in: Reference Module in Food Science Reference Module in Food Science 2016, Smithers G. W., Trinetta V., Editor, Elsevier Science, Oxford/Amsterdam , Amsterdam, pp.1-10, 2015
Lactobacillus acidophilus is one of the best well-known species of the genus Lactobacillus in lactic acid bacteria (LAB) group and exists in the gastrointestinal tract and vagina of humans and animals, where the environment can be quite acidic. The morphological structure of Lb. acidophilus are Gram-positive, non-spore-forming rods with rounded ends that occur singly, in pairs, and in short chains that is usually 0.6–0.9 × 1.5–6 μm dimension. Lb. acidphilus is an obligately homofermentative LAB that growth in anaerobic condition while a few are facultative heterofermenters. There are variable techniques for reliable characterization of new strains of Lb. acidophilus. The identification of Lb. acidophilus is based on a polyphasic approach which consists in studying the genotypic (16S rRNA, rep-PCR and housekeeping genes), phenotypic (sugar fermentation and cellular morphology), and phylogenetic data. The microbicidal compounds produced by the Lb. acidophilus include organic acids, hydrogen proxides, diacetyl, ammonia, and bacteriocins. Many strains of the genus Lactobacillus are generally accepted as human probiotics. Their probiotic properties are due to their bile resistance and their ability to adhere to the intestinal microbiota, which allow them to replace pathogenic bacteria and confer a well being the host. The metabolic activity of Lb. acidophilus leads to the production of flavor, and aroma that create organoleptic properties for fermented foods and inhibits foods spoilage. Different commercially available products were inoculated with Lb. acidophilus strains. The most known ones are dairy products (milk, yogurt and kefir) but other non-dairy products exist such as soymilk and fermented vegetables/fruits juices and even fermented meat with Lb acidophilus are present on the market. There are many health benefits of Lb. acidophilus including treatment of gastrointestinal diseases (constipation and diarrhea), competitiveness against pathogenic bacteria, reduction of cholesterol biosynthesis, inhibition of intestinal bacterial enzymes that convert pre-carcinogens into active carcinogens, predigestion of lactose which permits to lactose-intolerant persons to consume dairy products without any discomfort, as well as antimicrobial activity against Helicobacter pylori, Candida albicans and different species of molds.