Date of Submission

Spring 2013

Academic Program

Biology; Science, Technology and Society

Project Advisor 1

William Maple

Abstract/Artist's Statement

I investigated whether Aspergillus niger and Penicillium chrysogenum (formerly known as Penicillium notatum), two common species of Ascomycetes, were capable of breaking down di-2-ethylhexyl phthalate (DEHP), a frequently-used plasticizer, which builds up in the environment and can act as an endocrine disruptor when ingested by humans and animals. To test whether A. niger and P. chrysogenum were capable of metabolizing DEHP as a carbon source, I cultured both species on a glucose-free agar medium, containing only basic mineral salts and a minimal amount of agar, and on a glucose-enriched agar. Both glucose-free and glucose-enriched plates were subjected to one of three DEHP exposure treatments. In the first, I mixed DEHP directly into the growth media; in the second, I added the DEHP to the surface of the growth media after it had solidified; the third group was DEHP-free control. Overall, the presence of glucose was a far stronger predictor of colony vitality than the presence of DEHP; both species grew into larger and denser colonies on glucose-enriched plates. However, both species were able to grow and sporulate on plates where DEHP was the most abundant carbon source, suggesting that even if P. chrysogenum and A. niger are incapable of metabolizing DEHP, the presence of DEHP does not interfere with their ability to metabolize the polysaccharides in agarose. Additionally, the fungi exhibited different growth patterns in response to the two modes of DEHP exposure: fungi exposed to surface level DEHP tended to form numerous smaller, more dispersed colonies than fungi on the control plates. Fungi growing on DEHP/agar-mixed medium usually formed about the same number of colonies as control plates but the DEHP-exposed colonies tended to be somewhat denser and smaller in area. These results suggest that both A. niger and P. chrysogenum are both at least somewhat tolerant of DEHP, but it is unclear whether or not these species can metabolize DEHP.

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