Hydrophobicity-driven interfacial behavior in food-grade Lactobacillus: Cross-validation of natural surface variance...

Research on the surface properties of lactic acid bacteria (LAB) has traditionally emphasized isolated measurements, while systematic studies that correlative analysis of multiple surface properties relate these features to one another are still limited. The aim of this study was to provide the first integrated investigation of Lactobacillus surface chemistry by combining comprehensive molecular profiling with multi-technique physicochemical validation to achieve a systematic characterization of LAB surface properties. An initial screening of 42 Lactobacillus strains based on zeta potential and hydrophobicity led to the selection of eight representative strains for in-depth analysis. Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed that the most hydrophobic and hydrophilic strains, L. acidophilus ATCC4356 (1-1) and L. helveticus AG10-1 (8-8), exhibited the highest N/C (0.134) and O/C (0.530) ratios, indicating protein-rich and polysaccharide-dominant surfaces, respectively. Water contact angles (58.7°-100.4°) in contact angle measurement (CAM) were closely aligned with hydrophobicity levels determined by microbial adhesion to solvents (MATS), ranging from 4.61 % to 64.42 %. MATS and CAM agreed on hydrophobicity but diverged sharply in their assessment of Lewis acid-base (AB) properties (R² < 0.20). Highly hydrophobic strains, lacking steric hindrance from hydrophilic polysaccharides, exhibited overall greater autoaggregation, though this behavior was also moderately influenced by zeta potential providing electrostatic repulsion between cells. These findings provide new insight into the molecular basis of Lactobacillus surface functionality and emphasize the importance of multi-method strategies for selecting and characterizing strains for probiotic development and biointerface applications.