Cell Surface Display Fungal Laccase as a Renewable Biocatalyst for Degradation of Persistent Micropollutants Bisphenol A and Sulfamethoxazole

Strategic approaches for designing yeast strains as protein secretion and display platforms

Yeast has been established as a versatile platform for expressing functional molecules, owing to its well-characterized biology and extensive genetic modification tools. Compared to prokaryotic systems, yeast possesses advanced cellular mechanisms that ensure accurate protein folding and post-translational modifications. These capabilities are particularly advantageous for the expression of human-derived functional proteins. However, designing yeast strains as an expression platform for proteins requires the integration of molecular and cellular functions. By delving into the complexities of yeast-based expression systems, this review aims to empower researchers with the knowledge to fully exploit yeast as a functional platform to produce a diverse range of proteins. This review includes an exploration of the host strains, gene cassette structures, as well as considerations for maximizing the efficiency of the expression system. Through this in-depth analysis, the review anticipates stimulating further innovation in the field of yeast biotechnology and protein engineering.

Biodegradation of bisphenol A by a Pichia pastoris whole-cell biocatalyst with overexpression of laccase from Bacillus pumilus and investigation of its potential degradation pathways

Bisphenol A (BPA), an endocrine disrupter with estrogen activity, can infiltrate animal and human bodies through the food chain. Enzymatic degradation of BPA holds promise as an environmentally friendly approach while it is limited due to lower stability and recycling challenges. In this study, laccase from Bacillus pumilus TCCC 11568 was expressed in Pichia pastoris (fLAC). The optimal catalytic conditions for fLAC were at pH 6.0 and 80 °C, with a half-life T1/2 of 120 min at 70 °C. fLAC achieved a 46 % degradation rate of BPA, and possible degradation pathways were proposed based on identified products and reported intermediates of BPA degradation. To improve its stability and degradation capacity, a whole-cell biocatalyst (WCB) was developed by displaying LAC (dLAC) on the surface of P. pastoris GS115. The functionally displayed LAC demonstrated enhanced thermostability and pH stability along with an improved BPA degradation ability, achieving a 91 % degradation rate. Additionally, dLAC maintained a degradation rate of over 50 % after the fourth successive cycles. This work provides a powerful catalyst for degrading BPA, which might decontaminate endocrine disruptor-contaminated water through nine possible pathways.

A cellulosomal yeast reaction system of lignin-degrading enzymes for cellulosic ethanol fermentation

Biofuel production from lignocellulose feedstocks is sustainable and environmentally friendly. However, the lignocellulosic pretreatment could produce fermentation inhibitors causing multiple stresses and low yield. Therefore, the engineering construction of highly resistant microorganisms is greatly significant. In this study, a composite functional chimeric cellulosome equipped with laccase, versatile peroxidase, and lytic polysaccharide monooxygenase was riveted on the surface of Saccharomyces cerevisiae to construct a novel yeast strain YI/LVP for synergistic lignin degradation and cellulosic ethanol production. The assembly of cellulosome was assayed by immunofluorescence microscopy and flow cytometry. During the whole process of fermentation, the maximum ethanol concentration and cellulose conversion of engineering strain YI/LVP reached 8.68 g/L and 83.41%, respectively. The results proved the availability of artificial chimeric cellulosome containing lignin-degradation enzymes for cellulosic ethanol production. The purpose of the study was to improve the inhibitor tolerance and fermentation performance of S. cerevisiae through the construction and optimization of a synergistic lignin-degrading enzyme system based on cellulosome.

Perspective on Lignin Conversion Strategies That Enable Next Generation Biorefineries

The valorization of lignin, a currently underutilized component of lignocellulosic biomass, has attracted attention to promote a stable and circular bioeconomy. Successful approaches including thermochemical, biological, and catalytic lignin depolymerization have been demonstrated, enabling opportunities for lignino-refineries and lignocellulosic biorefineries. Although significant progress in lignin valorization has been made, this review describes unexplored opportunities in chemical and biological routes for lignin depolymerization and thereby contributes to economically and environmentally sustainable lignin-utilizing biorefineries. This review also highlights the integration of chemical and biological lignin depolymerization and identifies research gaps while also recommending future directions for scaling processes to establish a lignino-chemical industry.

Highly efficient low-temperature biodegradation of polyethylene microplastics by using cold-active laccase cell-surface display system

To eliminate efficiency restriction of polyethylene microplastics low-temperature biodegradation, a novel InaKN-mediated Escherichia coli surface display platform for cold-active degrading laccase PsLAC production was developed. Display efficiency of 88.0% for engineering bacteria BL21/pET-InaKN-PsLAC was verified via subcellular extraction and protease accessibility, exhibiting an activity load of 29.6 U/mg. Cell growth and membrane integrity revealed BL21/pET-InaKN-PsLAC maintained stable growth and intact membrane structure during the display process. The favorable applicability was confirmed, with 50.0% activity remaining in 4 days at 15 °C, and 39.0% activity recovery retention after 15 batches of activity substrate oxidation reactions. Moreover, BL21/pET-InaKN-PsLAC possessed high polyethylene low-temperature depolymerizing capacity. Bioremediation experiments proved that the degradation rate was 48.0% within 48 h at 15 °C, and reached 66.0% after 144 h. Collectively, cold-active PsLAC functional surface display technology and its significant contributions to polyethylene microplastics low-temperature degradation constitute an effective improvement strategy for biomanufacturing and microplastics cold remediation.

Microbial strategies for degradation of microplastics generated from COVID-19 healthcare waste

COVID-19 pandemic has led to the generation of massive plastic wastes, comprising of onetime useable gloves, masks, tissues, and other personal protective equipment (PPE). Recommendations for the employ of single-use disposable masks made up of various polymeric materials like polyethylene, polyurethane, polyacrylonitrile, and polypropylene, polystyrene, can have significant aftermath on environmental, human as well as animal health. Improper disposal and handling of healthcare wastes and lack of proper management practices are creating serious health hazards and an extra challenge for the local authorities designated for management of solid waste. Most of the COVID-19 medical wastes generated are now being treated by incineration which generates microplastic particles (MPs), dioxin, furans, and various toxic metals, such as cadmium and lead. Moreover, natural degradation and mechanical abrasion of these wastes can lead to the generation of MPs which cause a serious health risk to living beings. It is a major threat to aquatic lives and gets into foods subsequently jeopardizing global food safety. Moreover, the presence of plastic is also considered a threat owing to the increased carbon emission and poses a profound danger to the global food chain. Degradation of MPs by axenic and mixed culture microorganisms, such as bacteria, fungi, microalgae etc. can be considered an eco-sustainable technique for the mitigation of the microplastic menace. This review primarily deals with the increase in microplastic pollution due to increased use of PPE along with different disinfection methods using chemicals, steam, microwave, autoclave, and incineration which are presently being employed for the treatment of COVID-19 pandemic-related wastes. The biological treatment of the MPs by diverse groups of fungi and bacteria can be an alternative option for the mitigation of microplastic wastes generated from COVID-19 healthcare waste.

