“Micro-
organisms can help decontaminate sites like this one through
bioremediation.”
Bioremediation
We offer services to the bioremediation industry. For example, using a combination of respirometry and bioassays in conjunction with bacterial counts, we can identify factors that may cause the remediation process to progress at sub-optimal rates, or to completely stall. Our laboratory services and bench-scale tests are a cost-effective method to avoid problems in the field, or to overcome them (photo 1).
Our bioremediation research focuses on the use of fungi. Fungi are nature's best recyclers, having catabolic pathways for an extremely wide variety of organic materials. Lignin-degrading (white rot) fungi are of particular interest since they are the only organisms in nature that can efficiently degrade all the structural components of wood. Some of the same degradative systems have low substrate specificity, and can degrade man-made compounds that are of concern as pollutants. Interestingly, the same organisms that rot wood, are the best ones at degrading chemicals like pentachlorophenol (PCP) and creosote that humans use to preserve the wood.
Our interest in this area stemmed from observations of mushrooms of the white rot fungus
Trametes hirsuta on a preservative-treated railroad tie. When we cut the tie, it was evident the fungus had caused extensive decay, despite the preservatives. We noted that genetically different colonies of the fungus were growing on each side of a black reaction line
(indicated by arrow in photo 2, left) where they confronted each other. Pure cultures of these, and other strains were recovered from this and other pieces of preservative-treated wood..
When some of these isolates were tested using radiolabelled (14C) PCP and benzopyrene (the latter being a carcinogenic component of creosote), it was found they could rapidly degrade the compounds. The carbon from the PCP was recovered mainly as CO2. The benzopyrene was partly degraded into CO2, and partly into more oxidized compounds that could in turn be degraded by bacteria into CO2 .
The isolates were grown in suitable reactors and mushrooms were produced in culture (photo
3, right). Single spore isolates from these mushrooms were grown and crossed, giving new strains. When some of these were grown on nutrient agar onto which a crystal of PCP was placed, the hyphae actually grew towards the crystal, although they did not touch it (photo
4, below). Tests with 14C PCP showed they actively degraded the preservative.
We have continued working with T. hirsuta isolates and have developed methods for using this fungus to degrade wood preservatives in a variety of substrates. The normal habitat of
T. hirsuta is wood, but we found that if the water content of soil was maintained at the appropriate level, and suitable nutrients were added, the fungus would also grow and degrade pollutants in this substrate. In a 1995 publication (Boyle, C.D. Can. J. Microbiol. 41: 345-353) we presented a method that is very effective for removing the wood preservative pentachlophenol (PCP) from sawdust or soil.
Remediation companies who want to use our method to treat soil or wood should contact us. We also are looking for financial support for further research, possibly focused on the use of cyclodextrins as solubilizers to enhance biodegradation of non-polar organopollutants. Further information is available in some of our publications, or by
contacting us.
Some of our publications concerning bioremediation:
Boyle, C.D. 2002. Pentachlorophenol degradation by white-rot fungi: Balancing toxicity against degradation using pH. Soil Biol. Biochem. (Submitted).
Boyle, C.D. , Wiesner, C. and A. Richardson. 1998. Factors affecting the degradation of polyaromatic hydrocarbons in soil by white-rot fungi. Soil Biol. Biochem. 30:873-882.
Boyle, C.D. 1995. Development of a practical method for inducing white-rot fungi to grow into and degrade organopollutants in soil. Can. J. Microbiol. 41: 345-353.
Boyle, C. D. 1995. Bioremediation of polyaromatic hydrocarbon contaminated soils using white-rot fungi. 1995. Final Report for DESRT Program, Environment Canada, N.B. Dept. of Environment.
Boyle, C. D., S. Kamra and C. Wiesner. 1995. Inducing White rot fungi to grow in and degrade pollutants in non-sterilized soil. p.407-416 in: M. Moo-Young, W.A. Anderson and A.M. Chakrabarty (Eds). Environmental Biotechnology: Principles and Applications. Proceedings of the International Symposium on Environmental Biotechnology. July 4-8, 1994. Waterloo, Ontario. Kluwere Academic Publishers. the Netherlands.
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