Detoxification of azo dyes mediated by cell-free supernatant culture with manganese-dependent peroxidase activity: Effect of Mn2+ concentration and H2O2 dose

Spent substrate of Ganodorma lucidum as a new bio-adsorbent for adsorption of three typical dyes

Spent substrate of Ganodorma lucidum (SSGL), waste from cultivation of Ganoderma lucidum, was firstly used as a bio-adsorbent to adsorb three typical dyes malachite green, safranine T and methylene blue, and the adsorption thermodynamics and dynamics were also studied. SSGL was rich of hydroxyl group and carbonyl group, which had the potential to be an efficient bio-adsorbent for the three dyes removal from water and wastewater, and the treatment model should be eco-friendly. The experimental data fit well with the Langmuir and Freundlich isotherm, and the adsorption of dyes took place mainly on monolayer surface of SSGL. The experimental data fit also well with the adsorption thermodynamics, the adsorption were spontaneous and mainly a chemical adsorption. SSGL could adsorb the dyes rapidly and achieve an equilibrium in a short time, and the experimental data fit well with the second-order kinetics model.

Ferrocene-catalyzed heterogeneous Fenton-like degradation mechanisms and pathways of antibiotics under simulated sunlight: A case study of sulfamethoxazole

Readily-available and efficient catalyst is essential for activating oxidants to produce reactive species for deeply remediating water bodies contaminated by antibiotics. In this study, Ferrocene (Fc) was introduced to establish a heterogeneous photo-Fenton system for the degradation of sulfonamide antibiotics, taking sulfamethoxazole as a representative. Results showed that the removal of sulfamethoxazole was effective in Fc-catalyzed photo-Fenton system. Electron spin resonance and radical scavenging experiments verified that there was a photoindued electron transfer process from Fc to H₂O₂ and dissolved oxygen resulting in the formation of OH that was primarily responsible for the degradation of sulfamethoxazole. The reactions of OH with substructure model compounds of sulfamethoxazole unveiled that aniline moiety was the preferable reaction site of sulfamethoxazole, which was verified by the formation of hydroxylated product and the dimer of sulfamethoxazole in Fc-catalyzed photo-Fenton system. This heterogeneous photo-Fenton system displayed an effective degradation efficiency even in a complex water matrices, and Fc represented a long-term stability by using the catalyst for multiple cycles. These results demonstrate that Fc-catalyzed photo-Fenton oxidation may be an efficient approach for remediation of wastewater containing antibiotics.

Multiwalled carbon nanotube-supported CuCo2S4 as a heterogeneous Fenton-like catalyst with enhanced performance

CuCo₂S₄/MWCNTs, an enhanced Fenton-like catalyst, exhibited a high catalytic rate, broad pH tolerance and good reusability.

Degradation and detoxification of the triphenylmethane dye malachite green catalyzed by crude manganese peroxidase from Irpex lacteus F17

Malachite green (MG), a recalcitrant, carcinogenic, and mutagenic triphenylmethane dye, was decolorized and detoxified using crude manganese peroxidase (MnP) prepared from the white rot fungus Irpex lacteus F17. In this study, the key factors (pH, temperature, MG, Mn(2+), H2O2, MnP) in these processes were investigated. Under optimal conditions, 96 % of 200 mg L(-1) of MG was decolorized when 66.32 U L(-1) of MnP was added for 1 h. The K m, V max, and k cat values were 109.9 μmol L(-1), 152.8 μmol L(-1) min(-1), and 44.5 s(-1), respectively. The decolorization of MG by MnP followed first-order reaction kinetics with a kinetic rate constant of 0.0129 h(-1). UV-vis and UPLC analysis revealed degradation of MG. Furthermore, seven different intermediates formed during the MnP treatment of 0.5 h were identified by LC-TOF-MS. These degradation products were generated via two different routes by either N-demethylation of MG or the oxidative cleavage of the C-C double bond in MG. Based on ecotoxicity analyses performed on bacteria and algae, it was confirmed that MG metabolites produced by the MnP-catalyzed system were appreciably less toxic than the parent compound. These studies indicate the potential use of this enzyme system in the clean-up of aquatic and terrestrial environments.

