Abstract

Spore-forming bacteria are among the most problematic contaminants in fluid milk. They can survive pasteurization, grow at refrigeration temperatures, and secrete heat-stable enzymes, making them a major cause of spoilage in both pasteurized and reconstituted milk products. Current nonthermal strategies for reducing spore counts, including microfiltration and bactofugation, are often costly and inconsistent. The increasing consumer demand for natural additives in food products has sparked interest in the use of bacterially-derived antimicrobial compounds, particularly those from generally recognized as safe (GRAS) organisms, as an alternative method of dairy preservation. This study explores the antimicrobial potential of ten soil-derived Bacillus and Paenibacillus strains previously isolated by our lab. These strains were screened for activity against a panel of dairy-relevant spoilage and pathogenic bacteria, including spore-forming isolates recovered from spoiled milk samples. Antimicrobial assays revealed that several producer strains exhibited broad-spectrum inhibitory activity. Genomic analysis using Illumina sequencing and antiSMASH identified biosynthetic gene clusters encoding diverse classes of natural products, including ribosomally synthesized and post-translationally modified peptides (RiPPs), nonribosomal peptides, and polyketides. Select compounds contained in the cell-free supernatant of producer strain Paenibacillus profundus 7.5 were further enriched using solid phase extraction and tested for antimicrobial activity. Together, these findings demonstrate the promise of using soil-derived antimicrobial compounds as biopreservatives in fluid milk. Several strains produced compounds having activity against both Gram-positive and Gram-negative bacteria. The study provides valuable insight into underexplored natural antimicrobials from Bacillus and Paenibacillus, laying the groundwork for future research and development of natural, non-thermal milk preservation strategies that align with consumer demand and industry needs.

Degree

MS

College and Department

Life Sciences; Microbiology and Molecular Biology

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-08-05

Document Type

Thesis

Keywords

Paenibacillus profundus, antimicrobial compounds, milk, spore-forming bacteria

Language

english

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Life Sciences Commons

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