Optimization of growth conditions for enhancing the production of microbial laccase and its application in treating antibiotic contamination in wastewater

Laccase mediated transformation of fluoroquinolone antibiotics: Analyzing degradation pathways and assessing algal toxicity

Improper waste disposal or inadequate wastewater treatment can result in pharmaceuticals reaching water bodies, posing environmental hazards. In this study, crude extracts containing the laccase enzyme from Pleurotus florida, Pleurotus eryngii, and Pleurotus sajor caju were used to degrade the fluoroquinolone antibiotics (FQs) levofloxacin (LEV), norfloxacin (NOR), ciprofloxacin (CIP), ofloxacin (OFL), and enrofloxacin (ENR) in aqueous solutions. The results for the fungi derived laccase extracts were compared with those obtained using commercially sourced laccase. Proteomics analysis of the crude extracts confirmed the presence of laccase enzyme across all three tested species, with proteins matching those found in Trametes versicolor and Pleurotus ostreatus. In vivo studies were conducted using species pure lines of fungal whole cells. The highest degradation efficiency observed was 77.7% for LEV in the presence of P. sajor caju after 25 days of treatment. Degradation efficiencies ranged from approximately 60-72% for P. florida, 45-76% for P. eryngii, and 47-78% for P. sajor caju. A series of in vitro experiments were also conducted using crude extracts from the three species and outcomes compared with those obtained when commercial laccase was used confirmed laccase as the enzyme responsible for antibiotic removal. The degradation efficiencies in vitro surpassed those measured in vivo, ranging from approximately 91-98% for commercial laccase, 77-92% for P. florida, 76-92% for P. eryngii, and 78-88% for P. sajor caju. Liquid chromatography-high-resolution mass spectrometry (LC-MS/MS) identified the degradation products, indicating a consistent enzymatic degradation pathway targeting the piperazine moiety common to all tested FQs, irrespective of the initial antibiotic structure. Phytoplankton toxicity studies with Dunaliella tertiolecta were performed to aid in understanding the impact of emerging contaminants on ecosystems, and by-products were analysed for ecotoxicity to assess treatment efficacy. Laccase-mediated enzymatic oxidation shows promising results in reducing algal toxicity, notably with Pleurotus eryngii extract achieving a 97.7% decrease for CIP and a 90% decrease for LEV. These findings suggest the potential of these naturally sourced extracts in mitigating antibiotic contamination in aquatic ecosystems.

Is Laccase derived from Pleurotus ostreatus effective in microplastic degradation? A critical review of current progress, challenges, and future prospects

Exploration of Pleurotus ostreatus as a biological agent in the degradation of persistent plastics like polyethylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate, revealing a promising avenue toward mitigating the environmental impacts of plastic pollution. Leveraging the intrinsic enzymatic capabilities of this fungus, mainly its production of laccase, presents a sustainable and eco-friendly approach to breaking down complex polymer chains into less harmful constituents. This review focused on enhancements in the strain's efficiency through genetic engineering, optimized culture conditions, and enzyme immobilization to underscore the potential for scalability and practical application of this bioremediation process. The utilization of laccase from P. ostreatus in plastic waste management demonstrates a vital step forward in pursuing sustainable environmental solutions. By using the potential of fungal bioremediation, researchers can move closer to a future in which the adverse effects of plastic pollution are significantly mitigated, benefiting the health of our planet and future generations.

Micropollutants (ciprofloxacin and norfloxacin) remediation from wastewater through laccase derived from spent mushroom waste: Fate, toxicity, and degradation

Fluoroquinolone antibiotics frequently found in environmental matrices (wastewater treatment plants, hospital wastewater, industrial wastewater and surface wastewater) causes potential threat to the environment. Enzymatic treatment for degradation of antibiotics from environmental matrices is a green and sustainable approach. Focusing on this, this study aimed to degrade two frequently found fluroquinolone emergent pollutants, ciprofloxacin and norfloxacin from wastewater. The trinuclear cluster of copper ions present in laccase has the ability to effectively remove organic micropollutants (OMPs). The uniqueness of this study is that it utilizes laccase enzyme extracted from spent mushroom waste (SMW) of P. florida for degradation of ciprofloxacin and norfloxacin and to achieve highest degradation efficiency various parameters were tweaked such as pH (3-6), temperature (30 °C and 50 °C), and ABTS (0.05, 0.6, and 1 mM) concentration. The results showed that the most effective degradation of ciprofloxacin (86.12-75.94%) and norfloxacin (83.27-65.94%) was achieved in 3 h at pH 4.5, temperature 30 °C, and 2,2'-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 0.05 mM concentration. Nevertheless, achieving degradation at 50 °C for both antibiotics, indicates thermostability nature of laccase (P. florida). Further, the fate of transformed products obtained from laccase mediated degradation was confirmed by liquid chromatography (LC-MS). Both the antibiotics undergo decarboxylation, depiperylyzation, dealkylation and defluorination as a result of laccase-mediated bond breakage. Anti-microbial activity of the biodegraded products was monitored by residual anti-bacterial toxicity test (E. coli and Staphylococcus aureus). The biodegraded products were found to be non-toxic and resulted in the growth of E. coli and Staphylococcus aureus, as determined by the agar-diffusion method. Moreover, the storage stability of laccase was determined for 28-day duration at varying pH (3-10) and temperature (4-50 °C). The maximum storage stability was obtained at pH 4.5 and temperature 30 °C. Therefore, utilizing SMW for the degradation of OMPs from wastewater not only benefits in degradation but also reuses SMW agro waste, shedding light on agro waste management. Thus, SMW is a one-pot solution for both OMPs biodegradation and circularity in the economy.

