A novel GRAS antimicrobial to control Listeria in the dairy processing environment

Obj 1. Conduct comprehensive analyses of biological activities and stability of A. oryzae extract. Obj 2. Identify bioactive compounds within the A. oryzae metabolic extract. Obj 3. Conduct mechanistic investigation of bactericidal activities against L. monocytogenes. Abstract: Despite various control strategies in the dairy processing environments, Listeria monocytogenes continues to cause numerous foodborne outbreaks due to its ubiquitous presence and resilience to adverse processing conditions and sanitation treatments. Consumer demand for natural and organic food products has driven major research efforts in bio-preservatives. With the exception of nisin, other plant-based extracts have limited commercial applications and the mechanisms of inhibition are not well understood. The genetic diversity of L monocytogenes, which results in vastly different antimicrobial resistance and biofilm formation across strains, further compromises the efficacies of these natural products. Our study examines the GRAS fungus Aspergillus oryzae as a promising source of anti-Listeria bioactive compounds. In addition to potent activities against Listeria growth and biofilm, the A. oryzae metabolic extract is stable through heat treatments, proteinase K, and long-term storage, indicating that it is compatible with dairy processing conditions. In this study, we will address several properties required for the commercial success of the extract: i) efficacies against broad L. moncoytogenes strains and isolates, ii) activities against biofilm, iii) stability under dairy processing conditions and storage, and iv) neutral flavor profiles that do not interfere with final product quality. Additionally, we will attempt to at least partially purify the bioactive compounds, and elucidate the molecular mechanisms of bactericidal activities. We envision that such mechanistic understanding will inform hurdle technology, as well as strategies to prevent resistant mutants