Characteristic features and dye degrading capability of agar-agar gel immobilized manganese peroxidase

Immobilization of enzymes has been regarded as an efficient approach to develop biocatalyst with improved activity and stability characteristics under reaction conditions. In the present study, purified manganese peroxidase (MnP) from Ganoderma lucidum IBL-05 was immobilized in agar-agar support using entrapment technique. Maximum immobilization yield was accomplished at 4.0% agar-agar gel. The immobilized MnP exhibited better resistance to changes in pH and temperature than the free enzyme, with optimal conditions being pH 6.0 and 50 °C. The kinetic parameters Km and Kcat/Km for free and entrapped MnP were calculated to be 65.6 mM and 6.99 M(-1) s(-1), and 82 mM and 8.15 M(-1) s(-1), respectively. Thermo-stability was significantly improved after immobilization. After 120 h, the insolubilized MnP retained its activity up to 71.9% and 60.3% at 30 °C and 40 °C, respectively. It showed activity until 10th cycle and retained 74.3% residual activity after 3th cycle. The effects of H2O2, ionic strength and potential inhibitors on activity of free and immobilized enzyme were investigated. Moreover, the decolorization of three structurally different dyes was monitored in order to assess the degrading capability of the entrapped MnP. The decolorization efficiencies for all the tested dyes were 78.6-84.7% after 12h. The studies concluded that the toxicity of dyes aqueous solutions was significantly reduced after treatment. The remarkable catalytic, thermo-stability and re-cycling features of the agar-agar immobilized MnP display a high potential for biotechnological applications.

Production of versatile peroxidase from Pleurotus eryngii by solid-state fermentation using agricultural residues and evaluation of its catalytic properties

Interest in production of ligninolytic enzymes has been growing over recent years for their use in various applications such as recalcitrant pollutants bioremediation; specifically, versatile peroxidase (VP) presents a great potential due to its catalytic versatility. The proper selection of the fermentation mode and the culture medium should be an imperative to ensure a successful production by an economic and available medium that favors the process viability. VP was produced by solid-state fermentation (SSF) of Pleurotus eryngii, using the agricultural residue banana peel as growth medium; an enzymatic activity of 10,800 U L(-1) (36 U g(-1) of substrate) was detected after 18 days, whereas only 1800 U L(-1) was reached by conventional submerged fermentation (SF) with glucose-based medium. The kinetic parameters were determined by evaluating the H2O2 and Mn(2+) concentration effects on the Mn(3+)-tartrate complex formation. The results indicated that although the H2O2 inhibitory effect was observed for the enzyme produced by both media, the reaction rates for VP obtained by SSF were less impacted. This outcome suggests the presence of substances released from banana peel during the fermentation, which might exhibit a protective effect resulting in an improved kinetic behavior of the enzyme.

Induction, purification and characterization of a novel manganese peroxidase from Irpex lacteus CD2 and its application in the decolorization of different types of dye

Manganese peroxidase (MnP) is the one of the important ligninolytic enzymes produced by lignin-degrading fungi which has the great application value in the field of environmental biotechnology. Searching for new MnP with stronger tolerance to metal ions and organic solvents is important for the maximization of potential of MnP in the biodegradation of recalcitrant xenobiotics. In this study, it was found that oxalic acid, veratryl alcohol and 2,6-Dimehoxyphenol could stimulate the synthesis of MnP in the white-rot fungus Irpex lacteus CD2. A novel manganese peroxidase named as CD2-MnP was purified and characterized from this fungus. CD2-MnP had a strong capability for tolerating different metal ions such as Ca2+, Cd2+, Co2+, Mg2+, Ni2+ and Zn2+ as well as organic solvents such as methanol, ethanol, DMSO, ethylene glycol, isopropyl alcohol, butanediol and glycerin. The different types of dyes including the azo dye (Remazol Brilliant Violet 5R, Direct Red 5B), anthraquinone dye (Remazol Brilliant Blue R), indigo dye (Indigo Carmine) and triphenylmethane dye (Methyl Green) as well as simulated textile wastewater could be efficiently decolorized by CD2-MnP. CD2-MnP also had a strong ability of decolorizing different dyes with the coexistence of metal ions and organic solvents. In summary, CD2-MnP from Irpex lacteus CD2 could effectively degrade a broad range of synthetic dyes and exhibit a great potential for environmental biotechnology.