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

Area of Science:

• Food microbiology
• Microbial ecology
• Biocontrol strategies

Background:

• Predictive models for lactic acid bacteria (LAB)-based biocontrol often fail in complex food matrices.
• Discrepancies arise between planktonic culture results and real-world food environments.

Purpose of the Study:

• To compare the competitive dynamics of Lactiplantibacillus plantarum (LP4) and Salmonella enterica (N25) in liquid versus alginate-encapsulated systems.
• To assess how spatial structure influences the efficacy of LAB biocontrol against pathogens.

Main Methods:

• Utilized logistic, Weibull, and Lotka-Volterra models to quantify growth/decline kinetics and interspecific competition.
• Compared pathogen-to-bacterium ratios (1000:1 to 1:1000) in planktonic and encapsulated environments.
• Validated findings in UHT milk to account for chemical buffering and diffusion.

Main Results:

• Spatial structuring in alginate encapsulation reduced competitive intensity by 44% compared to liquid cultures.
• Salmonella enterica exhibited a shift from inactivation (liquid) to growth (encapsulated) despite the presence of Lactiplantibacillus plantarum.
• Chemical buffering and diffusion constraints in UHT milk confirmed the impact of the food matrix on pathogen persistence.

Conclusions:

• Broth-based models overestimate biocontrol efficacy in structured food environments.
• Matrix-specific correction factors are crucial for accurate quantitative microbial risk assessment.
• Understanding spatial effects is vital for developing reliable biocontrol strategies.