Comparative biotransformation of pentachlorophenol in soils by solid substrate cultures of Lentinula edodes

Abstract

Sterilised and non-sterilised soils contaminated with pentachlorophenol (PCP) were inoculated with solid substrate cultures of Lentinula edodes LE2 ("shiitake" mushroom) to simulate monoculture bioremediation treatments and treatments in which the fungus competes with natural microflora. With monocultures of L. edodes, rates of PCP depletion were rapid for the initial 4 weeks and, although thereafter the rate decreased, 99% biotransformation was obtained in 10 weeks. In mixed culture, PCP biotransformation by L. edodes was markedly slower and only 42% of the PCP was depleted after 10 weeks. Maximal rates of PCP transformation, biomass (ergosterol) accumulation and oxidative enzymes (phenol oxidase and manganese-peroxidase) production were observed after 2 weeks of incubation. In monocultures, phenol oxidase activity was 195.5 U g-1 and Mn-peroxidase 138.4 U g-1. In mixed cultures, fungal enzyme activities were markedly lower: 70.33 U g-1 for phenol oxidase and 85.0 g-1 for Mn-peroxidase. Analyses of soil metabolites after 10 weeks revealed that monocultures of L. edodes had eliminated both PCP and pentachloroanisole. Pentachloroanisole, however, was detected in soils with the mixed microflora. Both dechlorination and mineralisation of the xenobiotic compound were effected by L. edodes LE2.

Physiological Characterization of Fungal Inoculum for Biotechnological Remediation of Soils

“…The results suggested the relevance of the enzymatic levels, especially for the peroxidases present in the inoculum soon after its inoculation in the soil on the quality of the inoculum to be employed. The capacity of basidiomycetes to degrade chlorophenols, including pentachlorophenol as already reported in literature (Okeke et al 1997;Ullah et al 2000;Seradati et al 2003;Machado et al 2005a;Soares et al 2011) was proved here. There are difficulties to use the concentrations above 200 mg kg -1 pentachlorophenol, given the basidiomycetes' sensibility to the pollutant (Leontievsky et al 2001;Ahn et al 2002;Walter et al 2004).…”

Microbial degradation of chlorinated phenols

“…In a similar field study, P. sordida, Phanerochaete chrysosporium and Trametes hirsuta removed 89, 72 and 55% of PCP from a soil contaminated with 672 mg PCP kg -1 soil (Lamar et al 1993). Degradation of PCP was evaluated with the white-rot fungus, Lentinula edodes, in sterile and non-sterile soils (Okeke et al 1997). In a 10 week long experiment, 99 and 42% elimination of PCP was observed with L. edodes inoculated into sterile and non-sterile soil.…”

“…Pentachloroanisole formation from PCP metabolism is well established (Lamar and Dietrich 1990;Okeke et al 1997;Tuomela et al 1999;Chung et al 2001). Also the conversion of 3,4-and 2,4-dichlorophenols to their respective anisoles has been reported (Coulter et al 1993;Deschler et al 1998).…”

Biological removal of phenol from wastewaters: a mini review

“…Stanisavljevic and Nedic (2004) reported a process for phenol removal comprising a reaction step in which phenol was polymerized in the presence of an enzyme HRP. Experimental results showed the potential of the proposed Gurujeyalakshmi and Oriel (1989) Polyphenol oxidase Mushroom Burton et al (1993) Polyphenol oxidase Trametes trogii Garzillo et al (1998) Polyphenol oxidase Transgenic tomato Steffens and Li (2002) Polyphenol oxidase Potato Loncar et al (2011) Phenol oxidase Lentinula edodes LE2 Okeke et al (1997) Catechol 2,3 dioxygenase…”