Fungal enzyme production and biodegradation of polychlorinated dibenzo-p-dioxins and dibenzofurans in contaminated sawmill soil

Abstract

Soils that are contaminated with the most recalcitrant organic contaminants, such as high molecular weight polyaromatic hydrocarbons (HMW PAH) and polychlorinated dibenzo-pdioxins and dibenzofurans (PCDD/F), cannot be degraded efficiently by conventional composting. The only available treatment method for these soils, which destroys the contaminants, is combustion at high temperature. This thesis examines three alternative fungal methods to treat these soils: 1) treatment with fungal enzymes, 2) treatment with fungal inoculum, and 3) fungal treatment used as a pre-treatment to improve the energy efficacy in combustion. Manganese peroxidase (MnP), which belongs to lignin-modifying enzymes (LME), was produced and used to treat PCDD/F-contaminated soil in the laboratory scale. Nevertheless, no degradation with a MnP preparation was observed, although a substantial amount of MnP activity was found in the soil still after 10 days of incubation. Both PAH-and PCDD/Fcontaminated soils were treated with fungal inoculum in the laboratory scale. HMW PAHs were degraded significantly more by the fungi than by the indigenous microbes alone in the laboratory experiments, where the PAH concentration of soil was 3500 mg kg -1 (sum of 16 PAH). Treatment with Phanerochaete velutina (inoculum) resulted to degradation of 96 % of 4-ring PAHs and 39 % of 5-and 6-ring PAHs in three months. With PCDD/F-contaminated soil, no degradation was observed in the control, but the degradation of PCDD/Fs with fungal treatments was significant (P. velutina: 62 %, Stropharia rugosoannulata: 64 % of WHO-TEQ value). Fungal treatment of PAH-contaminated soil was also applied in the field scale (2 t). However, both P. velutina (inoculum) and control treatment resulted in equal degradation in soil with lower PAH concentration (1400 mg kg -1 , sum of 16 PAH): 94 % of the 16 PAHs were degraded in three months. Fungal treatment was even applied as a pre-treatment for contaminated soil with high organic matter content, and which will be later combusted. In the pilot-scale (300 kg), 13 % degradation of the original organic matter content was obtained in 6 months. To conclude, fungal treatment is reasonable to apply for soils with organic contaminants that cannot be bioremediated by composting. With soils contaminated by chlorinated dioxins, this is always the case, but also PAH-contaminated soils with high total concentration or high proportion of HMW-PAHs. In addition, with fungal treatment the amount of organic matter in the soil can be reduced and the efficacy of the combustion process is improved. Tiivistelmä Kaikkein vaikeimmin hajoavilla orgaanisilla yhdisteillä kuten monirenkaisilla polyaromaattisilla hiilivedyillä (PAH) sekä polyklooratuilla dibenzo-p-dioksiineilla ja -furaaneilla (PCDD/F) pilaantuneita maita ei pystytä tehokkaasti kunnostamaan perinteisellä kompostoinnilla. Ainoa käytössä oleva puhdistusmenetelmä, joka hajottaa pilaavat yhdisteet, on maan poltto korkeassa lämpötilassa. Tämä väitöskirja esittelee kolme vaihtoehtoista valkolah...

Transcriptomic Profile of Lignocellulose Degradation from Trametes versicolor on Poplar Wood

“…This suggested that growth on poplar wood significantly altered T. versicolor's expression of enzymes that hydrolyze methyl and benzoic acid groups. Catechol and benzoate were important products in lignin degradation (Aranda et al 2010;Sari et al2012;Cruz-Morató et al 2013;Anasonye et al 2014), but were also produced during aminobenzoate degradation. From these results it was inferred that lignin degradation may have been related to aminobenzoate degradation or have similar intermediate compounds.…”

Degradation of Pharmaceuticals and Personal Care Products by White-Rot Fungi—a Critical Review

“…Extracellular enzymes of white-rot fungi (WRF) are characterized by their capacity to degrade the complex structure of lignin, which also enables them to degrade a wide range of resistant pollutants including synthetic dyes, chlorophenols, polychlorinated biphenyls and polycyclic aromatic hydrocarbons [18,19,20,21,22,23]. WRF and their lignin modifying enzymes (LMEs) have been investigated recently for the degradation of a broad spectrum of PPCPs [24,25,26,27].…”

Exposure of Aspergillus flavus NRRL 3357 to the Environmental Toxin, 2,3,7,8-Tetrachlorinated Dibenzo-p-Dioxin, Results in a Hyper Aflatoxicogenic Phenotype: A Possible Role for Caleosin/Peroxygenase (AfPXG)

“…Such pollutants, namely polychlorinated dibenzo- p -dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), are considered the most toxic group of Persistent Organic Pollutants (POPs) (WHO, 2016). Due to their physicochemical properties, dioxins can persist in the environment and bioaccumulate in the organisms of a given ecosystem, including bacteria, fungi, plants, animals, and humans (Field and Sierra-Alvarez, 2008; Ishida et al, 2010; Anasonye et al, 2014; Hanano et al, 2014b).…”