Recent advances in the breakdown of microplastics: strategies and future prospectives

Microplastics pollution is becoming a major environmental issue, and exposure to microplastics has been associated with numerous adverse results to both the ecological system and humans. This work summarized the state-of-the-art developments in the breakdown of microplastics, including natural weathering, catalysts-assisted breakdown and biodegradation. Characterization techniques for microplastic breakdown involve scanning electron microscopy, Fourier infrared spectroscopy, X-ray photoelectron spectroscopy, etc. Bioavailability and adsorption capacity of microplastics may change after they are broken down, therefore leading to variety in microplastics toxicity. Further prospectives for should be focused on the determination and toxicity evaluation of microplastics breakdown products, as well as unraveling uncultivable microplastics degraders via cultivation-independent approaches. This work benefits researchers interested in environmental studies, particularly the removal of microplastics from environmental matrix.

Insights into the Applications of Extracellular Laccase-Aided Humification in Livestock Manure Composting

Traditional composting is a well-suited biotechnology for on-farm management of livestock manure (LM) but still leads to the release of toxic micropollutants and imbalance of nutrients. One in situ exoenzyme-assisted composting has shown promise to ameliorate the agronomical quality of end products by improving humification and polymerization. The naturally occurring extracellular laccase from microorganisms belongs to a multicopper phenoloxidase, which is verified for its versatility to tackle micropollutants and conserve organics through the reactive radical-enabled decomposition and polymerization channels. Laccase possesses an indispensable relationship with humus formation during LM composting, but its potential applications for the harmless disposal and resource utilization of LM have until now been overlooked. Herein, we review the extracellular laccase-aided humification mechanism and its optimizing strategy to maintain enzyme activity and in situ production, highlighting the critical roles of laccase in treating micropollutants and preserving organics during LM composting. Particularly, the functional effects of the formed humification products by laccase-amended composting on plant growth are also discussed. Finally, the future perspectives and outstanding questions are summarized. This critical review provides fundamental insights into laccase-boosted humification that ameliorates the quality of end products in LM composting, which is beneficial to guide and advance the practical applications of exoenzyme in humification remediation, the carbon cycle, and agriculture protection.

Bimetal heterointerfaces towards enhanced electro-activation of O2 under room condition

Efficient catalysts for oxygen (O₂) activation under room condition are required for effective wet air oxidation (WAO) technology. Here, we report a novel manganese-cobalt-based composite (MnO-CoO@Co) fabricated on a graphite felt (GF) support for catalyzing the electro-activation of O₂ under room condition. Abundant Co-MnO and CoO-MnO heterointerfaces are formed in the composite. In comparison to the single-metal counterparts, i.e. CoO@Co/GF (16.99 wt% Co) and MnO/GF (26.83 wt% Mn), the bimetal MnO-CoO@Co/GF (5.29 wt% Co and 8.79 wt% Mn) displays an improved oxygen storage capacity and provides more active sites to accommodate surface adsorbed oxygen species. Notably, the strong synergy derived from bimetal heterointerfaces enhances the electron transfer and oxygen mobilization during the electro-activation of O₂, thereby significantly reducing the reaction barrier. MnO-CoO@Co/GF exhibits excellent efficiency and stability in electrocatalytic WAO (ECWAO) towards the removal of pharmaceuticals and personal care products (PPCPs) over a wide pH range from 4.0 to 10.0. A model pollutant sulfamethoxazole (SMX) acquires mineralization efficiency of 78.4 ± 2.1% and mineralization current efficiency of 157.89% at +1.0 V of electrode potential. The toxicity of PPCPs can be totally eliminated after the ECWAO treatment. This work highlights the synergy derived from bimetal heterointerfaces in O₂ electrocatalysis, and provides a promising approach for advanced WAO catalysts in PPCPs pollution control.

A review on the microbial degradation of chlorpyrifos and its metabolite TCP

Chlorpyrifos (CPF) falls under the category of organophosphorus pesticides which are in huge demand in the agricultural sector. Overuse of this pesticide has led to the degradation of the quality of terrestrial and aquatic life. The chemical is moderately persistent in the environment but its primary metabolite 3,5,6-trichloro-2-pyridinol (TCP) is comparatively highly persistent. Thus, it is important to degrade the chemical and there are many proposed techniques of degradation. Out of which bioremediation is considered to be highly cost-effective and efficient. Many previous studies have attempted to isolate appropriate microbial strains to degrade CPF which established the fact that chlorine atoms released while mineralising TCP inhibits further proliferation of microorganisms. Thus, it has been increasingly important to experiment with strains that can simultaneously degrade both CPF and TCP. In this review paper, the need for degrading CPF specifically the problems related to it has been discussed elaborately. Alongside these, the metabolism pathways undertaken by different kinds of microorganisms have been included. This paper also gives a detailed insight into the potential strains of microorganisms which has been confirmed through experiments conducted previously. It can be concluded that a wide range of microorganisms has to be studied to understand the possibility of applying bioremediation in wastewater treatment to remove pesticide residues. In addition to this, in the case of recalcitrant pesticides, options of treating it with hybrid techniques like bioremediation clubbed with photocatalytic biodegradation can be attempted.

Environmental emission, fate and transformation of microplastics in biotic and abiotic compartments: Global status, recent advances and future perspectives

The intensive use and wide-ranging application of plastic- and plastic-derived products have resulted in alarming levels of plastic pollution in different environmental compartments worldwide. As a result of various biogeochemical mechanisms, this plastic litter is converted into small, ubiquitous and persistent fragments called microplastics (<5 mm), which are of significant and increasing concern to the scientific community. Microplastics have spread across the globe and now exist in virtually all environmental compartments (the soil, atmosphere, and water). Although these compartments are often considered to be independent environments, in reality, they are very closely linked. Ample research has been done on microplastics, but there are still questions and knowledge gaps regarding the emission, occurrence, distribution, detection, environmental fate and transport of MPs in different environmental compartments. The current article is intended to provide a systematic overview of MP emissions, pollution conditions, sampling and analytical approaches, transport, fates and transformation mechanisms in different environmental compartments. It also identifies research gaps and future research directions and perspectives.

