Valorizing fungal diversity for the degradation of fluoroquinolones.

Continued widespread use of antibiotics, especially fluoroquinolones, raises environmental concerns, as its driving bacterial resistance and disrupts microbial ecosystems. Here we investigate the biodegradation of ten fluoroquinolone antibiotics (six for medical use and four for veterinary use) by ligninolytic fungi, including Trametes versicolor, Bjerkandera adusta, Porosterum spadiceum, Irpex lacteus, Pleuroteus ostreatus, Phanerochaete chrysosporium, Pycnoporus cinnabarinus, Ganoderma lucidum, and Gloeophyllum trabeum. The results show significant variations between strains in the efficiency of antibiotic transformation. B. adusta and P. spadiceum were the fungi that most efficiently reduced antibiotic concentrations and were able to totally degrade eight and six antibiotics, respectively, within a 15-day period. T. versicolor and P. ostreatus also showed the ability to effectively degrade antibiotics. Specifically, T. versicolor degraded six out of the ten fluoroquinolone antibiotics by more than 70 %, while P. ostreatus degraded the tested antibiotics between 43 % and 100 %. The remaining antibiotic activity did not always correlate with a reduction in antibiotic concentrations, which points to the presence of post-transformation antimicrobial metabolites. This study also explores the potential mechanisms used by these fungi to remove selected models of fluroquinolones via enzymatic routes, such as oxidation by laccases, heme-peroxidases, and cytochrome P450, or via adsorption on fungal biomass.

Fungal Bioremediation of the ß-Lactam Antibiotic Ampicillin under Laccase-Induced Conditions.

Due to widespread overuse, pharmaceutical compounds, such as antibiotics, are becoming increasingly prevalent in greater concentrations in aquatic ecosystems. In this study, we investigated the capacity of the white-rot fungus, Coriolopsis gallica (a high-laccase-producing fungus), to biodegrade ampicillin under different cultivation conditions. The biodegradation of the antibiotic was confirmed using high-performance liquid chromatography, and its antibacterial activity was evaluated using the bacterial growth inhibition agar well diffusion method, with Escherichia coli as an ampicillin-sensitive test strain. C. gallica successfully eliminated ampicillin (50 mg L-1) after 6 days of incubation in a liquid medium. The best results were achieved with a 9-day-old fungal culture, which treated a high concentration (500 mg L-1) of ampicillin within 3 days. This higher antibiotic removal rate was concomitant with the maximum laccase production in the culture supernatant. Meanwhile, four consecutive doses of 500 mg L-1 of ampicillin were removed by the same fungal culture within 24 days. After that, the fungus failed to remove the antibiotic. The measurement of the ligninolytic enzyme activity showed that C. gallica laccase might participate in the bioremediation of ampicillin.

Optimized decolorization of two poly azo dyes Sirius Red and Sirius Blue using laccase-mediator system.

Factors, namely pH, laccase-like activity, dyes concentration as well as 1-Hydroxybenzotriazole (HBT) concentration was examined. The results indicated that the maximum decolorization yield and rate reached 98.30 ± 0.10% and 5.84 ± 0.01%/min, respectively for Sirius Blue, and 99.34 ± 0.47% and 5.85 ± 0.12%/min, respectively for Sirius Red after 4 h. The presence of the redox mediator 1-hydroxybenzotriazole (HBT) greatly improved the decolorization levels. The optimum concentrations of HBT, dyes, and laccase were 0.62 mM, 50 mg/L, and 0.89 U/mL respectively at pH 4.58 for both dyes. Phytotoxicity tests using treated and untreated dyes proved that the applied treatment slightly decreased the toxicity of the by-products. However, the germination index (GI) increased from 14.6 to 36.08% and from 31.6 to 36.96% for Sirius Red and Sirius Blue, respectively. The present study focused on the treatment of two recalcitrant azo dyes, namely: Sirius Blue (Direct Blue 71) and Sirius Red (Direct Red 80). The decolorization was performed using cell-free supernatant from Coriolopsis gallica culture with high laccase activity. Response surface methodology (RSM) and Box-Behnken design were applied to optimize the decolorization of the two tested dyes. The effect of four.

Biodegradation and toxicity reduction of nonylphenol, 4-tert-octylphenol and 2,4-dichlorophenol by the ascomycetous fungus Thielavia sp HJ22: Identification of fungal metabolites and proposal of a putative pathway.

