Theses and Dissertations

Dongdi Sun

Issuing Body

Mississippi State University

Advisor

Mlsna, Todd, E.

Committee Member

Wipf, David O.

Committee Member

Zhang, Dongmao

Committee Member

Emerson, Joseph P.

Committee Member

Gwaltney, Steven R.

Date of Degree

5-9-2015

Document Type

Dissertation - Open Access

Major

Chemistry

Degree Name

Doctor of Philosophy

College

College of Arts and Sciences

Department

Department of Chemistry

Abstract

My research focuses on the development of a novel method for the fast detection of aflatoxin-producing fungi from the volatile organic compounds that they produce. Aflatoxins have received great attention because of their demonstrated potent carcinogenic effect in susceptible laboratory animals and their acute toxicological effects in humans. Traditional detection and quantification techniques are considered time-consuming, high cost, and require technical professionals. The `odor' or so called volatile metabolites released by a fungus is the key for fast detection. Several researchers have reported that diverse fungi species have unique volatile metabolite patterns. This study focuses on answering several questions: Is it possible to discriminate aflatoxins-producing fungi from other fungi based on volatile metabolites? What are the key discriminating biomarkers related to each fungus? Does the growth environment have an effect on the production of volatile metabolites? What chemicals are consistently emitted by a fungus under varied conditions? To answer these questions, one toxigenic and one nontoxigenic A. flavus isolate were studied to evaluate the microbial volatile organic compound (MVOC) profiles. The results described in chapter two of this dissertation indicate that MVOC production is time-dependent and that aflatoxigenic and non-aflatoxigenic strains have different MVOC expression patterns. Chapter three describes the effects of experimental parameters on fungal volatile metabolites. The identity and quantity of MVOCs can be affected by many factors including SPME fiber type, fungal growth media, and growth temperature. A CAR/PDMS coated fiber performed better than the other SPME fibers by collecting a larger variety and quantity of MVOCs. Fungi grown on the chemical defined liquid media produced much larger quantities of MVOCs compared to the other media. The highest MVOC production results were found at 30 degrees Celsius. The fungi discrimination study was extended in chapter four by including 3 toxigenic and 3 non-toxigenic isolates using multivariate analysis. The results indicate that volatile patterns vary even at the fungal isolate level and that discrimination of aflatoxin-producing fungi from non-toxigenic fungi is possible.

URI

https://hdl.handle.net/11668/20569

Comments

multivariate analysis||microbial volatile organic compounds||Aspergillus flavus

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