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Fungal-Based bioremediation; Emerging pollutants; Aquatic ecosystems; Pharmaceuticals; Pollutant degradation, Fungal enzymes; Environmental cleanup; Sustainable remediation; Fungal biotechnology

Introduction

Aquatic ecosystems are increasingly threatened by emerging pollutants a class of contaminants that includes pharmaceuticals, personal care products, industrial chemicals, and microplastics. These pollutants are typically resistant to conventional treatment methods, which often fail to effectively remove or neutralize them from aquatic environments. Emerging pollutants, many of which are not routinely monitored, pose a significant challenge due to their persistence, bioaccumulation potential, and toxicity to aquatic organisms and humans. In recent years, bioremediation has garnered attention as a promising, sustainable alternative for removing or neutralizing these pollutants [1]. Among various biological agents used in bioremediation, fungi have emerged as one of the most effective groups due to their metabolic diversity and unique enzymatic systems capable of breaking down a wide variety of organic contaminants. Unlike bacteria, fungi possess an extensive network of hyphae that can penetrate contaminated matrices, and their extracellular enzymes are capable of breaking down complex compounds, making them highly efficient in degrading pollutants that are difficult for other organisms to process. Fungi, particularly white-rot fungi such as Phanerochaete chrysosporium, brown-rot fungi, and mycorrhizal fungi, produce a wide range of enzymes, including laccases, peroxidases, lignin peroxidases, and cytochrome P450s, that enable them to degrade various organic pollutants [2]. These enzymes can oxidize pollutants, such as pharmaceuticals, pesticides, and hydrocarbons, into less toxic or more easily degradable forms. Additionally, the mycelial networks of fungi can adsorb and concentrate pollutants from the surrounding medium, further enhancing the removal efficiency. Fungal bioremediation in aquatic ecosystems holds promise for addressing the challenges posed by emerging pollutants. However, several factors, including the availability of nutrients, pH, temperature, and oxygen levels, can influence fungal activity and the overall success of bioremediation efforts. Moreover, scaling up fungal-based remediation from laboratory conditions to real-world applications requires addressing challenges related to environmental variability, fungal species selection, and bioreactor design [3]. This review aims to explore the potential of fungal-based bioremediation for cleaning up emerging pollutants in aquatic ecosystems. It provides an overview of the mechanisms by which fungi degrade pollutants, the factors that influence their effectiveness, and the current limitations and challenges. Furthermore, the review discusses recent innovations in fungal biotechnology, including genetic engineering and synthetic biology, that have the potential to enhance the bioremediation capabilities of fungi and expand their application to large-scale environmental cleanup efforts.

Review of Literature

Fungal-based bioremediation has been extensively studied as a promising approach for addressing the contamination of aquatic ecosystems by emerging pollutants. Several key areas have emerged in the literature regarding the role of fungi in degrading and detoxifying pollutants, including mechanisms of degradation, fungal species selection, bioreactor designs, and challenges in large-scale application [4]. Below is a summary of the significant contributions and findings:

Fungal mechanisms for pollutant degradation

Fungi are known for their ability to degrade a wide range of organic pollutants due to their diverse enzymatic systems. The most notable enzymes involved in fungal bioremediation include:

Laccases: These enzymes are involved in the oxidation of aromatic compounds, making them effective in breaking down pollutants such as phenolic compounds, dyes, and plastics. Studies have shown that laccases from fungi like Trametes versicolor and Phanerochaete chrysosporium can degrade environmental pollutants like pesticides, polycyclic aromatic hydrocarbons (PAHs), and pharmaceuticals in aquatic systems (Zhao et al., 2020). Peroxidases these enzymes, particularly lignin peroxidases and manganese peroxidases, are essential for the degradation of complex organic pollutants, including aromatic compounds and lignin derivatives [5]. Phanerochaete chrysosporium has been widely studied for its ligninolytic enzymes and their role in the breakdown of organohalides and dioxins (Tushar et al., 2021). Cytochrome P450s: Fungi like Aspergillus and Penicillium have cytochrome P450 enzymes that enable them to metabolize a wide array of xenobiotic compounds, including pharmaceuticals and pesticides. These enzymes help fungi adapt to and break down toxic compounds by altering their chemical structures (Singh et al., 2019). Fungal degradation often involves oxidative reactions, where pollutants are broken down into less toxic or more easily degradable compounds [6]. The extracellular secretion of enzymes and the mycelial network formed by fungi allow them to reach pollutants within solid matrices and water, facilitating pollutant absorption and transformation.

