Location: Microbial and Chemical Food Safety
2022 Annual Report
Objectives
Objective 1: To mitigate issues with bacterial pathogen-contaminated irrigation waters, examine the use of biochar as an antimicrobial and filtration intervention, for example, combining biochar filtration with ARS pre-existing zero-valent water filtration technology.
Objective 2: Examine the use of adding biochar to compost piles, in order to inactivate pathogens in the compost, but especially the problematic “toes” of manure piles.
Approach
The approach of project will follow two objectives. The first objective will evaluate the ability of biochar filters to remove pathogenic bacteria from surface irrigation waters with or without zero valent iron and sand-composite filtration. Biochar pyrolysis will be optimized for this purpose by altering the residence time, temperature and biofeedstock with an in-house biochar slow-pyrolysis reactor. The optimized water filtration units will then be scaled up to reduce pathogens in irrigation water, lowering the risk of foodborne illness from irrigated fresh produce. Second, pyrolysis will be further optimized for maximal antimicrobial efficacy of biochar. This biochar will then be utilized in lab-scale and field-trial dairy and poultry compost experiments with the goal of more rapidly inactivating EHEC and Salmonella. Successful results will allow for shorter composting times prior to field application, which will decrease the chances for pathogenic bacteria to survive the process and contaminate field crops. Stakeholders will be consulted and collaborated with for all objectives, and technology will be transferred to the appropriate entities. Overall, the results and outcomes from this project plan will increase the safety of fresh fruits and vegetables and lower the burden of human-related illnesses caused by foodborne pathogens by providing practical intervention solutions for farmers, packers, processors and distributers of fresh produce, related to foodborne pathogens.
Progress Report
This is the first report for project 8072-41420-022-000D, which began Jan. 5, 2021, entitled “Mitigation of Foodborne Pathogens in Water and Fresh Produce via Application of Biochar.” Surface waters used for irrigating fruit and vegetable crops sometimes become contaminated with pathogens such as enterohemorrhagic Escherichia coli (EHEC) and Salmonella, which has led to foodborne outbreaks in recent years. Pathogens can also be transferred to produce in fields via composted dairy and poultry manures. Previous studies have shown that biochar may be an effective matrix for filtering pathogen-contaminated water as well as inactivating foodborne pathogens in agricultural compost. Under Objective 1, we made significant progress to understand the optimal temperatures necessary to produce antimicrobial biochar, which would have utility in inactivating foodborne bacterial pathogens. In our studies, we tested biochars slow-pyrolyzed at various times (30 min., 1 h, 2 h) and pyrolysis temperatures (300, 350, 400, 450, 500, 600 and 700 degrees Celsius) against a two-strain composite of Escherichia. coli O157:H7 in model soil at 10 percent concentration biochar. During these studies, we determined that the primary factor influencing the inactivation of these bacteria by the biochar is alkaline pH, which is enhanced at higher pyrolysis temperatures. Therefore, it was determined that 700 degrees Celsius for 1 h appears to be the optimal time/temperature combination to produce antimicrobial alkaline biochar, which aligns with this year’s Objective 1, Milestone number 1 to “Optimize production of antimicrobial biochar by varying pyrolysis residence time, temperature.” These results were necessary for completion of Objective 2, Milestone number 1, described below, and will also be beneficial for future studies examining the inactivation of bacterial pathogens in crop soil, dairy manure and poultry litter.
Under Objective 2, we made significant progress to understand the minimum concentration of biochar (processed under the conditions determined in Objective 1, Milestone number 1, for example, 700 degrees Celsius for 1 h) necessary to inactivate E. coli O157:H7 in model soil. This aligns with this year’s Objective 2, Milestone number 1 to “Test the minimum percent concentration of optimized antimicrobial biochar from Objective 1, 12 month milestone for ability to inactivate foodborne pathogens in soil.” A series of concentrations of the 700 degrees Celsius, 1 h-pyrolyzed biochar (1.5 2.0, 2.5, 3.0, and 3.5 percent) was challenged in the model soil against E. coli O157:H7 over a period of 6 weeks. During this time, it was determined that biochar added at the 3.5 percent level was sufficient to inactivate >5 log CFU (colony forming units) of E. coli O157:H7 inoculated into the soil. Biochar added at the 3.0 percent level inactivated approximately 4 log colony forming units of E. coli O157:H7, which seems to be the breakpoint at which the biochar begins to lose its biocidal efficacy. These results will be beneficial for future studies examining the inactivation of bacterial pathogens in crop soil, dairy manure and poultry litter.
Accomplishments
Review Publications
Fan, X., Jin, Z.T., Baik, J.I., Gurtler, J., Mukhopadhyay, S. 2021. Combination of aerosolized acetic acid and chlorine dioxide-releasing film to inactivate Salmonella enterica and affect quality of tomatoes and Romaine lettuce. Journal of Food Safety. 41:e12922. https://doi.org/10.1111/jfs.12922.
Kingsley, D.H., Annous, B.A. 2021. Evaluation of SDS and GRAS liquid disinfectants for mitigation of potential HAV contamination of berries. Journal of Applied Microbiology. 15123. https://doi.org/10.1111/jam.15123.
Eppinger, M., Almeria, S., Allure-Guardia, A., Bagi, L.K., Kalalah, A.A., Gurtler, J., Fratamico, P.M. 2022. Genome sequence analysis and characterization of shiga toxin 2 production by escherichia coli O157:H7 strains associated with a laboratory infection. Frontiers in Cellular and Infection Microbiology. 12. https://doi.org/10.3389/fcimb.2022.888568.
Gurtler, J., Dong, X., Zhong, B., Lee, R. 2022. Efficacy of a mixed peroxyorganic acid antimicrobial wash solution against Salmonella, Escherichia coli O157:H7 or Listeria monocytogenes on cherry tomatoes. Journal of Food Protection. 85(5):773–777. https://doi.org/10.4315/JFP-21-368.
