Stress resistance of the biofilm and planktonic forms of Lactobacillus delbrueckii in adverse environments.

This article focuses on the comparative analysis of biofilm and planktonic forms of Lactobacillus delbrueckii 5E, a strain isolated from traditional fermented dairy products, emphasizing its physicochemical properties, antimicrobial, antioxidant activities, and stress tolerance. The study found that L. delbrueckii 5E produces high levels of lactic acid contributing to pH-dependent antimicrobial effects and exhibits significant antioxidant activity through its cell-free fermentation supernatant, bacterial suspension, and cell-free extract. Biofilm formation on polyacrylonitrile electrospun membranes enhanced the strain’s survival under various environmental stresses—including heat, osmotic pressure, bile salts, potassium sorbate, hydrogen peroxide, and simulated gastrointestinal fluids—compared to planktonic cells. Additionally, the biofilm consistently released viable planktonic bacteria, suggesting potential for stable probiotic delivery and industrial applications in food preservation and fermentation processes.