The physicochemical surface characteristics of Lactobacillus casei Original Research Article

The surface and interfacial properties of five strains of Lactobacillus casei, commonly found in cheese, were investigated in an attempt to identify surface properties that might be exploited to effect adsorption of the cells onto milk fat globules. All measures of surface hydrophobicity revealed these strains to be moderately hydrophobic compared to a reference strain of Mycobacterium smegmatis which was very hydrophobic. In chromatography experiments, L. casei had no affinity for either hydrophobic (octyl-sepharose) or control (sepharose) columns in conditions of physiological pH and low ionic strength, despite a favorable free energy of interfacial interaction (ΔGIFIW2) as derived from contact angle measurements. Adhesion of L. casei strains to these materials was effected by manipulation of eluent pH and ionic strength. In contrast, adhesion of L. casei strains to n-hexadecane concurred with ΔGIFIW2. Surfaces of L. casei strains subjected to X-ray photoelectron spectroscopy exhibited similar amounts of carbon and oxygen but displayed considerable diversity in surface nitrogen and phosphorous contents. Carbon existed predominantly as C-(O, N) and oxygen as -OH on L. casei surfaces but carbon on M. smegmatis surfaces was present predominantly as C-(C,H).