PRACTICAL APPLICATION OF BIOCONTROL YEAST
Foodborne Toxin Detection and Prevention
2011 Annual Report
1a.Objectives (from AD-416)
1. To explore improvements to formulation of biocontrol yeast for field application by growers. Types of formulations are wet formulations with additives (preservatives, nutritional supplements, surfactants for spreading) and dry formulations for delivery of viable yeast as a dry powder for tank mixing. 2. Evaluation of yeast longevity under different storage and application conditions: time and temperature. 3. Application for controlling l of other microbial pathogens: plant pathogenic fungi, microbial contaminants of crops (Salmonella, E. Coli)
1b.Approach (from AD-416)
Objective 1. Protective additives will be added to wet and dry yeast formulations and evaluated for improved shelf-life under lab conditions. Spray trials in the field may be used to evaluate effects on durability on plant leaves and fruits. Surfactants will be in the tank mix for even spreading. Objective 2. Yeast durability in a fully diluted mixture will be evaluated through time and temperatures series in lab so the upper threshold that might be expected under grower conditions. Objective 3. Ability to control fungi on agricultural crops. evaluations will be done using greenhouse tests on plants and pathogens of significance in tree fruit-nut and vegetable crops. Salmonella is a particular problem on almond. Initial experiments may involve field sprays on almond followed by collection of nuts and inoculation with Salmonella in lab-greenhouse and monitor Salmonella population Non-pathogenic E. Coli strains applied to lettuce and spinach in the greenhouse followed by yeast spray applications to determine whether potential control is possible. The effectiveness of the yeast against additional fungi of agricultural importance will initially be evaluated on tomato and potato.
Saprophytic yeast, Pichia anomala has been demonstrated to inhibit the growth of Aspergillus flavus as well as aflatoxin production by this fungus. A stable liquid formulation is highly desirable because most of the biocontrol yeast products are dispersed in water and delivered by spraying or dipping to the agricultural and horticultural crops. A wet formulation has been developed. By adding certain compounds, the formulation of yeast cells can be stored at 40C for up to fourteen months with very little change in viability. The results were validated by flow cytometry analysis and fluorescent microscopy using viability stains. Pichia anomala was tested as a biocontrol agent to reduce the growth of A. flavus on almond fruits. A bioassay is being developed to screen compounds which can enhance the efficacy of yeast cells. The ADODR monitored this project through site visits, emails and phone calls. The goal of the specific cooperative agreement is to develop practical applications of P. anomla to control pathogenic fungi and bacteria, which contributes directly to Objective 4 of the in-house project.