation of some contaminants. Interestingly, TiO2 and ZnO-immobilized SBP displayed better degradation efficiency of a few emerging pollutants than the free enzyme. Furthermore, a combined enzyme-chemical oxidation remediation strategy was employed to degrade two recalcitrant pollutants, which suggest a novel application of these novel hybrid peroxidase-photocatalysts. Lastly, the reusability profile indicated that the TiO2-SBP hybrid biocatalyst retained up to 95% degradation efficiency of a model pollutant (2-mercaptobenzothiazole) after four consecutive degradation cycles.

As a result of their unique structural and multifunctional characteristics, organic–inorganic hybrid nanoflowers (hNFs), a newly developed class of flower-like, well-structured and well-oriented materials has gained significant attention. The structural attributes along with the surface-engineered functional entities of hNFs, e.g., their size, shape, surface orientation, structural integrity, stability under reactive environments, enzyme stabilizing capability, and organic–inorganic ratio, all significantly contribute to and determine their applications. Although hNFs are still in their infancy and in the early stage of robust development, the recent hike in biotechnology at large and nanotechnology in particular is making hNFs a versatile platform for constructing enzyme-loaded/immobilized structures for different applications. For instance, detection- and sensing-based applications, environmental- and sustainability-based applications, and biocatalytic and biotransformation applications are of supreme interest. Considering the above points, herein we reviewed current advances in multifunctional hNFs, with particular emphasis on (1) critical factors, (2) different metal/non-metal-based synthesizing processes (i.e., (i) copper-based hNFs, (ii) calcium-based hNFs, (iii) manganese-based hNFs, (iv) zinc-based hNFs, (v) cobalt-based hNFs, (vi) iron-based hNFs, (vii) multi-metal-based hNFs, and (viii) non-metal-based hNFs), and (3) their applications. Moreover, the interfacial mechanism involved in hNF development is also discussed considering the following three critical points: (1) the combination of metal ions and organic matter, (2) petal formation, and (3) the generation of hNFs. In summary, the literature given herein could be used to engineer hNFs for multipurpose applications in the biosensing, biocatalysis, and other environmental sectors.

Organic pollutants, especially those found in water bodies, pose a direct threat to various aquatic organisms as well as humans. A variety of different remediation approaches, including chemical and biological methods, have been developed for the degradation of various organic pollutants. However, comparative mechanistic studies of pollutant degradation by these different systems are almost non-existent. In this study, the degradation of a model thiazole pollutant, thioflavin T (ThT), was carried out in the presence of either an advanced oxidation process (ultraviolet (UV) + H2O2) or a chloroperoxidase enzyme system (CPO + H2O2). The degradation was followed both spectrophotometrically and using liquid chromatography-mass spectroscopy (LC-MS), and the products formed were identified using tandem liquid chromatography-mass spectrometry-mass spectrometry (LC-MS-MS). The results show that the two remediation approaches produced different sets of intermediates, with only one common species (a demethylated form of ThT). This suggests that different degradation schemes were operating in the two systems. Interestingly, one of the major intermediates produced by the CPO + H2O2 system was a chlorinated form of thioflavin. Phytotoxicity studies showed that the CPO + H2O2-treated ThT solution was significantly (p