Degradation of Adsorbed Bisphenol A by Soluble Mn(III)

Bisphenol A (BPA), a high production volume chemical and potential endocrine disruptor, is found to be associated with sediments and soils due to its hydrophobicity (log K_OW of 3.42). We used superfine powdered activated carbon (SPAC) with a particle size of 1.38 ± 0.03 μm as a BPA sorbent and assessed degradation of BPA by oxidized manganese (Mn) species. SPAC strongly sorbed BPA, and desorption required organic solvents. No degradation of adsorbed BPA (278.7 ± 0.6 mg BPA g^-1 SPAC) was observed with synthetic, solid α-MnO₂ with a particle size of 15.41 ± 1.35 μm; however, 89% mass reduction occurred following the addition of 0.5 mM soluble Mn(III). Small-angle neutron scattering data suggested that both adsorption and degradation of BPA occurred in SPAC pores. The findings demonstrate that Mn(III) mediates oxidative transformation of dissolved and adsorbed BPA, the latter observation challenging the paradigm that contaminant desorption and diffusion out of pore structures are required steps for degradation. Soluble Mn(III) is abundant near oxic-anoxic interfaces, and the observation that adsorbed BPA is susceptible to degradation has implications for predicting, and possibly managing, the fate and longevity of BPA in environmental systems.

Making Waves: Biocatalysis and Biosorption: Opportunities and Challenges Associated with a New Protein-Based Toolbox for Water and Wastewater Treatment

New water and wastewater treatment technologies are required to meet the demands created by emerging contaminants and resource recovery needs, yet technology development is a slow and uncertain process. Through evolution, nature has developed highly selective and fast-acting proteins that could help address these issues, but research and application have been limited, often due to assumptions about stability and economic feasibility. Here we highlight the potential advantages of cell-free, protein-based water and wastewater treatment processes (biocatalysis and biosorption), evaluate existing information about their economic feasibility, consider when a protein-based treatment process might be advantageous, and highlight key research needs.

Bioremoval and tolerance study of sulfamethoxazole using whole cell Trichoderma harzianum isolated from rotten tree bark

Antibiotic contamination raises concerns over antibiotic resistance genes (ARGs), which can severely impact the human health and environment. Sulfamethoxazole (SMX) is a widely used antibiotic that is incompletely metabolized in the body. In this study, the research objectives were (1) to isolate the native strain of Trichoderma sp. from the environment and analyze the tolerance toward SMX concentration by evaluating fungal growth, and (2) to investigate the potential of SMX removal by fungi. The potential fungi isolated from rotten tree bark showed 97% similarity to Trichoderma harzianum (Accession no. MH707098.1). The whole cell of fungi was examined in vitro; the strain Trichoderma harzianum BGP115 eliminated 71% of SMX after 7 days, while the white rot fungi Trametes versicolor, demonstrated 90% removal after 10 days. Furthermore, the tolerance of fungal growth toward SMX concentration at 10 mg L^-1 was analyzed, which indicated that Trichoderma harzianum BGP115 (the screened strain) exhibited more tolerance toward SMX than Trametes versicolor (the reference strain). The screened fungi isolated from rotted tree bark demonstrated the ability of SMX bioremoval and the potential to be tolerant to high concentrations of SMX.

A comprehensive insight into the application of white rot fungi and their lignocellulolytic enzymes in the removal of organic pollutants

Environmental problems resultant from organic pollutants are a major current challenge for modern societies. White rot fungi (WRF) are well known for their extensive organic compound degradation abilities. The unique oxidative and extracellular ligninolytic systems of WRF that exhibit low substrate specificity, enable them to display a considerable ability to transform or degrade different environmental contaminants. In recent decades, WRF and their ligninolytic enzymes have been widely applied in the removal of polycyclic aromatic hydrocarbons (PAHs), pharmaceutically active compounds (PhACs), endocrine disruptor compounds (EDCs), pesticides, synthetic dyes, and other environmental pollutants, wherein promising results have been achieved. This review focuses on advances in WRF-based bioremediation of organic pollutants over the last 10 years. We comprehensively document the application of WRF and their lignocellulolytic enzymes for removing organic pollutants. Moreover, potential problems and intriguing observations that are worthy of additional research attention are highlighted. Lastly, we discuss trends in WRF-remediation system development and avenues that should be considered to advance research in the field.

Engineering Microbes to Bio-Upcycle Polyethylene Terephthalate

Polyethylene terephthalate (PET) is globally the largest produced aromatic polyester with an annual production exceeding 50 million metric tons. PET can be mechanically and chemically recycled; however, the extra costs in chemical recycling are not justified when converting PET back to the original polymer, which leads to less than 30% of PET produced annually to be recycled. Hence, waste PET massively contributes to plastic pollution and damaging the terrestrial and aquatic ecosystems. The global energy and environmental concerns with PET highlight a clear need for technologies in PET "upcycling," the creation of higher-value products from reclaimed PET. Several microbes that degrade PET and corresponding PET hydrolase enzymes have been successfully identified. The characterization and engineering of these enzymes to selectively depolymerize PET into original monomers such as terephthalic acid and ethylene glycol have been successful. Synthetic microbiology and metabolic engineering approaches enable the development of efficient microbial cell factories to convert PET-derived monomers into value-added products. In this mini-review, we present the recent progress of engineering microbes to produce higher-value chemical building blocks from waste PET using a wholly biological and a hybrid chemocatalytic-biological strategy. We also highlight the potent metabolic pathways to bio-upcycle PET into high-value biotransformed molecules. The new synthetic microbes will help establish the circular materials economy, alleviate the adverse energy and environmental impacts of PET, and provide market incentives for PET reclamation.

