Using Protective Cultures to Control Listeria monocytogenes in Microbiomes from Small-Scale Dairy Production Facilities

Project Overview

Project Type: Graduate Student
Funds awarded in 2019: $14,940.00
Projected End Date: 09/30/2022
Grant Recipient: The Pennsylvania State University
Region: Northeast
State: Pennsylvania
Graduate Student:
Faculty Advisor:
Jasna Kovac
The Pennsylvania State University

Information Products

Biofilms in the Dairy Industry (Article/Newsletter/Blog)
Listeria in the Dairy Industry (Article/Newsletter/Blog)


  • Animal Products: dairy


  • Animal Production: dairy food products safety
  • Education and Training: extension
  • Pest Management: biological control, sanitation

    Proposal abstract:

    One of the most important aspects of agricultural sustainability is the production of safe and wholesome food. According to the Center for Dairy Excellence, Pennsylvania produces over 15% of the total milk supply in the U.S. and 99% of Pennsylvania dairy farms are family owned. Many of them are small farms that process the milk they produce in order to add value to the product. Previous research from Penn State indicates that small-scale dairy processors face food safety challenges that can compromise their businesses, particularly as scrutiny by food safety regulators increases. One of the main microbiological food safety hazards associated with the dairy supply chain is Listeria monocytogenes (Lm). Lm is a pathogenic bacterium frequently linked with outbreaks related to dairy foods, including soft cheese, ice cream, and raw milk. While Lm is typically susceptible to the cleaning and sanitizing regimens, it is challenging to eradicate from processing environment when it becomes a member of the biofilms formed by the facility microbiota. Once Lm establishes itself in a biofilm, it is less susceptible to sanitizers and can contaminate ready-to-eat food products over extended periods of time. Here, I propose to investigate the feasibility of a novel Lm biocontrol strategy using protective bacterial cultures to inhibit the growth of Lm in small-scale dairy processing facility microbiomes. I will share my results with stakeholders by developing extension fact sheets for farmstead dairy processors and by presenting my research on Penn State extension events.

    Project objectives from proposal:

    Objective 1: Characterization of small-scale dairy processing facility microbiomes.

    -Expected outcome: Characterization of environmental microbiomes collected from small-scale dairy processing environments.

    -Deliverables: Microbiome sequences made publicly available; table with relative abundances of bacteria and results of statistical analyses of microbial diversity.

    -Potential pitfalls and alternative approaches: I have learned microbiome characterization methods while assisting with a project in apple-packing facilities. Dairy processing environments will likely contain less soil, but more fat compared to apple facility samples, which may act as PCR inhibitors. If this occurs, I will further optimize PCR conditions and test different master mixes that are less susceptible to the inhibitors.

    Objective 2: Measure the ability of protective cultures to effectively colonize small-scale dairy environment microbiome biofilms.

    -Expected outcome: Protective cultures will colonize the dairy processing environment microbiome biofilms and remain in high concentration in a microbiome biofilm within a week period.

    -Deliverable: Spreadsheet with quantification results of protective cultures in biofilms of small-scale dairy facility microbiomes.

    -Potential pitfalls and alternative approaches: If the cultures selected do not show the ability to effectively colonize the environmental biofilm, other lactic acid bacteria will be tested. We will also attempt to isolate other bacteria from small-scale environment microbiomes, since native strains will more likely be able to survive and remain active in similar environments.

    Objective 3: Test the efficacy of protective cultures against Listeria monocytogenes within an in vitro grown dairy environment microbiome biofilm.

    -Expected outcome: Protective cultures will be able to inhibit the survival and growth of Lm in dairy processing facility microbiome biofilms.

    -Deliverables: Spreadsheet with log10MPN reduction of Lm in facility microbiome biofilms after adding protective cultures.

    -Potential pitfalls and alternative approaches: If the selected tested cultures do not show the ability to effectively colonize the environmental biofilm, we will test other lactic acid bacteria, including those isolated from sampled small-scale dairy processing environments.

    Objective 4: Development of educational materials for dissemination of results among stakeholders.

    -Expected outcomes: Educational video covering cleaning and sanitation practices for control of Lm and fact sheets will be developed and disseminated among stakeholders through Penn State Extension workshops.

    -Deliverables: Educational video, fact sheets and workshop lectures.

    -Potential pitfalls and alternative approaches: If the proposed biocontrol strategy does not show promising results, we will still share information on good hygiene and sanitation practices with shareholders, as this can help them improve safety of their food products.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.