Technological challenges in the production and formulation of probiotics

Probiotic production technologies should provide in a cost effective manner high-quality, safe end-products with long enough shelf-life. Working with living microbes is demanding since viability losses occur easily if the microbial cultures encounter stressful situations and conditions. Microbes have unique optimal growth conditions and maintaining these optimal conditions in batch cultures in fermenters can be difficult. Furthermore, various down-stream processing steps of probiotic production (e.g. harvesting, freezing and drying) unavoidably cause stress to microbes. Probiotics have usually been isolated from the human GI-tract and they are well adapted to that special environment. Microbes that survive and thrive in the Gl-tract can therefore be difficult to propagate in the laboratory. If possible, production strain should therefore be chosen based both on functional properties and technological robustness. Factors that effect probiotic viability during production and formulation include e.g. strain characteristics, nutrients or matrix to which the strain is formulated, pH, atmosphere, possible accompanying microbes, storage time and temperature. There are several steps of probiotic production where probiotic viability and stability can be enhanced. These steps include strain selection and improvement of strain properties, production conditions, formulation, and packaging and storage. However, the technological robustness of a probiotic strain can also be improved. This can be done by activating the stress genes of the strain during processing with suitable sublethal treatments, or by genetically modifying the strain to make it more robust. Viability and stability as well as the factors affecting them are highly strain-specific and therefore treatments aiming at enhancing probiotic viability have to be tailored for each strain.