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Abstract

Basidiocarps of Pycnoporus coccineus and P. sanguineus were collected from Kanchanaburi, Phetchaburi, and Mae Hong Son provinces in Thailand. Liquid culture of P. coccineus isolates provided higher laccase and manganese peroxidase activities than those of P. sanguineus. Lignin peroxidase activity was not detectable in any of the three Pycnoporus isolates. P. coccineus Thongkred 013 BCU, the best laccase producer among these isolates, was selected to optimize laccase production. The highest laccase yield (5.97 ± 0.40 U/ml) was obtained when grown at 28°C for 8 days in basal medium containing 2% (w/v) glucose and 0.25% (w/v) peptone at an initial pH of 5.0. The optimum conditions for stability and activity of the crude laccase enzyme were at pH 3.5 and room temperature (25 ± 2°C). FeSO4 (10 mM) and SDS (1% w/v) were both inhibitory to the laccase activity. When five different types of polycyclic aromatic hydrocarbons (PAHs) were individually added to liquid culture of P. coccineus at 100 ppm, the oxidation of anthracene, pyrene, and fluoranthene detected within 24 h were 59.7, 50.7, and 49.8%, respectively, whereas only 25.3% of benzo[a]pyrene and 32.4% of phenanthrene were oxidized. When P. coccineus crude laccase (1 U/ml) was used, these PAHs were more readily oxidized, with 76.4 and 74.3% of pyrene and anthracene, respectively, being oxidized within 2 h and 84.2% of fluoranthene oxidized within 24 h. Benzo[a]pyrene and phenanthrene oxidation by the enzyme were enhanced when 1 mM 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) was added as a mediator to the reaction mixture, resulting in 66.3 and 50.5% of the initial 100 ppm being oxidized after 24 h.

Biodegradation of polycyclic aromatic hydrocarbons commonly found in coal slurry using white rot fungi isolated from east kalimantan

“…Common screening reagents used are guaiacol, 2,2-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), syringaldazine and polymeric dyes like Remazol brilliant blue-R (RBB-R) (D'Souza et al, 1999;Kameshwar & Qin, 2017). The colorless guaiacol and ABTS are oxidized in the presence of phenol oxidases to form reddish-brown and green compounds, respectively (Afrida et al, 2009;Thongkred et al, 2011). In the presence of laccase, the pale yellow syringaldazine is oxidized to a purple-colored compound, whereas the blue RBB-R dye is decolorized by the combined action of peroxidases and hydrogen peroxide-producing oxidases (Ang et al, 2011).…”

“…The lignin modifying enzyme was screened using a petri dish as described by Kiiskinen et al (2004) and Thongkred et al (2011). The media was prepared with 0.2% (w/v) glucose solidified with 1.8% (w/v) agar and 2% (w/v) potato dextrose broth.…”

“…PAHs were quantified by high performance liquid chromatography (HPLC) using the suitable columns and conditions described previously by Thongkred et al (2011).…”

“…Previously, all of those genus were known to produce ABTS-oxidizing enzyme. Ganoderma can oxidize ABTS, whereas Coriolopsis, Pycnoporus, and Trametes have a stronger response to ABTS-oxidizing enzyme secretion (Dhouib et al, 2005;Thongkred et al, 2011;Wang et al, 2018). Therefore, the 4 isolates were selected for the next experiment.…”

“…When the concentration was increased to 100 ppm, there was less growth inhibition happened to both fluoranthene and pyrene to 4 isolates, since they were still able to grow more than 80%, while there was a strictly decrease of growth happened due to the addition of phenanthrene. Thongkred et al (2011) discovered that the growth of Pycnoporus coccineus Thongkred 013 BCU was depleted to only 22%, 20%, and 24.6% during a tolerance test with media containing 100 ppm (individual phenanthrene, fluoranthene, and pyrene), respectively. Meanwhile, Trametes polyzona RYNF13 was found to be tolerant to phenanthrene and pyrene when 4 mg/ml of each individual PAH in diethyl ether was sprayed on wood meal-based agar (WMBA) (Teerapatsakul et al, 2017).…”