Immobilization of yeast cell walls with surface displayed laccase from Streptomyces cyaneus within dopamine-alginate beads for dye decolorization

High amounts of toxic textile dyes are released into the environment due to coloring and wastewaters treatment processes' inefficiency. To remove dyes from the environment and wastewaters, researchers focused on applying immobilized enzymes due to mild reaction conditions and enzyme nontoxicity. Laccases are oxidases with wide substrate specificity, capable of degradation of many different dye types. Laccase from Streptomyces cyaneus was expressed on the surface of Saccharomyces cerevisiae EBY100 cells. The specific activity of surface-displayed laccase was increased by toluene-induced lysis to 3.1 U/g of cell walls. For cell wall laccase immobilization within hydrogel beads, alginate was modified by dopamine using periodate oxidation and reductive amination and characterized by UV-Vis, FTIR, and NMR spectroscopy. Cell wall laccase was immobilized within alginate and dopamine-alginate beads additionally cross-linked by oxygen and laccase. The immobilized enzyme's specific activity was two times higher using dopamine-alginate compared to native alginate beads, and immobilization yield increased 16 times. Cell wall laccase immobilized within dopamine-alginate beads decolorized Amido Black 10B, Reactive Black 5, Evans Blue, and Remazol Brilliant Blue with 100% efficiency and after ten rounds of multiple-use retained decolorization efficiency of 90% with Evans Blue and 61% with Amido Black.

Removal of pharmaceuticals and personal care products using native fungal enzymes extracted during the ligninolytic process

Significant concentrations of pharmaceuticals and personal care products (PPCPs) have been detected in aquatic environment. Fungal enzymatic processes can oxidize these persistent PPCPs; thus, these processes have attracted considerable attention from the scientific community. Here, we evaluated the efficacy of the removal of PPCPs using native fungal enzymes derived from Bjerkandera spp. TBB-03 under various conditions. Among the eight lignocellulosic substrates, ash, which showed the highest laccase production, was selected as the sole enzyme inducer. TBB-03 laccase was found to exhibit remarkable stability under varied pH and temperature conditions. Acetaminophen and bisphenol A were effectively removed by TBB-03 laccase under various conditions, except at pH 8. Although TBB-03 laccase could not efficiently remove single-state sulfamethoxazole directly, a 22% of improvement in sulfamethoxazole removal was observed in the presence of acetaminophen. Overall, our proposed approach showed that Bjerkandera adusta TBB-03 can be potentially applied for further research regarding PPCP remediation.

Feed-additive of bioengineering strain with surface-displayed laccase degrades sulfadiazine in broiler manure and maintains intestinal flora structure

Sulfonamide antibiotics (SAs) are excreted into the ecosystem unchanged through feces and urine because of their low adsorption and degradation in the guts of humans and animals. In this study, a novel whole-cell biocatalyst with fungal laccase on the cell surface of Escherichia coli Nissle 1917 was developed to degrade sulfadiazine (SDZ). Engineered strain EcN-IL showed laccase enzyme activity of 2 ± 1 U/mg dry weight of cell and degraded 37 ± 1% of SDZ at temperature 40 °C and pH 5 within 3 h in vitro. Strain EcN-IL with 500 mg/kg of SDZ was employed as a food supplement to feed chicken broilers, which can reduce the residue of SDZ in broiler manure by 58 ± 2% and also reduced dysbiosis of the gut microbiota due to overuse of antibiotics. The genetically engineered EcN-IL has laid a foundation for degrading SDZ in broilers and their manure.

Performance indicators for a holistic evaluation of catalyst-based degradation-A case study of selected pharmaceuticals and personal care products (PPCPs)

Considerable efforts have been made to develop effective and sustainable catalysts, e.g., carbon-/biochar-based catalyst, for the decontamination of organic pollutants in water/wastewater. Most of the published studies evaluated the catalytic performance mainly upon degradation efficiency of parent compounds; however, comprehensive and field-relevant performance assessment is still in need. This review critically analysed the performance indicators for carbon-/biochar-based catalytic degradation from the perspectives of: (1) degradation of parent compounds, i.e., concentrations, kinetics, reactive oxidative species (ROS) analysis, and residual oxidant concentration; (2) formation of intermediates and by-products, i.e., intermediates analysis, evolution of inorganic ions, and total organic carbon (TOC); and (3) impact assessment of treated samples, i.e., toxicity evolution, disinfection effect, and biodegradability test. Five most frequently detected pharmaceuticals and personal care products (PPCPs) (sulfamethoxazole, carbamazepine, ibuprofen, diclofenac, and acetaminophen) were selected as a case study to articulate the performance indicators for a holistic evaluation of carbon-/biochar-based catalytic degradation. This review also encourages the development of alternative performance indicators to facilitate the rational design of catalysts in future studies.

Recent advancement in remediation of synthetic organic antibiotics from environmental matrices: Challenges and perspective

Continuous discharge and persistence of antibiotics in aquatic ecosystem is identified as emerging environment health hazard. Partial degradation and inappropriate disposal induce appearance of diverse antibiotic resistant genes (ARGs) and bacteria, hence their execution is imperative. Conventional methods including waste water treatment plants (WWTPs) are found ineffective for the removal of recalcitrant antibiotics. Therefore, constructive removal of antibiotics from environmental matrices and other alternatives have been discussed. This review summarizes present scenario and removal of micro-pollutants, antibiotics from environment. Various strategies including physicochemical, bioremediation, use of bioreactor, and biocatalysts are recognized as potent antibiotic removal strategies. Microbial Fuel Cells (MFCs) and biochar have emerged as promising biodegradation processes due to low cost, energy efficient and environmental benignity. With higher removal rate (20-50%) combined/ hybrid processes seems to be more efficient for permanent and sustainable elimination of reluctant antibiotics.