Optimization of laccase enzyme extraction from spent mushroom waste of Pleurotus florida through ANN-PSO modeling: An ecofriendly and economical approach

The cardinal focus of this study is to optimize the best reaction conditions for maximizing laccase activity from spent mushroom waste (SMW) of Pleurotus florida. Optimization process parameters were studied by the modeling techniques, artificial neural networking (ANN) embedded in particle swarm optimization (PSO), and response surface model (RSM). The best topology of ANN-PSO architecture was obtained on 4-10-1. The R², IOA, MSE, and MAE values of the ANN model were obtained as 0.98785, 0.9939, 0.0023, and 0.0251 while, that of the RSM model were obtained as 0.74290, 0.9210, 0.0244, and 0.1110 respectively. The higher values of R², IOA, and lower values of MSE and MAE of the ANN-PSO model depict that ANN-PSO outperformed compared to RSM and also verified the effectiveness of the ANN-PSO model. The ANN-PSO model performance demonstrates the robustness of the technique in optimizing laccase activity in SMW of P. florida. The optimization results revealed that pH 4.5, time 3 h, solid: solution ratio 1:5, and ABTS concentration of 1 mM was optimal for achieving maximum laccase activity at temperature 30 °C. The enzymatic activity of crude laccase enzyme was obtained as 1.185 U ml^-1 without loss of enzyme activity. Additionally, crude laccase enzyme was 1.74 fold partially purified, and 83.54% of the enzyme was yielded. Out of all the independent process variables, ABTS and pH had an influence on laccase activity. Therefore, we anticipate that the findings of this investigation will reduce the ambiguity in maximizing laccase activity and ease the screening process. This study also highlights the comparative cost evaluation of crude laccase enzyme extracted from P. florida and commercial enzymes. There is a great potential for the utilization of the laccase enzyme extracted from SMW and using it for the degradation of recalcitrant micropollutants. Thus, SMW promises a cost-effective and sustainable approach leading towards circular economy.

Improved laccase production from Pleurotus floridanus using deoiled microalgal biomass: statistical and hybrid swarm-based neural networks modeling approach

Fungal laccases are versatile biocatalyst and occupy a prominent place in various industrial applications due to its broad substrate specificity. The simplest method to enhance the laccase production is by usage of cheap substrates in the fermentation processes incorporating modeling approaches for optimization. Integrated biorefinery concept is receiving wide popularity by making use of various products from microalgal biomass. The research aimed to identify the potential of deoiled microalgal biomass (DMB), a waste product from algal biorefinery as a nutrient supplement to enhance laccase production in Pleurotus floridanus by submerged fermentation. The maximum production was obtained in the presence of DMB as an additional nutrient supplement and copper sulfate as an inducer. The predictive capabilities of the two methodologies Response Surface Methodology (RSM) and hybrid Particle swarm optimization (PSO)-based Artificial Neural Network (ANN) were compared and validated. The results showed that ANN coupled with PSO predicted with more accuracy with an R 2 value of 0.99 than the RSM model with an R 2 value of 0.97. The optimized condition as predicted by superior model hybrid PSO-based ANN was glucose (3.51%), DMB (0.545%), pH (4.9), temperature (24.68 ℃) and CuSO4 (1.35 mM). The experimental laccase activity was 80.45 ± 0.132 U/mL which was 1.3 fold higher than unoptimized condition. This study promotes the usage of DMB as a novel supplement for the improved production of Pleurotus floridanus laccase.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03404-y.

