Shelf life of alginate beads containing lactobacilli and bifidobacteria: characterisation of microspheres containing Lactobacillus delbrueckii subsp. bulgaricus

Summary Capsules, containing different microorganisms ( Lactobacillus plantarum , L. casei , L. delbrueckii subsp. bulgaricus , L. delbrueckii subsp. delbrueckii , L. reuteri , L. rhamnosus , Bifidobacterium breve and B. animalis subsp. lactis ), were produced through a simple extrusion protocol and dipped in a CaCl 2 solution (0.5% or 8%). Beads were characterised, to assess the encapsulation yield (EY) and the shelf life at 4 °C (defined as the time to retain inside a cell count of 6 log CFU g −1 ); then, L. delbrueckii subsp. bulgaricus was used as target for system optimisation, through the study of the kinetic of cell release, as a function of the concentration of CaCl 2 solution, agitation (150 rpm) and recycling. The EY was 50% or higher, and the shelf life was at least 30 days. Concerning beads containing L. delbrueckii subsp. bulgaricus , the release of cells from capsules followed a biphasic (diauxic) trend and the microsphere could be used successfully for two times, as only after third reuse, the amount of release cells decreased.