How microbial community composition, sorption and simultaneous application of six pharmaceuticals affect their dissipation in soils

Pharmaceuticals may enter soils due to the application of treated wastewater or biosolids. Their leakage from soils towards the groundwater, and their uptake by plants is largely controlled by sorption and degradation of those compounds in soils. Standard laboratory batch degradation and sorption experiments were performed using soil samples obtained from the top horizons of seven different soil types and 6 pharmaceuticals (carbamazepine, irbesartan, fexofenadine, clindamycin and sulfamethoxazole), which were applied either as single-solute solutions or as mixtures (not for sorption). The highest dissipation half-lives were observed for citalopram (average DT_50,S for a single compound of 152 ± 53.5 days) followed by carbamazepine (106.0 ± 17.5 days), irbesartan (24.4 ± 3.5 days), fexofenadine (23.5 ± 20.9 days), clindamycin (10.8 ± 4.2 days) and sulfamethoxazole (9.6 ± 2.0 days). The simultaneous application of all compounds increased the half-lives (DT_50,M) of all compounds (particularly carbamazepine, citalopram, fexofenadine and irbesartan), which is likely explained by the negative impact of antibiotics (sulfamethoxazole and clindamycin) on soil microbial community. However, this trend was not consistent in all soils. In several cases, the DT_50,S values were even higher than the DT_50,M values. Principal component analyses showed that while knowledge of basic soil properties determines grouping of soils according sorption behavior, knowledge of the microbial community structure could be used to group soils according to the dissipation behavior of tested compounds in these soils. The derived multiple linear regression models for estimating dissipation half-lives (DT_50,S) for citalopram, clindamycin, fexofenadine, irbesartan and sulfamethoxazole always included at least one microbial factor (either amount of phosphorus in microbial biomass or microbial biomarkers derived from phospholipid fatty acids) that deceased half-lives (i.e., enhanced dissipations). Equations for citalopram, clindamycin, fexofenadine and sulfamethoxazole included the Freundlich sorption coefficient, which likely increased half-lives (i.e., prolonged dissipations).

Homogeneously catalytic oxidation of phenanthrene by the reaction of extracellular secretions of pyocyanin and Nicotinamide Adenine Dinucleotide

Application of biological methods on polycyclic aromatic hydrocarbons (PAHs) treatment is always limited by its low degradation efficiency. In this work, a catalytic oxidation pathway of phenanthrene resulted by extracellular secretions of P. aeruginosa NY3 was proposed. Results of the in vitro experiments showed that, the extracellular secretions of Pyocyanin (Pyo) and Nicotinamide Adenine Dinucleotide (NADH) acted as homogeneous catalysts because which produced H₂O₂, hydroxyl free radical and superoxide anion radical continuously under aerobic conditions. These produced reactive oxygen species oxidized the phenanthrene in aqueous solution, leading to the cleavage of the phenanthrene ring and the formation of phthalates products and low molecular weight metabolites (such as alkanoic acids). The ratio of BOD₅/COD of phenanthrene-containing wastewaters was greatly improved after treating with Pyo and NADH. Results of the in vivo experiments showed that, pre-degradation of phenanthrene by extracellular fluid simultaneously containing Pyo and NADH, promoted cell growth of P. aeruginosa NY3, which confirmed the improvement of bioavalability of phenanthrene-containing wastewaters by the catalytic oxidation of Pyo and NADH. Further details of the free radical detection indicated that, the increase in secretion of Pyo by a bacterium was favorable to the production of H₂O₂ in the extracellular fluid.

Potential use of two aryl sulfotransferase cell-surface display systems to detoxify the endocrine disruptor bisphenol A

Bisphenol A (BPA) is one of the most common toxic endocrine disruptors in the environment. A fast, efficient and environmental-friendly method for BPA detoxification is urgently needed. In this study, we show that the enzymatic transformation of BPA into a non-estrogenic BPA sulfate can be performed by the aryl sulfotransferase (ASTB) from Desulfitobacterium hafniense. We developed and compared two Escherichia coli ASTB cell-surface displaying systems using the outer membrane porin F (OprF) and the lipoprotein outer membrane A (Lpp-OmpA) as carriers. The surface localization of both fusion proteins was confirmed by Western blot and flow cytometry analysis as well as the enzymatic activity assay of the outer membrane fractions. Unfortunately, Lpp-OmpA-ASTB cells had an adverse effect on cell growth. In contrast, the OprF-ASTB cell biocatalyst was stable, expressing 70% of enzyme activity for 7 days. It also efficiently sulfated 90% of 5 mM BPA (1 mg/mL) in wastewater within 6 h.

Chlorpyrifos degradation efficiency of Bacillus sp. laccase immobilized on iron magnetic nanoparticles

The present study explored the immobilization of laccase onto iron magnetic nanoparticles (MNPs) to enhance its enzymatic properties and applications. The immobilization process was optimized using Box-Behnken design (BBD). BBD showed significance towards the quadratic model with experimental data. Maximum laccase activity recovery (99%) of the predicted model was observed at 0.75 mg/mL of laccase concentration, 200 mg/mL of MNPs, 0.3% cross linking with carbodiimide, and 3 h of cross-linking time. The magnetization activity of MNPs (8 emu/g) and the immobilized laccase with MNPs (4 emu/g) was analyzed using vibrating sample magnetometer (VSM). Maximum activity of immobilized laccase was observed at pH 7.0 and 55 °C. The immobilized laccase has greater stability (100 h) and significant chlorpyrifos (pesticide) degradation activity. High-performance liquid chromatography (HPLC) results confirmed the degraded metabolic products of chlorpyrifos. In all, the immobilized laccase was superior to free laccase, showing promising structural and application characteristics.

Microbial degradation and other environmental aspects of microplastics/plastics

Microplastic (MP) pollution is a significant environmental concern due to the persistence of MPs and their potential adverse effects on biota. Most scientific studies have examined the distribution, ingestion, fate, behavior, amount, and effect of MPs. However, few studies have described the development of methods for the removal and remediation of MPs. Therefore, in this review, we summarize the recent literature regarding the microbial-mediated degradation of MPs and discuss the associated degradation characteristics and mechanisms. Different types and combinations of microorganisms, such as bacteria, fungi, bacterial consortia, and biofilms, that can degrade different MPs are categorized. This article summarizes approximately 50 recent papers. Twelve and 6 papers reported that bacteria and fungi, respectively, can degrade MPs. Nine articles indicated that bacterial consortia have the ability to degrade MPs, and 6 articles found that biofilms can also utilize MPs. Furthermore, to evaluate their associated degradation effects, the corresponding structural changes (i.e., macro size, surface morphology, and functional groups) in MPs after microbial degradation are examined. In addition, MP biodegradation is affected by microbial characteristics and environmental factors; therefore, the environmental factors (i.e., temperature, pH and strain activity) influencing MP degradation and the associated degradation effects (i.e., weight loss, degradation rate, and molecular weight change) are generalized. Furthermore, the mechanisms associated with the microbial-mediated degradation of MPs are briefly discussed. Finally, prospects for the degradation of MPs using microbes and future research directions are envisioned. This review provides the first systematic summary of the microbial-mediated degradation of MPs and provides a reference for future studies investigating effective means of MP pollution control.