A study on the adsorption property and mechanism of β-cyclodextrin/polyvinyl alcohol/polyacrylic acid hydrogel for ciprofloxacin

Polyvinyl alcohol (PVA), acrylic acid (AA), and β-cyclodextrin (β-CD) were used as monomers, and ammonium persulfate was used as an initiator. Orthogonal tests were optimized the experimental condition, and aqueous polymerization was used to prepare poly-β-cyclodextrin/polyvinyl alcohol/polyacrylic acid (β-CD/PVA/PAA) hydrogel. The samples were characterized by FT-IR (Fourier transform infrared), SEM (Scanning electron microscopy), and XRD (X-ray diffraction). β-CD/PVA/PAA hydrogel was analyzed, which influenced external environmental factors on the β-CD/PVA/PAA hydrogel adsorption performance, and the kinetic behavior of β-CD/PVA/PAA hydrogel on ciprofloxacin (CIP) adsorption was explored. The results concluded that the prepared β-CD/PVA/PAA hydrogel has a well-defined three-dimensional network structure. The decrease in the pH of the CIP solution and the adsorption temperature reduces the adsorption reaction of β-CD/PVA/PAA hydrogel on CIP. The kinetics of CIP adsorption by β-CD/PVA/PAA hydrogel confirmed the pseudo-second-order kinetic model (R 2 > 0.997), the maximum equilibrium adsorption amounts is 372.12 mg/g, the removal rate reaches 74.42%. The adsorption process was mainly chemisorption, the adsorption isotherm fits the Freundlich adsorption isotherm model (R 2 > 0.946), and the adsorption process was heterogeneous with multi-molecular layer adsorption. The adsorption process inclined more toward the adsorption of inhomogeneous multi-molecular layers. The β-CD/PVA/PAA hydrogel retained 80% adsorption properties after three adsorption-desorption under optimal conditions.

Biological oxidation methods for the removal of organic and inorganic contaminants from wastewater: A comprehensive review

Enzyme-based bioremediation is a simple, cost-effective, and environmentally friendly method for isolating and removing a wide range of environmental pollutants. This study is a comprehensive review of recent studies on the oxidation of pollutants by biological oxidation methods, performed individually or in combination with other methods. The main bio-oxidants capable of removing all types of pollutants, such as organic and inorganic molecules, from fungi, bacteria, algae, and plants, and different types of enzymes, as well as the removal mechanisms, were investigated. The use of mediators and modification methods to improve the performance of microorganisms and their resistance under harsh real wastewater conditions was discussed, and numerous case studies were presented and compared. The advantages and disadvantages of conventional and novel immobilization methods, and the development of enzyme engineering to adjust the content and properties of the desired enzymes, were also explained. The optimal operating parameters such as temperature and pH, which usually lead to the best performance, were presented. A detailed overview of the different combination processes was also given, including bio-oxidation in coincident or consecutive combination with adsorption, advanced oxidation processes, and membrane separation. One of the most important issues that this study has addressed is the removal of both organic and inorganic contaminants, taking into account the actual wastewaters and the economic aspect.

Biotransformation of the Fluoroquinolone, Levofloxacin, by the White-Rot Fungus Coriolopsis gallica

The wastewater from hospitals, pharmaceutical industries and more generally human and animal dejections leads to environmental releases of antibiotics that cause severe problems for all living organisms. The aim of this study was to investigate the capacity of three fungal strains to biotransform the fluoroquinolone levofloxacin. The degradation processes were analyzed in solid and liquid media. Among the three fungal strains tested, Coriolopsis gallica strain CLBE55 (BRFM 3473) showed the highest removal efficiency, with a 15% decrease in antibiogram zone of inhibition for Escherichia coli cultured in solid medium and 25% degradation of the antibiotic in liquid medium based on high-performance liquid chromatography (HPLC). Proteomic analysis suggested that laccases and dye-decolorizing peroxidases such as extracellular enzymes could be involved in levofloxacin degradation, with a putative major role for laccases. Degradation products were proposed based on mass spectrometry analysis, and annotation suggested that the main product of biotransformation of levofloxacin by Coriolopsis gallica is an N-oxidized derivative.

Biodegradation and biodetoxification of batik dye wastewater by laccase from Trametes hirsuta EDN 082 immobilised on light expanded clay aggregate

The biodegradation and biodetoxification of batik industrial wastewater by laccase enzyme immobilised on light expanded clay aggregate (LECA) were investigated. Laccase from Trametes hirsuta EDN 082 was covalently immobilised by modifying the LECA surface using (3-aminopropyl)trimethoxysilane and glutaraldehyde. The enzymatic characterisation of LECA-laccase showed promising results with an enzyme loading of 6.67 U/g and an immobilisation yield of 66.7% at the initial laccase activity of 10 U/g LECA. LECA-laccase successfully degraded batik industrial wastewater containing indigosol dye up to 98.2%. In addition, the decolorisation extent was more than 95.4% after four cycles. The phytotoxicity assessment of Vigna radiata and the microbial toxicity of two pathogenic bacteria, Bacillus subtilis and Pseudomonas aeruginosa, showed biodetoxification of treated batik dye wastewater. The characterisation using 3D light microscopy, scanning electron microscopy and Fourier transform infrared for LECA-laccase confirmed that laccase was successfully immobilised on LECA, and the decolorisation achieved through the combination of adsorption and enzymatic degradation. This study offers an environmentally friendly, effective and affordable LECA-laccase as a method for batik dye wastewater treatment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02806-8.