Understanding PlyP100: A precision fermentation product to improve the safety of queso fresco

Precision fermentation is an emerging field in which genetic engineering tools are used to modify microorganisms so that they can transform abundant materials into value-added products. In the food industry, precision fermentation is used primarily in two ways: improving fermented foods by using modified strains to ferment substrates and using microbial cell factories to make food ingredients or additives. By using precise genome editing tools in generally recognized as safe (GRAS) microorganisms, this technology is argued to be a safe and consumer-benefitting advance to the food industry. Some examples include producing wine with milder flavors by using an engineered strain of yeast capable of malolactic fermentation, making flavor molecules without chemical synthesis, preventing the formation of acrylamide in fried foods by fermenting the doughs with precursor-consuming yeast, and providing sustainable protein options in the form of animal-free milk and egg proteins constructed by microbial cells. Chapter 1 of this thesis is a review of these and other recent examples of precision fermentation in the food industry, including methods to improve the flavor, safety, and sustainability of food products. One such example of using precision fermentation to improve the safety of food products is the production of endolysins by bacterial expression. Endolysins are enzymes encoded by lytic bacteriophages that can cleave the peptidoglycan (PG) layer of Gram-positive bacterial cells from the inside to release phage progeny at the end of the lytic cycle. Research has shown that these enzymes can also cleave the PG of bacterial cells from the outside, which makes them a candidate for a food antimicrobial that is innocuous to humans and effective against pathogenic bacteria. Endolysins as antimicrobials show promise specifically for foods like queso fresco, which is a ready-to-eat, refrigerated product with a near-neutral pH and sub-inhibitory salt concentration, making it susceptible to Listeria monocytogenes contamination and growth. PlyP100, from GRAS Listeria phage P100, is an endolysin that has been previously reported to have a listeriastatic effect when applied to contaminated queso fresco in a miniaturized model. In Chapter 2 of this thesis, the structure and function of PlyP100 expressed by E. coli were analyzed using biochemical and microbiological methods to gain insight into its enzymatic mechanism and strain specificity. The work presented in Chapter 2 not only sheds light on how this and similar endolysins function, but also provides the background for future structure-based engineering efforts to improve PlyP100 as a precision fermentation product.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Food Science & Human Nutrition

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Bateman, Karson R

Contributors dc:contributor

• Miller, Michael J
• Jin, Yong-Su

• precision fermentation
• endolysin
• queso fresco
• PlyP100
• Listeria monocytogenes
• food safety

Statement dc:rights

• Copyright 2025 Karson Bateman

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129554

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129554