Reducing residual antibiotic levels in animal feces using intestinal Escherichia coli with surface-displayed erythromycin esterase

Antibiotics are widely used in livestock and poultry industries, which results in large quantities of antibiotic residues in manure that influences subsequent treatments. In this study, an Escherichia coli strain was engineered to display erythromycin esterase on its cell surface. The engineered strain (E. coli ereA) efficiently degraded erythromycin by opening the macrocyclic 14-membered lactone ring in solution. Erythromycin (50 mg/L) was completely degraded in a solution by E. coli ereA (1 × 10⁹ CFU/mL) within 24 h. E. coli ereA retained over 86.7 % of the initial enzyme activity after 40 days of storage at 25 °C, and 78.5 % of the initial activity after seven repeated batch reactions in solution at 25 °C. Mice were fed with E. coli ereA and real-time quantitative PCR data showed that E. coli ereA colonized in the mice large intestine. The mice group fed E. coli ereA exhibited 83.13 % decrease in erythromycin levels in their feces compared with the mice group not fed E. coli ereA. E. coli ereA eliminated antibiotics from the source preventing its release into the environment. The surface-engineered strain therefore is an effective alternative agent for treating recalcitrant antibiotics, and has the potential to be applied in livestock and poultry industries.

Efficient biodegradation of highly crystallized polyethylene terephthalate through cell surface display of bacterial PETase

Polyethylene terephthalate (PET) is one of the most widely used plastics in the world. Accumulation of the discarded PET in the environment is creating a global environmental problem. Recently, a bacterial enzyme named PETase was found to have the novel ability to degrade the highly crystallized PET. However, the enzymatic activity of native PETase is still low limiting its possible use in recycling of PET. In this study, we developed a whole-cell biocatalyst by displaying PETase on the surface of yeast (Pichia pastoris) cell to improve its degradation efficiency. Our data shows that PETase could be functionally displayed on the yeast cell with enhanced pH and thermal stability. The turnover rate of the PETase-displaying yeast whole-cell biocatalyst towards highly crystallized PET dramatically increased about 36-fold compared with that of purified PETase. Furthermore, the whole-cell biocatalyst showed stable turnover rate after seven repeated use and under some chemical/solvent conditions, and its ability to degrade different commercial highly crystallized PET bottles. Our results reveal that PETase-displaying whole-cell biocatalyst affords a promising route for efficient biological recycling of PET.

Ligninolytic enzymes and its mechanisms for degradation of lignocellulosic waste in environment

Ligninolytic enzymes play a key role in degradation and detoxification of lignocellulosic waste in environment. The major ligninolytic enzymes are laccase, lignin peroxidase, manganese peroxidase, and versatile peroxidase. The activities of these enzymes are enhanced by various mediators as well as some other enzymes (feruloyl esterase, aryl-alcohol oxidase, quinone reductases, lipases, catechol 2, 3-dioxygenase) to facilitate the process for degradation and detoxification of lignocellulosic waste in environment. The structurally laccase is isoenzymes with monomeric or dimeric and glycosylation levels (10–45%). This contains four copper ions of three different types. The enzyme catalyzes the overall reaction: 4 benzenediol + O₂ to 4 benzosemiquinone + 2H₂O. While, lignin peroxidase is a glycoprotein molecular mass of 38–46 kDa containing one mole of iron protoporphyrin IX per one mol of protein, catalyzes the H₂O₂ dependent oxidative depolymerization of lignin. The manganese peroxidase is a glycosylated heme protein with molecular mass of 40–50kDa. It depolymerizes the lignin molecule in the presence of manganese ion. The versatile peroxidase has broad range substrate sharing typical features of the manganese and lignin peroxidase families. Although ligninolytic enzymes have broad range of industrial application specially the degradation and detoxification of lignocellulosic waste discharged from various industrial activities, its large scale application is still limited due to lack of limited production. Further, the extremophilic properties of ligninolytic enzymes indicated their broad prospects in varied environmental conditions. Therefore it needs more extensive research for understanding its structure and mechanisms for broad range commercial applications.

Characterization of a robust cold-adapted and thermostable laccase from Pycnoporus sp. SYBC-L10 with a strong ability for the degradation of tetracycline and oxytetracycline by laccase-mediated oxidation

A native laccase (Lac-Q) with robust cold-adapted and thermostable characteristics from the white-rot fungus Pycnoporus sp. SYBC-L10 was purified, characterized, and used in antibiotic treatments. Degradation experiments revealed that Lac-Q at 10.0 U mL^-1 coupled with 1.0 mmol L^-1 ABTS could degrade 100% of the tetracycline or oxytetracycline (50 mg L^-1) within 5 min with a static incubation at 0 °C (pH 6.0). The presence of the Mn²⁺ ion inhibited the removal rate of tetracycline and oxytetracycline by the Lac-Q-ABTS system, and the presence of Al³⁺, Cu²⁺, and Fe³⁺ accelerated the removal rate of tetracycline and oxytetracycline by the Lac-Q-ABTS system. Furthermore, the growth inhibition of Bacillus altitudinis SYBC hb4 and E. coli by tetracycline antibiotics revealed that the antimicrobial activity was significantly reduced after treatment with the Lac-Q-ABTS system. Finally, seven transformation products of oxytetracycline (namely TP 445, TP 431, TP 413, TP 399, TP 381, TP 367, and TP 351) were identified during the Lac-Q-mediated oxidation process by using UPLC-MS/MS. A possible degradation pathway including deamination, demethylation, and dehydration was proposed. These results suggest that the Lac-Q-ABTS system shows a great potential for the treatment of antibiotic wastewater containing different metal ions at various temperatures.

The Use of Algae and Fungi for Removal of Pharmaceuticals by Bioremediation and Biosorption Processes: A Review

The occurrence and fate of pharmaceuticals in the aquatic environment is recognized as one of the emerging issues in environmental chemistry. Conventional wastewater treatment plants (WWTPs) are not designed to remove pharmaceuticals (and their metabolites) from domestic wastewaters. The treatability of pharmaceutical compounds in WWTPs varies considerably depending on the type of compound since their biodegradability can differ significantly. As a consequence, they may reach the aquatic environment, directly or by leaching of the sludge produced by these facilities. Currently, the technologies under research for the removal of pharmaceuticals, namely membrane technologies and advanced oxidation processes, have high operation costs related to energy and chemical consumption. When chemical reactions are involved, other aspects to consider include the formation of harmful reaction by-products and the management of the toxic sludge produced. Research is needed in order to develop economic and sustainable treatment processes, such as bioremediation and biosorption. The use of low-cost materials, such as biological matrices (e.g., algae and fungi), has advantages such as low capital investment, easy operation, low operation costs, and the non-formation of degradation by-products. An extensive review of existing research on this subject is presented.

