Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Nannapaneni, Ramakrishna

Committee Member

White, Shecoya

Committee Member

Abdallah-Ruiz, Angelica

Committee Member

Dhowlaghar, Nitin

Date of Degree

8-7-2025

Original embargo terms

Visible MSU Only 2 Years

Document Type

Graduate Thesis - Campus Access Only

Major

Food Science, Nutrition and Health Promotion (Food Science & Technology)

Degree Name

Master of Science (M.S.)

College

College of Agriculture and Life Sciences

Department

Department of Biochemistry, Nutrition and Health Promotion

Abstract

Listeria monocytogenes is a significant foodborne pathogen known for its ability to cross-contaminate food products by persisting in food processing environments, even after standard sanitation cycles. This persistence presents an ongoing challenge for the food industry, highlighting the continuous need for effective, broad-spectrum disinfectants that can target L. monocytogenes on various surfaces and in water systems. Ferrate (FeVIO₄²⁻), a high-oxidizing compound primarily used in synthetic organic transformations, water oxidation catalysis, and wastewater remediation, has gained attention for its antimicrobial potential. However, its efficacy against foodborne pathogens, particularly L. monocytogenes, remains largely unexplored. This study evaluated the antimicrobial effectiveness of potassium ferrate against two strains of L. monocytogenes: Bug600 (serotype 1/2a) and ScottA (serotype 4b). The research was conducted in both aqueous environments and on two common food-contact surfaces, stainless steel coupons (SSC) and plastic cutting board pieces (CBP). For the water trials, L. monocytogenes cells were inoculated at initial concentrations of 10⁴ to 10⁵ CFU/ml. These suspensions were treated with potassium ferrate at concentrations ranging from 1 to 16 mg/ml. Recovery of surviving cells was assessed by both spot plating at 2, 5, 10, 15, 20, and 30-min intervals and by spread plating at 5 and 10 min on non-selective tryptic soy agar (TSA) supplemented with esculin. The spot plating results visually validated the CFU data, demonstrating a clear reduction in L. monocytogenes growth at higher ferrate concentrations. On TSA-esculin plates, decreasing black zone formation—a marker of Listeria esculin hydrolysis was observed with increasing potassium ferrate concentration and exposure time. At concentrations of ≥4 mg/ml for 10 min, almost no black precipitate formed, confirming near-complete inactivation of both Bug600 and ScottA strains. For surface studies, SSC and CBP were inoculated with L. monocytogenes at 10⁷ CFU/ml and exposed to potassium ferrate concentrations between 1 and 8 mg/ml for 5 or 10 min. Surviving firmly attached cells were recovered by vortexing with buffered peptone water and spread plating on TSA-esculin. Results showed a potassium ferrate concentration-dependent reduction in L. monocytogenes counts on both surfaces. Reductions ranged from 3 log CFU/ml at 2 mg/ml to over 5 log CFU/ml at 8 mg/ml within 5 to 10 min of exposure. Similar efficacy trends were observed for both L. monocytogenes strains in water and on both surfaces, demonstrating ferrate’s broad-spectrum potential. This study provides preliminary data for potential investigation of potassium ferrate as an effective disinfectant for reducing L. monocytogenes contamination under some food processing environments. Further research is recommended to optimize disinfection protocols and maximize the complete elimination of persistent L. monocytogenes in wastewater, on food-contact and non-food-contact surfaces, and in facility floors and drains.

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