Fungal species in aquatic bioremediation

A variety of fungal species have been identified for their potential in aquatic bioremediation of emerging pollutants. Among the most studied species are:

White-Rot Fungi: These fungi, such as Phanerochaete chrysosporium, Trametes versicolor, and Bjerkandera adusta, have been extensively studied for their ability to degrade complex organic pollutants in contaminated water bodies. Their lignin-degrading enzymes enable them to break down not only lignin but also various xenobiotics (Nehra et al., 2020). Brown-Rot fungi although less commonly studied in aquatic environments, brown-rot fungi like Coniophora puteana have shown potential in breaking down complex organic matter and pollutants, including hydrocarbons (Bugg et al., 2018). Mycorrhizal fungi arbuscular mycorrhizal fungi (AMF) such as Glomus species have been explored for their role in degrading pesticides and heavy metals in aquatic ecosystems [7]. Their ability to interact symbiotically with plants enhances pollutant uptake, facilitating a more comprehensive cleanup strategy (Hussain et al., 2020).

Environmental factors influencing fungal bioremediation

Fungal performance in the degradation of pollutants is influenced by several environmental parameters:

pH and Temperature: Optimal pH and temperature conditions are crucial for fungal enzyme activity. Fungi such as Phanerochaete chrysosporium have demonstrated high activity in neutral to slightly acidic pH, while temperature ranges of 20-30°C often support higher enzyme activity for degradation (Sang et al., 2019). Nutrient availability fungi require adequate carbon and nitrogen sources for optimal growth [8]. The addition of nutrients such as nitrogen or glucose can significantly enhance fungal activity and biodegradation rates in aquatic environments (Matsui et al., 2019). Oxygen levels aerobic conditions generally support more efficient fungal degradation of organic pollutants. However, certain fungi, including white-rot species, can also operate under low-oxygen conditions, which makes them versatile for various aquatic environments (Zhao et al., 2020).

Fungal bioremediation in aquatic ecosystems

Several studies have highlighted the potential of fungal bioremediation in aquatic systems, especially for pollutants such as:

Pharmaceuticals: Fungi like Phanerochaete chrysosporium have been successfully applied to degrade pharmaceuticals such as acetaminophen, diclofenac, and carbamazepine in aquatic ecosystems (Sharma et al., 2021). pesticides fungal species, including Aspergillus niger, Trametes versicolor, and Penicillium spp., have been studied for the degradation of various pesticides like chlorpyrifos, atrazine, and endosulfan (Bae et al., 2020). microplastics recent studies have also explored fungal bioremediation as a potential solution for the degradation of microplastics in aquatic environments [9]. Fungi such as Aspergillus terreus and Penicillium simplicissimum have shown the ability to break down plastic polymers by secreting enzymes that degrade ester linkages in plastic polymers (Li et al., 2021).

Challenges and Limitations

Despite the promise of fungal-based bioremediation, several challenges remain: While fungal remediation has shown success in laboratory and small-scale trials, the scaling up of fungal bioremediation systems to large contaminated sites is still a challenge. The complex dynamics of fungal growth in aquatic environments and the ability to sustain fungal populations over time require more research. Fungal growth in aquatic systems maintaining fungal growth in aquatic systems can be difficult due to low nutrient availability, high water flow, and the need for aeration [10]. These factors can hinder fungal colonization and pollutant degradation in large aquatic ecosystems.Ecological impact introducing large quantities of fungi into natural aquatic environments may have unintended ecological consequences. Research is needed to assess the potential risks of introducing non-native fungal species into sensitive ecosystems.

Conclusion

Fungal-based bioremediation has demonstrated considerable potential as an effective and sustainable strategy for addressing the contamination of aquatic ecosystems by emerging pollutants. Fungi, particularly white-rot and brown-rot species, are capable of degrading a wide variety of toxic organic pollutants, including pharmaceuticals, pesticides, and even microplastics, through their versatile enzymatic systems. The development of fungal bioremediation strategies, coupled with advances in fungal biotechnology, genetic engineering, and synthetic biology, can further enhance the efficiency and scalability of these systems for real-world applications. However, several challenges remain in the implementation of fungal-based bioremediation on a large scale. These include optimizing environmental conditions (e.g., pH, temperature, nutrient availability), managing fungal growth in dynamic aquatic environments, and ensuring the ecological safety of introducing non-native fungal species. Overcoming these challenges will require continued research into the physiology of fungi in aquatic systems, the development of innovative bioreactor designs, and more robust field trials to assess the long-term efficacy and ecological impact of fungal bioremediation techniques. In summary, while fungal bioremediation offers a promising approach to clean up emerging pollutants from aquatic ecosystems, further studies are required to optimize these strategies and make them feasible for large-scale environmental remediation projects. The integration of fungal-based approaches with other bioremediation technologies and the exploration of new fungal species will continue to advance the field and provide a more sustainable solution for managing environmental pollution in the future.

Acknowledgement

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Conflict of Interest

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