Immobilized laccase on bentonite-derived mesoporous materials for removal of tetracycline

Bentonite is a natural and environmentally clay mineral, and bentonite-derived mesoporous materials (BDMMs) were obtained conveniently from the alkali and acid treatment of bentonite. In the present study, BDMMs were explored for immobilization of laccase obtained from Trametes versicolor. As a result, bentonite-derived mesoporous materials-Laccase (BDMMs-Lac) was developed for the removal of tetracycline (TC). The enzyme immobilization process was carried out through physical adsorption contact (ion exchange adsorption, hydrogen bond adsorption, and Van der waals adsorption) between the BDMMs and laccase. The process of immobilization remarkably increased its operating temperature. The BDMMs-Lac exhibited over 60% removal efficiency for TC within 3 h in the presence of 1-hydroxybenzotriazole (HBT). In conclusion, BDMMs-Lac showed more promising potential than free laccase for practical continuous applications.

Laccase removal of 2-chlorophenol and sulfamethoxazole in municipal wastewater

Laccases were studied for their ability to remove two compounds, 2-chlorophenol and sulfamethoxazole, in batch studies, both in buffered solutions and in wastewater samples from different points in a municipal water resource recovery facility. Two enzymes with and without a mediator (acetosyringone) were investigated: a commercial product derived from Myceliphthora thermophile and a laboratory-generated enzyme mix derived from Tramates versicolor. The chlorophenol was removed rapidly by the commercial enzyme in the presence of acetosyringone, but the primary products were coupling complexes of the reactants. Excellent removal was achieved without acetosyringone by the natural enzyme mix. Sulfamethoxazole was poorly removed in all laboratory-generated chemically buffered solutions, but was very well removed, without the addition of mediators, in secondary effluent suspensions from a municipal water resource recovery facility. Mechanistic studies are still required, but the results suggest that treatment via direct addition of enzymes is feasible to remove recalcitrant compounds in municipal wastewater.

Biocatalytic Degradation of Parabens Mediated by Cell Surface Displayed Cutinase

Parabens are emerging environmental contaminants with known endocrine-disrupting effects. This study created a novel biocatalyst (named as SDFsC) by expressing the enzyme Fusarium solani pisi cutinase (FsC) on the cell surface of Baker's yeast Sacchromycese cerevisiae and demonstrated successful enzyme-mediated removal of parabens for the first time. Parabens with different side chain structures had different degradation rates by the SDFsC. The SDFsC preferentially degraded the parabens with relatively long alkyl or aromatic side chains. The structure-dependent degradability was in a good agreement with the binding energy between the active site of FsC and different parabens. In real wastewater effluent solution, the SDFsC effectively degraded 800 μg/L of propylparaben, butylparaben, and benzylparaben, either as a single compound or as a mixture, within 48 h. The estrogenic activity of parabens was considerably reduced as the parent parabens were degraded into 4-hydroxybenzoic acid via hydrolysis pathway by the SDFsC. The SDFsC showed superior reusability and maintained 93% of its initial catalytic activity after six rounds of paraben degradation reaction. Results from this study provide scientific basis for developing biocatalysis as a green chemistry alternative for advanced treatment of parabens in sustainable water reclamation.

Spore cells from BPA degrading bacteria Bacillus sp. GZB displaying high laccase activity and stability for BPA degradation

Laccase has been applied extensively as a biocatalyst to remove different organic pollutants. This study characterized a spore-laccase from the bisphenol A (BPA)-degrading strain Bacillus sp. GZB. The spore-laccase was encoded with 513 amino acids, containing spore coat protein A (CotA). It showed optimal activity at 70 °C and pH = 7.2 in presence of 2, 6-dimethoxyphenol. At 60 °C, optimal activity was also seen at pH = 3.0 and pH = 6.8 with 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulfonate) and syringaldazine, respectively. The spore-laccase was stable at high temperature, at acidic to alkaline pH values, and in the presence of different organic solvents. Spore-laccase activity was increased by introducing Cu²⁺, Mg²⁺, and Na⁺, but was strongly inhibited by Fe²⁺, Ag⁺, l-cysteine, dithiothreitol, and NaN₃. The cotA gene was cloned and expressed in E. coli BL21 (DE3); the purified protein was estimated as having a molecular weight of ~63 kDa. Different synthetic dyes and BPA were effectively decolorized or degraded both by the spore laccase and recombinant laccase. When BPA oxidation was catalyzed using laccase, there was an initial formation of phenoxy radicals and further oxidation or CC bond cleavage of the radicals produced different organic acids. Detailed reaction pathways were developed based on nine identified intermediates. The acute toxicity decreased gradually during BPA degradation by laccase. This study is the first report about a genus of Bacillus that can produce a highly active and stable laccase to degrade BPA.

Application of advanced oxidation processes and toxicity assessment of transformation products

Advanced Oxidation Processes (AOPs) are the techniques employed for oxidation of various organic contaminants in polluted water with the objective of making it suitable for human consumption like household and drinking purpose. AOPs use potent chemical oxidants to bring down the contaminant level in the water. In addition to this function, these processes are also capable to kills microbes (as disinfectant) and remove odor as well as improve taste of the drinking water. The non-photochemical AOPs methods include generation of hydroxyl radical in absence of light either by ozonation or through Fenton reaction. The photochemical AOPs methods use UV light along with H₂O₂, O₃ and/or Fe⁺² to generate reactive hydroxyl radical. Non-photochemical method is the commonly used whereas, photochemical method is used when conventional O₃ and H₂O₂ cannot completely oxidize organic pollutants. However, the choice of AOPs methods is depended upon the type of contaminant to be removed. AOPs cause loss of biological activity of the pollutant present in drinking water without generation of any toxicity. Conventional ozonation and AOPs can inactivate estrogenic compounds, antiviral compounds, antibiotics, and herbicides. However, the study of different AOPs methods for the treatment of drinking water has shown that oxidation of parent compound can also lead to the generation of a degradation/transformation product having biological activity/chemical toxicity similar to or different from the parent compound. Furthermore, an increased toxicity can also occur in AOPs treated drinking water. This review discusses various methods of AOPs, their merits, its application in drinking water treatment, the related issue of the evolution of toxicity in AOPs treated drinking water, biocatalyst, and analytical methods for identification of pollutants /transformed products and provides future directions to address such an issue.

