Selection of useful probiotic lactic acid bacteria from the Lactobacillus acidophilus group and their applications to functional foods

Abstract

ABSTRACTIn the present review, a new mass screening system for selecting probiotic strains from Lactobacillus (L) acidophilus group lactic acid bacteria (LAB) with strong adhesion to the human intestinal tract is described. Characteristics of antimicrobial peptides (bacteriocin), lactose‐hydrolyzing enzymes and immunostimulative oligo DNA motifs in L. gasseri strains are also described. Finally, the use of L. acidophilus LAB, selected by our screening method, that have strong adhesion to the human colonic mucosa in functional yogurt products is described. Adhesiveness to the human intestine is one of the most important characteristics of probiotic LAB. A new screening system that involves a combination of three methods is proposed: rat colonic mucin (RCM)‐micro plate assay, Carnoy's histochemical staining method and carbohydrate probe binding assay. By using an RCM‐coated poly‐vinylidene‐diflouride membrane that mimics the human colonic mucous layer, a new lectin was isolated and its structure was clarified by gene cloning. Furthermore, the structures and functions of a new cyclic bacteriocin (gassericin A), new lactose‐hydrolyzing enzymes, and new immunostimulating oligo DNA motifs from Lactobacillus gasseri (B1 subgroup) were clarified. A new functional yogurt ‘Fit down’ is proposed, that is fermented by an adhesive strain of L. acidophilus LA67 selected by our screening and contains antihypertensive peptides derived from whey proteins by protease digestion. In the future, superior functional foods containing more effective probiotic LAB are expected to be developed by the use of the proposed mass screening system.