Probiotic bacteria: safety, functional and technological properties

Because of their perceived health benefits, probiotics have been incorporated into a range of dairy products, including yoghurts, soft-, semi-hard and hard cheeses, ice cream, milk powders and frozen dairy desserts. However, there are still several problems with respect to the low viability of probiotic bacteria in dairy foods. This review focuses mainly on current knowledge and techniques used in the microencapsulation of probiotic microorganisms to enhance their viability during fermentation, processing and utilization in commercial products. Microencapsulation of probiotic bacteria can be used to enhance the viability during processing, and also for the targeted delivery in gastrointestinal tract.

Recent advances in microencapsulation of probiotics for industrial applications and targeted delivery

Probiotics have been defined in several ways, depending on our understanding of the mechanisms of action of their effects on health and well-being of humans. The term probiotic was coined by Lilly and Stillwell [1] to describe substances produced by one microorganism, that stimulate the growth of another, thus meaning the opposite of antibiotics. Parker [2] subsequently defined probiotics as organisms and substances that contribute to intestinal balance. This definition, however, did not exclude antibiotics. At present, the most commonly used definition is that of Fuller [3] : Probiotics are live microbial feed supplements which beneficially affect the host animal by improving its intestinal microbial balance . Recently a European expert group widened the definition to include mechanisms other than just microflora mediated ones. The definition was as follows: Probiotics are live microbial food ingredients that have a beneficial effect on human health [4,5] . To include the current application and scientific data on proven effects of probiotics we propose the following definition: Probiotics are microbial cell preparations or components of microbial cells that have a beneficial effect on the health and well-being of the host . This definition implies that probiotics do not necessarily need to be viable. Non-viable forms of probiotics have also been shown to have health effects [6] . The definition does not restrict the use of probiotics in foods; several other applications have been reported to have beneficial health effects. Not only whole microbial cells, but also parts of cells have been observed to improve host health. Metabolites are, however, not included in the current definition. Thus, it excludes antibiotics. The proposed definition is based on the mechanisms of action, selection criteria, viability and non-viability, and scientifically documented health effects that will be discussed.

Probiotics: how should they be defined?

Lactobacilli and bifidobacteria are extremely rare causes of infection in humans, as are probiotics based on these organisms. This lack of pathogenicity extends across all age groups and to immunocompromised individuals. Strains used for new probiotics should be chosen from the commensal flora of humans and should not carry intrinsic resistance to antibiotics that would prevent treatment of a rare probiotic infection. Vigilance regarding the detection of possible rare cases of infection due to probiotics should be maintained, and isolates should be sent to reference centers for molecular characterization and confirmation.

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Safety of Probiotics That Contain Lactobacilli or Bifidobacteria

Studies of lactic acid bacteria (LAB) as delivery vehicles have focused mainly on the development of mucosal vaccines, with much effort being devoted to the generation of genetic tools for antigen expression in different bacterial locations. Subsequently, interleukins have been co-expressed with antigens in LAB to enhance the immune response that is raised against the antigen. LAB have also been used as a delivery system for a range of molecules that have different applications, including anti-infectives, therapies for allergic diseases and therapies for gastrointestinal diseases. Now that the first human trial with a Lactococcus strain that expresses recombinant interleukin-10 has been completed, we discuss what we have learnt, what we do not yet understand and what the future holds for therapy and prophylaxis with LAB.

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S.E. Birkeland

Papers

Demonstration of safety of probiotics — a review