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Environmental and Ecological Approaches to Eliminate Fungal Contamination and Mycotoxin Production in Plant Products


The overall objective of this project is to develop commercially viable methods for the control of pathogens in tree nuts (almonds, pistachios and walnuts) and raisins which lead to foodborne illness in humans and animals. This includes both the control of fungal pathogens (mycotoxins) as well as bacterial pathogens such as E. coli and Salmonella. One approach will be the development of biocontrol agents using bacteria, yeast and non-toxigenic Aspergillus carbonarius. In addition, a better understanding of organic and conventional farming systems will provide new insights on mycotoxin control. The specific objectives for the period covered by this project plan are as follows:

Objective 1: Define the critical control points for pathogen contamination during the production stream. Place particular emphasis on agricultural water sources including dairy waste water. Using both cultural and non-cultural based methods we will identify the points in the developmental process, as well as the processing cycle where tree nuts are most likely to become contaminated with human pathogenic bacteria and mycotoxigenic fungi.

Objective 2: Evaluate the microbial ecology of organic v. conventional practices. Although several surveys have reported that consumers equate organically grown food stuffs with higher levels of food safety, little is known about how these practices affect the microbial population structure or mycotoxin levels in tree nuts. We will address the influence of phyllosphere microbial community on the population diversity of A. flavus in tree nut orchards, and A. carbonarius on grape surfaces in both farming systems.

Objective 3: Delineate the factors affecting cross-contamination during processing and develop a potential intervention strategy during storage. A number of experiments point to a strong possibility that cross-contamination of toxigenic fungi is possible during processing and storage, although no research appears to have been done on the transfer in actual (not laboratory) processing and storage conditions. Development of novel approaches to prevent the growth of storage fungi and production of harmful toxins is a high priority in the almond industry. Edible films and coatings (EFC) containing antimicrobial natural compounds will be tested for their efficiency to reduce mycotoxin in stored almonds.

Objective 4: Develop biological-control/intervention technologies using competitive or antagonistic microorganisms such as yeasts or bacteria that can be mass-produced and effectively utilized in a variety of pre- or post-harvest environments. Bacterial and yeast biocontrol agents will be tested in almond orchards and vineyards to control A. flavus and A. carbonarius, as well as human pathogenic bacteria, E. coli and Salmonella. EPA registration of the patented yeast, Pichia anomala will be pursued for commercial application. Methods to enhance the biocontrol efficacy will be developed.

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Approach: Develop mentods to control insect pests and toxic fungi of tree nuts. Insects include naval orangeworm, codling moth and peach twig borer. Feeding damage by these insects leads to infection by aflatoxigenic aspergilli. Control methods for insects are to be environmentally benign and employ semiochemicals to disrupt insect behavior. Control of toxic fungi focuses on biological control using competitive or antagonistic microorganisms. These microorganisms include either yeasts or bacteria that can be mass-produced and effectively utilized in a variety of pre- or post harvest environments. Replacing 5325-42000-036-00D (1/11).
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Campbell, Bruce
Haff, Ronald
Hua, Sui
McGarvey, Jeffery
Palumbo, Jeffrey
Project Reports:
Published Journal Articles USDA ARS (NP 108):
Bacterial population structure and dynamics during the development of almond drupes
McGarvey JA, Connell JH, Stanker LH, Hnasko R .
J Appl Microbiol. 2014 Jun;116(6):1543-52.
The major volatile compound 2-phenylethanol from the biocontrol yeast, Pichia anomala, inhibits growth and expression of aflatoxin biosynthetic genes of Aspergillus flavus
Hua SS, Beck JJ, Sarreal SB, Gee W.
Mycotoxin Res. 2014 May;30(2):71-8.
Bacterial population dynamics during the ensiling of Medicago sativa (alfalfa) and subsequent exposure to air
McGarvey JA, Franco RB, Palumbo JD, Hnasko R, Stanker L, Mitloehner FM.
J Appl Microbiol. 2013 Jun;114(6):1661-70.
Distribution and mycotoxigenic potential of Aspergillus section Nigri species in naturally contaminated almonds
Palumbo JD, O'Keeffe TL.
J Food Prot. 2013 Apr;76(4):702-6.
Multiplex PCR analysis of fumonisin biosynthetic genes in fumonisin-nonproducing Aspergillus niger and A. awamori strains
Palumbo JD, O'Keeffe TL, Gorski L.
Mycologia. 2013 Mar;105(2):277-84.
Ethanol and Volatile Fatty Acid Production from Lignocellulose by Clostridium cellulolyticum
Williams K, Zheng Y, McGarvey J, Fan Z, Zhang R.
ISRN Biotech. 2013;2013:1-7.
Characterization of aflatoxigenic and non-aflatoxigenic Aspergillus flavus isolates from pistachio
Hua SS, McAlpin CE, Chang PK, Sarreal SB.
Mycotoxin Res. 2012 Feb;28(1):67-75.
Non-Journal Publications:
Liquid formulations sustaining the viability of a superior yeast strain Pichia anomala WRL-076 for mycotoxin control - (Abstract Only)
Hua, S.T., Hernlem, B.J., Yokoyama, W.H., Parfitt, D.E., Sarreal, S.L. 2012. Liquid formulations sustaining the viability of a superior yeast strain Pichia anomala WRL-076 for mycotoxin control. American Society for Microbiology General Meeting. [abstract].
High sensitive and throughput screening of Aflatoxin using MALDI-TOF-TOF-PSD-MS/MS - (Abstract Only)
Hua, S.T., Woo, N., Sultan, O., Fagerquist, C.K. 2012. High sensitive and throughput screening of Aflatoxin using MALDI-TOF-TOF-PSD-MS/MS. Meeting Abstract. [abstract].
Novel approach to inhibit the growth of Aspergilus flavus and aflatoxin production by essential oil edible film - (Abstract Only)
Accepted Publication (28-Feb-11)
Effects of oxygenated drinking water on gaseous emissions, rumen microorganisms and milk production in dairy cattle - (Abstract Only)
Accepted Publication (15-Feb-11)
The Effects of Sodium Bisulfate on the Bacterial Population Structure of Dairy Cow Waste - (Abstract Only)
Accepted Publication (11-Jan-11)
Food Safety Categories:
Food and Feed Handling and Processing
On-Farm Food Safety
Sanitation and Pathogen Control
Contaminants and Contamination
Farm-to-Table Categories:
On-farm food production
Food processing