Saturday, 15 July 2006

Selection of Chilean Native Wood-Rot Fungi for Bioremediation of Allophanic Soil Contaminated with Chlorophenols.

Gonzalo R. Tortella, Rubilar Olga Margarita, Mora Maria de la Luz, and Diez Maria Cristina. Univ de La Frontera, Francisco Salazar 01145, Temuco, Chile

Possible environmental problems associated with the application of chlorinated organic compounds to soil are the contamination of ground and surface waters, toxicity to soil biota and plants, and entrance into the human food chain. Microbial mineralization probably represents the most important route for the detoxification of organic pollutants in soils. Chlorinated phenols, including pentachlorophenol (PCP), are susceptible to microbial attack and maybe used as carbon and energy sources (McAllister et al., 1996). The rate of biodegradation depends on biological and physicochemical factors, such as the type and number of microorganisms, soil pH, oxygen and nutrient availability, temperature conditions, and water availability (McAllister et al., 1996, Mannisto et al., 2001). White rot fungi, which grow on wood, secrete one or more of the three extracellular enzymes that are essential for the degradation of the lignin: Lignin Peroxidase (LiP), Manganese Peroxidase (MnP) and laccase. These enzymes, alone or in combination with other processes, can also mineralise lignin to inorganic, non-toxic end products. They are highly unspecific with respect to the range of their substrates. Therefore the ligninolytic enzymes produced by white rot fungi are capable of transforming or mineralising a wide range of organochlorides with structures similar to lignin, including chlorophenols. The aim of this work was to isolate native wood-rot fungi from forestry of the Southern Chile, and to evaluate its ligninolytic capacity. Native wood-rot fungi were isolated from forestry of the southwest of Chile (38 46` S and 72 38` W), to be evaluated for their enzyme activities and resistance to di, tetra and pentachlorophenols. The ligninolytic activity, detected through decolorization test using Poly R-478, showed that only 25% of the all strains demonstrated a high ligninolytic capacity. Peroxidasas, laccases, cellulases, xylanases and tyrosinases were qualitatively determined in the strains that presented ligninolytic activity, however peroxidases and laccases activity were observed in most of the strains. The presence of other enzymes, such as, tyrosinase was not detected. On the other hand, fungal resistance to chlorophenols was presented only in 2,4-diclorophenol (100% of the strains grew in 25 ppm and 64% in 50 ppm). In addition, only 14% of the strains evaluated grew in 2,4,6-trichlorophenol and 7% in pentaclorophenol. It is concluded, that the qualitative technique used in this study, allowed the selection of a high percentage of wood-rot fungi with enzymatic activity, mainly (peroxidasas and laccases). However these strains did not presented resistance to tri and pentachlorophenols. References: (i)McAllister, K., Lee, H. and Trevors, J.T., 1996. Microbial degradation of pentachlorophenol. Biodegradation 7, 1-40. (ii)Mannisto, M.K., salkinoja-Salonen, M.S. and Puhakka, J.A., 2001. In situ polychlorophenol bioremediation potential of the indigenous bacterial community of boreal groundwater. Wat. Res. 35(10): 2496-2504. Acknowledgements: Supported by FONDECYT 1050614 projects.

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