CRISPR-Cas9 engineered Saccharomyces cerevisiae for endolysin delivery to combat Listeria monocytogenes

Listeriosis is an infection caused by the consumption of food contaminated with Listeria monocytogenes. It leads to febrile gastroenteritis, central nervous system infections, and even death in risk populations. Bacteriophage endolysins selectively kill bacteria hydrolyzing their cell walls and have emerged as a potential tool for listeriosis control. Ply511 is an anti-Listeria endolysin that has activity against all serovars of L. monocytogenes. The yeast Saccharomyces cerevisiae has been used to produce endolysins for biocontrol, but prior efforts relied on plasmids, which can lead to gene loss and include selection markers unsuitable for therapeutic use. Integration of endolysins in its genome has also been previously demonstrated, relying however, on selection markers for selection and maintenance of the modifications. This study explores S. cerevisiae as a generally regarded as safe (GRAS) platform for producing and displaying Ply511 through CRISPR-Cas9 integration, offering a marker-free and stable solution for Listeria biocontrol. Our results demonstrate that the surface display of Ply511 does not lead to bacterial reduction. In contrast, we show that yeast secreting endolysin significantly reduces L. monocytogenes in cells, supernatants, and cell extracts. The strongest effect was observed with concentrated spent supernatant and cell extract, which reduced L. monocytogenes below the lower limit of quantification. Additionally, the spent supernatant exhibited active anti-Listeria activity in milk. This study highlights yeast-secreted endolysins as a promising platform for listeriosis control and demonstrates the yeast secretion of endolysins can be used for the biocontrol of pathogenic bacteria. KEY POINTS: • S. cerevisiae was edited using CRISPR-Cas9 to display or secrete endolysin Ply511. • Cells, supernatants, and extracts of yeast secreting Ply511 act against L. monocytogenes. • Demonstrates the yeast-based delivery of endolysins to control L. monocytogenes.