Research on the biodegradation of emerging pollutants is gained great focus regarding their detrimental effects on the environment and humans. The objective of the present study was to evaluate the ability of the ascomycetes Thielavia sp HJ22 to remove the phenolic xenobiotics nonylphenol (NP), 4-tert-octylphenol (4-tert-OP) and 2,4-dichlorophenol (2,4-DCP). The strain showed efficient degradation of NP and 4-tert-OP with 95% and 100% removal within 8 h of incubation, respectively. A removal rate of 80% was observed with 2,4-DCP within the same time. Under experimental conditions, the degradation of the tested pollutants concomitantly increased with the laccase production and cytochrome P450 monooxygenases inhibition. This study showed the involvement of laccase in pollutants removal together with biosorption mechanisms. Additionally, results demonstrated the participation of cytochrome P450 monooxygenase in the elimination of 2,4-DCP. Liquid chromatography-mass spectrometry analysis revealed several intermediates, mainly hydroxylated and oxidized compounds with less harmful effects compared to the parent compounds. A decrease in the toxicity of the identified metabolites was observed using Aliivibrio fischeri as bioindicator. The metabolic pathways of degradation were proposed based on the identified metabolites. The results point out the potential of Thielavia strains in the degradation and detoxification of phenolic xenobiotics.

Removal of Acid Orange 51 by micro zero-valent iron under different operational conditions and evaluation of toxicity.

The removal of Acid Orange 51 (AO 51) dye in aqueous solution by microscale zero-valent iron (m-ZVI) was investigated. The m-ZVI powder was characterized granulometrically by laser particle sizer and morphologically by transmission electron microscopy (TEM). The effects of pH, m-ZVI concentration, H2O2 addition, and dye concentration on the decolorization of AO 51 were experimentally investigated. Results indicate that the removal efficiency is independent from pH values, increases with increasing ZVI dosage, and decreases with dye concentration. With 1 g/L of m-ZVI, AO 51 was effectively removed without and with addition of 25 mM H2O2, yielding a decolorization efficiency of around 70% and 98%, respectively, at pH 3 within 60 min of reaction time. The involvement of ˙OH in oxidizing AO 51 was examined by measuring the removal rates based on ˙OH scavenging molecule. Finally, the disappearance of AO 51 was estimated by monitoring the UV-Vis spectral evolution after 120 min of treatment while the Fourier-Transform Infrared spectroscopy (FT-IR) was performed to verify the occurrence of organic sorption on m-ZVI surface. The scanning electron microscope (SEM) images before and after the reaction illustrated morphological changes on m-ZVI surface. The detoxification of the treated solution was demonstrated using phytotoxicity test.

Prickly pear cactus cladodes powder of Opuntia ficus indica as a cost effective biosorbent for dyes removal from aqueous solutions.

The textiles manufacturing is one of the core industries that release a huge amount of dyes during the dyeing process. As a result, the growing demand of an efficient and low-cost treatment has given rise to alternative adsorbents. In the present study, prickly pear cactus cladodes powder (PPCP) of Opuntia ficus indica was investigated as an ecofriendly and low-cost biosorbent of Acid orange 51 (AO51) and Reactive Red 75 (RR75) dyes commonly used in dyeing. The FTIR spectroscopic characterization of PPCP showed the heterogeneity in surface structure and functional groups which confers to the biosorbent its capability to interact with acidic (AO51) and reactive (RR75) dyes molecules. Effects of pH, temperature, initial dye concentration and adsorbent dose on adsorption yield were investigated. The dyes uptake process was closely fitted to the pseudo-second order kinetic for both dyes. Experimental data were analyzed by applying the Langmuir, Freundlich, Dubinin-Raduskevich, Temkin, Redlich-Peterson, and BET isotherms equations. The models of BET and Langmuir were considered as the best isotherms models fitting experimental data, respectively, of RR75 and AO51. The maximum Langmuir monolayer biosorption capacities were of 198.9 and 45 mg g-1, respectively for RR75 and AO51.

A halotolerant laccase from Chaetomium strain isolated from desert soil and its ability for dye decolourization.

A novel fungal laccase produced by the ascomycete Chaetomium sp. isolated from arid soil was purified and characterized and its ability to remove dyes was determined. Extracellular laccase was purified 15-fold from the crude culture to homogeneity with an overall yield of 50% using ultrafiltration and anion-exchange chromatography. The purified enzyme was found to be a monomeric protein with a molecular mass of 68 kDa, estimated by SDS-PAGE, and with an isoelectric point of 5.5. The optimal temperature and pH value for laccase activity toward 2,6-DMP were 60 °C and 3.0, respectively. It was stable at temperatures below 50 °C and at alkaline conditions. Kinetic study showed that this laccase showed higher affinity on ABTS than on 2,6-DMP. Its activity was enhanced by the presence of several metal ions such as Mg2+, Ca2+ and Zn2+, while it was strongly inhibited by Fe2+, Ag+ and Hg2+. The novel laccase also showed high, remarkable sodium chloride tolerance. Its ability to decolorize different dyes, with or without HBT (1-hydroxy-benzotriazole), as redox mediator, suggests that this protein may be useful for different industrial applications and/or bioremediation processes.