Evaluation of Minimal Nutritional Requirements of Lactic Acid Bacteria Used in Functional Foods.

HÉBERT, E. M., RAYA, R. AND DE GIORI, G.S.

Environmental Microbiology: Methods and Protocols. Series Methods in Biotechnology

Humana Press Inc

Lugar: Totowa, New Jersey; Año: 2004; p. 139 - 148

1. IntroductionThe lactic acid bacteria (LAB) are important industrial microorganisms because of their role in food fermentations, especially dairy products. In addition, it has been showed that LAB exhibit a range of physiological and therapeutic effects in the consumers, including immune stimulation, pathogen exclusion, production of bioactive peptides, and health-related products (1). Foods containing such bacteria are included within “functional foods” category and are described as foods that promote health beyond providing basic nutrition.LAB are strictly fermentative and have complex nutritional requirements, needing to be supplied with carbohydrates, amino acids, peptides, fatty acid esters, salts, nucleic acid derivates, and vitamins. The growth requirements of LAB make them unable to growth on simple mineral media supplemented with a carbon source. These organisms are auxotrophic for several amino acids (2, 3). However, some residual genetic material for biosynthesis is still present, since mutagenesiscan render some lactobacilli prototrophic (3), and thus loss of the ability to synthesize an amino acid may be conditional rather than absolute. For example, the alanine requirement of Lactobacillus delbrueckii subsp. delrueckii ATCC 9649 can be bypassed by the addition of vitamin B6 to the medium (4). The search for nutrients and specially amino acids constitutes a real challenge for LAB.  Chemically defined media have been developed for these bacteria (5, 6) fordifferent purposes, including investigations of the nutritional requirements of bacteria cells (2, 3), identification of specific components and isolation of auxotrophic mutants (3). A defined medium that supports sustained growth of a LAB at a constant specific growth rate is required for metabolic investigations, including the isolation of bioactive molecules.2In this chapter, we describe a chemically defined medium (CDM) that allows an optimal growth of different LAB; mainly those can be used for the production of fuctional foods, such as Lactobacillus casei, Lactobacillus helveticus, Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus fermentum, Lactobacillus delbrueckii subsp. lactis and Lactobacillus acidophilus. This CDM allows the study of minimal nutritional requirements of the LAB above mentioned.