Factors controlling the rate of perfluorooctanoic acid degradation in laccase-mediator systems: The impact of metal ions

Abstract

This study investigated the factors that regulated the degradation of perfluorooctanoic acid (PFOA) in laccase-catalyzed oxidative humification reactions with 1hydroxybenzotriazole (HBT) as a mediator. The reaction rates were examined under conditions with key factors varied, including initial PFOA concentrations, laccase and HBT dosages, and the ionic contents of the reaction solutions. The PFOA degradation followed pseudo-first order kinetics, and the rate constants (k) were similar for the high (100 μmole L-1) and low (1.00 μmole L-1) initial PFOA concentrations, respectively at 0.0040 day-1 (r 2 = 0.98) and 0.0042 day-1 (r 2 = 0.86) under an optimum reaction condition tested in this study. The metal ions contained in the reaction solution appeared to have a strong impact on PFOA degradation. Differential UV-Vis spectrometry revealed that Cu 2+ can complex with PFOA, which plays an essential role to enable PFOA degradation, probably by bridging the negatively charged PFOA and laccase, so that the free radicals of HBT that are released from laccase can reach and react with PFOA. It was also found that Fe 3+ plays a similar role as Cu 2+ to enable PFOA degradation in the laccase-HBT reaction system. In contrast, Mg 2+ and Mn 2+ cannot complex with PFOA under the investigated conditions, and do not enable PFOA degradation in the laccase-HBT system. Fluoride and partially fluorinated compounds were detected as PFOA degradation products using ion chromatography and high resolution mass spectrometry. The structures of the products suggest the reaction pathways involving free-radical initiated decarboxylation, rearrangement, and cross-coupling. Capsule: The factors that regulate the degradation of perfluorooctanoic acid (PFOA) in laccase-catalyzed oxidative humification reactions are identified and elucidated.

Fungal biotransformation of 6:2 fluorotelomer alcohol

“…and Penicillium sp., respectively. (Desai & Nityanand, 2011) and may be able to transform PFOA (Luo et al, 2015;Luo et al, 2017). These previous reports and the ability of the six fungal isolates to tolerate high PFOA and PFOS concentrations suggest that these isolates may be able to transform fluorinated substances.…”

“…Although few studies have reported the biotransformation of organic pollutants by species in Lachnum sp. , one report demonstrated that Lachnum spartinae could produce laccase, an extracellular fungal enzyme known to biotransform many environmental pollutants (Desai & Nityanand, ) and may be able to transform PFOA (Luo et al., ; Luo et al., ). These previous reports and the ability of the six fungal isolates to tolerate high PFOA and PFOS concentrations suggest that these isolates may be able to transform fluorinated substances.…”

The Valorization of Biolignin from Esparto Grass (Stipa tenacissima L.) Produced by Green Process CIMV (Compagnie Industrielle de la Matière Végétale) for Fertilization of Algerian Degraded Soil: Impact on the Physicochemical and Biological Properties

“…The reactivity of laccase with biolignin is explained by the chemical structure of the latter, which resists degradation during the first stage at 30 days and degrades during the second stage at 120 days, as confirmed by Albrecht et al [31]. The biochemistry of laccase has a broad class of phenoloxidase in soils [60]. It is a multicopper, and it can oxidize organic and inorganic compounds besides biolignin, also with compounds that may be present (including mono-, di-, and polyphenols, aminophenols, methoxy phenols, etc.)…”

“…According to Sinsabaugh [60], the increase in laccase activity observed during the first stage is marked by the conditions pH: 7.39-7.62, ω%: 20-25, and T • C: 13-14, and in the second stage is marked by pH 7.80-7.62, ω% 9-11, and T • C 35-38. The values < 0.05.10 −2 IU/g reported by Fujii et al [33] for a forest soil (humid environment) are lower than those observed in our trial.…”

“…The dynamics of laccase activity (Figure 4C) a priori is interpreted by the variation in microbial biomasses under environmental conditions-temperature, pH, moisture, aeration concentration of organic matter, lignin and nitrogen content in the soil-that contribute positive (potential activity) or negative (low activity) feedback [60].…”