Binding of acridine orange by probiotic Lactobacillus rhamnosus strains of human origin

Abstract

Binding of mutagens by lactic acid bacteria is one of the mechanisms responsible for their antimutagenic activity. Viable and heat-killed cells of Lactobacillus strains bind acridine orange (AO) rapidly, which occurs predominantly through extracellular cell wall components. Binding of AO by the cells depends on pH, cell-density and AO concentration. Cells treated with HCl, NaOH, MgCl2 and CaCl2 have a reduced capacity to bind AO, implicating the role of carbohydrates, proteins and teichoic acids. AO adsorption involves hydrophilic interactions, as evidenced by urea treatment not altering AO binding. Simulated gastrointestinal fluid treatment does not affect the binding of AO. The stability of the AO complexes formed with tested strains was assessed by repetitive aqueous extraction; 10–17% of AO extractable (100 μg/ml) with a phosphate buffer (0.1 M, pH 7). Moreover, such probiotic strains present in functional foods can prove to be useful in the removal of food-contaminants, apart from conferring other beneficial effects.