- Unexpected Rye Seed Growth in a Lab Study of Mycoremediation of Contaminated Incinerator Ash
The pit-burner style municipal incinerator at the City of Powell River, British Columbia, was in use between 1972–1990s. During that time 28,200 m3 of ash laden with heavy metals and synthetic organics accumulated on the site. Lead, copper, zinc, barium, polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCBs), polychlorinated dibenzenodioxins (dioxins), and polychlorinated dibenzenofurans (furans) were identified as components of the ash waste (Pottinger Gaherty Environmental Consultants Ltd. 1996). The Powell River Botanical Society is investigating the possibility of converting the site into a botanical garden. For this to occur the contaminants on this site must be either broken down, stabilized, or removed. Helianthus annuus (sunflowers) and Alnus rubra (red alder) are being considered for ecological restoration at the Powell River site (Adesodun et al. 2010, Akhtar 2013, Callender et al. 2016). Mycoremediation can provide a promising alternative to costly removal of the ash. The fungi can directly remove or neutralize the toxins, or through symbiosis they can indirectly assist plants to do the same. Wood-decomposing fungi are effective in remediation by increasing soil acidity and increasing the solubility of inorganic metal compounds by producing oxalic acid (Kartal et al. 2004). Many other fungi can directly remediate contaminated sites through their ability to store, concentrate, and detoxify heavy metals (Brandl et al. 2001, Humar et al. 2004, Stamets 2005).
Mycorrhizal fungi also work indirectly by contributing to phytoremediation. A number of studies have explored the use of mycorrhizal fungi in association with other plant species for ecological restoration (Khan 2003, Singh 2006, Turnau et al. 2006). Plants offer a nonintrusive alternative approach to complement engineering-based remediation [End Page 19] methods (Pilon-Smits 2005, Salt et al. 1998, Weyens et al. 2009). The symbiotic mycorrhizal fungi can help plants to grow on toxic sites (Kramer 2010).
Click for larger view
View full resolution
We prepared a mixture of incinerator ash, mycorrhizal fungi, sterilized wood chips, and sterilized seeds of Secale cereale (rye) as a growth medium for an experiment to compare the efficacy of different mycorrhizal treatments to support the growth of sunflowers and/or red alder for ecological restoration at the Powell River incinerator site. However, some of the S. cereale seeds survived the sterilization process and unexpectedly grew in the growth medium in three of the four mycorrhizal treatments, and we are reporting these surprising results in this article.
Pleurotus cystidiosus, Schizophyllum commune strain 9034, Schizophyllum commune strain 6328, and Phlebiopsis gigantea were chosen for this study (Arun et al. 2014 for Schizophyllum, Bhattacharya et al. 2014 for Pleurotus, Steffen 2003, and Valentín et al. 2013 for Phlebiopsis [Table 1]). Pleurotus cystidiosus is an oyster mushroom commonly used in mycoremediation, S. commune-9034 and S. commune-6328 are two strains of split gill mushroom, and P. gigantea is a saprotrophic fungus used as a biocontrol agent against root rot in conifers and is considered to be the most widely distributed fungus in nature.
These four strains of fungi were cultured in the lab of Dr. William Hintz, professor of fungal genetics and molecular biology at the University of Victoria. They were grown on a Potato Dextrose Agar (PDA) medium. The fungi were obtained from the University of Alberta’s Microfungus Collection and Herbarium through the Faculty of Agricultural, Life & Environmental Sciences (available through secure.devonian.ualberta.ca/uamh/searchcatalogue.php).
The fungi arrived as spores and were initially cultured on regular Trypticase Soy Agar (TSA) plates and then transferred to Potato Dextrose Agar (PDA). Twenty 1 mm × 1 mm cubes (four strains of fungi, five replicates of each) were cut from the agar and transferred to liquid cultures of 100 mL of TSA medium and grown for five days to create working cultures. Working cultures were inoculated onto sterilized S. cereale seed spawn in Erlenmeyer flasks. The spawn was the medium in which the mycelium was grown in preparation for inoculating...