Plasmonic photocatalysis: complete degradation of bisphenol A by a gold nanoparticle-reduced graphene oxide composite under visible light

Bisphenol A is a well-known endocrine disruptor that comes from plastic/epoxy resin-based consumer products, pollutes our environment and is responsible for various human diseases. Thus, its removal from water/food/the environment is becoming a challenging issue. Here we report the visible light photocatalytic degradation of bisphenol A using a gold nanoparticle based composite with reduced graphene oxide. The nanocomposite captures visible light and produces hydroxyl radicals that oxidize bisphenol A into smaller organic fragments such as phenol derivatives and aliphatic aldehydes/ketones. The composition of the nanocomposite has been optimized for most efficient degradation of bisphenol A under visible light and the approach may be extended for the sunlight-based removal of bisphenol A from water/food/the environment.

Multienzyme immobilized polymeric membrane reactor for transformation of lignin model compound

We have developed a multienzyme functionalized membrane reactor for bioconversion of lignin model compound involving enzymatic catalysis. Layer-by-layer approach was used to immobilize three different enzymes (glucose oxidase, peroxidase and laccase) into pH-responsive membranes. This novel membrane reactor couples the in situ generation of hydrogen peroxide (by glucose oxidase) to oxidative conversion of a lignin model compound, guaiacylglycerol-B-guaiacylether (GGE). Preliminary investigation of the efficacy of these functional membranes towards GGE degradation is demonstrated under convective flow mode. Over 90% of the initial feed could be degraded with the multienzyme immobilized membranes at a residence time of approximately 22 seconds. GGE conversion product analysis revealed formation of oligomeric oxidation products with peroxidase, which might be potential hazard to membrane bioreactors. These oxidation products could be further degraded by laccase enzymes in the multienzymatic membranes explaining the potential of multienzyme membrane reactors. The multienzyme incorporated membrane reactors were active for about a month time of storage at 4 °C, and retention of activity was demonstrated after repetitive use.

Characterizing Isozymes of Chlorite Dismutase for Water Treatment

This work investigated the potential for biocatalytic degradation of micropollutants, focusing on chlorine oxyanions as model contaminants, by mining biology to identify promising biocatalysts. Existing isozymes of chlorite dismutase (Cld) were characterized with respect to parameters relevant to this high volume, low-value product application: kinetic parameters, resistance to catalytic inactivation, and stability. Maximum reaction velocities (V_max) were typically on the order of 10⁴ μmol min^-1 (μmol heme)^-1. Substrate affinity (K_m) values were on the order of 100 μM, except for the Cld from Candidatus Nitrospira defluvii (NdCld), which showed a significantly lower affinity for chlorite. NdCld also had the highest susceptibility to catalytic inactivation. In contrast, the Cld from Ideonella dechloratans was least susceptible to catalytic inactivation, with a maximum turnover number of approximately 150,000, more than sevenfold higher than other tested isozymes. Under non-reactive conditions, Cld was quite stable, retaining over 50% of activity after 30 days, and most samples retained activity even after 90–100 days. Overall, Cld from I. dechloratans was the most promising candidate for environmental applications, having high affinity and activity, a relatively low propensity for catalytic inactivation, and excellent stability.

Overview on the Biochemical Potential of Filamentous Fungi to Degrade Pharmaceutical Compounds

Pharmaceuticals represent an immense business with increased demand due to intensive livestock raising and an aging human population, which guarantee the quality of human life and well-being. However, the development of removal technologies for these compounds is not keeping pace with the swift increase in their use. Pharmaceuticals constitute a potential risk group of multiclass chemicals of increasing concern since they are extremely frequent in all environments and have started to exhibit negative effects on micro- and macro-fauna as well as on human health. In this context, fungi are known to be extremely diverse and poorly studied microorganisms despite being well suited for bioremediation processes, taking into account their metabolic and physiological characteristics for the transformation of even highly toxic xenobiotic compounds. Increasing studies indicate that fungi can transform many structures of pharmaceutical compounds, including anti-inflammatories, β-blockers, and antibiotics. This is possible due to different mechanisms in combination with the extracellular and intracellular enzymes, which have broad of biotechnological applications. Thus, fungi and their enzymes could represent a promising tool to deal with this environmental problem. Here, we review the studies performed on pharmaceutical compounds biodegradation by the great diversity of these eukaryotes. We examine the state of the art of the current application of the Basidiomycota division, best known in this field, as well as the assembly of novel biodegradation pathways within the Ascomycota division and the Mucoromycotina subdivision from the standpoint of shared enzymatic systems, particularly for the cytochrome P450 superfamily of enzymes, which appear to be the key enzymes in these catabolic processes. Finally, we discuss the latest advances in the field of genetic engineering for their further application.

Evaluating the Development of Biocatalytic Technology for the Targeted Removal of Perchlorate from Drinking Water

Removing micropollutants is challenging in part because of their toxicity at low concentrations. A biocatalytic approach could harness the high affinity of enzymes for their substrates to address this challenge. The potential of biocatalysis relative to mature (nonselective ion exchange, selective ion exchange, and whole-cell biological reduction) and emerging (catalysis) perchlorate-removal technologies was evaluated through a quantitative sustainable design framework, and research objectives were prioritized to advance economic and environmental sustainability. In its current undeveloped state, the biocatalytic technology was approximately 1 order of magnitude higher in cost and environmental impact than nonselective ion exchange. Biocatalyst production was highly correlated with cost and impact. Realistic improvement scenarios targeting biocatalyst yield, biocatalyst immobilization for reuse, and elimination of an electron shuttle could reduce total costs to $0.034 m^-3 and global warming potential (GWP) to 0.051 kg CO₂ eq m^-3: roughly 6.5% of cost and 7.3% of GWP of the background from drinking water treatment and competitive with the best performing technology, selective ion exchange. With less stringent perchlorate regulatory limits, ion exchange technologies had increased cost and impact, in contrast to biocatalytic and catalytic technologies. Targeted advances in biocatalysis could provide affordable and sustainable treatment options to protect the public from micropollutants.