Spatial structure-mediated attenuation of protective LAB-pathogen competition: Quantitative modeling in structured...

The predictive reliability of LAB-based biocontrol is often compromised by the disparity between planktonic models and structured food matrices. We investigated the competitive dynamics between Lactiplantibacillus plantarum (LP4) and Salmonella enterica (N25) in liquid versus alginate-encapsulated systems across N25:LP4 initial ratios (1000:1-1:1000). Logistic, Weibull, and Lotka-Volterra models quantified growth/decline kinetics and interspecific competition. Spatial structure markedly attenuated competitive intensity: at a 1:1 ratio, the apparent competition coefficient (α₂₁) decreased by 44% from 2.58 (liquid) to 1.45 (encapsulated). Simultaneously, the pathogen's apparent net growth rate (r₁) shifted from negative (-0.730 h^-1) in liquid to positive (0.979 h^-1) under encapsulation, indicating a transition from inactivation to growth despite LAB presence. Validation in UHT milk supported that chemical buffering and diffusion constraints jointly shape pathogen persistence. These findings show that broth-based models can overestimate biocontrol efficacy in structured environments, highlighting the need for matrix-specific correction factors for quantitative microbial risk assessment.