Fungi in Pentachlorophenol Adsorption and Degradation: Novel Bioremediation and Biotechnological Tools.

downloadAutore del lavoro candidato: Luciano Bosso

SINTESI CONTENENTE UNA BREVE DESCRIZIONE DEL LAVORO SVOLTO E DEI RISULTATI OTTENUTI: Pentachlorophenol (PCP) has been used worldwide as a wood preservative and pesticide. PCP toxicity and extensive use has placed it among the worst environmental pollutants, and therefore its microbiological degradation to develop bioremediation techniques has been intensively studied. The current study, part of a wider bioremediation project, is a longterm evaluation of the remediation ability of naturally selected microorganisms versus PCP in laboratoryscale experiments. The main aims of this thesis were: i) to define PCP sensitivity, adsorption and degradation of Byssochlamys nivea (Westling 1909), Scopulariopsis brumptii (Samson and Klopotek 1972) and Anthracophyllum discolor (Mont. Singer 1951) in m icrobiological culture media; ii) to test B. nivea and S. brumptii as antagonists against two Oomycetes: Phytophthora cinnamomi and Phytophthora cambivora; iii) to evaluate the response of an agricultural soil to PCP, with or without compost (biostimulation) and B. nivea and S. brumptii (bioaugmentation), in terms of effects of the contaminants on the main chemical, biochemical and biological soil properties. B. nivea and S. brumptii showed a good PCP tolerance (12.5 and 25 mg PCP L1) although hyphal size, biomass, patulin and spore production decreased for increasing concentrations of PCP. It was shown that these two fungi can completely deplete 12.5 and 25 mg PCP L-1 in a submerged culture after 28 days of incubation at 28 °C. Electrolyte Leakage Assays showed that the fungi have a good tolerance at 25 mg PCP1. B. nivea and S. brumptii were able to inhibit the growth of P. cinnamomi and P.cambivora on solid media and in liquid culture. Volatile organic compounds (VOCs) did not produce growth reduction of oomycetes strains. The PCP that was adsorbed by A. discolor pellets was >80% compared to pH values of 5 and 5.5, which were the two concentrations being analyzed. PCP adsorption significantly decreased in a medium of pH > 6.0. The Infrared Spectroscopy (FTIR) results showed that amides, alkanes, carboxylates, carboxyl and hydroxyl groups may possibly be important to the PCP adsorption for pellets of A. discolor. In microcosm soil experiment, the addition of PCP severely depressed some of the tested biochemical properties (i.e. microbial biomass, soil respiration, dehydrogenase activity and fluore scein diacetate hydrolysis) suggesting an inhibitory effect on microbial activity. The compost had a buffer effect against the PCP, limiting the decrease of soil biochemical activity vs. of the control. After 28 day of incubations the compost and the fungal strains reduced of 95% the extractable PCP. The natural fresh soil showed a good capacity of reduction of extractable PCP (88%). The main soil processes (i.e. microbial degradation, biostimulation by compost and sorption to organic matter) were likely occurred in the contaminated soil when was added PCP and are involved in PCP depletion. Our results indicate that B. nivea and S. brumptii have an interesting potential for bioremediation and biocontrol strategy. A. discolor may be used as a natural biosorbent for liquid solutions which are contaminated by PCP.